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We present results on very thin NiO films which are able to detect 3 ppm of acetone, toluene and n-butyl acetate in synthetic air and to operate at 300°C. NiO films with 25 and 50 nm thicknesses were prepared by dc reactive magnetron sputtering on alumina substrates previously coated by Pt layers as heater and as interdigitated electrodes. Annealed NiO films are indexed to the (fcc) crystalline structure of NiO and their calculated grain sizes are in the range from 22 to 27 nm. Surface morphology of the examined samples was influenced by a rough and compact granular structure of alumina substrate. Nanoporous NiO film is formed by an agglomeration of small grains with different shapes while they are created on every alumina grain. [ABSTRACT FROM AUTHOR]

This study presents different approaches to increase the sensing area of NiO based semiconducting metal oxide gas sensors. Micro- and nanopatterned laser induced periodic surface structures (LIPSS) are generated on silicon and Si/SiO2 substrates. The surface morphologies of the fabricated samples are examined by FE SEM. We select the silicon samples with an intermediate Si3N4 layer due to its superior isolation quality over the thermal oxide for evaluating the hydrogen and acetone sensitivity of a NiO based test sensor. [ABSTRACT FROM AUTHOR]

In this paper, experimental results are presented on the deposition of colloidal gold nanoparticles on the surfaces of TiO2 prepared on silicon/silicon dioxide. Important procedures, such as titanium dioxide surface hydrophilization as well as functionalization by an organosilane coupling agent (3-aminopropyl) trimethoxysilane and (3-mercaptopropyl) trimethoxysi-lane were investigated in order to obtain a metal oxide surface with the most convenient properties for immobilization of gold nanoparticles having a dense and uniform distribution. TiO2 nanotips prepared by reactive ion etching of oxide surface covered with self-mask gold nanoparticles are demonstrated. [ABSTRACT FROM AUTHOR]

Voltammetric sensors based on bismuth film electrodes are an attractive alternative to other sensors for application in electroanalysis of heavy metals. Bismuth film electrodes can be formed by a similar method on the same substrates as mercury. These systems were used most frequently for simultaneous determination of heavy metals such as Pb, Cd and Zn by anodic stripping voltammetry. Our voltammetric sensor was fabricated on an alumina substrate. A photoresist film prepared by pyrolysis of positive photoresist S-1813 SP15 on the alumina substrate was used as an electrode support for bismuth film deposition. The influence of the Nafion membrane on the measurement sensitivity of the sensor and mechanical stability of the bismuth film were investigated. The sensor was successfully applied for determination of Pb, Cd and Zn in an aqueous solution in the concentration range of 0.2 to 10 µg L−1 by square wave anodic stripping voltammetry on an in-situ formed bismuth film electrode with Nafion-coating. Parameters of the sensor such as sensitivity, linearity, detection limit, repeatability and life-time were evaluated. In the best case, the detection limits were estimated as 0.07, 0.11 and 0.63 µg L−1 for Pb, Cd and Zn, respectively. Finally, the applicability of the sensor was tested in analysis of Pb, Cd and Zn in real samples of tap and river water using the method of standard additions. [ABSTRACT FROM AUTHOR]

Abstract: Bismuth film microelectrodes have a potential to replace toxic mercury used most frequently for determination of heavy metals by anodic stripping voltammetry. We developed diamond-like carbon microelectrodes doped by nitrogen as a support for bismuth electroplating. Bismuth-plated as well as bare microelectrode arrays were used for lead determination in aqueous solutions. The influence of many parameters on responses was investigated. [Copyright &y& Elsevier]

The optimization of electrode properties is an inseparable part of the analytical process which can highly improve the quality of obtained results in electrochemical sensing methods. This paper investigates the role of doping level, morphology and structure of boron-doped diamond (BDD) electrodes in electrochemical sensing of heavy metals in the presence of bismuth. To study the influence of doping level and morphology, a large set of BDD films with varying boron-to-carbon and carbon-to-hydrogen ratios in the deposition gas mixture was grown using hot filament chemical vapor deposition method. The set was used for fabrication of electrodes (the active area 0.43 mm2 was opened in 400 nm SiO 2 by standard optical lithography) for simultaneous electrochemical determination of zinc, cadmium and lead. Square wave anodic stripping voltammetry was utilized for this purpose. The influence of BDD properties on limit of detection (LOD) and sensitivity (S) of the electrodes was also investigated. The highest sensitivity was observed for electrodes prepared with 10 000 ppm boron-to-carbon ratio and lower methane concentrations. The findings prove the importance of selecting an appropriate electrode prior to progressing to electrochemical measurements. • The importance of selecting an appropriate electrode prior to progressing to electrochemical measurements is demonstrated. • Significant influence of doping level and morphology on the simultaneous determination of Zn, Cd and Pb was confirmed. • All electrode types with boron doping level about 2*1021 cm−3 showed the best sensitivity for all determined metal ions. • Most consistent results were achieved using the electrodes with sub-micro sized grains. [ABSTRACT FROM AUTHOR]

Highlights • Potentiostatic electrodeposition under light is proposed for fabrication of Cu 2 O. • Better carrier collection due to larger grain size expected for light deposited sample. • Light deposition Cu 2 O revealed increase of the photoresponse by 0.87 mA/cm2. • Photocurrent of 3.37 mA/cm2 at −20 mV with respect to RHE is achieved. Abstract A novel approach based on the application of light irradiation during the electrodeposition is proposed to prepare Cu 2 O structures for photoelectrochemical water splitting. Potentiostatic deposition of Cu 2 O layers under irradiation and in the dark was carried out from lactate-stabilized copper sulfate on Ag coated glass substrates. The higher growth speed for light deposited samples is related to the contribution of photogenerated carriers to the reduction of electrolyte and electrodeposition of Cu 2 O. The light deposited samples exhibited higher photoresponse of 3.37 mA/cm2 compared to 2.5 mA/cm2 measured for dark deposited sample. Better carrier collection due to larger grain size and lower impurity incorporation are suggested as possible sources of the higher photoresponse for light deposited sample. The presented study demonstrates the light electrodeposition as an attractive way for preparation of highly photoactive Cu 2 O structures for water splitting applications. [ABSTRACT FROM AUTHOR]

Highlights • Ruthenium oxide suggested as a transparent catalytic gate for MIS photoanode. • Lower Fermi level pinning observed for ruthenium oxide compared to Ni MIS structure. • Photovoltage of 0.46 V was achieved at ∼1×sun illumination. • Low overpotential 0.12 V required for 10 mA/cm2 photoanode current in 1 M KOH. Abstract This paper presents an electrical and photoelectrochemical comparison of MIS photoanodes with a metal organic chemical vapor deposited RuO 2 layer and evaporated Ni layer to provide a deeper insight into the interface properties of such structures. The unique properties of RuO 2 such as high transparency, high conductance, high catalytic activity, and high work function make this material an excellent candidate for a Schottky contact of MIS photoanodes for water splitting. In contrast to the Ni-based MIS structure, no Fermi level pinning was observed when RuO 2 was used. This allowed achieving a high measured photovoltage of 0.46 V compared to 0.3 V for a Ni based structure. The ability to achieve the high photovoltage by utilization of RuO 2 catalyst is an important achievement for fabrication of high performing MIS structures. [ABSTRACT FROM AUTHOR]

Patterning of metal oxide nanostructures with different shapes and well-defined size may play an important role in the improvement of MEMS systems, sensors and optical devices. We investigated the effects of HSQ e-beam resist processing on the fabrication of sputtered TiO2 nanostructures. They were patterned using direct write e-beam lithography combined with ICP-RIE etching in CF4/Ar plasma. Experimental results confirmed that the HSQ resist with a thickness of about 600 nm is suitable as a masking material for optimal etching process and allows patterning of the dots array in TiO2 sputtered films with a thickness up 150 nm. TiO2 arrays with a minimal dots diameter of 180 nm and spacing of 1000 nm were successfully developed. [ABSTRACT FROM AUTHOR]

Today, boron-doped diamond (BDD) is among the key materials for electrochemical sensing and advanced oxidation of micropollutants. Therefore, a cost-effective fabrication of large-area BDD electrodes is of high interest. We present an implementation of a liquid-phase boron precursor trimethyl borate for large-area deposition of boron-doped diamond films by linear antenna microwave plasma CVD. Trimethyl borate vapors were used not only as a source of boron for doping but also as the only source of carbon and oxygen, while completely saturating the requirements for the growth of high-quality boron-doped diamond films. However, to allow for control over the doping level through maintaining the B/C and B/O ratios, carbon dioxide was employed as an additional source of carbon and oxygen. The film morphology was controllable from microcrystalline to ultra-nanocrystalline by changing the concentrations of trimethyl borate. Using this unique precursor system, we were able to grow diamond films with a doping level in range from 8 × 1017 cm−3 to 2 × 1022 cm−3 and resistivity as low as 1.16 × 10−2 Ω·cm. Low activation energies were calculated from the Arrhenius plot and growth rates as high as up to 170 nm/h for the low pressure microwave plasma CVD were reached. The investigation of the plasma emission spectrum revealed a chemical composition similar to that of hydrogen-rich plasmas with methane, and the proposed chemical reactions indicate that the diamond growth takes place via the hydroxyl radical. The results demonstrated that trimethyl borate is a suitable source of carbon and boron for the large-area growth of highly boron-doped diamond via low pressure microwave plasma CVD methods. [Display omitted] • Boron-doped diamond grown only from a trimethyl borate and hydrogen gas mixture, with no further hydrocarbon required. • Control over the doping level and morphology by changing the B/C and B/O ratios achieved by adding carbon dioxide. • High growth rates, high doping levels, and low resistivity values were reached. • Trimethyl borate is a low-cost and safe liquid source for large-area MWCVD growth of doped diamond films. [ABSTRACT FROM AUTHOR]

The surface nanostructuring of boron doped diamond (BDD) can further enhance its unique properties e.g. in electrochemical sensing, photoelectrochemical cells, field emission devices and various kinds of sensors. Here we present an investigation of plasmatic nanostructuring of BDD films without use of a time-consuming masking process. RF plasma technique was used to etch surface nanostructures with dimensions ranging from tenths to hundreds of nm in width and height. The size and shape of achieved diamond nanostructures were influenced only by applied etching parameters. We have found that the etched carbon is re-deposited in an amorphous form creating a mask and this self-masking process is responsible for the final shape of obtained structures. Therefore, this technique is effectively controllable by changing plasma power, gas type and pressure which influence the energy of incident ions and thus the sputtering yield and re-deposition of masking material. Utilization of various gas types, pressures and RF powers revealed the physical type of etching to be dominant over the chemical at both high and low energy ions. The nanostructured surfaces were then observed and characterized by SEM and Raman spectroscopy to investigate the nanostructures dimensions and to confirm the remaining diamond quality. Image 1 • RF plasma technique was used to etch BDD surface nanostructures with dimensions ranging from tenths to hundreds of nm. • The main reason for formation of nanostructures is the self-masking re-deposition of etched material from the diamond layer. • Ions with higher energy act more physically and etch the surface independently on the intergranular diamond structure. • Lower energy ions combine the physical and chemical part of etching promoting the formation of columnar like nanostructures. [ABSTRACT FROM AUTHOR]