Visible-Light-Active Iodide-Doped BiOBr Coatings for Sustainable Infrastructure.

The search for efficient materials for sustainable infrastructure is an urgent challenge toward potential negative emission technologies and the global environmental crisis. Pleasant, efficient sunlight-activated coatings for applications in self-cleaning windows are sought in the glass industry, particularly those produced from scalable technologies. The current work presents visible-light-active iodide-doped BiOBr thin films fabricated using aerosol-assisted chemical vapor deposition. The impact of dopant concentration on the structural, morphological, and optical properties was studied systematically. The photocatalytic properties of the parent materials and as-deposited doped films were evaluated using the smart ink test. An optimized material was identified as containing 2.7 atom % iodide dopant. Insight into the photocatalytic behavior of these coatings was gathered from photoluminescence and photoelectrochemical studies. The optimum photocatalytic performance could be explained from a balance between photon absorption, charge generation, carrier separation, and charge transport properties under 450 nm irradiation. This optimized iodide-doped BiOBr coating is an excellent candidate for the photodegradation of volatile organic pollutants, with potential applications in self-cleaning windows and other surfaces.

Transparent and conducting boron doped ZnO thin films grown by aerosol assisted chemical vapor deposition.

ZnO based transparent conducting oxides are important as they provide an alternative to the more expensive Sn : In2O3 that currently dominates the industry. Here, we investigate B-doped ZnO thin films grown via aerosol assisted chemical vapour deposition. B : ZnO films were produced from zinc acetate and triethylborane using either tetrahydrofuran or methanol (MeOH) as the solvent. The lowest resistivity of 5.1 × 10-3 Ω cm along with a visible light transmittance of ∼75-80% was achieved when using MeOH as the solvent. XRD analysis only detected the wurtzite phase of ZnO suggesting successful solid solution formation with B3+ substituting Zn2+ sites in the lattice. Refinement of the XRD patterns showed minimal distortion to the ZnO unit cell upon doping when MeOH was the solvent due to the immiscibility of the [BEt3] solution (1.0 M solution in hexane) in methanol that limited the amount of B going into the films, thus preventing excessive doping.

Enhanced Photoacoustic Visualisation of Clinical Needles by Combining Interstitial and Extracorporeal Illumination of Elastomeric Nanocomposite Coatings.

Ultrasound (US) image guidance is widely used for minimally invasive procedures, but the invasive medical devices (such as metallic needles), especially their tips, can be poorly visualised in US images, leading to significant complications. Photoacoustic (PA) imaging is promising for visualising invasive devices and peripheral tissue targets. Light-emitting diodes (LEDs) acting as PA excitation sources facilitate the clinical translation of PA imaging, but the image quality is degraded due to the low pulse energy leading to insufficient contrast with needles at deep locations. In this paper, photoacoustic visualisation of clinical needles was enhanced by elastomeric nanocomposite coatings with superficial and interstitial illumination. Candle soot nanoparticle-polydimethylsiloxane (CSNP-PDMS) composites with high optical absorption and large thermal expansion coefficients were applied onto the needle exterior and the end-face of an optical fibre placed in the needle lumen. The excitation light was delivered at the surface by LED arrays and through the embedded optical fibre by a pulsed diode laser to improve the visibility of the needle tip. The performance was validated using an ex-vivo tissue model. An LED-based PA/US imaging system was used for imaging the needle out-of-plane and in-plane insertions over approach angles of 20 deg to 55 deg. The CSNP-PDMS composite conferred substantial visual enhancements on both the needle shaft and the tip, with an average of 1.7- and 1.6-fold improvements in signal-to-noise ratios (SNRs), respectively. With the extended light field involving extracorporeal and interstitial illumination and the highly absorbing coatings, enhanced visualisation of the needle shaft and needle tip was achieved with PA imaging, which could be helpful in current US-guided minimally invasive surgeries.

Production of an EP/PDMS/SA/AlZnO Coated Superhydrophobic Surface through an Aerosol-Assisted Chemical Vapor Deposition Process.

In this study, a superhydrophobic coating on glass has been prepared through a single-step aerosol-assisted chemical vapor deposition (AACVD) process. During the process, an aerosolized precursor containing polydimethylsiloxane, epoxy resin, and stearic acid functionalized Al-doped ZnO nanoparticles was deposited onto the glass at 350 °C. X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy showed that the precursor was successfully coated and formed a nano/microstructure (surface roughness: 378.0 ± 46.1 nm) on the glass surface. The coated surface had a water contact angle of 159.1 ± 1.2°, contact angle hysteresis of 2.2 ± 1.7°, and rolling off-angle of 1°, indicating that it was superhydrophobic. In the self-cleaning test of the coated surface at a tilted angle of 20°, it was shown that water droplets rolled and washed out dirt on the surface. The stability tests showed that the surface remained superhydrophobic after 120 h of exposure to ultraviolet (UV) irradiation and even after heat exposure at 350 °C. In addition, the surface was highly repellent to water solutions of pH 1-13. The results showed that the addition of the functionalized nanoparticles into the precursor allowed for the control of surface roughness and provided a simplified single-step fabrication process of the superhydrophobic surface. This provides valuable information for developing the manufacturing process for superhydrophobic surfaces.

Fabrication of C-Doped Titanium Dioxide Coatings with Improved Anti-icing and Tribological Behavior.

The accumulation of ice on solid surfaces can cause serious losses and accidents. Current anti-icing/deicing coatings find it difficult to maintain their properties under frequent mechanical wear. In this work, the aerosol-assisted chemical vapor deposition method was employed to prepare C-doped titanium dioxide coatings that have both photothermal properties and excellent wear resistance. The temperature of the sample surface reached 37.6 °C after 2 sun (2 kW/m2) irradiation for 30 min at -30 °C. Compared to a pristine titanium dioxide coating, the C-doped titanium dioxide coatings demonstrated superior antifriction behavior, with the friction coefficient reduced by 47% under dry conditions. These wear resistance properties make C-doped titanium dioxide coatings highly suitable for a range of outdoor applications, especially for anti-icing purposes.

Robust Protection of III-V Nanowires in Water Splitting by a Thin Compact TiO2 Layer.

Narrow-band-gap III-V semiconductor nanowires (NWs) with a suitable band structure and strong light-trapping ability are ideal for high-efficiency low-cost solar water-splitting systems. However, due to their nanoscale dimension, they suffer more severe corrosion by the electrolyte solution than the thin-film counterparts. Thus, short-term durability is the major obstacle for using these NWs for practical water-splitting applications. Here, we demonstrated for the first time that a thin layer (∼7 nm thick) of compact TiO2 deposited by atomic layer deposition can provide robust protection to III-V NWs. The protected GaAs NWs maintain 91.4% of its photoluminescence intensity after 14 months of storage in ambient atmosphere, which suggests the TiO2 layer is pinhole-free. Working as a photocathode for water splitting, they exhibited a 45% larger photocurrent density compared with unprotected counterparts and a high Faraday efficiency of 91% and can also maintain a record-long highly stable performance among narrow-band-gap III-V NW photoelectrodes; after 67 h photoelectrochemical stability test reaction in a strong acid electrolyte solution (pH = 1), they show no apparent indication of corrosion, which is in stark contrast to the unprotected NWs that fully failed after 35 h. These findings provide an effective way to enhance both stability and performance of III-V NW-based photoelectrodes, which are highly important for practical applications in solar-energy-based water-splitting systems.

Zn and N Codoped TiO2 Thin Films: Photocatalytic and Bactericidal Activity.

We explore a series of Zn and N codoped TiO2 thin films grown using chemical vapor deposition. Films were prepared with various concentrations of Zn (0.4-2.9 at. % Zn vs Ti), and their impact on superoxide formation, photocatalytic activity, and bactericidal properties were determined. Superoxide (O2•-) formation was assessed using a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium sodium salt (XTT) as an indicator, photocatalytic activity was determined from the degradation of stearic acid under UVA light, and bactericidal activity was assessed using a Gram-negative bacterium E. coli under both UVA and fluorescent light (similar to what is found in a clinical environment). The 0.4% Zn,N:TiO2 thin film demonstrated the highest formal quantum efficiency in degrading stearic acid (3.3 × 10-5 molecules·photon-1), while the 1.0% Zn,N:TiO2 film showed the highest bactericidal activity under both UVA and fluorescent light conditions (>3 log kill). The enhanced efficiency of the films was correlated with increased charge carrier lifetime, supported by transient absorption spectroscopy (TAS) measurements.

A Hierarchical 3D TiO2 /Ni Nanostructure as an Efficient Hole-Extraction and Protection Layer for GaAs Photoanodes.

Photoelectrochemical (PEC) water splitting is a promising clean route to hydrogen fuel. The best-performing materials (III/V semiconductors) require surface passivation, as they are liable to corrosion, and a surface co-catalyst to facilitate water splitting. At present, optimal design combining photoelectrodes with oxygen evolution catalysts remains a significant materials challenge. Here, we demonstrate that nickel-coated amorphous three-dimensional (3D) TiO2 core-shell nanorods on a TiO2 thin film function as an efficient hole-extraction layer and serve as a protection layer for the GaAs photoanode. Transient-absorption spectroscopy (TAS) demonstrated the role of nickel-coated (3D) TiO2 core-shell nanorods in prolonging photogenerated charge lifetimes in GaAs, resulting in a higher catalytic activity. This strategy may open the potential of utilizing this low-cost (3D) nanostructured catalyst for decorating narrow-band-gap semiconductor photoanodes for PEC water splitting devices.

Iron-Intercalated Zirconium Diselenide Thin Films from the Low-Pressure Chemical Vapor Deposition of [Fe(η5-C5H4Se)2Zr(η5-C5H5)2]2.

Transition metal chalcogenide thin films of the type Fe x ZrSe2 have applications in electronic devices, but their use is limited by current synthetic techniques. Here, we demonstrate the synthesis and characterization of Fe-intercalated ZrSe2 thin films on quartz substrates using the low-pressure chemical vapor deposition of the single-source precursor [Fe(η5-C5H4Se)2Zr(η5-C5H5)2]2. Powder X-ray diffraction of the film scraping and subsequent Rietveld refinement of the data showed the successful synthesis of the Fe0.14ZrSe2 phase, along with secondary phases of FeSe and ZrO2. Upon intercalation, a small optical band gap enhancement (E g(direct) opt = 1.72 eV) is detected in comparison with that of the host material.

Flexible and Self-Powered Photodetector Arrays Based on All-Inorganic CsPbBr3 Quantum Dots.

Flexible devices are garnering substantial interest owing to their potential for wearable and portable applications. Here, flexible and self-powered photodetector arrays based on all-inorganic perovskite quantum dots (QDs) are reported. CsBr/KBr-mediated CsPbBr3 QDs possess improved surface morphology and crystallinity with reduced defect densities, in comparison with the pristine ones. Systematic material characterizations reveal enhanced carrier transport, photoluminescence efficiency, and carrier lifetime of the CsBr/KBr-mediated CsPbBr3 QDs. Flexible photodetector arrays fabricated with an optimum CsBr/KBr treatment demonstrate a high open-circuit voltage of 1.3 V, responsivity of 10.1 A W-1 , specific detectivity of 9.35 × 1013 Jones, and on/off ratio up to ≈104 . Particularly, such performance is achieved under the self-powered operation mode. Furthermore, outstanding flexibility and electrical stability with negligible degradation after 1600 bending cycles (up to 60°) are demonstrated. More importantly, the flexible detector arrays exhibit uniform photoresponse distribution, which is of much significance for practical imaging systems, and thus promotes the practical deployment of perovskite products.

Resonant Ta Doping for Enhanced Mobility in Transparent Conducting SnO2.

Transparent conducting oxides (TCOs) are ubiquitous in modern consumer electronics. SnO2 is an earth abundant, cheaper alternative to In2O3 as a TCO. However, its performance in terms of mobilities and conductivities lags behind that of In2O3. On the basis of the recent discovery of mobility and conductivity enhancements in In2O3 from resonant dopants, we use a combination of state-of-the-art hybrid density functional theory calculations, high resolution photoelectron spectroscopy, and semiconductor statistics modeling to understand what is the optimal dopant to maximize performance of SnO2-based TCOs. We demonstrate that Ta is the optimal dopant for high performance SnO2, as it is a resonant dopant which is readily incorporated into SnO2 with the Ta 5d states sitting ∼1.4 eV above the conduction band minimum. Experimentally, the band edge electron effective mass of Ta doped SnO2 was shown to be 0.23m 0, compared to 0.29m 0 seen with conventional Sb doping, explaining its ability to yield higher mobilities and conductivities.

Enhanced Photocatalytic and Antibacterial Ability of Cu-Doped Anatase TiO2 Thin Films: Theory and Experiment.

Multifunctional thin films which can display both photocatalytic and antibacterial activity are of great interest industrially. Here, for the first time, we have used aerosol-assisted chemical vapor deposition to deposit highly photoactive thin films of Cu-doped anatase TiO2 on glass substrates. The films displayed much enhanced photocatalytic activity relative to pure anatase and showed excellent antibacterial (vs Staphylococcus aureus and Escherichia coli) ability. Using a combination of transient absorption spectroscopy, photoluminescence measurements, and hybrid density functional theory calculations, we have gained nanoscopic insights into the improved properties of the Cu-doped TiO2 films. Our analysis has highlighted that the interactions between substitutional and interstitial Cu in the anatase lattice can explain the extended exciton lifetimes observed in the doped samples and the enhanced UV photoactivities observed.

Highly conductive and transparent gallium doped zinc oxide thin films via chemical vapor deposition.

Degenerately doped ZnO is seen as a potential substitute to the ubiquitous and expensive Sn doped In2O3 as a transparent electrode in optoelectronic devices. Here, highly conductive and transparent Ga doped ZnO thin films were grown via aerosol assisted chemical vapor deposition. The lowest resistivity (7.8 × 10-4 Ω.cm) and highest carrier concentration (4.23 × 1020 cm-3) ever reported for AACVD grown ZnO: Ga was achieved due to using oxygen poor growth conditions enabled by diethylzinc and triethylgallium precursors.

Reducing Oxygen Evolution Reaction Overpotential in Cobalt-Based Electrocatalysts via Optimizing the "Microparticles-in-Spider Web" Electrode Configurations.

Sluggish kinetics of the multielectron transfer process is still a bottleneck for efficient oxygen evolution reaction (OER) activity, and the reduction of reaction overpotential is crucial to boost reaction kinetics. Herein, a correlation between the OER overpotential and the cobalt-based electrode composition in a "Microparticles-in-Spider Web" (MSW) superstructure electrode is revealed. The overpotential is dramatically decreased first and then slightly increased with the continuous increase ratio of Co/Co3 O4 in the cobalt-based composite electrode, corresponding to the dynamic change of electrochemically active surface area and charge-transfer resistance with the electrode composition. As a proof-of-concept, the optimized electrode displays a low overpotential of 260 mV at 10.0 mA cm-2 in alkaline conditions with a long-time stability. This electrochemical performance is comparable and even superior to the most currently reported Co-based OER electrocatalysts. The remarkable electrocatalytic activity is attributed to the optimization of the electrochemically active sites and electron transfer in the MSW superstructure. Theoretical calculations identify that the metallic Co and Co3 O4 surface catalytic sites play a vital role in improving electron transport and reaction Gibbs free energies for reducing overpotential, respectively. A general way of boosting OER kinetics via optimizing the electrode configurations to mitigate reaction overpotential is offered in this study.

n-Type conducting P doped ZnO thin films via chemical vapor deposition.

Extrinsically doped ZnO thin films are of interest due to their high electrical conductivity and transparency to visible light. In this study, P doped ZnO thin films were grown on glass substrates via aerosol assisted chemical vapour deposition. The results show that P is a successful dopant for ZnO in the V+ oxidation state and is able to reduce resistivity to 6.0 × 10-3 Ω cm while maintaining visible light transmittance at ∼75%. The thins films were characterized by X-ray diffraction studies that showed only Bragg peaks for the wurtzite ZnO phase. Fitting of the diffraction data to a Le Bail model also showed a general expansion of the ZnO unit cell upon doping due to the substitution of Zn2+ ions with the larger P5+.

A novel adjuvant drug-device combination tissue scaffold for radical prostatectomy.

Prostate cancer is a leading cause of death in men and despite improved surgical procedures that aid tumor resection, the risk of recurrence after surgery as a result of positive resection margins remains significant. Adjuvant chemotherapy is often required but this is associated with toxicity. Improved ways of delivering highly toxic chemotherapeutic drugs in a more controlled and targeted manner after the prostate has been removed during surgery could reduce the risk of recurrence and avoid systemic toxicity. The aim of this study was to develop a novel drug-device combination tissue scaffold that can be used to deliver the chemotherapeutic agent, docetaxel, into the tissue cavity that is created following radical prostatectomy. The device component investigated consisted of highly porous, poly(dl-lactide-co-glycolide) microparticles made using thermally induced phase separation. A facile method was established for loading docetaxel with high efficiency within one hour. Sustained drug release was observed from the microparticles when placed into a dynamic system simulating tissue perfusion. The drug released from the microparticles into perfusates collected at regular time intervals inhibited colony formation and exhibited sustained cytotoxicity against 3D spheroids of PC3 prostate cancer cells over 10 days. In conclusion, this study demonstrates the concept of combining docetaxel with the biodegradable microparticles at the point of care is technically feasible for achieving an effective drug-device combination tissue scaffold. This approach could provide an effective new approach for delivering adjuvant chemotherapy following radical prostatectomy.

Origin of High-Efficiency Photoelectrochemical Water Splitting on Hematite/Functional Nanohybrid Metal Oxide Overlayer Photoanode after a Low Temperature Inert Gas Annealing Treatment.

A simplistic and low-cost method that dramatically improves the performance of solution-grown hematite photoanodes for solar-driven water splitting through incorporation of nanohybrid metal oxide overlayers was developed. By heating the α-Fe2O3/SnO2-TiO2 electrode in an inert atmosphere, such as argon or nitrogen, the photocurrent increased to over 2 mA/cm2 at 1.23 V versus a reversible hydrogen electrode, which is 10 times higher than that of pure hematite under 1 sun (100 mW/cm2, AM 1.5G) light illumination. For the first time, we found a significant morphological difference between argon and nitrogen gas heat-treated hematite films and discussed the consequences for photoresponse. The origin for the enhancement, probed via theoretical modeling, stems from the facile incorporation of low formation energy dopants into the Fe2O3 layer at the interface of the metal oxide nanohybrid overlayer, which decreases recombination by increasing the electrical conductivity of Fe2O3. These dopants diffuse from the overlayer into the α-Fe2O3 layer readily under inert gas heat treatment. This simple yet effective strategy could be applied to other dopants to increase hematite performance for solar energy conversion applications.

Aerosol-assisted chemical vapour deposition of transparent superhydrophobic film by using mixed functional alkoxysilanes.

A method for the preparation of transparent superhydrophobic silica coatings on glass substrates via aerosol-assisted chemical vapour deposition (AACVD) is described. A multi-layer process to produce dual scale silica nanoparticles films, by using different functional alkoxysilanes was investigated. A first layer of 3-methacryloxypropyltrimethoxysilane (MPS) and a second layer of tetraethylorthosilicate (TEOS) were deposited at different temperatures to generate micro and nano particles of silica. Finally, a layer of perfluorooctyltriethoxysilane was deposited on top of the two layers to achieve superhydrophobicity. The transparent superhydrophobic film showed transparency of 90% in the visible light region with a static water contact angle of 165° and a sliding angle lower than 1°. Various durability tests were performed on the transparent superhydrophobic film, showing a constant water repellency after corrosion and organic solvents tests, strong resistance under UV light, and thermal stability up to 400 °C. Sandpaper mechanical robustness durability test showed superhydrophobicity for up to 5 rubbing cycles. In this study, a novel strategy to achieve highly transparent superhydrophobic glass surfaces using AACVD of alkoxysilanes, to produce surfaces with excellent durability is described. This shows great potential to obtain silica superhydrophobic films for large-scale applications.

Dispelling the Myth of Passivated Codoping in TiO2.

Modification of TiO2 to increase its visible light activity and promote higher performance photocatalytic ability has become a key research goal for materials scientists in the past 2 decades. One of the most popular approaches proposed this as "passivated codoping", whereby an equal number of donor and acceptor dopants are introduced into the lattice, producing a charge neutral system with a reduced band gap. Using the archetypal codoping pairs of [Nb + N]- and [Ta + N]-doped anatase, we demonstrate using hybrid density functional theory that passivated codoping is not achievable in TiO2. Our results indicate that the natural defect chemistry of the host system (in this case n-type anatase TiO2) is dominant, and so concentration parity of dopant types is not achievable under any thermodynamic growth conditions. The implications of passivated codoping for band gap manipulation in general are discussed.

Low-Cost One-Step Fabrication of Highly Conductive ZnO:Cl Transparent Thin Films with Tunable Photocatalytic Properties via Aerosol-Assisted Chemical Vapor Deposition.

Low-cost, high-efficiency, and high quality Cl-doped ZnO (ZnO:Cl) thin films that can simultaneously function as transparent conducting oxides (TCOs) and photocatalysts are described. The films have been fabricated by a facile and inexpensive solution-source aerosol-assisted chemical vapor deposition technique using NH4Cl as an effective, cheap, and abundant source of Cl. Successful ClO substitutional doping in the ZnO films was evident from powder X-ray diffraction, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry results, while scanning electron microscopy reveals the impact of Cl doping on the ZnO thin film morphology. All ZnO:Cl films deposited were transparent and uncolored; optical transmittance in the visible region (400-700 nm) exceeded 80% for depositions using 5-20 mol % Cl. Optimal electrical properties were achieved when using 5 mol % Cl with a minimum measured resistivity of (2.72 ± 0.04) × 10-3 Ω·cm, in which the charge carrier concentration and mobility were measured at (8.58 ± 0.16) × 1019 cm-3 and 26.7 ± 0.1 cm2 V-1 s-1 respectively, corresponding to a sheet resistance (R sh) of 41.9 Ω□-1 at a thickness of 650 nm. In addition to transparent conducting properties, photocatalytic behavior of stearic acid degradation in the ZnO:Cl films was also observed with an optimal Cl concentration of 7 mol % Cl, with the highest formal quantum efficiency (ξ) measured at (1.63 ± 0.03) × 10-4 molecule/photon, while retaining a visible transparency of 80% and resistivity ρ = (9.23 ± 0.13) × 10-3 Ω·cm. The dual functionality of ZnO:Cl as both a transparent conductor and an efficient photocatalyst is a unique combination of properties making this a particularly unusual material.