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Graphene supported transition metal clusters are of great interest for potential applications, such as catalysis, due to their unique properties. In this work, a simple approach to deposit Au101(PPh3)21Cl5 (Au101NC) on reduced graphene oxide (rGO) via an ex situ method is presented. Reduction of graphene oxide at native pH (pH ≈ 2) to rGO was performed under aqueous hydrothermal conditions. Decoration of rGO sheets with controlled content of 5 wt% Au was accomplished using only pre-synthesised Au101NC and rGO as precursors and methanol as solvent. High resolution scanning transmission electron microscopy indicated that the cluster size did not change upon deposition with an average diameter of 1.4 ± 0.4 nm. It was determined that the rGO reduction method was crucial to avoid agglomeration, with rGO reduced at pH ≈ 11 resulting in agglomeration. X-ray photoelectron spectroscopy was used to confirm the deposition of Au101NCs and show the presence of triphenyl phosphine ligands, which together with attenuated total reflectance Fourier transform infrared spectroscopy, advocates that the deposition of Au101NCs onto the surface of rGO was facilitated via non-covalent interactions with the phenyl groups of the ligands. Inductively coupled plasma mass spectrometry and thermogravimetric analysis were used to determine the gold loading and both agree with a gold loading of ca. 4.8–5 wt%. The presented simple and mild strategy demonstrates that good compatibility between size-specific phosphine protected gold clusters and rGO can prevent aggregation of the metal clusters. This work contributes towards producing an agglomeration-free synthesis of size-specific ligated gold clusters on rGO that could have wide range of applications.

The photocatalytic properties of titania (TiO2) have prompted research utilising its useful ability to convert solar energy into electron–hole pairs to drive novel chemistry. The aim of the present work is to examine the properties required for a synthetic method capable of producing thin TiO2 films, with well defined, easily modifiable characteristics. Presented here is a method of synthesis of TiO2 nanoparticulate thin films generated using RF plasma capable of homogenous depositions with known elemental composition and modifiable properties at a far lower cost than single-crystal TiO2. Multiple depositions regimes were examined for their effect on overall chemical composition and to minimise the unwanted contaminant, carbon, from the final film. The resulting TiO2 films can be easily modified through heating to further induce defects and change the electronic structure, crystallinity, surface morphology and roughness of the deposited thin film.

The effect of thermal treatment on the structure and electrical/optical properties of vapor phase-polymerized poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:Tos) and polypyrrole:tosylate (PPy:Tos) polymer films was investigated. Thermal treatment was applied postpolymerization but prior to washing the embedded oxidant layer out of the polymer film. Structural and chemical changes arising from the treatment were studied in the context of their conductive and electrochromic behavior. Spectroscopic analysis indicated a rise in the doping levels of both conductive polymers when exposed to thermal treatment. Additionally, an increase in the film thickness was recorded after the oxidant and other unbound species were removed from the polymer layer using an ethanol rinse. As such, a strong indication that polymerization continued even in the absence of (external) monomer vapor was present. This film thickness increase was most pronounced for PPy:Tos but also present in the PEDOT:Tos film. Heat-treated films exhibited enhanced cohesion, making them more robust and therefore increasing the viability for the material to be used in the optoelectronics area. This robustness, due to additional (cross-linking) oligomer growth, came at the expense of lower conductivity relative to their untreated counterparts. Refereed/Peer-reviewed

Silicon is touted as a replacement for the commercially utilized carbon anode in lithium ion batteries. However, two drawbacks have hindered its use: low electronic conductivity and significant volume changes during lithiation/delithiation. Numerous studies have examined ways to improve silicon thin films with doped and reactive (i.e., oxidized, nitrated, and hydrogenated) forms summarized herein. Factors affecting electrochemical performance and cycling stability are compared against pure silicon, with the two alternatives generally showing better results. Most of the improvements for doped silicon have been attributed to higher electronic conductivity. Treatment gases such as: oxygen, nitrogen, and hydrogen, have been used to produce reactive silicon films. For oxidized silicon reaction products (i.e., lithium silicate, lithiated silicon, and lithium oxide) during cycling were found to serve as a buffer layer and/or matrix, helping to negate volume changes during charge/discharge. Improvements in nitrated silicon films were attributed to large lithiation capacity, high lithium ion conductivity, and mechanical stability. The improvement in cyclability performance for hydrogenated silicon films has yet to be fully developed and further systematic investigations are warranted Refereed/Peer-reviewed

The vapor phase polymerization (VPP) technique is used to produce thin films of poly(3,4-ethylenedioxythiopene) (PEDOT) in which the Fe(III)Tosylate oxidant is altered. The oxidant is changed with the addition of an amphiphilic co-polymer having different molecular weights, namely 2800 Da. and 5800 Da. Resulting PEDOT films produce conductivities of ≈1500 and ≈3000 S cm−1 respectively. Small angle X-ray diffraction (SA-XRD) indicates that the oxidant incorporating the larger molecular weight co-polymer possesses ordered structure and that this in turn helps “template” the PEDOT during film formation. The structure and composition of the bottom (i.e. initial film formation) and top (i.e. final film formation) PEDOT surfaces are studied using surface sensitive analytical techniques; small angle X-ray diffraction (SA-XRD), ultraviolet photoelectron spectroscopy (UPS), 2D grazing incidence X-ray diffraction (2D-GIXD), metastable induced electron spectroscopy (MIES) and neutral impact collision ion scattering spectroscopy (NICISS). The results indicate that the increase in conductivity using the larger molecular weight co-polymer additive is due to the film having larger lamella- and π-stacking regions in addition to doping levels which remain unchanged throughout film formation. These conclusions are further supported by results obtained on a model PEDOT:Tosylate system using density functional theory (DFT) calculations Refereed/Peer-reviewed

Superhydrophobic coatings are reported as promising candidates for anti-icing applications. Various studies have shown that as well as having ultra water repellency the surfaces have reduced ice adhesion and can delay water freezing. However, the structure or texture (roughness) of the superhydrophobic surface is subject to degradation during the thermocycling or wetting process. This degradation can impair the superhydrophobicity and the icephobicity of those coatings. In this review, a brief overview of the process of droplet freezing on superhydrophobic coatings is presented with respect to their potential in anti-icing applications. To support this discussion, new data is presented about the condensation of water onto physically decorated substrates, and the associated freezing process which impacts on the freezing of macroscopic droplets on the surface. Refereed/Peer-reviewed

The one step fabrication of nanocomposite films of conducting polymers with 2D nanoparticles is investigated in this study. Specifically, the inclusion of nanomaterials (single layer graphene, single layer molybdenum disulfide) within PEDOT is achieved using the vapor phase polymerization (VPP) technique. This facile process allows for the formation of thin films of the order of less than 200 nm, which display a wide range of enhanced properties (mechanical, optical, and electrochemical). Herein, in a typical example with added graphene (

An oxygen plasma treatment was employed to modify the surface of carbon electrodes used in capacitive deionization (CDI). X-ray photoelectron spectroscopy analysis of samples showed that oxygen plasma is mainly attaching oxygenated groups on the PTFE binder used in these electrodes. By functionalizing the binder it can increase the hydrophilicity of the electrode surface and increase the available specific surface area. 2.5 min of plasma treatment resulted in the largest improvement of CDI performance of electrodes. Thermodynamic study of CDI performance showed that the modified electrodes followed Langmuir and Freundlich isotherms resulting from the increased interaction between the enhanced electrodes and water. The kinetic study showed that the CDI process followed a pseudo-first order adsorption kinetics. The calculated adsorption rate constants suggested that plasma modification can accelerate ion adsorption of electrodes. Refereed/Peer-reviewed

The reduced pressure synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) with sheet-like morphology has been achieved with the introduction of an amphiphilic triblock copolymer into the oxidant thin film. Addition of the copolymer not only results in an oxidant thin film which remains liquid-like under reduced pressure but also induces structured growth during film formation. PEDOT films were polymerized using the vacuum vapor phase polymerization (VPP) technique, in which we show that maintaining a liquid-like state for the oxidant is essential. The resulting conductivity is equivalent to commercially available indium tin oxide (ITO) with concomitant optical transmission values. PEDOT films can be produced with a variety of thicknesses across a range of substrate materials from plastics to metals to ceramics, with sheet resistances down to 45 Ω/□ (ca. 3400 S·cm−1), and transparency in the visible spectrum of >80% at 65 nm thickness. This compares favorably to ITO and its currently touted replacements. Refereed/Peer-reviewed

Electrocatalytic materials play a critical role in emerging clean energy technologies such as batteries and fuel cells. Herein, we report the fabrication of a unique conducting polymer alloy thin film electrocatalyst based on poly(3,4-ethylenedioxythiophene) (PEDOT) and a polymeric additive, polyethylene glycol-polydimethylsiloxane-polyethylene glycol. These polymeric films displayed electrocatalytic activity for the Oxygen Reduction Reaction (ORR) higher than that of platinum or other polymeric electrodes. Furthermore, the metal-free polymeric electrodes were not susceptible to 'poisoning' when exposed to methanol. The fabrication parameters affecting the ORR performance of the polymeric electrodes and the mechanism of the improvement of the ORR catalysis were comprehensively investigated and benchmarked against commercial Pt electrodes. The application of the conducting polymer alloy electrode in a zinc-air battery demonstrated high power output and stable performance. Refereed/Peer-reviewed

Vacuum vapour phase polymerisation (V-VPP) was used to synthesis high conductivity poly(3,4-ethylenedioxythiophene) (PEDOT) on glycol/oxidant coated substrates. Thermo gravimetric analysis (TGA) indicated that up to 15 wt.-% glycol was able to complex with the Fe(Tos)3 oxidant solution and that this loading produced PEDOT with the highest conductivity, namely 1487 S cm-1. Further addition beyond 15 wt.-% resulted in an unbounded excess of glycol which appeared to inhibit the polymerisation process, resulting in reduced doping levels and conductivity. XPS data showed that glycol was incorporated within the PEDOT matrix after polymer synthesis, and that this may contribute to the high conductivity achieved using the V-VPP technique. XPS data also confirmed that the highest conductivity coincided with the highest recorded doping level, d = 28.4%. Refereed/Peer-reviewed

Large-scale electrochromic devices were manufactured using vacuum vapour phase polymerised (VPP) poly(3,4-ethylenedioxythiophene) (PEDOT). Homogeneous 3,4-ethylenedioxythiophene (EDOT) and water vapour distribution within the large 115 L VPP chamber is paramount for the reproducible synthesis of high conductivity PEDOT thin films. Obtaining these conditions, however, was not trivial. The issue was resolved by synthesising PEDOT under vacuum, however, this altered the dynamics of the polymerisation process. As a result, surfactant addition, monomer and water vapour distribution, monomer and chamber temperature, and polymerisation times were all systematically investigated. Controlling these parameters has resulted in PEDOT with conductivity exceeding 1100 S · cm−1, with a best of 1485 S · cm−1, and electrochromic devices with an optical switch of Δ%Tx ≥ 50%. The resulting high conductivity and optical range are due to long undisrupted PEDOT polymer chains coupled with low levels of oligomers within the matrix. Refereed/Peer-reviewed

Elemental analysis of sequentially formed PPy/PEDOT polymer blends using liquid-like oxidant layers by vapor phase polymerization (VPP) has provided conclusive evidence for a 'bottom up' growth mechanism during polymerization. Chemical analysis by XPS of the top surface of the polymer thin film formed by sequential polymerization of pyrrole monomer, followed by EDOT monomer, revealed the outer most layer to be PEDOT. ToF-SIMS depth profiling confirmed this result, indicating the diminishing presence of PEDOT fragments with concomitant increasing PPy fragments as a function of depth from the top surface, an indication that PEDOT was stationed above PPy. When the polymerization process was reversed (i.e. EDOT followed by pyrrole) the opposite was observed. By extension we propose that the same growth mechanism exists for any VPP conducting polymer where a (viscous) liquid-like oxidant layer is utilized Refereed/Peer-reviewed

The synthesis of high conductivity poly(3,4-ethylenedioxythiophene) (PEDOT) films using vacuum vapour phase polymerisation is reported. Water vapour is introduced into the chamber and results suggest that it acts as a proton scavenger during polymerisation. Process optimisation leads to PEDOT films that have high conductivity and a blue-black appearance. Poor quality films have lower conductivity and a characteristic greenish colour. UV-vis-NIR spectra show that poor PEDOT films are characterised by higher absorption in the UV-vis region and an absorption plateau in the NIR region, which suggests an increased level of disrupted conjugation along the polymer backbone or higher oligomer content. Conversely, high quality PEDOT is characterised by an extended NIR absorption tail and lower absorption in the UV-vis region.

Despite many investigations of the conducting polymer polypyrrole, its ultimate potential for electrochromic and organic electronic applications has been hampered by a lack of electrical stability. In this study the stability of polypyrrole has been enhanced by introducing a triblock copolymer, poly(ethylene glycol) - poly(propylene glycol) - poly(ethylene glycol) (PEG-PPG-PEG), into the oxidant solution in the vapour phase polymerisation (VPP) process. The inclusion of this triblock copolymer produces polypyrrole thin films with (favorably) smooth and uniform morphology, an RMS surface roughness of ca. 4 nm, combined with an increase in electrical switching stability and conductivity. When the homopolymers PEG or PPG are employed in the oxidant, the resulting films do not show the same magnitude of stability, morphological or electrical enhancement. Increasing the amount of PEG-PPG-PEG in the oxidant solution yields a decrease in the thickness of the polypyrrole films with a concomitant reduction in the measured band gap and a red shift of the absorbance peak. This enhanced polypyrrole demonstrates the expected electrochromic behaviour, but with a greater than 20-fold increase in electrical switching stability. Refereed/Peer-reviewed

The oxidant, Fe(III) tosylate, was used in the vapour phase polymerisation (VPP) of PEDOT. The amphiphilic co-polymer poly(ethylene glycol-ran-propylene glycol) was added and its influence examined. Both the PEDOT conductivity and optical contrast range increased with the inclusion of the co-polymer, with the maximum being recorded at 4 wt.-%. Loadings higher than this resulted in a systematic decrease in both conductivity and optical contrast. Evidence indicates that in addition to the beneficial anti-crystallisation effect to the oxidant layer, the co-polymer also reduces the effective reactivity of the oxidant, as demonstrated by slower polymerisation rates. Confirmation of the change in polymerisation rate was obtained using a quartz crystal microbalance (QCM). The slower polymerisation rate results in higher conductivity and optical contrast; however, XPS data confirmed that the co-polymer remained within the PEDOT film post-washing and this result explains why the performance decreases at high surfactant loadings.

The investigation of poly(3,4-ethylenedioxythiophene) (PEDOT) exposed to several example amines has shown that they bind to the conducting polymer through a nucleophilic attack on the positively charged carbon atoms. The PEDOT films were polymerized using the vacuum vapor phase polymerization (VPP) technique, and their electrical and optical properties subsequently modified by adsorbing aniline, ammonia or urea. Analysis of the surface chemistry shows that the reversibility of the binding depends on the nature of the amine, although a portion is chemisorbed to the PEDOT. This mechanism allows the polymer surface to be decorated with biomolecules or nanoparticles, as demonstrated by attachment of poly(allylamine) coated silica nanoparticles to the PEDOT. This understanding provides the opportunity to control PEDOT properties, and opens the pathway to extend the utility of these electroactive, optoactive, and bioactive materials. Refereed/Peer-reviewed

Vacuum vapour phase polymerization (VVPP) is a facile means of producing flexible PEDOT thin films having conductivities in excess of 1500 S cm−1. The process is understood to utilize water as the effective proton scavenger during synthesis. The originating source of water, under vacuum condition however, was unknown. The location of the water within the oxidant solution was examined, with individual components desiccated and thermo-gravametric analysis (TGA) performed to ascertain the root source. The co-polymer PEG-PPG-PEG provides some water, while the majority originates from coordinated water associated with the iron tosylate oxidant, and from free water residing within the solvent carrier. Importantly, with the incorporation of the co-polymer water remains locked within the oxidant layer under vacuum and this allows the VVPP reaction to proceed without the need for an external water supply. Furthermore PEG-PPG-PEG serves the multi-functional role of inhibiting crystal formation within the oxidant layer, and reducing the effective reactivity of the oxidant. Finally, an examination of literature suggests that the choice of oxidant may depend on the type of VPP process used. Refereed/Peer-reviewed

Parameters affecting the quality of vapour phase polymerised (VPP) PEDOT and their influence on electrochromic device performance were investigated. Specifically, the role of water during synthesis was examined and a polymerisation mechanism proposed. Paradoxically, water vapour is essential for PEDOT polymerisation, however, too high a loading leads to crystallite formation in the oxidant layer, rendering the oxidant inactive. Changes in water vapour affect the doping level of the polymer, presumably due to poor conjugation along the polymer's backbone during synthesis. The addition of a surfactant, PPG-ran-PEG, was studied using XPS. The surfactant inhibited oxidant crystal growth and slowed the rate of PEDOT polymerisation, reducing film defects and improving PEDOT conductivity. Controlling and optimising the levels of water vapour and surfactant during synthesis resulted in reproducible, high conductivity, high optical switch, PEDOT films. Finally, complementary dual-polymer electrochromic devices utilising (pre- and post-process-enhanced) VPP PEDOT and PMAS (control) were fabricated and changes in switching transmission evaluated. Refereed/Peer-reviewed

The conductivity of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic) acid (PEDOT–PSS) thin-films was increased by up to 900 times with the addition of linear-diols. Three series of linear-diols were investigated. It is proposed that three mechanisms contribute to improved conductivity; conformational changes in the polymer from coil to expanded, spatial separation of PEDOT–PSS grains and charge screening. The variation in conductivity with temperature indicates that diols affect both intra- and inter-chain charge transports. Electrochromic devices were constructed using standard and enhanced conductivity PEDOT–PSS. Switching times from bleached to darkened states were reduced while darkened to bleached states remained unaltered. Total percent transmission change (%ΔTx) remained constant indicating that enhanced conductivity PEDOT–PSS improves switching but does not lead to additional electrochromic redox sites being accessed.

Vapor phase polymerization was used to synthesize high conductivity poly(3,4-ethylenedioxyphenylene) (PEDOT). The monomer is presented to an oxidant-rich substrate in vapor form and even for short polymerization times, 10-30 min, Fe(III) tosylate has a propensity for water absorption leading to crystal formation. Poor oxidant treatment before polymerization or high humidity during polymerization can create holes in the PEDOT film decreasing its conductivity. The addition of an amphiphilic copolymer poly(ethylene glycol)-ran-poly-(propylene glycol) suppresses crystal growth allowing better film formation. The humidity level during synthesis was optimized at 35% relative humidity (RH), producing a conductivity of 761 S cm- 1 . Additionally, the copolymer extends the RH range that is tolerable for polymer synthesis.

Vapor phase polymerization (VPP) is at the forefront for synthesizing high conductivity poly(3,4- ethylenedioxythiophene) (PEDOT) as an alternative to indium tin oxide (ITO). Little attention, however, has been directed to the oxidant layer used in the polymerization process. In this study the observation of an oxidant layer (oxidant + PEG-PPG-PEG) possessing liquid-like properties during the vacuum synthesis of PEDOT is reported. This is in contrast to the other oxidant layer variants studied which are observed as solid (pristine oxidant) or gel-like (oxidant + pyridine). Tailoring of the liquid-like properties leads to confluent PEDOT films with a conductivity of 2500 S cm 1, placing this PEDOT within the conductivity range of commercially available ITO. Building on the liquid-like observation, XPS and ToF-SIMS experiments reveal that PEDOT growth is via a bottom-up mechanism with transportation of new oxidant up to the forming PEDOT layer. Refereed/Peer-reviewed