Poly(dimethylsiloxane) as a pre-coating in layer-by-layer films containing phosphotungstate nanoclusters electrochemically sensitive toward s-triazines

One of the major advantages of the Layer-by-Layer (LbL) deposition technique is the possible control of molecular architecture, not only to achieve optimized properties but also to seek synergy among different materials. In this study, LbL films containing nanoclusters of a Keggin type polyoxometalate, phosphotungstic acid (HPW), alternated with the polycation poly(allylamine hydrochloride) (PAH) were deposited on indium-tin oxide (ITO) substrates. The electrochemical properties of the hybrid LbL film investigated in acidic conditions indicated no significant desorption of HPW, when a layer of poly(dimethylsiloxane) terminated with 3-aminopropyl groups (PDMS) was previously deposited on the ITO substrate. Such effect occurred because PDMS prevents desorption of HPW from the hybrid film, as shown by X-ray Photoelectron Spectroscopy (XPS) analyses. The porous structures of the films were revealed by Fourier transform infrared reflection absorption spectroscopy, scanning electron microscopy and XPS. PDMS/PAH as a pre-coating allowed the HPW/PAH films to be sensitive to the electrochemical detection of the triazines atrazine and melamine. In conclusion, the precise control of the LbL films architecture is important to develop opportunities for new applications. © 2014 The Royal Society of Chemistry.One of the major advantages of the Layer-by-Layer (LbL) deposition technique is the possible control of molecular architecture, not only to achieve optimized properties but also to seek synergy among different materials. 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Projection of participant recruitment to primary care research: a qualitative study.

BACKGROUND: Recruitment to clinical trials remains a challenge, particularly in primary care settings. Initial projections of participant recruitment need to be as accurate as possible in order to avoid the financial, clinical and ethical costs of trial extensions or failures. However, estimation of recruitment rates is challenging and often poorly executed, if attempted at all. We used qualitative methods to explore the experiences and views of researchers on the planning of recruitment in this setting. METHODS: Participants had registered accrual to a UK-based primary care research study between April 2009 and March 2012. We conducted nine interviews with chief investigators or study managers, using a semi-structured topic guide. Analysis was conducted using the framework approach. RESULTS: Three themes are presented: 1) the factors affecting recruitment rates, 2) the use of planning techniques, and 3) influences on poor estimation. 1) A large number of factors affecting recruitment rates were discussed, including those relating to the study protocol, the clinical setting and the research setting. Use of targeted mail-outs to invite apparently eligible individuals to participate was preferred in order to eliminate some of the uncertainty in the recruitment rate associated with opportunistic clinician referrals. 2) The importance of pilot work was stressed. We identified significant uncertainty as to how best to schedule trial timelines to maximise efficiency. 3) Several potential sources of bias involved in the estimation of recruitment rates were explored and framed as technological, psychological or political factors. CONCLUSIONS: We found a large number of factors that interviewees felt impact recruitment rates to primary care research and highlighted the complexity of realistic estimation. Suitable early planning of the recruitment process is essential, and there may be potential to improve the projection of trial timelines by reducing biases involved in the process. Further research is needed to develop formal approaches that would be suitable for use in this setting

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The incorporation of hydrogen into Si, under different electrochemical conditions including anodization in fluoride solutions where porous silicon is formed, is studied by NRA and in situ capacitance measurements. Results suggest a large near surface concentration of H whilst simulation show that the maximum penetration depth is governed by volume diffusion of H and material removal. Diffusion coefficients are found to be dependent on electrochemical conditions and ranged between 10−13 and 10−11 cm2 s−1. The interplay of H permeation with porous silicon layer formation is discussed

DNA adsorption at functionalized Si/buffer interfaces studied by x-ray reflectivity

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Analysis of CapacitancePotential Measurements at the Silicon−Electrolyte Interface Revisited

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Phenyl layers on H–Si(111) by electrochemical reduction of diazonium salts: monolayer versus multilayer formation

We have studied the formation of phenyl layers by electrochemical reduction of aryl diazonium salts (N2/Ph/R with R/Br and CH2Br) on atomically flat H-terminated Si(111) electrodes. The surface density, compactness and thickness of layers are investigated as functions of the electrolysis parameters used during the modification (applied potential, charge passed) and the end group, using Rutherford backscattering measurements, electrochemical capacitance/voltage curves, and AFM/STM observations. Results indicate that some surface polymerization occurs above a critical charge Q *, the value of which depends on both the potential and the R-group. Results are interpreted within the frame of a kinetic model. It is shown that dense and ordered monolayers are nevertheless obtainable by monitoring the charge Q close to Q * and by proper choice of the grafting potential. Kinetic Monte Carlo simulations and structural models of the interface are presented to discuss the formation of 2D domains in monolayers. The electronic properties of the modified interface are discussed briefly. # 2003 Elsevier B.V. All rights reserved

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Molecularly Tunable "Organic Capacitors" at Silicon/Aqueous Electrolyte Interfaces1

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Thermal decomposition of alkoxy monolayers grafted on silicon: A mechanistic model

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