Silicon Hydride Research Articles

Group superatoms: A new concept in cluster science

A promising research area in nanomaterials is the use of superatomic clusters as building blocks for creating novel molecules or materials with tailored properties. However, assembling these superatoms into functional materials is challenging, and a thorough understanding of this process is still lacking. In this study, we introduce a new concept called the “superatomic family,” which refers to superatoms that share similar valence electron structures but differ in size. We demonstrate this concept with the synthesized [Au6{Ni3(CO)6}4]2− cluster and the designed [Au16{Ni6(CO)10}4]2− and [Au31{Ni10(CO)15}4]5− clusters. These serve as analogs to simple hydrocarbons, such as methane (CH4), silicon hydride (SiH4), and germanium hydride (GeH4). In these supermolecular structures, the central cores of Au6, Au16, and Au31 exhibit the formation of superatomic SP3 hybridized orbitals, which influence the molecular shape and bonding. Moreover, we explored superatomic bonding involving SP3–SP3 hybridized cores, representing a single superatomic bond between members of the superatomic family, analogous to CH3–SiH3 bonds. By integrating the concept of group superatoms into the Lewis structure framework, we present a powerful approach for predicting and engineering cluster properties, thus opening a vast landscape of nanomaterial design possibilities.

Fabrication of superhydrophobic all-biomass aerogels with ultralight, elasticity and degradability for efficient oily wastewater treatment

Oily wastewater has seriously threatened the water ecology and human health. Superhydrophobic biomass-based aerogels are ideal candidates to remedy the oily wastewater, but facing challenges for the usage of toxic small molecules crosslinker and the rational construction of elasticity. Herein, we employed the natural non-toxic citral as crosslinker, and then constructed a superhydrophobic chitosan/bamboo cellular fibers aerogel (S-CS/BCF-A) with ultra-light, high elasticity and degradation performances. Wherein the hydrolysis of methyltrichlorosilane produced silicon hydride and hydrogen chloride, enhanced the hydrophobicity of the aerogel surface and partially reduced rigidity of the pore walls, respectively. The S-CS/BCF-A displayed outstanding fatigue durability, which benefited for its lamellar-fiber interweaved structure. In addition, this aerogel could undergo tape-peeling, UV radiation, and organic solvents immersion without superhydrophobic variation, even in seriously abrasing that the surface still maintained high hydrophobicity. The as-made aerogel possessed high oil adsorption capacity (17.95–44.57 g/g), combined with pump-supported device for effectively recovering large-area oil spills (66,348 L·m−2·h−1). Furthermore, the resultant aerogel could efficiently separate the immiscible oil-water mixture and emulsifying wastewater (types of Oil-in-Water and Water-in-Oil emulsions). This work provides a rational design method for constructing the elastic, durable and biodegradable aerogels, used for speedy and economical separation of oil-water mixtures.

Stabilization of halide perovskites with silicon compounds for optoelectronic, catalytic, and bioimaging applications

AbstractSilicon belongs to group 14 elements along with carbon, germanium, tin, and lead in the periodic table. Similar to carbon, silicon is capable of forming a wide range of stable compounds, including silicon hydrides, organosilicons, silicic acids, silicon oxides, and silicone polymers. These materials have been used extensively in optoelectronic devices, sensing, catalysis, and biomedical applications. In recent years, silicon compounds have also been shown to be suitable for stabilizing delicate halide perovskite structures. These composite materials are now receiving a lot of interest for their potential use in various real‐world applications. Despite exhibiting outstanding performance in various optoelectronic devices, halide perovskites are susceptible to breakdown in the presence of moisture, oxygen, heat, and UV light. Silicon compounds are thought to be excellent materials for improving both halide perovskite stability and the performance of perovskite‐based optoelectronic devices. In this work, a wide range of silicon compounds that have been used in halide perovskite research and their applications in various fields are discussed. The interfacial stability, structure–property correlations, and various application aspects of perovskite and silicon compounds are also analyzed at the molecular level. This study also explores the developments, difficulties, and potential future directions associated with the synthesis and application of perovskite‐silicon compounds.image

In Situ Monitoring of Allylamine and 1,1,3,3-Tetramethyldisiloxane Reaction to Form 2,2,7,7-Tetramethyl-1-oxa-3-aza-2,7-disilacycloheptane Using Raman Spectroscopy

The cyclic siloxazane, i.e., 2,2,7,7-tetramethyl-1-oxa-3-aza-2,7-disilacycloheptane (1), is a useful industrial intermediate that is challenging to produce. One method to synthesize 1 is through concurrent dehydrocoupling and hydrosilylation reactions between 1 and allylamine. This chemistry is highly exothermic and also generates a significant amount of H2. Raman spectroscopy was demonstrated to be an effective analytical method to track both reactions. It enables a safe reaction scale-up by monitoring the consumption of allyl groups and the silicon hydride (SiH) groups. Both functional groups could be readily quantified by using a solvent as an internal standard. It is found that the observed SiH signal can be attributed to an intermediate species, which would undergo a relatively slower hydrosilylation reaction. Interesting kinetics behavior is observed that leads to a mechanistic understanding of the catalyst's role in catalyzing the two elementary steps. The ability to track these moieties is critical to the development of a safe process that avoids accumulation of SiH intermediates.

Sorption properties of nanostructured ball-milled porous silicon for solid-state hydrogen storage up to 80 bar

Solid-state storage is a feasible solution to store hydrogen compared to commercially available techniques. The disadvantage of using metal and complex hydrides for storage is the elevated temperature operation (>400 °C) and slow reaction kinetics. Porous materials like carbon nanostructures, metal-organic frameworks, zeolites, and porous polymers possess high surface energy and hydrogen affinity. However, cryogenic temperature operation and low storage at ambient conditions are major limitations for practical storage applications. Modifying the material morphology and storage parameters to enhance hydrogen storage is under intense investigation. This study focuses on nanostructuring porous silicon (PS), evaluating its structural characteristics, and investigating its ability to store hydrogen at up to 80 bar. The challenges of large particle size and low-pressure hydrogen storage in the novel porous material is addressed with possible mechanisms. The discussion explored the potential of utilizing interconnected pores via nanoscale engineering and increased charging pressure to optimize hydrogen exposure. Nanostructuring the hand-grinded porous Si (HGPS) reduces crystallite size, boosts surface energy and enhances thermodynamics. At 80 bar and 120 °C, the ball-milled PS (BMPS) exhibits a hydrogen storage capacity of 10.7 wt%. The isosteric heat of adsorption is utilized to optimize storage conditions to achieve useable capacity. The hydrogen adsorption pressure is optimized between 40 and 60 bar, where the storage capacity ranges from 2 wt% and 6 wt% (meeting the hydrogen storage target set by the US Department of Energy). X-ray Photoelectron Spectroscopy investigates surface states and bonding involving silicon hydrides. The effect of nanostructuring on decomposition energy is observed by differential scanning calorimetry. The decreased crystallite size, examined through X-ray diffraction and Raman spectroscopy, exposes nanopores accessible to hydrogen. The accessibility enhances storage capacity in free and surface-affixed states, rendering BMPS for reversible storage applications. The lower temperature requirement for hydrogen adsorption and release from storage material aligns with Sustainable Development Goal 7 (SDG 7) on affordable and clean energy.

Pt(II) complexes bearing P,N-donor ligands as catalysts in chemoselective hydrosilylation, hydrogermylation, and hydroboration of terminal alkenes

In this report, we present the synthesis of six novel neutral platinum complexes employing readily available P,N-donor ligands through a straightforward two-step procedure. Subsequently, we investigated their catalytic activity in the hydroelementation of terminal olefins, highlighting their versatile utility in material and natural product chemistry. The efficient addition of silicon, germanium, and boron hydrides to the CC bond at low catalyst loading occurred exclusively in an anti-Markovnikov manner. Furthermore, our substrate scope encompasses a wide range of aliphatic and aromatic alkenes, featuring substituents with varying electronic properties. In contrast to many previous Pt-complexes, our catalytic system displayed exceptional chemoselectivity towards other unsaturated functional groups, such as carbonyl and internal CC bonds. Notably, it also exhibited remarkable tolerance to hydroxyl, alkoxyl, silyl, and thioether moieties. Additionally, we accentuated the prowess of our catalyst, showcasing its capability to sustain consistent activity and selectivity throughout numerous catalytic cycles.

Leaching of catalyst platinum from cured silicone elastomers: A preliminary study for comparing reagents

Addition curing systems involve two-part silicones which require the mixture of a silicone polymer with a catalyst to initiate the cure. Platinum is the most commonly used metal catalyst for addition curing of silicones by hydrosilylation which involves the crosslinking by the addition reaction of silicon hydride species to unsaturated bonds, mainly CC, but also CO or CN double bonds. After crosslinking of the polymers, the platinum catalyst cannot be recovered but remains in the silicone materials throughout the entire product life. In the end, platinum is disposed of together with the silicones and is thus lost to the value chain. The overall objective of this work was to develop a recycling process for the recovery of platinum from addition-cured silicone elastomers. In the first step, this was achieved by efficient digestion methods and by optimizing the leaching processes for exemplary commercial silicone elastomer products. Two different silicone materials were investigated, both of which were crosslinked with a platinum catalyst. The initial Pt content in the tested samples was 12.6 ± 0.2 mg/kg for a commercial silicone impression material and 6.3 ± 0.5 mg/kg for a silicone baking mold, measured by graphite furnace atomic absorption spectrometry (GF-AAS). Samples were first frozen with liquid nitrogen to improve brittleness and then crushed with a simple food processor to obtain a silicone granule. Various acid mixtures, mainly based on sulfuric acid, were investigated as digestion methods in order to extract platinum from the silicone network. These had different effects on the dissolution behavior of silicone samples and the amount of platinum extracted in each case. The amount of platinum leached from the filtrate of the digested samples in each case was measured by ICP-OES to evaluate the efficiency of different leaching mixtures. In addition, the dissolved platinum species present in the solutions was identified by UV/VIS as tetrachloridoplatinate(II) complex. The best platinum leaching results so far were obtained with two methods, both of which used a leaching mixture based on sulfuric acid and hexamethyldisiloxane (M2). In the presence of hydrochloric acid, 9.6 ± 1.6 mg platinum/kg was leached from the silicone impression material and 4.2 ± 0.8 mg platinum/kg from the silicone baking mold. With the additional use of aqua regia instead of hydrochloric acid, 10.4 ± 2.8 mg platinum/kg was extracted from the silicone impression material and 4.8 ± 1.0 mg platinum/kg was extracted from the silicone baking mold. These methods were replicated with n = 3. Using statistical evaluation methods (F-test, t-test, and confidence interval), no significant difference was found between these two best methods. Recovery of platinum(0) from leach mixtures has not yet been achieved due to high dilution and very low platinum concentration in samples and will be part of another study.

Effect of surface modification of nanosilica by hydride-groups on morphology, strength and resistance of epoxy-composites

A chemical modification of fumed silica surface by active groups can enlarge its functional capabilities as a polymer filler. As a result, a new possibility in the formation of reinforced polymeric composites appears.In this work, silica with grafted silicon hydride (≡Si–H) groups was found to be active in the processes of hydrosilylation of active bonds in monomers during their polymerization. Hydride-silylated silica was obtained via his treatment with triethoxysilane. The presence of grafted silicon hydride groups was confirmed by means of IR spectroscopy, and their concentration measured by titrimetric and spectrophotometric analysis was found to be about 0.4 mmol/g. Silica-epoxy composites were prepared and the resulted materials after curing were subject to compression, bending, micro-hardness and adhesion mechanical tests.According to experimental results, the synthesized hydride-silica fillers let to enhance the important strength properties of the epoxy-polymer already at 2 wt% loading. In particular, the elastic modulus for compression increased by 30–40%, the one for bending – by 1.2–1.5 times, the flexural strength – by 1.5–2 times, and adhesion to steel – by 2.5–2.8 times. These effects are achieved due to good compatibility and homogeneous distribution of the filler in the resin, as shown by SEM microscopy (after hydride-modification, the silica agglomerates in epoxy disappear). IR-spectroscopy shows a possible increasing of epoxy conversion's rate after 2%-filling by hydride-silica. Thus, preliminary results indicate that fumed silica with grafted silicon hydride groups shows promise as active reinforcing filler for epoxy polymers.The work demonstrates the potential of nanosilica filler surface hydride-silylation for low-cost strengthening of epoxy polymers for industry and repair.

Ab initio study of the structure and properties of amorphous silicon hydride from accelerated molecular dynamics simulations

This paper presents a large-scale ab initio simulation study of amorphous silicon hydride (a-Si1-xHx) with an emphasis on the structure and properties of the material across a range of hydrogen concentration by combining accelerated molecular dynamics (MD) simulations with first-principles density-functional calculations. The accelerated MD scheme relied on classical metadynamics, which enabled the development of 2500+ high-quality structural models of a-Si1-xHx, with system sizes ranging from 150 to 6000 atoms and hydrogen concentrations vary from 6 to 20 at.%. The resulting amorphous networks were found to be completely free from any coordination defects and that they all exhibited a pristine band-gap in their electronic spectrum. The microstructural properties of hydrogen distributions were examined with an emphasis on the presence of isolated and clustered environments of hydrogen atoms. The results were compared with experimental data obtained from X-ray diffraction, infrared spectroscopy and nuclear magnetic resonance studies.

Far-UV absorption spectra of SiH2 and dibridged Si2H2 isolated in solid argon

We employ electron bombardment during the deposition of an Ar matrix containing a small proportion of SiH4 to generate various silicon hydrides. Subsequently, the irradiation of a matrix sample at 365 nm decomposes SiH2 and dibridged Si2H2 in solid Ar, which we identify through infrared spectroscopy. We further recorded the corresponding ultraviolet absorption spectra at each experimental stage. An intense band observed in the range of 170–203 nm is largely destroyed upon 365-nm photolysis, which is assigned to the C1B2 ← X1A1 transition of SiH2. Moreover, a moderate band observed in the region of 217–236 nm is reduced slightly, which is assigned to the 31B2 ← X1A1 transition of dibridged Si2H2. These assignments are made based on the observed photolytic behavior, and the prediction of the vertical excitation energies with the corresponding oscillator strengths by using time-dependent density functional theory and equation-of-motion coupled cluster theory.

Isotope engineering of near-field radiative thermal diodes

Guided by a rational design approach centering on the electromagnetic local density of states (LDOS), we explore the potential of isotopically engineering radiative thermal diodes for enhanced rectification with a focus on the near field. Based on fluctuational electrodynamics, we theoretically demonstrate that for thermal diodes pairing thin films of intrinsic silicon (i-Si) and lithium hydride (LiX), the rectification ratio can increase by over six times with varying isotopic compositions. This is because by leveraging the isotope-induced shift and broadening of the surface phonon polaritons in LiX, more LDOS contrast provided by i-Si can be effectively converted into thermal rectification. Moreover, we show that such improvement is fairly robust, as evidenced by the prediction of over 20% rectification enhancement across a wide physical and geometric parameter space. Finally, inspired by insights from the i-Si-based thermal diodes, we propose general guidelines for implementing isotope engineering in the design of practical devices, which are further illustrated via representative diodes employing vanadium dioxide and silicon carbide as the active materials. Our work highlights the efficacy of isotopes in boosting the performance of radiative thermal diodes, which also holds promise for broader applications such as thermal transistors, thermal switches, and thermophotovoltaics.

Alan Graham MacDiarmid. 14 April 1927—7 February 2007

Alan G. M ac Diarmid was an inorganic chemist by training who pioneered the field of synthetic metals. He grew up in a family that lived frugally, and he had to work in the Chemistry Department of the Victoria University of Wellington as a laboratory assistant before he could undertake part-time degree studies. He was awarded a Fulbright Scholarship to the University of Wisconsin, where he completed his first PhD with Norris Hall. The desire to receive a higher degree in the UK led to a Shell Scholarship to complete a second doctorate with Harry Emeléus FRS. After a sojourn at the University of St Andrews, Alan M ac Diarmid was appointed to an academic position at the University of Pennsylvania, where he remained essentially for his whole career. His early research was based on the properties of silicon hydrides, but he also became interested in poly(sulfur nitride). This led to a search in collaboration with Alan J. Heeger for intrinsically conducting non-metallic materials. A chance meeting with Hideki Shirakawa at the University of Tokyo led to M ac Diarmid being shown thin metallic-like films of poly(acetylene) made in Shirakawa's laboratory. Shirakawa travelled to Philadelphia to collaborate with M ac Diarmid and Heeger on the halogen ‘doping’ of poly(acetylene), which led to the discovery that the doped material was an excellent conductor. Thus, the field of synthetic metals was born. This paradigm-shifting work in which a polymer was shown to be a conductor led to the award of the 2000 Nobel Prize in Chemistry to these three individuals. M ac Diarmid went on to study in great detail the properties of polyaniline; the fact that it could be processed from solution and further modified by oxidative and protonic doping led to all sorts of potentially interesting opportunities in optoelectronics. From all this research, the modern field of organic electronic materials emerged as an important disruptive technology whose advancement depended on an entirely new branch of interdisciplinary science.

Reductive Cleavage of C(sp2)–CF3 Bonds in Trifluoromethylpyridines

A reductive detrifluoromethylation protocol has been developed making use of an earth-abundant alkoxide base and silicon hydride species. A variety of pyridine and quinoline substrates bearing alkyl, aryl, and amino functional groups are reduced in moderate to high yields. The reaction is chemoselective for C(sp2)-CF3 groups located at the 2-position on the pyridine ring, leaving trifluoromethyl groups located elsewhere on the molecule intact. Preliminary mechanistic studies demonstrate that the combination of silane and base generates a strongly reducing system that may transfer an electron to electron-deficient π systems.

High-Translucency Zirconia Following Chemical Vapor Deposition with SiH4: Evidence of Surface Modifications and Improved Bonding.

To evaluate the effect of plasma-enhanced chemical vapor deposition (PECVD) with silicon hydride (SiH4) at different times on HT-zirconia surface characteristics and bonding of composite cement before and after thermocycling. Blocks of HT zirconia were obtained, polished, sintered and divided into five groups, according to PECVD time (n = 31): Zr-30 (30 s), Zr-60 (60 s), Zr-120 (120 s) and Zr-300 (300 s). The control group (Zr-0) did not receive PECVD. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS) in conjunction with field-emission scanning electron microscopy (FE-SEM), x-ray photoelectron spectroscopy (XPS), goniometry, and profilometry tests were used for chemical and topographic characterization. Monobond N silane (Ivoclar Vivadent) was applied to the surface, and a cylinder of composite cement (Variolink N) was made (3 x 3 mm). Half of the specimens of each group were stored for 24 h or subjected to thermocycling (6 x 103 cycles). A shear bond strength (SBS) test was performed. Results were subjected to one-way ANOVA and Tukey's tests (α = 0.05). For experimental groups, XPS showed that formation of Si-O bonds contributed to increased surface free energy (SFE). FE-SEM and EDS showed that the longer the deposition time, the greater the amount of silicon on the surface. Zr-60 and Zr-300 presented higher and lower surface roughnesses, respectively. The silicon penetrated the microstructure, causing higher stress concentrations. The bond strength to composite cement was improved after all PECVD deposition times. The PECVD technique with SiH4, associated with chemical treatment with primer based on silane methacrylate, is a solely chemical surface treatment capable of maintaining bonding between composite cement and HT zirconia.

HYDROGENATION OF SILICON, ALUMINUM AND CHLORINE AS CONSTITUENTS OF TARFAYA OIL SHALE (MOROCCO) AT 550°C AND 750°C

The formation of hydrogen chloride as well as silicon hydrides and aluminum hydrides called silanes and alanes respectively are formed when oil shale are thermally treated with hydrogen. These elements are part of the constituents of this oil shale. This work was carried out by a thermobalance (Red Croft) in the dynamic regime for thermal hydrogenation at 550°C and 750°C. The quantitative identification of the elements was done by X-ray diffraction using a dispersive method, a technique that is coupled to the scanning microscope. This work being the continuation of the one already carried out at a temperature of 550°C (A.Attaoui and M. Hafid: 2022), we have extended this to higher temperatures where we have decompositions in addition to kerogen as well as mineral matter. Studies comparing the thermal decomposition of oil shale and kerogen have shown that the mineral matter in oil shale provides surfaces capable of cracking high molecular weight products by thermal or catalytic mechanisms (A.K. Burnham, A. K and J.A.Happe: 1984). These studies indicate that reactions involving the cleavage of carbon-carbon bonds and carbon-hydrogen bonds on mineral surfaces (R.A.Regtop et al: 1985). These authors demonstrated that the carbonized residue in spent shale can increase the magnitude of secondary reactions.

Thermal reactivity of pyrrole and its methyl derivatives on silicon (111) hydride surfaces

To understand how steric and molecular geometry may influence silicon surface reactions, thermal grafting of pyrrole and its methyl derivatives, namely 2,4-Dimethylpyrrole and 2,5-dimethylpyrrole was performed on planar silicon (111) hydride surfaces to form ultrathin monolayer (<0.5 nm). The samples were then analyzed with detailed XPS and FTIR-ATR to elucidate the chemical profiles on the surfaces while AFM and contact angle measurements were taken to examine physical characteristics. Together with DFT calculations, we had shown the different geometry of pyrrole derivatives can alter the way surface bond were formed. From our analysis, Pyrrole and 2,4-Dimethylpyrrole was found to react via Si-N bonding while 2,5-Dimethylpyrrole may have been grafted via Si-C linkage. Furthermore, the close proximity of between silicon surface atom and the aromaticity of pyrrole in conjugation to methyl group had help to reduce oxidation effect of the surface during thermal reaction. These corroborations between structure and reactivity are considered to be highly important towards realization of stable sub-nanometer ultrathin organic monolayer grafts on silicon surface, especially in the context for advanced molecular electronics.

Porous silicon surface modification via a microwave-induced in situ cyclic disulfide (S-S) cleavage and Si-S bond formation

Porous silicon (pSi) materials have gained a great deal of attention from various research fields, and their surface-functionalization is one of the critical points for their applications. In this study, a new surface modification method of Si-H-terminated pSi materials via microwave-induced Si-S bond formation is disclosed. The silicon hydride (Si−H) functionality on the pSi surface could react with the 5-membered cyclic disulfide (S-S) compound (DL-α-lipoic acid in this study) by microwave-induced in situ S-S bond cleavage and Si-S bond formation. This surface chemistry is fast responsive (<10 min) and more efficient than other methods such as vortexing, heating stirring, or ultrasonication. The reaction maintains the primary porous structure of pSi materials including pSi wafer, pSi rugate filer, and pSi nanoparticles. An additional functional group such as carboxylic acid is demonstrated to be readily introducible on the pSi surface for further applications. Overall, this study has successfully demonstrated the porous silicon surface modification via a microwave-induced in situ cyclic disulfide (S-S) cleavage and Si-S bond formation.

INVESTIGATION OF SILICON-HYDRIDE NANODOTPROPERTIES USING DENSITY FUNCTIONAL THEORY

&#x0D; &#x0D; &#x0D; The work aims to elucidate the optical and structural properties of silicon hydride nanoclusters and its bulk via density functional calculations. The molecular geometry is fully optimized with the help of DFT method using Gaussian 09 and Gaussian View 05 Software. Bandgaps are calculated using two approaches; first one using HOMO-LUMO concept and the second one is extracted from UV-vis spectrum. The calculated bandgap of silicon hydride is 3.7 eV. XRD data has also been analyzed using VESTA software, which shows the presence of a silicon matrix that contains organized silicon clusters forming an amorphous silicon matrix. A comprehensive investigation of amorphous films by X-ray diffraction (XRD) shows that the strongest peak in XRD patterns occurs at approximately 30.95°. Using XRD data, average size of optimized silicon hydride nano-cluster has been found to be 158.5 nm. Apparently large value of the cluster size can be attributed to the partially amorphous nature of silicon hydride nanocluster. The partial amorphous nature of silicon hydride is further confirmed from the analysis of its Raman spectrum. An overestimation of size in this case is not ruled out. Raman spectrum is calculated to further confirm deviations in nano-crystalline behavior. We also investigate and reveal properties using IR-spectrum, UV-vis-spectrum, NMR spectrum, and HOMO-LUMO gap.&#x0D; &#x0D; &#x0D;

The Surface Potential of Zero Charge Controls the Kinetics of Diazonium Salts Electropolymerization

AbstractOne of the central fundamental properties of solid/liquid interfaces is the potential of zero charge (pzc), where no excess charge prevails at the electrode surface. Applying potential on either side of the pzc can control adsorption of molecules on surfaces and is paramount for any interfacial process. However, the impact of pzc on electrode processes has been only demonstrated for reactions involving the adsorption of inorganic ions and gases. Here, the direct relationship between the pzc and electropolymerization rate of a small organic molecule was reported. The electrochemical reduction of diazonium salts, which are the most commonly used molecules to form thin films of molecules on electrode surfaces, was tested. The kinetics of the surface reaction and the reduction potential in electrochemical measurements depended on the pzc of the surface following the order of gold&gt;platinum&gt;carbon&gt;indium‐tin‐oxide&gt;fluorine‐doped tin‐oxide&gt;silicon hydride. The immediate consequence of this finding was that the concentration of the diazonium salt molecules became critical in defining the electrochemical reduction mechanism. At higher concentrations, the mechanism was pzc‐controlled adsorption‐dominated inner‐sphere electron transfer whereas at lower concentrations, diffusion‐based outer‐sphere electron transfer dominated.

Spectroscopic review of hydrogenated, carbonated and oxygenated group IV alloys

Semiconductors based on group IV elements are widely used in the fields of micro-electronics, optics and photonics. The group IV alloys are processed using plasma enhanced chemical vapor deposition and its opto-electrical properties are a result of the material composition and structure. Infrared and Raman spectroscopy are complementary and powerful tools for providing these essential material characteristics. In this work, the vibrational modes present in hydrogenated, oxygenated and carbonated group IV alloys are investigated in a unique range of amorphous and nano-crystalline SiX≥0Ge1−X:H films and their alloys with C, O and Sn. Measurements are performed both post-deposition and following extended exposure to the ambient and de-ionized water. This comprehensive review is of value in the fields of material science and engineering as a single work of reference for group IV peak identification. Additionally, the effect of electrical screening, the influence of the dielectric medium on the peak frequency of a vibrational mode, is illustrated using the experimentally observed frequency shifts of X-O and X-H (X = C, Si, Ge) vibrational modes. All experimentally observed center frequencies of silicon hydride stretching modes in silicon solids and corresponding silicon-hydride configurations are identified using a straightforward Lorentz-Lorenz model approximation and considering all potential hydrogenated volume deficiencies within a tetrahedrally coordinated amorphous and nanocrystalline lattice. It shows that the stretching mode signature can reveal detailed information on the volume deficiencies in IV-valence alloys.