The prevalence of healthcare-associated infection caused by multidrug-resistant bacteria is of critical concern worldwide. It is reported on the development of a bactericidal surface prepared by use of a simple, upscalable, two-step dipping strategy to incorporate crystal violet and di(octyl)­phosphinic- acid-capped zinc oxide nanoparticles into medical grade silicone, as a strategy to reduce the risk of infection. The material is characterized by UV–vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and transmission electron microscopy (TEM) and confirmed the incorporation of the ZnO nanoparticles in the polymer. The novel system proves to be a highly versatile bactericidal material when tested against both Staphylococcus aureus and Escherichia coli, key causative micro-organisms for hospital-acquired infection (HAI). Potent antimicrobial activity is noted under dark conditions, with a significant enhancement exhibits when the surfaces are illuminated with a standard hospital light source. This polymer has the potential to decrease the risk of HAI, by killing bacteria in contact with the surface.

Almost half of solar energy reaching the Earth is in the infrared, and for solar cells, IR absorbing/emitting quantum dots are highly effective photovoltaic materials. As a possible approach to generating such materials, an investigation into the incorporation of group IIB metal ions during the shelling of II–VI and III–V semiconductor core/shell quantum dots is presented. Quantum dot shells consist of ZnS and an additional metal sulphide, obtained from the decomposition of metal dithiocarbamate single-source precursors. Resultant quantum dots are characterized and interrogated using transmission electron microscopy, high-resolution transmission electron microscopy, electron diffraction, time-of-flight-secondary ion mass spectroscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, photoluminescence emission and lifetime spectroscopy, and UV–vis spectroscopy. It is demonstrated that on incorporation of an additional metal sulphide during shelling, photoluminescence properties change dramatically according to the element and indeed, its concentration. Tunable infrared emission is achieved for Hg addition, thus a one-pot method for the synthesis of infrared emitting quantum dots from visible luminescent cores is hereby developed.

Combinatorial atmospheric pressure chemical vapor deposition (APCVD) is used to deposit anatase TiO₂ with a graded level of F-doping between 1.10 ≤ F:Ti (at%) ≤ 2.57 from the reaction of titanium tetrachloride, ethyl acetate and trifluoroacetic acid at 500 °C on glass. The photocatalytic activity and electrical resistivity of 200 allotted positions across a grid are screened using high-throughput techniques. A blue region of film is singled out for containing the lowest electrical resistivities of any previously reported doped or undoped TiO₂-based system formed by APCVD (ρ ≈ 0.22–0.45 Ω cm, n = 0.8–1.2 × 10¹⁸ cm⁻³, μ = 18–33 cm² V⁻¹ s⁻¹). The blue region contains a lower fluorine doping level (F:Ti ≈ 1.1–1.6%, E_bg ≈ 3.06 eV) than its neighboring colorless region (F:Ti ≈ 2.3–2.6%, E_bg ≈ 3.15–3.21 eV, ρ ≈ 0.61–1.3 Ω cm). State-of-the-art hybrid density functional theory calculations were employed to elucidate the nature of the different doping behaviors. Two distinct fluorine doping environments were present. At low concentrations, F substituting for O (F_O) dominates, forming blue F:TiO₂. At high concentrations, negatively charged fluorine interstitials (F_i⁻¹) begin to dominate, forming transparent F:TiO₂.

This paper reports the synthesis of highly conductive niobium doped titanium dioxide (Nb:TiO₂) films from the decomposition of Ti(OEt)₄ with dopant quantities of Nb(OEt)₅ by aerosol-assisted chemical vapor deposition (AACVD). Doping Nb into the Ti sites results in n-type conductivity, as determined by Hall effect measurements. The doped films display significantly improved electrical properties compared to pristine TiO₂ films. For 5 at.% Nb in the films, the charge carrier concentration was 2 × 10²¹ cm⁻³ with a mobility of 2 cm² V^–1 s^–1 . The corresponding sheet resistance is as low as 6.5 Ω sq^–1 making the films suitable candidates for transparent conducting oxide (TCO) materials. This is, to the best of our knowledge, the lowest reported sheet resistance for Nb:TiO₂ films synthesized by vapour deposition. The doped films are also blue in colour, with the intensity dependent on the Nb concentration in the films. A combination of synchrotron, laboratory and theoretical techniques confirmed niobium doping into the anatase TiO₂ lattice. Computational methods also confirmed experimental results of both delocalized (Ti⁴⁺) and localized polaronic states (Ti³⁺) states. Additionally, the doped films also functioned as photocatalysts. Thus, Nb:TiO₂ combines four functional properties (photocatalysis, electrical conductivity, optical transparency and blue colouration) within the same layer, making it a promising alternative to conventional TCO materials.

Layered anatase-rutile titania thin-films were synthesized via atmospheric-pressure chemical vapor deposition and characterized using X-ray diffraction, Raman spectroscopy and electron microscopy. The interposition of an amorphous TiO₂-based interlayer allowed direct vapor deposition of anatase on a rutile substrate, which is otherwise hindered by templating. This resourceful approach and the subsequent crystallization of the amorphous layer after annealing of the films allowed investigation on the impact of an efficient interface of the two anatase-rutile phases in the photodegradation of a model organic pollutant. Clear evidence is presented on the synergy between the two polymorphs and more importantly, on the charge flow across the interface, which, against much conventional understanding, it involves electron transfer from rutile to anatase and is in agreement with a recent theoretical model and electron paramagnetic resonance data. Here, an increasing density of trapped electrons on the anatase surface of the A/R film is confirmed by photoreduction of silver. This observation is attributed to a defect-free efficient contact between the two phases and the presence of small rutile particles that promote rapid electron transfer at the A-R interface of the films.

The first photoactivated doped quantum dot vector for metal-ion release has been developed. A facile method for doping copper(I) cations within ZnS quantum dot shells was achieved through the use of metal-dithiocarbamates, with Cu⁺ ions elucidated by X-ray photoelectron spectroscopy. Photoexcitation of the quantum dots has been shown to release Cu⁺ ions, which was employed as an effective catalyst for the Huisgen [3+2] cycloaddition reaction. The relationship between the extent of doping, catalytic activity, and the fluorescence quenching was also explored.

TiO₂ thin films are deposited by atmospheric pressure (AP)CVD of TiCl₄ and ethyl acetate on various substrates heated to 500 °C. The substrates investigated are four different grades of stainless steel (304, 304L, 316, and 316L), titanium metal, gold-coated titanium metal, and gold-coated stainless steel (316 grade). The TiO₂ films are analyzed by Raman spectroscopy (RS) to determine the percentage of anatase present. Predominantly anatase films are produced on all the substrates, demonstrating the versatility of this method. Scanning electron microscopy (SEM) images reveal a marked difference in particle size between regions of high anatase content and lower anatase content, indicative of a difference in growth rate between anatase and rutile particles. Selected samples are shown to be photocatalytically active by degradation of resazurin dye by UV light. The rate of degradation is significantly faster than on the self-cleaning Saint Gobain Bioclean™.

Titanium (IV) isopropoxide (TTIP) in methanol, ethanol, hexane, dichloromethane, and isopropanol solvents is used to deposit titanium dioxide thin films on glass and steel substrates at 550 °C using aerosol-assisted (AA)CVD. X-ray diffraction (XRD), and Raman spectra of the as-deposited films show that using methanol as the carrier solvent produces exclusively rutile films on steel, and predominantly rutile on glass substrates, while the use of the other solvents produces exclusively anatase phase on the steel under the same conditions. TiO₂ is also deposited by AACVD from a mixture of ethanol and methanol solvents. As little as 15% of methanol in ethanol produces rutile as the predominant phase. Using a dye-ink test, the titanium dioxide thin films produced with ethanol are shown to be more active photocatalysts than films produced with methanol. All the films show photo-induced superhydrophilicity but, surprisingly, films stored in the dark have a water contact angle above 100°.

This review focuses on the formation of doped titanium dioxide films by CVD. It describes a number of the functional applications of titanium dioxide films, and illustrates how these properties can be improved or modified by the introduction of anion and cation dopants. It details some of the underlying theory and looks at how density of states diagrams can be used to explain the doped film properties.

It has often been suggested that anatase–rutile mixtures/composites synergistically enhance photocatalysis. However, in the case of dense thin-films containing an intimate mix of both anatase and rutile phases, such an effect has not been observed. In synthesising combinatorial films with graded film thickness and phase, and applying established photocatalytic mapping methods, we were able to assess how dense thin-films of intimately mixed anatase–rutile mixtures affect photocatalytic performance. We found that no photocatalytic synergy between anatase–rutile composites (29≤rutile %≤83) within such dense thin-film systems exists. In fact, an increased presence of rutile caused the photocatalytic activity to fall. This was explained by the unfavourable energetics in the multiple electron transfers required between several neighbouring rutile and anatase sites for the photo-generated electron to reach the material’s surface; encouraging the trapping of electrons within the bulk and increasing the likelihood of charge recombination. The decrease in photocatalytic activity was found to vary linearly with rutile component.

A one-pot modified Turkevich synthesis was used to synthesise a range of colloids from pure Ag, through Ag/Au core-shell mixtures to pure Au by the thermal co-addition of trisodium citrate to auric acid and silver nitrate mixtures. The colloids were analysed by means of XRD and wide-beam energy dispersive X-ray (EDX) analysis. The UV/Vis spectroscopy showed a non-linear variation in the surface plasmon resonance band with the Au/Ag ratio, consistent with core-shell formation. High resolution transmission electron microscopy (HRTEM) imaging, in conjunction with thin-beam EDX line analysis, confirmed the presence of predominantly Ag cores and Au exteriors in the Au/Ag mixture. The argon ion sputtering with X-ray photoelectron spectroscopy (XPS) measurements of the particles also indicated a Ag-Au core-shell formation. Ag⁰, Au⁰ and significant levels of Au^I states were observed, which correlate with a Ag-Au core-shell model where the gold shell becomes partially oxidised at the surface. The subsequent titration of the colloids with methylene blue (MB) dye showed strong positive increases in the extinction coefficient at the absorption maximum. At the optimum levels of dye addition, a linear relationship was found between the average nanoparticle size and the number of dye solvation shells. The pure Au and Ag colloids showed the greatest propensity for an increase in the extinction coefficient of MB due to an enhanced transfer of the surface plasmons to the localised dye molecules and demonstrated the potential for increased functionality as light-activated agents in the lethal photosensitisation of bacteria.

Titanium dioxide (TiO₂) thin films are synthesized using aerosol-assisted (AA)CVD of titanium (IV) isopropoxide (TTIP) in methanol. Deposition is carried out on glass, steel, and titanium substrates at 400–550°C. The films produce morphologies that are radically different to those from typical aerosol-assisted processes, and from the use of TTIP in low or atmospheric pressure (AP)CVD. The films show some substrate-dependent morphology and properties. In particular at 550°C the films on steel show needle- and rod-like particles. X-ray diffraction (XRD) and Raman spectroscopy of the TiO₂ films show that on steel or titanium substrates only the rutile form can be obtained, whereas on glass either anatase, anatase/rutile mixtures, or rutile can be obtained, depending on substrate temperature. The TiO₂ films formed at 550°C on all substrates are hydrophobic to water droplets, with contact angles in the range 101–110°. These films become hydrophilic on heating to above 100°C in air, or superhydrophillic when irradiated under 254 nm radiation generating water-contact angles less than 5°. Surprisingly, use of TTIP under APCVD on steel substrates without an aerosol form exclusively the anatase form of TiO₂ at 400–550°C, whereas use of a methanolic aerosol delivery system for the TTIP forms rutile. Hence use of the methanol aerosol has a controlling influence on the deposition chemistry. The TiO₂ thin films are shown to be active photocatalysts using a dye-ink test, and are also shown to be able to photo-split water in a sacrificial system to evolve oxygen.

The use of an aerosol delivery system enabled fluorine-doped tin dioxide films to be formed from monobutyltin trichloride methanolic solutions at 350–550 °C with enhanced functional properties compared with commercial standards. It was noted that small aerosol droplets (0.3 μm) gave films with better figures of merit than larger aerosol droplets (45 μm) or use of a similar precursor set using atmospheric pressure chemical vapour deposition (CVD) conditions. Control over the surface texturing and physical properties of the thin films were investigated by variation in the deposition temperature and dopant concentration. Optimum deposition conditions for low-emissivity coatings were found to be at a substrate temperature of about 450 °C with a dopant concentration of 1.6 atm % (30 mol % F:Sn in solution), which resulted in films with a low visible light haze value (1.74 %), a high charge-carrier mobility (25 cm² V s⁻¹) and a high charge-carrier density (5.7×10²⁰ cm⁻³) resulting in a high transmittance across the visible (≈80 %), a high reflectance in the IR (80 % at 2500 nm) and plasma-edge onset at 1400 nm. Optimum deposition conditions for coatings with applications as top electrodes in thin film photovoltaics were found to be a substrate temperature of about 500 °C with a dopant concentration of 2.2 atm % (30 mol % F:Sn in solution), which resulted in films with a low sheet resistance (3 Ω sq⁻¹), high charge-carrier density (6.4×10²⁰ cm⁻³), a plasma edge onset of 1440 nm and the films also showed pyramidal surface texturing on the micrometer scale which corresponded to a high visible light haze value (8 %) for light scattering and trapping within thin film photovoltaic devices.

A comparison between two of the best performing photocatalysts in a series of nitrogen- and sulfur-doped titania visible light photocatalysts prepared by atmospheric pressure (AP)CVD is made against a sample of pure undoped titania. This study compares the ability of the samples to photo-oxidize stearic acid and kill Escherichiacoli bacteria using white light sources commonly found in UK hospitals. It is shown that both nitrogen- and sulfur-doped photocatalysts are bioactive with extraordinarily similar properties though the nitrogen-doped samples are found to perform very slightly better than the sulfur-doped samples. These materials are suggested for use as anti-microbial surfaces in healthcare environments and as self-cleaning glass.

The interest in highly water-repellent surfaces has grown in recent years due to the desire for self-cleaning surfaces. A super-hydrophobic surface is one that achieves a water contact angle of 150° or greater. This article explores the different approaches used to construct super-hydrophobic surfaces and identifies the key properties of each surface that contribute to its hydrophobicity. The models used to describe surface interaction with water are considered, with attention directed to the methods of contact angle analysis. A summary describing the different routes to hydrophobicity is also given.

Hybrid aerosol-assisted (AA) and atmospheric pressure (AP) CVD methodology is utilized, for the first time, to produce thin films of gold nanoparticle-doped vanadium dioxide. Good surface coverage, comparable to that of APCVD processes, is observed, and a variety of different film thicknesses and dopant levels are easily produced. The films are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Their optical and thermochromic behaviors are also determined. Incorporation of gold nanoparticles in the films leads to significant changes in the color of the film due to the presence of a surface plasmon resonance (SPR) band.

The technique of combinatorial atmospheric pressure (AP)CVD, a recent addition to the growing number of combinatorial materials methods, is used to form twelve members of the Ti_xV_1-xN alloy series with 0.29 < x < 0.94. This series of compounds has a rock-salt structure with TiN and VN as the end members. The twelve phases, which have potential use as heat mirror coatings, are all synthesized in a single experiment. The structure and properties of the materials are investigated using powder X-ray diffraction (XRD) and electron probe microanalysis (EPMA). The optical properties are considered using visible-IR spectroscopy (IRS), which allows the suitability of the films as solar control coatings to be investigated and optimized as a function of composition.

Zinc oxide (ZnO) thin films are deposited at 400–650 °C onto glass substrates by aerosol assisted (AA)CVD of a zinc acetate [Zn(C₂H₃O₂)₂] solution in methanol. The thin films show high transparency over the visible and infrared regions (80–95%) and a 001 (c-axis) preferred orientation. The surface morphology and crystallographic orientation are dependent on the substrate temperature. The photocatalytic activity of the films is determined using the destruction of stearic acid (SA) by UV irradiation. The rate is monitored via infrared spectroscopy (IRS) and shows appreciable activity, close to that seen for anatase titania, in the films deposited at 650 °C. Water droplet contact angles on both ambient and UV-irradiated ZnO surfaces are determined, and there is seen to be an increase in photoinduced hydrophillicity for all films, with a reduction in contact angle of around 50 °.