School of Chemistry

Unimolecular thermometers: core–shell polymer bottlebrushes with solvatochromic responses to temperature

2026-03-18T04:59:19Z

Unimolecular thermometers: core–shell polymer bottlebrushes with solvatochromic responses to temperature Zhang, Chenyou; Kerai, Simran; Hawtrey, Tom; New, Elizabeth; Muellner, Markus Core–shell molecular polymer bottlebrushes (MPBs) were designed with a thermoresponsive poly(DEGMA) core and stabilising poly(PEGMA) shell. Solvatochromic fluorophores embedded in the core report polarity changes as it dehydrates and collapses upon heating, yielding a distinct fluorescence response. These stable, unimolecular nanostructures function as aqueous nanoscale sensors.

Self-Assembly of Bottlebrush-Linear, Rod–Coil Copolymers into Discoidal Nanoparticles

2026-03-18T04:52:52Z

Self-Assembly of Bottlebrush-Linear, Rod–Coil Copolymers into Discoidal Nanoparticles Kerai, Simran; Takano, Shin; Zeng, Ping; Muellner, Markus Block copolymers can self-assemble into nanoscale objects with various morphologies, offering custom nanomaterials for diverse fields of application. However, achieving an amorphous 2D morphology through self-assembly in solution remains challenging. Here, we systematically investigate the structural requirements of rod (bottlebrush)–coil (linear) block copolymers for self-assembly into nanoscale discs by independently varying side chain and backbone lengths. We identify optimal polymer dimensions that yield well-defined nanodiscs with 50–200 nm diameters through direct self-assembly in water.

Self-assembly of thioether-based diblock copolymers: a comparative study of linear and bottlebrush architectures

2026-03-18T04:48:03Z

Self-assembly of thioether-based diblock copolymers: a comparative study of linear and bottlebrush architectures Takano, Shin; Nishimura, Tomoki; Cheng, Yen Theng; Muellner, Markus Amphiphilic diblock copolymers are widely studied for their ability to self-assemble into diverse nanostructures for various applications. Linear-linear diblock copolymers and linear-bottlebrush diblock copolymers exhibit distinct self-assembly due to differences in their molecular architecture. In this study, linear poly(ethylene glycol) (PEG) was used as the solvophilic block, and poly(2-(methylthio)ethyl methacrylate) (MTEMA, a thioether-containing polymer), was used as the solvophobic block to generate block copolymers where PMTEMA was either also a linear (LL) or a bottlebrush (LB) block. Comparing both architectures revealed differences in their self-assembly in aqueous environments. LL formed vesicles with broad size distributions while LB produced relatively uniform particles with ordered internal morphology, as confirmed by small-angle X-ray scattering (SAXS) and electron microscopy. The polymer particles could further be disassembled through an oxidizing agent which in turn allowed them to be used for oxidation-triggered release studies.

Carborane-Containing Polymer Nanoparticles via Light-Mediated Polymerisation-Induced Self-Assembly

2026-03-18T04:43:15Z

Carborane-Containing Polymer Nanoparticles via Light-Mediated Polymerisation-Induced Self-Assembly Zhang, Xinyi; Zeng, Haoxiang; Takano, Shin; Rendina, Louis; Muellner, Markus Carboranes are an important class of icosahedral carbon-boron clusters that have been intensively studied in the fields of medicinal, organometallic, and materials chemistry. In recent years, there have been efforts to incorporate carboranes into block copolymers to explore their biomedical applications. Few studies have used reversible deactivation radical polymerisation processes to the synthesize carborane-based polymers. In this work, we report the synthesis of a series of well-defined poly[oligo(ethylene glycol) methyl ether methacrylate]-block-poly(closo-1,2-carboranylethyl methacrylate) (POEGMA-b-PCbEMA) block copolymers by means of a photo-mediated reversible addition-fragmentation chain-transfer (RAFT) polymerisation, and report the formation of nanoparticles of various morphologies through polymerisation-induced self-assembly (PISA). Various parameters including temperature, irradiation source, degree of polymerisation of the core-forming block, solids and water content were found to have an impact on the polymerisation process and the final morphologies.

Design of Mixed PDMS-mPEG Slippery Covalently Attached Liquid-Like Surfaces

2026-03-16T01:57:14Z

Design of Mixed PDMS-mPEG Slippery Covalently Attached Liquid-Like Surfaces Cho, Jae Hyung; Gresham, Isaac J.; Katselas, Anthony; McHale, Glen; Neto, Chiara Low droplet friction is desirable in many circumstances in which liquids interact with solid surfaces. This study explores the fabrication of surface-grafted, liquid-like layers with ultralow static droplet friction, made from a mixture of hydrophobic polydimethylsiloxane (PDMS) and hydrophilic methoxy polyethylene glycol (mPEG). These mixed layers are prepared via a two-step spin coating process in which reactive ethanol solutions are applied to the surface in sequence. Both polymers are liquid at room temperature and, when mixed, lead to slippery layers with contact angles that can be tuned from that of pure PDMS to that of pure mPEG. A contact angle hysteresis of 0.9 ± 0.3° was obtained on mPEG9–12 layers. This is the lowest hysteresis reported for any hydrophilic covalently attached liquid surface and represents the lowest contact line friction ever observed on a solid planar surface. As the PDMS fraction in the mixed layer increased, so too did contact angle hysteresis, reaching a maximum value of 9° at 70% PDMS, before returning to 2° for the pure PDMS layer. Atomic force microscopy mapping of the liquid layers revealed that the two polymers are fully mixed on the surface, even at high surface fraction of both components. The model by Reyssat & Quéré, devised to explain contact angle hysteresis for surfaces with dilute defects, explains the observed results well. This study shows that liquid-like surfaces can be achieved that are more slippery than conventional self-assembled monolayers and share the same capacity to gradually tune surface wettability. These mixed layers are excellent model systems with which to study interfacial phenomena, such as wetting, adhesion, and friction, the interactions of proteins and cells with surfaces, and for applications, from increased heat transfer to efficient atmospheric water capture and antifouling.

Experimental Study of Gas Microbubbles on Oil-Infused Wrinkled Surfaces

2026-03-12T22:48:26Z

Experimental Study of Gas Microbubbles on Oil-Infused Wrinkled Surfaces James, Leo; Vega-Sanchez, Christopher; Mehta, Priya; Zhang, Xuehua; Neto, Chiara Lubricant-infused surfaces (LIS) have been shown to reduce hydrodynamic drag to a greater extent than theoretically expected, making them attractive candidates for microfluidic applications. The presence of nano- and micro-bubbles has been found to explain this property, but this observation is not widely acknowledged. This work investigated how the volume and distribution of lubricant in wrinkled Teflon LIS affects bubble durability. The lubricant is depleted from LIS by repeated immersion through an air–water interface, as well as by shearing, gravity drainage and spreading. The bubbles are imaged using confocal fluorescence microscopy at different levels of infused lubricant. The lubricant encasing the bubbles on LIS prevented bubbles from shrinking over several hours, compared to uninfused superhydrophobic Teflon wrinkles, in which bubbles more rapidly shrunk in height, typically within 30 min. The size of bubbles is independent of lubricant volume, likely due to lubricant redistribution underwater. These findings point toward the possibility of a short-term stabilization of bubbles on structured surfaces for drag reduction applications through the use of lubricant.

Molecular Origin of Slippery Behavior in Tethered Liquid Layers

2026-05-07T01:54:05Z

Molecular Origin of Slippery Behavior in Tethered Liquid Layers Rasera, Fabio; Gresham, Isaac, J.; Tinti, Antonio; Neto, Chiara; Giacomello, Alberto Slippery covalently attached liquid surfaces (SCALS) are a family of nanothin polymer layers with ultralow static droplet friction, characterized by a low contact angle hysteresis (CAH < 5°), which makes them ideally suited for self-cleaning, water harvesting, and antifouling applications. Recently, a Goldilocks zone of lowest CAH has been identified for polydimethylsiloxane (PDMS) SCALS of intermediate thickness (≈4 nm); yet, molecular-level insights are missing to reveal the underlying physical mechanism of this elusive, slippery optimum. In this work, the agreement between coarse-grained molecular dynamics simulations and atomic force microscopy data shows that nanoscale defects, as well as deformation for thicker layers, are key to explaining the existence of this “just right” regime. At low thickness values, insufficient substrate coverage gives rise to chemical patchiness; at large thickness values, two features appear: (1) a waviness due to a previously overlooked lateral microphase separation occurring in polydisperse brushes, and (2) layer deformation due to the contact line being larger than in thinner layers. The most pronounced slippery behavior occurs for smooth PDMS layers that do not exhibit nanoscale waviness. The converging insights from simulations, experiments, and a CAH theory provide design guidelines for tethered polymer layers with ultralow CAH.

Encapsulation of Oil Droplets Using Film-Forming Janus Nanoparticles

2026-01-19T01:33:48Z

Encapsulation of Oil Droplets Using Film-Forming Janus Nanoparticles Turpin, Geosmin; Nguyen, Duc; Sypkes, Kathryn Isobel; Vega-Sanchez, Christopher; Davery, Tim; Hawkett, Brian S.; Neto, Chiara Polymer Janus nanoparticles with one hard cross-linked polystyrene lobe and one soft film-forming poly(methyl methacrylate-co-butyl acrylate) lobe were synthesized by reversible addition–fragmentation chain transfer (RAFT)-mediated emulsion polymerization. The Janus nanoparticles adsorbed to oil/water and air/water interfaces, where the soft lobes coalesced, forming films of thickness between 25 and 250 nm; droplets of silicone oil could be stably encapsulated in polymer in this way. When prepared by mechanical mixing without additives, capsules of diameter 5–500 μm could be prepared, and with additives and application of heat, capsules of diameter around 5 μm were achieved, even with highly viscous silicone oil (20,000 cSt). In a microfluidic device, monodisperse capsules of diameter 180 μm could be formed. The particles were weakly surface-active and spontaneously assembled themselves at air/water interfaces. When added into a paint formula, the oil capsules improved the stain resistance of paint films. Silicone oil leakage from the capsules could be mitigated by incubating the capsules with silica nanoparticles, on which silicone oil reacts, creating grafted layers.

Selective delivery of remarkably high levels of gadolinium to tumour cells using an arsonium salt

2025-12-11T00:26:05Z

Selective delivery of remarkably high levels of gadolinium to tumour cells using an arsonium salt Windsor, Madeline S. A.; Busse, Madleen; Morrison, Daniel E.; Baker, Robert W.; Hill, Leila R.; Rendina, Louis M. The use of a triphenylarsonium vector for tumour cell-targeting leads to a dramatic increase in Gd3+ uptake in human glioblastoma multiforme cells by up to an order of magnitude over the isosteric triarylphosphonium analogue, with significant implications for ‘theranostic’ applications involving delivery of this important lanthanoid metal ion to tumour cells.

Gadolinium theranostics for the diagnosis and treatment of cancer

2025-12-11T00:16:44Z

Gadolinium theranostics for the diagnosis and treatment of cancer Robertson, Amy G.; Rendina, Louis M. According to the World Health Organization (WHO), there were 18.1 million new cancer cases and 9.6 million cancer deaths reported worldwide in 2018. These numbers are expected to rise over the next decade, and the development of new and effective cancer treatments and diagnostic tools is urgently required, particularly for aggressive and intractable malignant cancers such as those of the brain. An exciting field of cancer research involves combining therapeutic and diagnostic tools into a single ‘theranostic’ platform. The role of theranostics in the personalized management of oncology patients is increasing, as is the demand for new types of theranostic agents. Some of the most promising cancer theranostics exploit the lanthanoid metal gadolinium, an element possessing favourable therapeutic and imaging properties.

Significant cell uptake of Gd(III)-diphenylphosphoryl-diphenylphosphonium complexes: evidence for a new conformationally-dependent tumour cell targeting vector

2025-12-11T00:08:59Z

Significant cell uptake of Gd(III)-diphenylphosphoryl-diphenylphosphonium complexes: evidence for a new conformationally-dependent tumour cell targeting vector Hall, Andrew J.; Robertson, Amy G.; Baker, Robert W.; Hill, Leila R.; Rendina, Louis M. The synthesis, characterisation, and tumour cell uptake of six novel Gd(III)-diphenylphosphoryl-diphenylphosphonium complexes are reported. The propyl-linked Gd(III) complexes can accumulate inside human glioma cells at prodigious levels, approaching 1200%, over the parent triphenylphosphonium salts. DFT and quantum chemical topology analyses support a new type of conformationally-dependent tumour cell targeting vector.

Superior Tumor Cell Uptake by Mono- and Tri-Nuclear Rhodamine-Gadolinium(III) Agents

2025-12-05T01:43:25Z

Superior Tumor Cell Uptake by Mono- and Tri-Nuclear Rhodamine-Gadolinium(III) Agents Robertson, Amy G.; Hall, Andrew J.; Marfavi, Anita; Rendina, Louis M. The synthesis and characterization of a novel trinuclear rhodamine-Gd(III) complex, along with two analogous mononuclear rhodamine-Gd(III) complexes, are reported. All complexes displayed good selectivity in a human glioma cell line (T98G) when compared to a glial cell line (SVG p12), with low cytotoxicities. Superior tumor cell uptake for these Gd(III) complexes was observed at lower incubation concentrations compared to previously-reported delocalized lipophilic cations such as a rhodamine-lanthanoid(III) probe and Gd(III)-arylphosphonium complexes, with ca. 150 % and 250 % increases in Gd uptake, respectively.

Cutting edge rare earth radiometals: prospects for cancer theranostics

2025-12-05T01:19:09Z

Cutting edge rare earth radiometals: prospects for cancer theranostics Sadler, Alexander W. E.; Hogan, Leena; Fraser, Benjamin; Rendina, Louis M. With recent advances in novel approaches to cancer therapy and imaging, the application of theranostic techniques in personalised medicine has emerged as a very promising avenue of research inquiry in recent years. Interest has been directed towards the theranostic potential of Rare Earth radiometals due to their closely related chemical properties which allow for their facile and interchangeable incorporation into identical bifunctional chelators or targeting biomolecules for use in a diverse range of cancer imaging and therapeutic applications without additional modification, i.e. a “one-size-fits-all” approach. This review will focus on recent progress and innovations in the area of Rare Earth radionuclides for theranostic applications by providing a detailed snapshot of their current state of production by means of nuclear reactions, subsequent promising theranostic capabilities in the clinic, as well as a discussion of factors that have impacted upon their progress through the theranostic drug development pipeline.

Synthesis and tumour cell uptake studies of gadolinium(III)–phosphonium complexes

2025-12-05T00:30:26Z

Synthesis and tumour cell uptake studies of gadolinium(III)–phosphonium complexes Hall, Andrew J.; Robertson, Amy G.; Hill, Leila R.; Rendina, Louis M. The synthesis of a new series of Gd(III)-arylphosphonium complexes is described and the solution stability of selected compounds is reported. Their lipophilicity and uptake in human glial (SVG p12) and human glioblastoma multiforme (T98G) cell lines are presented. The in vitro cytotoxicity of all complexes was determined to be low at therapeutically-relevant concentrations. Selected Gd(III) complexes are potential candidates for further investigation as theranostic agents.

Tensile benefits of nanofibers in commercial paint films

2026-05-04T03:07:37Z

Tensile benefits of nanofibers in commercial paint films Turpin, Geosmin; Nguyen, Duc; Subramanian, Priya; Davey, Tim; Cheong, Siew Fong; Warr, Gregory G.; Neto, Chiara; Hawkett, Brian Polymerization-induced self-assembly (PISA) in dispersed phase polymerization enables the synthesis of fibers and other self-assembled nanostructures at the quantities and cost required for use in commodity paints. Here we studied the effect of adding three types of fibers to coatings of two commodity paints with different glass transition temperatures (Tg). Film-forming (FF) fibers and rigid polystyrene (PS) fibers analysed were synthesized by RAFT-PISA at ∼20 g scales with a promising degree of purity (75% and 63% respectively), with kilogram-scale synthesis also demonstrated. These fibers, as well as naturally sourced microfibrillated cellulose fibers, were added to paint, and their effect was tested on the stain resistance and tensile properties of the coatings produced. The fiber content added was determined by the desired viscosity needed for the application of coatings. The extensibility of both paint coatings was shown to decrease with the addition of the high Tg PS fibers, whereas extensibility and toughness increased with the addition of low Tg FF fibers. Cellulose fibers were seen to increase extensibility at low loadings, but in turn added hydrophilic and hygroscopic components, exposing the paint to increased staining. In contrast, the FF fibers showed a notable improvement in stain resistance in addition to the tensile benefits conferred. No significant change in strength was observed for any combination of paint and nanofibers.

Fluid Slip and Drag Reduction on Liquid-Infused Surfaces under High Static Pressure

2026-05-04T03:02:22Z

Fluid Slip and Drag Reduction on Liquid-Infused Surfaces under High Static Pressure Vega-Sanchez, Christopher; Neto, Chiara Liquid-infused surfaces (LIS) have been shown to reduce the huge frictional drag affecting microfluidic flow and are expected to be more robust than superhydrophobic surfaces when exposed to external pressure as the lubricant in LIS is incompressible. Here, we investigate the effect of applying static pressure on the effective slip length measured on Teflon wrinkled surfaces infused with silicone oil through pressure measurements in microfluidic devices. The effect of static pressure on LIS was found to depend on air content in the flowing water: for degassed water, the average effective slip length was beff = 2.16 ± 0.90 μm, irrespective of applied pressure. In gassed water, the average effective slip length was beff = 4.32 ± 1.06 μm at zero applied pressure, decreased by 55% to 2.37 ± 0.90 μm when the pressure was increased to 50 kPa, and then remained constant up to 200 kPa. The result is due to nanobubbles present on LIS, which are compressed or partially dissolved under pressure, and the effect is more evident when the size and portion of surface nanobubbles are higher. In contrast, on superhydrophobic wrinkles, the decline in beff was more sensitive to applied pressure, with beff = 6.8 ± 1.4 μm at 0 kPa and, on average, beff = −1 ± 3 μm for pressures higher than 50 kPa for both gassed and degassed water. Large fluctuations in the experimental measurements were observed on superhydrophobic wrinkles, suggesting the nucleation of large bubbles on the surface. The same pressure increase did not affect the flow on smooth substrates, on which gas nanobubbles were not observed. Contrary to expectations, we observed that drag reduction in LIS is affected by applied pressure, which we conclude is because, in a similar manner to superhydrophobic surfaces, they lose the interfacial gas, which lubricates the flow.

Visualizing Nanoscale Lubricant Layer Under Blood Flow

2026-05-04T03:07:33Z

Visualizing Nanoscale Lubricant Layer Under Blood Flow Hong, J.K.; Gresham, Isaac, J.; Daniel, Daniel; Waterhouse, Anna; Neto, Chiara Tethered-liquid perfluorocarbons (TLP) are a class of liquid-infused surfaces with the ability to reduce blood clot formation (thrombosis) on blood-contacting medical devices. TLP comprise a tethered perfluorocarbon (TP) infused with a liquid perfluorocarbon (LP); this LP must be retained to maintain the anti-thrombotic properties of the layer. However, the stability of the LP layer remains in question, particularly for medical devices under blood flow. In this study, the lubricant thickness is spatially mapped and quantified in situ through confocal dualwavelength reflection interference contrast microscopy (DW-RICM). TLP coatings prepared on glass substrates are exposed to the flow of 37% glycerol/water mixtures (v/v) or whole blood at a shear strain rate of around 2900 s-1 to mimic physiological conditions (similar to flow conditions found in coronary arteries). Excess lubricant (>2 μm film thickness) is removed upon commencement of flow. For untreated glass, the lubricant is completely depleted after 1 minute of shear flow. However, on optimized TLP surfaces, nanoscale films of lubricant (thickness between 100 nm – 2 μm) are retained over many tens of minutes of flow. The nanoscale films conform to the underlying structure of the TP layer and are sufficient to prevent the adhesion of red blood cells and platelets.

Competing Magnetic Interactions and the Role of Unpaired 4f Electrons in Oxygen-Deficient Perovskites Ba3RFe2O7.5 (R = Y, Dy)

2024-11-11T03:15:33Z

Competing Magnetic Interactions and the Role of Unpaired 4f Electrons in Oxygen-Deficient Perovskites Ba3RFe2O7.5 (R = Y, Dy) Brown, Alex J.; Avdeev, Maxim; Manjón-Sanz, Alicia; Brand, Helen E. A.; Ling, Chris D. Oxygen-deficient perovskite compounds with the general formula Ba3RFe2O7.5 present a good opportunity to study competing magnetic interactions between Fe3+ 3d cations with and without the involvement of unpaired 4f electrons on R3+ cations. From analysis of neutron powder diffraction data, complemented by ab initio density functional theory calculations, we determined the magnetic ground states when R3+ = Y3+ (non-magnetic) and Dy3+ (4f9). They both adopt complex long-range ordered antiferromagnetic structures below TN = 6.6 and 14.5 K, respectively, with the same magnetic space group Ca2/c (BNS #15.91). However, the dominant influence of f-electron magnetism is clear in temperature dependence and differences between the size of the ordered moments on the two crystallographically independent Fe sites, one of which is enhanced by R–O–Fe superexchange in the Dy compound, while the other is frustrated by it. The Dy compound also shows evidence for temperature- and field-dependent transitions with hysteresis, indicating a field-induced ferromagnetic component below TN.

Advances and challenges in slippery covalently-attached liquid surfaces

2024-10-18T02:00:30Z

Advances and challenges in slippery covalently-attached liquid surfaces Gresham, Isaac J.; Neto, Chiara Over the past decade, a new class of slippery, anti-adhesive surfaces known as slippery covalently-attached liquid surfaces (SCALS) has emerged, characterized by low values of contact angle hysteresis (CAH, less than 5◦) with water and most solvents. Despite their nanoscale thickness (1 to 5 nm), SCALS exhibit behavior similar to lubricant-infused surfaces, including high droplet mobility and the ability to prevent icing, scaling, and fouling. To date, SCALS have primarily been obtained using grafted polydimethylsiloxane (PDMS), though there are also examples of polyethylene oxide (PEO), perfluorinated polyether (PFPE), and short-chain alkane SCALS. Importantly, the precise physico-chemical characteristics that enable ultra-low CAH are unknown, making rational design of these systems impossible. In this review, we conduct a quantitative and comparative analysis of reported values of CAH, molecular weight, grafting density, and layer thickness for a range of SCALS. We find that CAH does not scale monotonically with any reported parameter; instead, the CAH minimum is found at intermediate values. For PDMS, optimal behavior is observed at advancing contact angle of 106◦, molecular weight between 2 and 10 kg mol􀀀 1, and grafting density of around 0.5 nm􀀀 2. CAH on SCALS is lowest for layers created from end-grafted chains and increases with the number of binding sites, and can generally be improved by increasing the chemical homogeneity of the surface through the capping of residual silanols. We review the existing literature on SCALS, including both synthetic and functional aspects of current preparative methods. The properties of reported SCALS are quantitatively analyzed, revealing trends in the existing data and highlighting areas for future experimental study.

Unlocking therapeutic potential: the role of adamantane in drug discovery

2024-08-30T06:10:43Z

Unlocking therapeutic potential: the role of adamantane in drug discovery Dane, Chianna; Cumbers, Grace A.; Allen, Beau; Montgomery, Andrew P.; Danon, Jonathan J.; Kassiou, Michael The unique structural and physicochemical properties of adamantane and its derivatives have attracted considerable attention in the field of medicinal chemistry. Substituting phenyl rings for adamantane or its derivatives has provided a promising strategy to introduce lipophilicity and escape the ‘flat land’ of modern drug discovery. Additionally, the unique three-dimensional structure of adamantane facilitates the precise positioning of substituents allowing for a more effective exploration of drug targets. Evidently, we have seen an increased use of adamantane in pharmaceutically relevant molecules. The following Account highlights our group’s research in five drug discovery programs over the past 15 years showcasing the use of adamantane and its analogues in these studies.

Quantifying Dual-Direction Energy Harvesting in Twisted Perylene Nonfullerene Acceptor Organic Photovoltaics

2026-05-04T03:07:35Z

Quantifying Dual-Direction Energy Harvesting in Twisted Perylene Nonfullerene Acceptor Organic Photovoltaics Goldingay, Alison; Stuart, Alexandra N.; Ghosh, Pratyush; Yadav, Suraj; Gangadharappa, Chandrasekhar; Patil, Satish; Rao, Akshay; Lakhwani, Girish Perylene monomers (PDI) and twisted dimers (TPDI) are investigated here as non- fullerene acceptors and are paired with the polymer donor PTB7-Th in organic photo- voltaic blends. A combination of device characteristics, morphology studies and tran- sient absorption techniques reveal a complete picture of the photophysics in these two systems. TPDI-based devices are shown to far outperform PDI-based devices, and intensity-dependent JSC and VOC measurements reveal that they do not suffer from non-geminate recombination to the same extent as PDI-based devices. Transient ab- sorption (TA) spectroscopy also demonstrates dual-direction energy harvesting from excitation of both PTB7-Th and (T)PDI domains. TA reveals that charges live signif- icantly longer in TPDI blends and are less susceptible to bimolecular recombination. The modelling of these processes allows for quantification of the relative contributions of each charge generation pathway. We find that TPDI-based devices benefit from a more balanced dual-direction charge generation process which can be linked to the favourable morphology in the TPDI:PTB7-Th blend, demonstrating the critical impor- tance of photoactive layer morphology considerations in the design of OPV acceptor materials.

The critical role of temperature-dependent mobilities in determining the open-circuit voltage of bulk-heterojunction organic solar cells

2026-05-04T03:07:35Z

The critical role of temperature-dependent mobilities in determining the open-circuit voltage of bulk-heterojunction organic solar cells Tang, Yahui; Lakhwani, Girish; McNeill, Christopher While solution-processed bulk-heterojunction organic solar cells (OSCs) continue to attract attention as their efficiencies approach 20%, the physical origin of the non-radiative energy loss in OSCs remains under debate. Understanding the temperature dependence of open-circuit voltage (VOC) is thus important because it provides unique insights into the origin of energy loss. Herein, we simulate the VOC vs. T relation of PTB7-Th:PC71BM bulk-heterojunction OSCs within the range of 160–295 K by incorporating experimentally measured temperature-dependent mobilities into the drift-diffusion model, assuming bimolecular recombination as the primary recombination mechanism. Significantly, we find that the temperature dependence of VOC can only be correctly reproduced by the model when the temperature dependence of the carrier mobilities is taken into account. The effect of the Langevin reduction coefficient on the temperature dependence of VOC is also investigated.

Distributed feedback lasers up to the 400th Bragg order with an organic active layer

2026-05-04T03:07:36Z

Distributed feedback lasers up to the 400th Bragg order with an organic active layer Li, Yun; Lakhwani, Girish The output characteristics and lasing threshold behaviour of higher order Bragg lasers is explored using an organic active layer spin-cast over substrate-defined fused-silica gratings. Gratings ranging from 1st to the 400th Bragg order of varying duty cycle are fabricated with standard e-beam lithography. Distinct diffraction orders are observed at lower Bragg orders but smears out towards higher orders due to overlapping diffracted orders. Significant variation in thresholds is observed with duty cycle for most Bragg orders. A dramatic reduction in threshold is observed with increasing cavity length. The lowest lasing thresholds obtained for 4th and 400th order distributed feedback (DFB) lasers are ~1.4 µJ cm-2 and 4 µJ cm-2, respectively, using F80.9BT0.1 as an active layer. 400th order Bragg lasers are fabricated with direct-write photolithography using a UV laser diode, with comparable thresholds to e-beam lithography fabricated devices.

Emission Decay Pathways Sensitive to Circular Polarization of Excitation

2026-05-04T03:07:30Z

Emission Decay Pathways Sensitive to Circular Polarization of Excitation Sharma, Ashish; Athanasopoulos, Stavros; Tapping, Patrick; Sabatini, Randy; McRae, Olivia; Müllner, Markus; Kee, Tak; Lakhwani, Girish The photophysical properties of conjugated materials can be strongly affected by the nature of intermolecular interactions. Toward this aim, supramolecular self-assembly facilitates efficient packing of molecules into ordered architectures, which allows efficient intermolecular coupling. However, the resulting electronic overlap imparts additional sensitivity to the disorder, predominantly because of the “nonlocal” origins of the photophysical properties. Understanding the nature and origin of the disorder in conjugated systems is a prerequisite to exploit the benefits of efficient intermolecular coupling. In this report, we utilize chirality as a marker to sensitively probe the nature of the disorder in thermodynamically assembled helical nanoaggregates of a chiral conjugated polymer poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzothiadia- zole)] (PFBT). Surprisingly, we find that one-handed intermolecular coupling in helical PFBT aggregates leads to differences in the decay pathways of left- and right-handed excitations. We attribute the emergence of this sensitivity to the disorder in the excitonic coupling of flexible, nonplanar polymer chain conformations, likely predominant at the edges of the aggregate. Our findings shed insights into the effect of disorder on the photophysical properties, which open up new opportunities for sensitively exploring the links between intermolecular coupling and photophysical properties of conjugated systems.

Chiral Metal–Organic Frameworks for Photonics

2024-08-26T07:07:30Z

Chiral Metal–Organic Frameworks for Photonics Hall, Lyndon; D'Alessandro, Deanna; Lakhwani, Girish Recently, there has been significant interest in the use of chiral Metal–Organic Frameworks (MOFs) and Coordination Polymers (CPs) for photonics applications. The promise of these materials lies in the ability to tune their properties through judicious selection of the metal and ligand components. Additionally, the interaction of guest species with the host framework can be exploited to realise new functionalities. In this review, we outline the methods for synthesising chiral MOFs and CPs, then analyse the recent innovations in their use for various optical and photonics applications. We focus on two emerging directions in the field of MOF chemistry – circularly polarised luminescence (CPL) and chiroptical switching – as well as the latest developments in the use of these materials for second-order nonlinear optics (NLO), particularly second-harmonic generation (SHG). The current challenges encountered so far, their possible solutions, and key directions for further research are also outlined. Overall, given the results demonstrated to date, chiral MOFs and CPs show great promise for use in future technologies such as optical communication and computing, optical displays, and all-optical devices.

Probing Through-Bond and Through-Space Interactions in Singlet Fission-Based Pentacene Dimers

2024-08-26T06:53:04Z

Probing Through-Bond and Through-Space Interactions in Singlet Fission-Based Pentacene Dimers Sharma, Ashish; Athanasopoulos, Stavros; Yun, Li; Sanders, Samuel N.; Kumarasamy, Elango; Campos, Luis M.; Lakhwani, Girish Inter-chromophoric interactions such as coulombic coupling and exchange interactions are crucial to the functional properties of numerous π-conjugated systems. Here, we use magnetic circular dichroism (MCD) spectroscopy to investigate inter-chromophoric interactions in singlet fission relevant pentacene dimers. Using a simple analytical model, we outline a general relationship between the geometry of pentacene dimers and their calculated MCD response. We analyse experimental MCD spectra of different covalently bridged pentacene dimers to reveal how the molecular structure of the ‘bridge’ affects the magnitude of through-space coulombic and through-bond exchange interactions in the system. Our results show that through-bond interactions are significant in dimers with conjugated molecules as bridging units and these interactions promote the overall electronic coupling in the system. Our generalized approach paves the way for the application of MCD to investigate inter-chromophoric interactions across a range of π-conjugated systems.

Achromatic polarization control in the visible

2024-11-26T04:46:32Z

Achromatic polarization control in the visible Sabatini, Randy P.; Lakhwani, Girish A special design of perovskite material is demonstrated to operate as a wideband, achromatic quarter-wave plate.

Improved optical confinement in ambipolar field-effect transistors toward electrical injection organic lasers

2024-08-26T06:12:51Z

Improved optical confinement in ambipolar field-effect transistors toward electrical injection organic lasers Li, Yun; Sabatini, Randy P.; Prasad, Shyamal K. K.; Hockings, Evan T.; Schmidt, Timothy W.; Lakhwani, Girish Increasing optical confinement is critical to lowering laser thresholds and increasing modal gain in semiconductor lasers. Here, mode-solver calculations are used to demonstrate that improvements to optical confinement are possible in organic field-effect transistor geometries by using high refractive index cladding layers. Optical experiments show that the proposed structure increases the efficiency of amplified spontaneous emission (ASE) and lowers ASE thresholds without incurring additional losses. The results suggest that the structure can be used to improve optical confinement for both optically pumped, and electrical injection organic lasers where thin, low refractive index active materials are required.

Pentacene–Bridge Interactions in an Axially Chiral Binaphthyl Pentacene Dimer

2024-11-26T04:41:55Z

Pentacene–Bridge Interactions in an Axially Chiral Binaphthyl Pentacene Dimer Sharma, Ashish; Athanasopoulos, Stavros; Kumarasamy, Elango; Phansa, Chanakarn; Asadpoordarvish, Amir; Sabatini, Randy P.; Pandya, Raj; Parenti, Kaia R.; Sanders, Samuel N.; McCamey, Dane R.; Campos, Luis M.; Rao, Akshay; Tayebjee, Murad J. Y.; Lakhwani, Girish Molecular chirality can be exploited as a sensitive reporter of the nature of intra-and inter-chromophore interactions in π-conjugated systems. In this report, we design an intramolecular singlet fission (iSF) based pentacene dimer with an axially chiral binaphtyl bridge (2,2'-(2,2'-dimethoxy-[1,1'-binaphthalene]-3,3'-diyl) n-octyl-di-isopropyl silylethynyl dipentacene, BNBP) to utilize its chiroptical response as a marker of iSF chromophore-bridge-chromophore (SFC-β-SFC) interactions. The axial chirality of the bridge enforces significant one-handed excitonic coupling of the pentacene monomer units; as such, BNBP exhibits significant chiroptical response in the ground- and excited-states. We analyze the chiroptical response of BNBP using the exciton coupling method and quadratic response density functional theory calculations to reveal that higher energy singlet transitions in BNBP involve significant delocalization of the electronic density on the bridging binaphthyl group. Our results highlight the promising application of chiroptical techniques to investigate the nature of SFC-β-SFC interactions that impact singlet fission dynamics.

Strong coupling and energy funnelling in an electrically conductive organic blend

2024-08-26T03:20:59Z

Strong coupling and energy funnelling in an electrically conductive organic blend Rahme, Matthew S.; Sabatini, Randy P.; McGregor, Sarah K. M.; Wawrzinek, Robert; Namdas, Ebinazar B.; Lo, Shih-Chun; Lakhwani, Girish Strong coupling between an exciton and a cavity photon mode offers the promise of lower lasing thresholds, which has attracted interest in organic systems working toward electrical injected lasing. However, current organic polariton lasers have yet to exhibit thresholds beyond the reach of traditional lasers. Here, we investigate the possibility of energy funnelling from host to guest in a polariton system. We construct a material blend containing a dithiophenyl diketopyrrolopyrrole dye with an electrically conductive fluorene-benzothiadiazole co-polymer matrix. We demonstrate that a polariton system can exhibit efficient host to guest energy transfer while maintaining both strong exciton-polariton coupling and polariton emission. We expect that energy funnelling will become an important tool to drive down polariton laser thresholds in organic systems.

Circular Intensity Differential Scattering Reveals the Internal Structure of Polymer Fibrils

2024-08-26T06:17:58Z

Circular Intensity Differential Scattering Reveals the Internal Structure of Polymer Fibrils Sharma, Ashish; Campbell, Alison; Leoni, Julien; Cheng, Yen Theng; Müllner, Markus; Lakhwani, Girish The optical and electronic properties of π-conjugated polymers in organic electronic devices depend on their intra and inter-chain interactions, dictated by the internal arrangement of the polymer chains in an amorphous or semi-crystalline aggregated state. Here, we discuss the utility of circular intensity differential scattering (CIDS) of circularly polarized light as a sensitive probe to identify the internal arrangement of the polymer chains in helical polymer aggregates. We advance existing theoretical models to utilize the CIDS response and extract structural properties such as the size, orientation and periodicity of a polymer aggregate. As an example, we analyze the CIDS signatures of helically assembled fibrillar aggregates of a chiral polymer poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzothiadiazole)](PFBT) in solution and reveal that PFBT fibrils incorporate at least 5 intertwined polymer chains. We anticipate our approach can be extended more generally to investigate the internal arrangement of supramolecular assemblies of wide range of fibrillar aggregates of π-conjugated polymers.

Molecularly isolated perylene diimides enable both strong exciton–photon coupling and high photoluminescence quantum yield

2024-08-26T02:31:52Z

Molecularly isolated perylene diimides enable both strong exciton–photon coupling and high photoluminescence quantum yield Sabatini, Randy P.; Zhang, Bolong; Gupta, Akhil; Leoni, Julien; Wong, Wallace W. H.; Lakhwani, Girish Strong coupling in organic media holds the promise of efficient room temperature polariton lasing with solution-processed materials. Currently, however, only five pure-organic materials have been shown to demonstrate polariton lasing. A major challenge is to achieve high exciton-photon coupling while maintaining high photoluminescence quantum yield. Here, we utilize a series of diimide perylene materials that possess sterically hindered substituents, dispersed within a polymer matrix. The rigid structures prevent aggregation and allow high photoluminescence quantum yield (PLQY) at large dye loadings. We demonstrate that these systems can exhibit substantial Rabi splittings at dye loadings that yield film PLQYs of up to 85%, making these perylene derivatives promising materials for polariton lasers.

Tunable Polymer Nanoreactors from RAFT Polymerization-Induced Self-Assembly: Fabrication of Nanostructured Carbon-Coated Anatase as Battery Anode Materials with Variable Morphology and Porosity

2026-05-04T03:07:31Z

Tunable Polymer Nanoreactors from RAFT Polymerization-Induced Self-Assembly: Fabrication of Nanostructured Carbon-Coated Anatase as Battery Anode Materials with Variable Morphology and Porosity Cheng, Yen Theng; Xia, Qingbo; Liu, Hongwei; Solomon, Marcello; Brisson, Emma; Blackman, Lewis; Ling, Chris; Muellner, Markus We demonstrate a modular synthesis approach to yield mesoporous carbon-coated anatase (denoted as TiO2/C) nanostructures. Combining polymerization-induced self-assembly (PISA) and reversible addition–fragmentation chain-transfer (RAFT) dispersion polymerization enabled the fabrication of uniform core–shell polymeric nanoreactors with tunable morphologies. The nanoreactors comprised of a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) shell and a poly(benzyl methacrylate) (PBzMA) core. We selected worm-like and vesicular morphologies to guide the nanostructuring of a TiO2 precursor, namely, titanium(IV) bis(ammonium lactato)dihydroxide (TALH). Subsequent carbonization yielded nanocrystalline anatase and simultaneously introduced a porous carbon framework, which also suppressed the crystal growth (∼5 nm crystallites). The as-prepared TiO2/C materials comprised of a porous structure, with large specific surface areas (>85 m2/g) and various carbon contents (20–30 wt %). As anode components in lithium-ion batteries, our TiO2/C nanomaterials improved the cycling stability, facilitated high overall capacities, and minimized the capacity loss compared to both their sans carbon and commercial anatase analogues.

Nanoscale Polymer Discs, Toroids and Platelets: a Survey of Their Syntheses and Potential Applications

2024-07-11T02:58:53Z

Nanoscale Polymer Discs, Toroids and Platelets: a Survey of Their Syntheses and Potential Applications Brisson, Emma; Worthington, Max; Kerai, Simran; Muellner, Markus Polymer self-assembly has become a reliable and versatile workhorse to produce polymeric nanomaterials. With appropriate polymer design and monomer selection, polymers can assemble into shapes and morphologies beyond well-studied spherical and cylindrical micellar structures. Steadfast access to anisotropic polymer nanoparticles has meant that the fabrication and application of 2D soft matter has received increasing attention in recent years. In this review, we focus on nanoscale polymer discs, toroids, and platelets: three morphologies that are often interrelated and made from similar starting materials or common intermediates. For each morphology, we illustrate design rules, and group and discuss commonly used self-assembly strategies. We further highlight polymer compositions, fundamental principles and self-assembly conditions that enable precision in bottom-up fabrication strategies. Finally, we summarise potential applications of such nanomaterials, especially in the context of biomedical research and template chemistry and elaborate on future endeavours in this space.

Loop to Linear: Exploring the Impact of Corona Topology on the Properties of Self-Assembled Polymer Nanoparticles

2024-07-11T02:49:18Z

Loop to Linear: Exploring the Impact of Corona Topology on the Properties of Self-Assembled Polymer Nanoparticles Zeng, Haoxiang; Muellner, Markus Macromolecular architecture plays a pivotal role in endowing distinct properties to polymer nanomaterials. We introduce a synthesis approach to produce cyclic polystyrene-b-poly(acrylic acid) block copolymers featuring UV-cleavable motifs by combining atom transfer radical polymerisation and copper-catalyzed azide–alkyne cycloaddition. The resulting cyclic copolymers could self-assemble into discrete nanoparticles. Their coronal topology could be altered from looped to linear poly(acrylic acid) chains upon UV irradiation while maintaining the original nanoparticle morphology, therefore achieving the post-assembly modification of polymer nanoparticles. Small molecule release profiles were markedly different for self-assemblies with looped or linear corona, as was their interaction with model cell membranes in electrochemical impedance spectroscopy assays. Compared to their linear counterparts, cyclic copolymer assemblies exhibited slower release and weakened membrane interactions.

Triplet dynamics reveal loss pathways in multi-resonant thermally activated delayed fluorescence emiters

2026-05-04T03:07:38Z

Triplet dynamics reveal loss pathways in multi-resonant thermally activated delayed fluorescence emiters Stuart, Alexandra Nicole; Lakhwani, Girish This repository contains the time-resolved emission data, time-resolved absorption data, and code used to deconvolute and model said data, for the paper "Triplet dynamics reveal loss pathways in multi-resonant thermally activated delayed fluorescence emiters" by A. N. Stuart et al. Data are in .csv files, and code is in a python notebook (.ipynb).

Micropatterned Substrates Made by Polymer Bilayer Dewetting and Collagen Nanoscale Assembly Support Endothelial Cell Adhesion

2024-05-14T06:29:03Z

Micropatterned Substrates Made by Polymer Bilayer Dewetting and Collagen Nanoscale Assembly Support Endothelial Cell Adhesion Thickett, Stuart; Moses, Joshua; Gamble, Jennifer; Neto, Chiara The ability to control protein and cell positioning on a microscopic scale is crucial in many biomedical applications, such as tissue engineering and the development of biosensors. We demonstrate here that the assembly of collagen on patterned surfaces produced by the dewetting of metastable poly(N-vinylpyrrolidone) (PNVP) films on top of polystyrene films supports the adhesion and survival of a biologically relevant cell type, human endothelial cells. Micropatterning of Type 1 collagen was achieved on such substrates by exploiting the different protein affinity of the two polymers, the effect of treatment with an air plasma, and the control over the nanoscale assembly of collagen using different adsorption conditions. The simplicity of the dewetting approach, coupled with the ability to coat and pattern non-planar substrates, gives rise to possible applications in the coating of biological implants such as arterial stents.

Synthesis and applications of polymeric Janus nanoparticles

2024-05-14T06:16:39Z

Synthesis and applications of polymeric Janus nanoparticles Duong, Hien; Nguyen, Duc; Neto, Chiara; Hawkett, Brian Research into Janus particles has received great attention over the past decade. In his Nobel lecture in 1991, Pierre-Gilles de Gennes suggested that asymmetric colloidal particles with different chemical compositions on the two lobes could have a special behaviour at interfaces, and named them “Janus grains.1 Due to their asymmetry, Janus particles have the ability to offer more advanced chemical and physical properties compared to that of their symmetric homogeneous counterparts and in particular may behave as amphiphilic surfactants. However, for years after de Gennes’ Nobel lecture, research into Janus particles was still slow, as evidenced by the limited number of publications in the field. The main limitations to the advancement of the field were the difficulty in synthesising well-defined Janus particles and also in characterising them, especially in the case of nanometer-sized Janus particles. From around 2005, the significance of Janus particles in a wide range of applications has become clear, including in surfactants, electrochemistry, catalysis, electronics, sensors, optics, superhydrophobic textiles and nanomedicine, and this has driven research to pursue different methods for the fabrication of Janus particles. In the past ten years, Janus particles have become a hot topic of research, as evidenced by the exponential growth in the number of publications in this area. Our latest search using the keyword “Janus particles” on Web of Science shows 1,608 published research papers on this topic which is more than 16 times higher than in 2010.

Structural And Magnetic Properties Of Some Vacancy Ordered Osmium Halide Perovskites

2026-05-04T03:02:22Z

Structural And Magnetic Properties Of Some Vacancy Ordered Osmium Halide Perovskites Saura-Múzquiz, Matilde; Avdeev, Maxim; Brand, Helen E. A.; Kennedy, Brendan James The structures and magnetic properties of the Os4+ (5d4) halides K2OsCl6, K2OsBr6, Na2OsBr6 and Na2OsBr6.6H2O are described. K2OsCl6 and K2OsBr6 have a cubic vacancy-ordered double perovskites structure but undergo different symmetry lowering structural phase transitions upon cooling associated with a combination of the relative size of the ions and differences in their chemical bonding. The structure of Na2OsBr6.6H2O has been determined for the first time and the thermal stability of this established using a combination of in-situ diffraction and TGA. Na2OsBr6.6H2O and Na2OsBr6 are isostructural with the analogous iridium chlorides, Na2IrCl6.6H2O and Na2IrCl6, dehydration proceeds via different intermediate phases. The magnetic moments of four compounds display Kotani-like behaviour consistent with a Jeff = 0 ground state, however the magnetic susceptibility measurements reveal unusual low temperature properties indicative of a weakly magnetic ground state.

Beyond the Ionic Radii: A Multifaceted Approach to Understand Differences between the Structures of LnNbO4 and LnTaO4 Fergusonites

2026-05-04T03:07:38Z

Beyond the Ionic Radii: A Multifaceted Approach to Understand Differences between the Structures of LnNbO4 and LnTaO4 Fergusonites Mullens, Bryce; Saura-Múzquiz, Matilde; Marlton, Frederick; Avdeev, Maxim; Brand, Helen E. A.; Mondal, S.; Vaitheeswaran, G.; Kennedy, Brendan James Synchrotron X-ray powder diffraction methods have been used to obtain accurate structures of the lanthanoid tantalates, LnTaO4, at room temperature. Three different structures are observed, depending on the size of the Ln cation: P21/c (Ln = La, Pr), I2/a (Ln = Nd-Ho), and P2/c (Ln = Tb-Lu). BVS analysis indicated that TaV is six-coordinate in these structures, with four short bonds and two longer bonds. Synchrotron X-ray powder diffraction methods were also used to observe the impact of Ta doping on the orthoniobates, Ln(Nb1-xTax)O4 (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Ho, Yb and Lu). Where both the niobate and tantalate oxide were isostructural (fergusonite structure, space group I2/a), complete solid solutions were prepared. In these solid solutions, the unit cell volume decreases as the Ta content increases. The subtle interaction evident between the LnO8 and BO6 sublattices in the fergusonite-type oxides was not observed in the related pyrochlore oxides. A combined synchrotron X-ray and neutron powder diffraction study of the series Ho(Nb1-xTax)O4 was used to determine accurate atomic positions of the anions, and hence, bond lengths. This revealed a change in the (Nb/Ta)-O bond lengths, reflective of the difference in the valence orbitals of Nb(4d) and Ta(5d). Examination of the partial density of states demonstrates differences in the electronics between Nb and Ta, leading to a difference in the bandgap. This study highlights the importance of the long B-O contacts in the fergusonite structures, and its potential impact on the I2/a to I41/a phase transition.

Neutron diffraction study of the tetragonal – monoclinic phase transition in NdNbO4 and NdTaO4

2026-05-04T03:07:31Z

Neutron diffraction study of the tetragonal – monoclinic phase transition in NdNbO4 and NdTaO4 Saura-Múzquiz, Matilde; Mullens, Bryce; Maynard-Casely, Helen Elizabeth; Kennedy, Brendan James Phase transition and high-temperature properties of NdNbO4 and NdTaO4 were studied in situ using powder neutron diffraction methods. Both oxides undergo a reversible phase transition from a monoclinic I2/a phase at low temperatures to a tetragonal I41/a phase at high temperatures. The phase transition has been investigated through analysis of the spontaneous strains and symmetry distortion modes. Well below the transition temperature, Tc, the thermal evolution of the lattice parameters and symmetry modes suggest the transition is continuous, although a small discontinuity in both the spontaneous strains and symmetry distortion modes shows the transition is strictly first order. Analysis of the refined structures reveals that the Nb and Ta cations are best described as having a distorted 6-coordinate arrangement in the monoclinic structure, with four short and two long bonds. Breaking of the two long bonds at high temperatures, resulting in a transformation of the Nb(Ta) coordination to a regular tetrahedron, is believed to be responsible for the first order nature of the transition.

Structure and electronic properties of a mu-oxo ruthenium bromide

2026-05-04T03:07:30Z

Structure and electronic properties of a mu-oxo ruthenium bromide Saura-Múzquiz, Matilde; Mullens, Bryce; Brand, Helen E. A.; Kennedy, Brendan James The crystal structure of potassium μ-oxo-bis[pentabromoruthenate] K4Ru2OBr10, determined from synchrotron X-ray powder diffraction, is described. Each Ru atom is surrounded by five Br atoms and one O atom. Magnetic measurements show the complex to be diamagnetic as a result of strong Ru–Ru interactions facilitated by the linear Ru–O–Ru linkage.

Experimental and Computational Insights into the Anomalous Thermal Expansion of NH¬4ReO4

2026-05-04T03:07:32Z

Experimental and Computational Insights into the Anomalous Thermal Expansion of NH¬4ReO4 Saura-Múzquiz, Matilde; Mullens, Bryce; Avdeev, Maxim; Jharapla, PK.; Vaitheeswaran, G.; Gupta, M. K.; Mittal, R.; Kennedy, Brendan James The temperature dependence of the structure and the ground state properties of scheelite type NH4ReO4 have been studied using neutron powder diffraction (NPD) and Density Functional Theory (DFT), respectively. Despite the large incoherent background in the experimental NPD, associated with the presence of hydrogen, accurate and precise structural parameters were obtained. Comparison of the results of the NPD and DFT studies shows that the observed anomalous thermal contraction in NH4ReO4 is a consequence of thermally induced rotational disorder of the NH4 groups. Comparing the experimentally determined and optimized structures reveals deformation of the NH4 tetrahedra that is responsible for the unusual tetragonal distortion of this material. The Raman Spectra of NH4ReO4 is presented and the modes are assigned based on the DFT calculations.

Long-Range A-Site Cation Disorder in NaA(MO4)2 (M = Mo, W) Double Scheelite Oxides

2023-12-11T05:42:24Z

Long-Range A-Site Cation Disorder in NaA(MO4)2 (M = Mo, W) Double Scheelite Oxides Mullens, Bryce; Nicholas, Maria; Marlton, Frederick; Brand, Helen E. A.; Gu, Qinfen; Maynard-Casely, Helen Elizabeth; Kennedy, Brendan James Synchrotron X-ray and neutron powder diffraction methods have been used to obtain accurate long-range average structures of some double scheelite compounds of the type NaA(BO4)2 (A = La, Pr, Nd, Sm, Lu, and Bi; B = Mo, W) at room temperature. Phase pure samples were synthesized using standard solid-state methods. Rietveld refinements using combined synchrotron X-ray diffraction (SXRD) and neutron diffraction (NPD) revealed a random distribution of the Na and A-type cations regardless of the presence of 6s2 lone pairs (such as Bi3+) and the difference in oxidation states and ionic radii between the cations. The NaA(BO4)2 (A = La, Pr, Nd, Sm, Lu, and Bi) series displayed linear trends in lattice parameters and AO8 polyhedra volume with the ionic radius of the A-type cation for the lanthanoids, but a deviation from the trend was observed for A = Bi3+. The NaBi(BO4)2 structure has a smaller than expected unit cell volume than based on extrapolation from the corresponding NaLn(BO4)2 series, possibly due to short-range ordering of the 6s2 lone pair electrons.

Tetrahedral displacive disorder in the scheelite-type oxide RbReO4

2026-05-04T03:07:35Z

Tetrahedral displacive disorder in the scheelite-type oxide RbReO4 Marlton, Frederick; Mullens, Bryce; Chater, Philip A.; Kennedy, Brendan James Oxides exhibiting the scheelite-type structure are an important class of functional materials with notable applications in photocatalysis, luminescence and ionic conductivity. Like all materials, understanding their atomic structure is fundamental to engineering their physical properties. This study outlines a detailed structural investigation of scheelite-type oxide RbReO4, which exhibits a rare long-range phase transition from I41/a to I41/amd upon heating. Additionally, in the long-range I41/a model, the Re-O tetrahedral distance undergoes significant contraction upon warming. Recent studies of other scheelite oxides have attributed this apparent contraction to incoherent local scale tetrahedral rotations. In this study we use X-ray pair distribution function analysis to show that RbReO4 undergoes a unique symmetry lowering process on the local scale, which involves incoherent tetrahedral displacements. The rare I41/a to I41/amd long-range phase transition was found to occur via a change from static to dynamic disorder on the local scale, which is due to the combination of the size of the A-site cation and lattice expansion. This demonstrates how careful manipulation of the ionic radius of the A-site in the scheelite structure can be used to induce local scale disorder, which has valuable implications for tailoring the physical properties of related materials.

Cation and lone pair order-disorder in the polymorphic mixed metal bismuth scheelite Bi3FeMo2O12

2026-05-04T03:07:33Z

Cation and lone pair order-disorder in the polymorphic mixed metal bismuth scheelite Bi3FeMo2O12 Saura-Múzquiz, Matilde; Marlton, Frederick; Mullens, Bryce; Liu, Jiatu; Maynard-Casely, Helen Elizabeth; Avdeev, Maxim; Blom, Douglas A.; Vogt, Thomas; Kennedy, Brendan James The Bi3FeMo2O12 system is examined as a rare example of a transition metal oxide which, upon heating, undergoes a symmetry lowering and 2:1 ordering of the transition metal cations. The compound was synthesised in the tetragonal scheelite structure (S.G. #88: I41/a) by a sol-gel method and converted into the monoclinic polymorph (S.G. #15: C2/c) by calcination above 500 °C. The structure of both polymorphs was analysed using a combination of X-ray and neutron diffraction data, and the temperature-dependent phase transition between these was investigated in situ using variable temperature neutron powder diffraction and scanning transmission electron microscopy. The results show that the structural phase transition takes place at low temperature (~500 °C) and is 1st order in nature, as evident from the coexistence of both structures. The transition from tetragonal to monoclinic results in reduction of the equivalent unit cell volume. The role of the Bi3+ 6s lone pairs in the temperature-driven phase transition has been studied using neutron pair distribution function analysis. Local structure analysis via neutron total scattering revealed the Bi3+ 6s lone pairs to be stereochemically active in both structures, with short correlation lengths in the tetragonal structure and long correlation lengths in the monoclinic structure, leading to the facile phase conversion and to a more efficient packing density with highly correlated lone pairs in the monoclinic structure. Magnetization isotherms of the tetragonal structure collected at 1.8 K exhibit ferromagnetic behavior, suggesting that the interplay between the observed short-range monoclinic order, defects and surface-to-bulk effects alters the magnetic interaction, leading to short range ferromagnetic interactions, which is highly unexpected given the low temperature antiferromagnetic order observed in the monoclinic structure.

Understanding the re-entrant phase transition in a non-magnetic scheelite

2026-05-04T03:07:36Z

Understanding the re-entrant phase transition in a non-magnetic scheelite Kennedy, Brendan James; Saura-Múzquiz, Matilde; Marlton, Frederick; Mullens, Bryce; Manjón-Sanz, Alicia María; Neuefeind, Joerg C.; Everett, Michelle; Brand, Helen E. A.; Mondald, S.; Vaitheeswaran, G. The stereochemical activity of lone pair electrons plays a central role in determining the structural and electronic properties of both chemically simple materials such as H2O, as well as more complex condensed phases such as photocatalysts or thermoelectrics. TlReO4 is a rare example of a non-magnetic material exhibiting a re-entrant phase transition and emphanitic behavior in the long-range structure. Here, we describe the role of the Tl+ 6s2 lone pair electrons in these unusual phase transitions and illustrate its tunability by chemical doping, which has broad implications for functional materials containing lone pair bearing cations. First-principles density functional calculations clearly show the contribution of the Tl+ 6s2 in the valence band region. Local structure analysis, via neutron total scattering, revealed that changes in the long-range structure of TlReO4 occur due to changes in the correlation length of the Tl+ lone pairs. This has a significant effect on the anion interactions, with long-range ordered lone pairs creating a more densely packed structure. This resulted in a trade-off between anionic repulsions and lone pair correlations that lead to symmetry lowering upon heating in the long-range structure, whereby lattice expansion was necessary for the Tl+ lone pairs to become highly correlated. Similarly, introducing lattice expansion through chemical pressure allowed long-range lone pair correlations to occur over a wider temperature range, demonstrating a method for tuning the energy landscape of lone pair containing functional materials.

Revisiting the cubic crystal structures of Sr4Nb2O9 and Sr5Nb2O10

2023-12-11T01:05:20Z

Revisiting the cubic crystal structures of Sr4Nb2O9 and Sr5Nb2O10 Ling, Chris D; Kennedy, Brendan J; Wang, Chun-Hai We have synthesized polycrystalline and single crystal samples of Sr4Nb2O9 and Sr5Nb2O10 and revisited the crystal structure of the high-temperature cubic phase. By careful analysis of single-crystal X-ray diffraction (SXRD), powder synchrotron X-ray diffraction (Syn-PXRD) and powder neutron diffraction (PND) data, we arrive at a structure model in space group 𝐹4#3𝑚 (216), a subgroup of the reported 𝐹𝑚3#𝑚 (225) model. The 𝐹4#3𝑚 model gives a better fit to the diffraction data, especially PND. We observed an interstitial oxide ion O3 on the 48h site near O1, which gives a tetrahedral Nb1−O polyhedron rather than an octahedral one as found in the 𝐹𝑚3#𝑚 (225) model. The temperature-dependent conductivities of Sr4Nb2O9 and Sr5Nb2O10 in dried O2 were studied using impedance spectroscopy. The activation energies of Sr4Nb2O9 and Sr5Nb2O10 were estimated to be 1.18(1) eV and 1.17(4) eV respectively. This crystallographic arrangement of O1 and O3 (spread over split sites) is likely a key structural factor behind oxide ionic migration in Sr4Nb2O9 and Sr5Nb2O10.

Pressure drop measurements in microfluidic devices: a review on the accurate quantification of interfacial slip

2026-05-07T02:24:19Z

Pressure drop measurements in microfluidic devices: a review on the accurate quantification of interfacial slip Vega-Sanchez, Christopher; Neto, Chiara The correct theoretical definition of boundary conditions of flow underpins all fluid dynamics studies, and is particularly important in situations in which the flow is confined on the nano- and micro-scale. Microfluidic devices are an excellent platform to measure boundary flow conditions, and the pressure drop versus flow rate method is particularly useful in detecting evidence of microscale interfacial slip and drag reduction. This review focuses on the pressure drop method, identifying the main experimental parameters affecting the accuracy and reproducibility of microfluidic experiments of slip, quantifying the magnitude and source of common errors, and providing practical solutions and guidelines. A summary of literature results of interfacial slip obtained with pressure drop measurements in microfluidic devices is also provided, and the slip results are directly compared to expected slip models. This review serves as an introduction for new researchers moving into the field of interfacial slip, and as reminder for established researchers of the need to create highly controlled experimental procedures in order to obtain reproducible and reliable measurements of boundary flow conditions. A direct comparison of accurate experiments with theoretical models is bound to bring about clarity about the mechanisms of slip on smooth and structured surfaces.

Detection of Nanobubbles on Lubricant-Infused Surfaces Using AFM Meniscus Force Measurements

2026-05-04T03:07:30Z

Detection of Nanobubbles on Lubricant-Infused Surfaces Using AFM Meniscus Force Measurements Peppor-Chapman, Sam; Vega-Sanchez, Christopher; Neto, Chiara So far, the presence of nanobubbles on lubricant-infused surfaces (LIS) has been overlooked, because of the difficulty in detecting them in such a complex system. We recently showed that anomalously large interfacial slip measured on LIS is explained by the presence of nanobubbles [Vega-Sánchez, Peppou-Chapman, Zhu and Neto, Nat. Commun., 2022 13, 351]. Crucial to drawing this conclusion was the use of atomic force microscopy (AFM) force− distance spectroscopy (meniscus force measurements) to directly image nanobubbles on LIS. This technique provided vital direct evidence of the spontaneous nucleation of nanobubbles on lubricantinfused hydrophobic surfaces. In this paper, we describe in detail the data collection and analysis of AFM meniscus force measurements on LIS and show how these powerful measurements can quantify both the thickness and distribution of multiple coexisting fluid layers (i.e., gas and oil) over a nanostructured surface. Using this technique, thousands of force curves were automatically analyzed. The results show that the interfacial tension of the nanobubbles is reduced from 52 ± 9 mN m−1 to 39 ± 4 mN m−1 by the presence of the silicone oil layer.