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John Albery was one of the most creative, innovative and distinguished physical chemists of his time. He was particularly noted for his pioneering work in electrochemistry and electroanalytical chemistry, proton transfer kinetics and isotope effects, and enzyme kinetics. His DPhil studies on rotating disc electrodes led to seminal papers in the 1960s on ring-disc electrodes, which laid the basis for the extensive development of a powerful tool for electrochemical diagnostics. Those doctoral studies also involved work on the mechanisms of proton transfer reactions, a subject that remained very dear to his heart, and later resulted in the application of Marcus theory to provide understanding of physical organic reactions. In a separate strand on kinetic processes, he developed the theory of enzyme catalysis, which gave important insights into reaction kinetics of biological catalysts. He was a marvellous teacher and an inspiration to generations of his students, both undergraduate and post-graduate. His legacy reached far and wide, with a scientific family that included more than a dozen professorial ‘offspring’. His talents were not only restricted to science but extended to the theatre and entertainment, with writing for the satirical programme That was the week that was , the production of two musicals and of numerous departmental and college cabarets and irreverent annual revues. John Albery had an irrepressible joie de vivre and was the instigator of and participant in many occasions that were full of fun and laughter and live on in the memory. But it was not all fun and games; he had a keen sense of social justice. He led the assault to admit women to the previously men-only colleges of Oxford, and in the 1970s he mounted a vigorous and successful campaign to secure permission for the great Jewish electrochemist Benjamin Levich to leave the Soviet Union.

Introduction The goal of this study was to compare the long-term outcomes of patients with intermittent claudication (IC) who completed supervised exercise therapy (SET) versus patients who either declined or prematurely discontinued SET. Methods A retrospective, observational, single-centre cohort study of patients with IC referred to SET. Outcomes included progression to chronic limb-threatening ischemia (CLTI), revascularization requirement, and cardiovascular death.1:1 propensity score matching (PSM) using nearest-neighbour (caliper=0.2) was performed. Multivariate analysis (MVA) and logistic-regression (LR) were used to identify significant effect modifiers to guide PSM. Time-to-event data were analysed using Kaplan-Meier survival analysis. Results 241 patients were referred to SET between July 2015 and July 2016. Forty-nine patients completed SET and 192 patients did not. There was no significant difference in age, diabetes, smoking-cessation, and medication compliance between groups. After PSM, 49 patients who declined SET and 41 patients who completed SET were analysed. Progression to CLTI was significantly lower (10.2% vs 65.9%; p Conclusion SET for claudication reduces requirement for future revascularisation by slowing disease progression.

Background: Effective interventions to improve diabetic foot ulcer (DFU) healing are urgently required. Extracorporeal shockwave therapy (ESWT) has the potential to transform DFU care, but is limited by uncertainties around clinical effectiveness and optimal dosing regimen. This protocol outlines the methodology of a systematic review that will address these unknowns. Methods: Databases and the grey literature will be searched for randomised controlled trials (RCTs) comparing ESWT plus standard ulcer care to standard ulcer care ± sham ESWT in patients with a DFU. The primary outcome of the review is time to ulcer healing. Two independent reviewers will screen search results against pre-determined eligibility criteria and extract data onto a pre-piloted spreadsheet. A meta-analysis is planned to compare time to healing for ESWT versus standard care and different doses of ESWT. The Risk of Bias 2 and GRADE tool will be used to assess the quality of the evidence. Outputs, dissemination, impact: The review will provide an estimate of the effect of ESWT on DFU healing and the impact of the ESWT dose on DFU healing. The systematic review will be submitted for publication in a peer-reviewed journal. A plain English summary will be produced. Outputs from the review will guide patient care and research.

Background: Frailty is an important clinical syndrome that is associated with adverse postoperative outcomes. The assessment of frailty provides an opportunity to enhance patient care. The National Vascular Registry (NVR) introduced frailty categories on all vascular procedure proformas in 2019. The aim of this survey was to capture the current practice of frailty assessment in vascular centres in the UK. Methods: A nationwide survey was carried out of all UK vascular centres who enter procedural data onto the NVR database. The Qualtrics online survey tool was used to distribute the survey through mailing lists and social media. The survey captured data on location of centres who responded, how frailty data are collected and vascular surgeons’ opinions of frailty assessments. The survey was live from 29 March 2022 to 29 May 2022. Results: The survey received responses from 48 UK vascular surgeons based in 31 UK vascular centres. Frailty assessment was undertaken in 61% (19/31) of centres that responded, of which 68% (13/19) used a frailty assessment tool. The Clinical Frailty Scale was the most frequently used tool (77%; 10/13). Vascular consultants personally perform frailty assessments in 47% (9/19) of centres and most assessments take place in the ward setting (68%; 13/19). Frailty was re-evaluated in 21% (4/19) of centres. Frailty status influenced clinical practice in 63% (12/19) of vascular centres. 58% (7/12) of responders plan to assess frailty in the future. Clinician-perceived barriers to assessing frailty was unfamiliarly with the tools and concerns over validity. Conclusion: There is variation in how frailty is measured in UK vascular centres. Uncertainty and concerns over validation of tools are perceived barriers to assessing frailty. Further research should target validation of frailty tools and their role in guiding patient care in vascular surgery.

Background: Surgical site infections (SSI) have a significant impact on morbidity and mortality within vascular surgery. Despite the publication of several guidelines, there is a lack of consensus regarding the most effective perioperative practice to minimise the incidence of SSI. This study aimed to assess the current practice of SSI prevention among UK vascular surgeons. Methods: An online survey developed using the current National Institute for Health Care and Excellence (NICE), Centers for Disease Control and Prevention (CDC) and World Health Organisation (WHO) SSI prevention guidelines was piloted in a tertiary vascular centre before being distributed by email to the members of the Vascular Society of Great Britain and Ireland. The survey contained 15 question domains across preoperative, perioperative and postoperative phases to establish current SSI prevention practice. The survey was open for 1 month with reminder emails at 2 and 3 weeks. Results: A total of 109 respondents from 47 UK hospitals completed the survey, 90 of which were consultants (82.6%). The median reported SSI rate was 7.5% (IQR 5–10%). Lower limb arterial and major limb amputations were highlighted as the highest risk procedures of SSI. Empirical criteria are used by 67.2% of respondents to diagnose SSI, and over half (52.2%) of surgeons used this alone. Most respondents use alcoholic chlorhexidine gluconate (69.6%) skin preparation and basic wound dressings (67.6%). Around half (52.5%) of respondents reported that they would use negative pressure wound therapy for closed wounds. Formal wound surveillance was not undertaken by 73.7% of respondents. Conclusions: There is little agreement in current guidelines on the best practice to prevent SSI. Unsurprisingly then, clinical practice follows suit and continues to show little consensus on prevention measures used. There also appears to be a disparity in registry level, clinical perception and literature data for SSI rates. Well-designed high-quality trials are needed to provide evidence-based recommendations in this field.

Background: Diabetes mellitus is one of the fastest growing health crises of our time. One of the major complications is diabetic foot ulcers, many of which fail to heal. Tenotomy – transection of tendon fibres – may help to redistribute pressure in the foot and therefore help ulcer healing and prevent recurrence. The aim of this survey was to explore the availability of pressure relieving adjuncts, including tenotomy, in diabetic foot services and interest in collaborating in further research studies. Methods: An online survey was performed of healthcare professionals involved in the management of diabetic foot ulcers to explore the multidisciplinary composition of diabetic foot services, offloading therapies available and interest in collaborating in further research. Results: The survey gained 168 responses from 10 countries. Most responders were orthopaedic surgeons (61.3%, 103/168). Of those who responded, 70.8% (119/168) had a dedicated diabetic foot clinic and 99 (58.9%) reported having an active tenotomy service. 73.8% (124/168) of responders wished to further collaborate and 82.1% (138/168) were willing to help involve their patients in a future trial. Conclusions: The results of this survey showed the variation in tenotomy practice and an appetite for collaborative research in this area. The Vascular Society of Great Britain and Ireland Diabetic Foot Specialist Interest Group will address these uncertainties through targeted collaborative research to investigate tenotomy as a potential clinical and cost-effective treatment in diabetic foot care.

In this paper, the physical chemistry of the absorption and desorption of water vapor for electrochemical gas sensors with commonly used sulfuric acid as the electrolyte is investigated. Electrochemical gas sensors are being increasingly used for monitoring toxic gases in the environment, and they are, in principle, simple devices, but in practice, their operation is complex. In particular, changes in atmospheric humidity and temperature can have significant effects on the sensor output. A model has been developed for the calculation of sensor weight changes as humidity varies, which are in good agreement with the analysis of experimental results. This then allows for the calculation of the rather more important electrolyte volume variations. Changes in acid molarity and physical characteristics of the electrolyte have also been determined. The effects on working electrode (WE) electrocatalytic activity are discussed, and potential problems with sensors for environmental monitoring are highlighted. In particular, changes in the electroactive area of the WE and, consequently, of the sensor output, and flooding of the WE catalyst aggregates which can lead to problems with electrolyte leakage from sensors are considered.

In this paper we present a new approach to the mechanism of inactivation of enveloped virus aerosols. The analysis is in terms of oxidation of the lipid bilayer of the viral envelope through a free radical chain reaction. The rate kinetics of the process for various enveloped viruses have been compared and the indications are that the inactivations are closely related. Promoting virus inactivation with UV light is briefly reviewed and discussed as an extension of the chain reaction mechanism, which with physicochemical analyses give insights into the process and of reaction complexities. An outline of a practical method of achieving a 3-log10 level of deactivation in 1 min is described with purified air being returned to healthcare environments.

ObjectiveGroin incision surgical site infections (SSI) following arterial surgery are common and are a source of considerable morbidity. This review evaluates interventions and adjuncts delivered immediately before, during, or after skin closure, to prevent SSIs in patients undergoing arterial interventions involving a groin incision.DesignSystematic review and meta-analysis.MethodsThis review was undertaken according to established international reporting guidelines and was prospectively registered with the International prospective register of systematic reviews (CRD42020185170). The MEDLINE, EMBASE and CENTRAL databases were searched using pre-defined search terms without date restriction. Randomised controlled trials (RCTs) and observational studies recruiting patients with non-infected groin incisions for arterial exposure were included; SSI rates and other outcomes were captured. Interventions reported in two or more studies were subject to meta-analysis.ResultsThe search identified 1,532 articles. 17 RCTs and 7 observational studies, reporting on 3,747 patients undergoing 4,130 groin incisions were included. A total of 7 interventions and 9 outcomes, were reported upon. Prophylactic closed incision Negative Pressure Wound Therapy (ciNPWT) reduced groin SSIs compared to standard dressings (Odds Ratio (OR) 0.34, 95% CI 0.23-0.51; pConclusionsThere is evidence that ciNPWT and subcuticular sutures reduce groin SSI in patients undergoing arterial vascular interventions involving a groin incision. Local antibiotics did not reduce groin wound SSI, although the strength of this evidence is lower. No other interventions demonstrated a significant effect.

Background Varicose veins impair quality of life and can lead to chronic leg ulcers. National Institute for Health and Care Excellence (NICE) guidelines (CG168) set out evidence‐based standards for patient management. In England, Clinical Commissioning Groups (CCGs) fund NHS care within their locality. The objective of this study was to evaluate CCGs' commissioning policies and compare them with CG168. Methods Searches were made for the published policies of all 206 English CCGs. They were reviewed for compliance with NICE guidelines and the associated quality standard. Areas of disagreement were analysed for themes. Results Some 203 CCGs (98·5 per cent) had a published policy and 190 (93·6 per cent) of these were published after publication of CG168. Only 73 of the policies (36·0 per cent) were compliant with CG168. Treatment was restricted on the basis of clinical disease severity in 119 CCGs (58·6 per cent); 29 (14·3 per cent) stipulated delay of treatment using a ‘trial’ of conservative treatment; 22 (10·8 per cent) used lifestyle‐related factors such as BMI and smoking status to ration treatment. Treatment was commissioned for uncomplicated symptomatic varicose veins in 87 CCGs (42·9 per cent), but some applied additional rationing mechanisms; 109 CCGs (53·7 per cent) would treat oedema, 183 (90·1 per cent) would treat skin and soft tissue damage, 202 (99·5 per cent) healed ulceration, and all would allow active ulcers to be treated. Discussion The majority of CCGs in England have commissioning policies that contradict NICE guidelines. Rationing strategies include disease severity, delay and patient lifestyle‐related factors, creating unwarranted geographical variation for varicose vein treatment, disregarding the NHS Constitution for England, and perhaps leading to an increase in costly treatment of chronic complications in the long term.

Two kinds of TiO2 films prepared by CVD and by anodization of titanium mesh are compared for the photocatalytic (PC) and photoelectrocatalytic (PEC) degradation of RDX aqueous solutions illuminated under a 200 W UV light. The PC activity of anodically formed TiO2 is lower than that with CVD-produced TiO2. The PC efficiencies of degradation of RDX with both anodized and CVD films are improved by applying a potential of 1 V versus saturated calomel electrode (SCE), with up to 95% of RDX being destroyed in two hours by a CVD-produced TiO2 film, and 81% by anodized TiO2. Chemical analysis shows that during RDX degradation, nitrite is the first mineralized product which is further oxidized to nitrate.

2007 marks the bicentennial of John Wiley & Sons' publishing business. In this editorial, the Editor takes a brief look back in time, examining the history and origins of a technique that would come to be known as chemical vapor deposition, and comments on the journal's rise to being the forum of choice for publishing the best research in this industrially and academically important field.

This review gives an overview of the characteristics of various non-thermal, non-equilibrium plasmas and discusses applications of AP-PECVD with dielectric barrier discharges, corona discharges, RF discharges, and microwave discharges.

In this paper we report on a study of an AP-PECVD process based on a simple, and very inexpensive, dielectric barrier discharge using a standard mains supply frequency. We have investigated the effect of a range of deposition parameters on the properties of silicon oxide layers grown from a HMDSO/O 2 /Ar system. It is shown that the flux of energetic species from the discharge generation is a critical parameter in determining the growth rate and characteristics of the deposited films. Growth rates up to 10 nm min -1 can be achieved and layer properties, such as refractive index and breakdown voltage, are comparable with those obtained by more conventional CVD processes. General optimum conditions for high growth rates and good quality films can be inferred from the results.

The kinetics of l -cystine hydrochloride reduction have been studied at a mercury-plated copper rotating disc electrode (RDE) and at a stationary mercury disc electrode (SMDE) in 0.1 mol dm −3 HCl at 298 K. The reduction of the disulphide is irreversible and hydrogen evolution is the major side reaction. In contrast to steady state electrode kinetic studies at a mercury drop electrode (which shows a well-defined limiting current), the mercury-plated Cu RDE shows overlap between disulphide reduction and hydrogen evolution. These effects are attributable to strong reactant adsorption with a calculated surface coverage close to 100%. A Tafel slope of −185 mV per decade is found with a cathodic transfer coefficient of 0.32 and a formal rate constant of 6.7 × 10 −9 m s −1 . The relative merits of steady state voltammetry at a mercury-plated copper RDE and linear sweep voltammetry at the SMDE are discussed, as is the mechanism of l -cysteine hydrochloride formation.

The reduction of the disulphide, l -cystine hydrochloride to the l -cysteine hydrochloride thiol, in 0.1 mol dm−3 HCl at 298 K, has been studied at pre-treated, circular, 0.50 cm2 lead disc electrodes using steady state linear sweep voltammetry, non-steady state voltammetry and controlled potential coulometry. The diffusion coefficient for l -cystine hydrochloride was approximately 4.8 × 10−10 m2 s−1 from the three techniques. Reduction of the disulphide was irreversible and hydrogen evolution occurred as a competitive reaction at approximately −1.35 V vs. SCE. Analysis of the mixed control kinetics, using a Koutecky–Levich approach, allowed the relative roles of charge transfer and mass transport to be resolved. Anomalously high Tafel slopes, of typically −183 mV, were observed due to disulphide adsorption. The charge transfer kinetics are consistent with the first electron gain being rate determining while reaction orders are +1 with respect to both the disulphide and proton concentrations. The mechanism of l -cystine hydrochloride reduction has been critically discussed.

Titanium dioxide thin film photo-semiconductor electrodes prepared by chemical vapour deposition (CVD) are compared for the photocatalytic (PC) and photoelectrocatalytic (PEC) degradation of 4-chlorophenol (4-CP) in aqueous solution. The efficiencies of PC degradation of 4-CP are low, but are found to be improved significantly by PEC with an applied potential. The effects of the film properties, particularly film thickness and crystalline form, on degradation rate by PEC have also been studied. For films deposited at 370 and 400 °C it is suggested that differences in behaviour could be related to depletion layer widths.

This paper describes a study by gas chromatography/mass spectrometry (GC-MS) of the gas phase thermal decomposition of HTMHD (where HTMHD is 2,2,6,6-tetramethylheptane-3,5-dione), [Y(TMHD) 3 ] and [Y(TMHD) 3 .hydrate] in the presence and absence of oxygen over the temperature range 200-600°C. The gas phase at the outlet of the reactor was condensed in a liquid nitrogen trap and analysed by GC-MS to try to elucidate the composition of the gas mixture in the reactor. On the basis of the identified decomposition products, decomposition processes of the various compounds are suggested. The results show that the compounds are, not unexpectedly, less thermally stable in oxygen and the mechanism of their thermal decomposition is changed. It is also shown that the residence time of the precursors in the reactor has significant effect of decomposition chemistry.

Thin oxide films have a number of applications in diverse areas such as microelectronics, precision optics and catalysis. The use of plasma enhanced chemical vapour deposition (PECVD) for depositing such films has an advantage over thermal CVD as there is the possibility of operating at reduced substrate temperatures whilst still producing films of high quality. However, PECVD traditionally requires a vacuum system. This can lead to higher capital and operating costs. For this reason some relatively new CVD processes based on various types of electrical discharge sustained at atmospheric pressure (AP-PECVD) have attracted considerable interest. We have investigated the use of a dielectric barrier discharge as a source of plasma. This very simple technique has potential for large volume applications and preliminary studies have given promising results for the properties of silicon dioxide layers.

While CVD has been extensively used for the preparation of thin films of inorganic materials, apart from its application to plasma polymerisation, very little has been reported on the formation of organic layers. In this paper we report the first CVD preparation of an organic pigment, quinacridone. A two-step CVD method and the effects of various deposition conditions on the deposition process are described. The characterisation of deposits by FTIR, Raman, XRD and chemical microanalysis analysis shows that they have very similar compositions and structures to commercial samples of the pigment.

he companion article by Mark Allendorf 1 highlights the importance of on-line CVD coating for flat glass manufacture. Two smaller, but fast growing, markets are those of precision optics and telecommunications. Both these markets are driven by the rapidly developing requirement for high throughputs. Current deposition methods rely on PVD techniques that are augmented with cumbersome tooling to move the complex geometries and thereby achieve time-averaged deposition over whole surface areas. Such techniques limit throughput and usually give a non-uniform deposit on parts of the coated sample, necessitating special alignment within an optic system and thereby incurring significant costs. The non-line-of-sight attribute of CVD makes the technology ideally suited for coating complex lens and fiber geometries that are used in optical telecommunication transmission and distribution systems and for other precision optics. The coatings of interest are usually oxides other than SnO2, such as TiO2 and SiO2. This article considers some aspects of the CVD of these materials. In particular, it describes a novel process for the deposition of the rutile form of titania at low temperatures and new approaches to thin film formation of silica by plasma enhanced CVD (PECVD) without the need for the use of a vacuum.

This paper describes the modelling and simulation of a lab-scale batch reactor process. The reactor is available to a consortium of researchers for studies into the optimisation and improved control of batch systems as well as the study of the use of on-line analytical instrumentation. The initial development of the process model equations and the system simulation is described. This includes the modelling of the chemical kinetics using both mathematical equations and experimental analyses and modelling of the process and control system. The initial results are promising and indicate the simulation could be used successfully for further control studies.

The crystalline structures of titanium dioxide (TiO 2 ) thin films deposited on various substrates by LPCVD for temperatures

An assessment of the available thermodynamic data of gaseous and condensed fullerene C{sub 70} is presented. Gibbs energy minimization of the gaseous C-H-O-Ar chemical system, including large polyaromatic hydrocarbons and the fullerenes C{sub 60} and C{sub 70}, helps to determine under which conditions C{sub 60} and C{sub 70} molecules are stable. The influence of the addition of halogen atoms in the gas phase on the improvement of the yield of these two fullerenes in different conditions is investigated by minimizing the Gibbs energy of the gaseous C-H-F-O-Ar chemical system. The evolution of the yields of the two fullerenes, and of the C{sub 70}/(C{sub 70} + C{sub 60}) ratio as a function of temperature, pressure, and C/H ratio in the reactants is illustrated and compared with corresponding experimental information from a literature review. In the light of these calculations, the possibility of the direct production of fullerene films containing variable amounts of C{sub 60} and C{sub 70} by a continuous process such as combustion or pyrolysis is discussed.

A batch reactor model was used to predict the reactant concentration decay during constant current density (2000 A m −2 ) electrolysis of l -cystine hydrochloride to l -cysteine hydrochloride at a variety of cathode materials in 2 M HCl at 298 K. A divided parallel plate reactor of 1 dm 2 projected cathode area was operated in the batch recycle mode with a catholyte volume of 2 dm 3 . The effect of the average linear flow velocity of the catholyte (0.033–0.123 m s −1 ) was studied and it was found that the system could be modelled as a batch reactor. At high reactant levels (i.e. at short times) the rate of reduction was under charge transfer control and at low reactant levels (i.e. at longer times) pure mass transport control ensued. The ability of the model to describe the experimental data was dependent on the hydrogen overpotential at the cathode material. A good fit was obtained at high hydrogen overpotential cathodes (such as mercury-plated copper and lead) but the fit was poorer at materials having a lower hydrogen overpotential (which include titanium, carbon, tin, stainless steel, copper, nickel and molybdenum).

In sensors with porous gas diffusion membranes, the major control of mass transport often occurs at the three phase boundary between the gas, the electrolyte and the electrocatalyst [1] . This interphase is poorly defined and difficult to control. An attempt has been made using sputter deposition to make a more reproducible and controlled working electrode–gas environment. The electrodes have been tested in commercial sensors for ppm levels of CO, H2S, SO2 and Cl2. All sensors showed the unexpected result of two response maxima as a function of thickness of platinum deposited. The electrochemical area of the film also showed a similar two maxima relationship. Cross-sectional SEM has been used for the analysis of the pore size distribution and the sensor response time and electrode resistance have also been measured, also as a function of electrode thickness. A simple model is proposed to explain the observed relationship. From a practical viewpoint, there is evidence that sputter deposition does allow better control of electrode structure than more traditional methods of production.

Platinum-aluminium alloys of various compositions were synthesised by using DC co-sputter deposition and then immersed in 4 M NaOH under open-circuit conditions. The selective dissolution of aluminium was studied with Rutherford backscattering spectroscopy (RBS) and secondary neutral mass spectrometry (SNMS). A threshold at Pt 0.4 Al 0.6 was observed. For platinum contents above 40 at%, RBS analysis showed that little aluminium dissolution occurs. There was also evidence for the formation of a thin (less than 5 nm thick) platinum-rich surface film. At platinum contents lower than 40 at% profuse aluminium dissolution occurred. RBS and SNMS analyses suggested that dissolution occurs throughout the film.

In Part I we reported the results of an emission spectroscopic study of the plasma obtained in an SiH4–N2–Ar mixture. It was shown that argon in metastable electronic excited states provides a high concentration of atomic nitrogen. In this part we report the results of a study of the influence of argon dilution on the growth rate, composition and properties of silicon nitride films. The exact influence of nitrogen dilution with argon depends on the process parameters and on the method of coupling of the RF power, but it is found in general that a high concentration of atomic nitrogen leads to changes in the relative amounts of Si–Hj and N–Hi bonds and in the Si/N ratio of deposited films. In particular, it is shown that hydrogen incorporation can be reduced and improved stoichiometry can be obtained. © 1998 John Wiley & Sons, Ltd.

An investigation has been made of the effect of dilution of nitrogen with NF3 on the properties of silicon nitride deposited by remote plasma-enhanced CVD (PECVD). For NF3/N2 mixtures with 1.5 %, films with the structure of silicon dioxide are formed, but they do not contain enough oxygen to give typical SiO2 IR spectra. It is suggested that the silicon dioxide structure arises because of isoelectronic substitution of oxygen by NF.

In this paper we report on a study by FTIR and mass spectroscopy of the gas phase thermal decomposition of [Y(TMHD) 3 ] for a temperature range 160–700 °C, and in the absence and presence of oxygen. Comparison of the results from both methods of analysis shows that the two techniques provide complementary information.

A direct, continuous method for the measurement of peroxodisulfate anion has been devised and assessed. The approach is based upon the reduction of the anion under mass transfer limiting conditions at an amalgamated copper rotating disk electrode. The preparation of the disk electrode by Hg electroplating was examined in detail in order to generate a reproducible surface. The system was calibrated by demonstrating that the limiting current density for peroxodisulfate reduction was directly proportional to its bulk solution concentration. An electrochemical cell arrangement was then developed to permit the continuous, in situ measurement of peroxodisulfate concentration during electrochemical synthesis.

The destruction of existing arsenals or deposits of chemical weapons is an important obstacle on the way to the successful implementation of the Chemical Weapons Convention which was opened for signature in 1993. Many approaches have been proposed and none can be seen as a panacea. Each has its merits and shortcomings. In this paper we review the different technologies and propose a new one, photocatalytic oxidation, which has the potential to fill an important gap: a cheap, small, mobile facility for chemical warfare agents which are difficult to transport or are deposited in a remote area. We report some relevant experimental results with this technology for the destruction of chemical weapons.

SnO 2 films have been succesfully prepared by chemical vapour deposition (CVD) by reaction of SnCl 2 with O 2 and a value of the activation energy of 58 kJ mol -1 has been measured. The temperature range 450–500 °C has been found to be the optimum for the reaction with resistivities of the films of 9×10 -4 Ω cm on silicon and 6×10 -4 Ω cm on Pyrex. These two values are the lowest reported so far for SnO 2 films which have not been deliberately doped. For their use as transparent conducting films, a figure of merit of 9.87×10 -3 □ Ω -1 was found for a 0.8 µm thick film; this is also the highest reported so far. Characterization of the films by XRD showed a preferred [200] orientation and the grain size obtained from the XRD and SEM micrographs was in excess of 0.4 µm. The SnO 2 films, when tested in an eletrochemical cell, were unstable. A surface electrochemical process has been suggested for the disintegration.

The effect of various diffusion barriers on the mass transport controlled current for an amperometric gas sensor with a porous membrane is considered. A general equation is derived which relates the total current to the diffusion parameters for each barrier. By varying the thickness of one barrier at a time, keeping all the other parameters constant, the relative roles of each of the barriers can be determined. This is done for CO and H2S sensors and in both bases it is shown that more than 70% of the transport control is provided by the electrolyte film in the porous electrode/membrane. This conclusion is supported by observations of the temperature dependence of the sensor currents. It is concluded that, in order to obtain more consistent and reproducible results from porous membrane covered amperometric gas sensors, a more controllable method of electrode manufacture and assembly would be desirable.

A study has been made of the electrochemical reduction of pentachlorophenol (PCP) on a lead electrode in both water and propylene carbonate. A combination of voltammetric measurements and analysis of reaction products by high performance liquid chromatography (HPLC) have established that the reduction of PCP in propylene carbonate occurs by two different pathways, depending upon the electrode potential. At -1.9V vs SCE, reduction is mediated by adsorbed hydrogen, whereas at -2.3V vs SCE direct reduction of PCP also occurs. A similar approach has established that the reduction of PCP in water follows only one reaction pathway, namely, direct electron transfer from lead to PCP.

A new concept is described for monitoring a biomolecule with a sensor having an enzyme entrapped in a conducting polymer. This is based on the sensitivity of the electroactive polymer itself to changes of pH in solution. The concept has been investigated for a glucose sensor with glucose oxidase (GOD) immobilized in a polypyrrole (PPy) layer on an inert platinum electrode. Measurements with a Pt/PPy/GOD electrode for glucose concentrations in the physiological range gave a linear correlation with logarithm of concentration over one decade with a satisfactory dynamic response. There was practically no change of slope or range of linear response to glucose after several days of use; this was in contrast to the amperometric response of the detector when there was about a 50% loss of sensitivity.

In this article we report on results obtained from studies of the effect of total pressure and carrier gas flow rate on the rate of precursor evaporation for typical precursors used in the MOCVD of high temperature superconductors (HTS). We find that this process is under significant mass transfer control and we consider the implications of this for growth of HTS. In particular, we discuss the problems associated with the use of solid precursors and possible strategies for solving the difficulties.

For the indirect determination of trace levels of organophosphorus pesticides in the environment, the irreversible inhibition of the activity of cholinesterases can be utilized with suitably designed electrochemical biosensors. This article reviews potentiometric and amperometric biosensors. For potentiometric biosensors, cholinesterases are immobilized on the active surface of pHsensing electrodes, since during the biocatalytic reaction protons are produced as well as choline. In amperometric biosensors, choline oxidase is employed, in addition to esterases, which allows the indirect monitoring of choline by measurement of the consumption of oxygen or the production of hydrogen peroxide. The applications of various types of biosensor to the determination of pesticide residues in environmental and food analysis are also discussed.