SiOH Species Research Articles

A comparative study of fibrous silica-based catalysts for improving methane production via CO2 methanation

The process of utilizing the greenhouse gas carbon dioxide (CO2) is crucial in addressing and reducing the impact of climate change. The CO2 methanation process, also known as the Sabatier reaction, is considered one of the appealing approaches since it provides synthetic natural gas (SNG), fulfilling the present needs. However, the CO2 methanation reaction demands an exceptionally effective catalyst capable of surpassing the energy barrier associated with eight proton-electron transfers from H2 molecules. Herein, the application of fibrous silica nanospheres along with the fibrous modification of mesostructured silica nanoparticles (MSN) towards CO2 methanation, called the Centre of Hydrogen energy silica (CHE-Si) and CHE-SM was reported. Both catalysts were successfully synthesized by utilizing micro-emulsion techniques and subsequently were characterized with x-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and N2 adsorption-desorption. FTIR results revealed that CHE-SM possessed superior Si-OH and Si-O species than CHE-Si despite displaying low surface area and pore volume. Consequently, CHE-SM achieved above 50% CO2 conversion and CH4 yield at 500 °C while CHE-Si exhibited lower performance. This discrepancy in catalytic performance was due to the fact that CHE-SM was comprised of more active sites that could adsorb and dissociate CO2 and H2 reactants.

MD simulation of chemically enhanced polishing of 6H-SiC in aqueous H2O2

Chemical enhanced polishing (CEP) is a widely employed final process for achieving precise surface shaping and planarization of semiconductor wafers. However, determining the chemical effect involved in material removal through experimental means is extremely challenging. In this study, we conducted reactive force field (ReaxFF) molecular dynamics (MD) simulations to gain insight into the chemical effects of CEP using an aqueous hydrogen peroxide (H2O2) diamond suspension as a polishing medium for 6H-SiC single crystals. The inclusion of aqueous H2O2 resulted in the formation of SiOH and COH species, which are comparatively easier to remove through mechanical abrasion. Furthermore, an increase in H2O2 concentration was found to enhance the material removal. The MD simulations also revealed that the chemical effects on the Si-face of 6H-SiC were more pronounced than those on the C-face due to the generation of a greater number of SiO species and the favourable atomic structure of the Si-face for chemical removal. The results showed that the material remove rate on the Si-face is greater than that on the C-face during polishing, aligning with the findings from MD simulation. Furthermore, a systematic experimental study was carried out to examine the influence of various conditions on material removal rate and surface quality in both polishing and lapping processes.

Low temperature oxidation of amorphous silicon nanoparticles

The oxide layer is important for the processing and applications of silicon nanoparticles as it provides chemical stability to the material. Herein, the thermal oxidation of sub-10-nm crystalline and amorphous silicon particles in dry air is investigated with nonisothermal kinetic analysis including Kissinger and Flynn-Wall-Ozawa methods at various heating rates. The results indicate that amorphous silicon nanoparticles have a considerably lower activation energy for oxidation (98 kJ/mol) compared to their crystalline counterparts (182 kJ/mol). In situ heating diffuse reflectance infrared Fourier transform spectroscopy was employed to monitor the evolution of surface species of Si nanoparticles during oxidation. The results suggest that backbond oxidation of higher hydrides contribute to the low onset temperature for oxidation of amorphous silicon nanoparticles. Besides, surface ${\mathrm{O}}_{3}\mathrm{Si}\text{\ensuremath{-}}\mathrm{H}$ and Si-OH species likely prevent the formation of a dense silicon oxide layer, resulting in the low temperature oxidation behavior of amorphous silicon nanoparticles. These results provide insight into kinetics and chemistry of amorphous silicon oxidation in the thin film regime.

Elucidating the Nature of the External Acid Sites of ZSM‐5 Zeolites Using NMR Probe Molecules

The identification of acid and nonacid species at the external surface of zeolites remains a major challenge, in contrast to the extensively-studied internal acid sites. Here, it is shown that the synthesis of zeolite ZSM-5 samples with distinct particle sizes, combined with solid-state NMR and computational studies of trimethylphosphine oxide (TMPO) adsorption, provides insight into the chemical species on the external surface of the zeolite crystals. 1 H-31 P HETCOR NMR spectra of TMPO-loaded zeolites exhibit a broad correlation peak at δP ∼35-55 ppm and δH ∼5-12 ppm assigned to external SiOH species. Pore-mouth Brønsted acid sites exhibit 31 P and 1 H NMR resonances and adsorption energies close to those reported for internal acid sites interacting with TMPO. The presence of an external tricoordinate Al-Lewis site interacting strongly with TMPO is suggested, resulting in 31 P resonances that overlap with the peaks usually ascribed to the interaction of TMPO with Brønsted sites.

Dehydrogenation of propane in the presence of CO2 over GaN/SiO2 catalysts: Relationship between the type of SiO2 and the activity

• Dehydrogenation of propane in the presence of CO 2 over GaN-supported catalysts. • The pore structures affected the catalytic behavior remarkably. • The 3D interconnected mesopores of KIT-6 are favorable to exclude the mass transfer disturbance. • The Si–OH species in Silicalite-1 is favorable to expose active sites of the Si–O–GaN species. • Both active sites and pore structures affect the apparent activation energy of the reaction. As a class of key building blocks in the chemical industry, propylene is mainly obtained from the by-product of naphtha steam cracking and refinery fluid catalytic cracking. Dehydrogenation of propane in the presence of CO 2 (CO 2 -ODHP), as an on-purpose process for producing propylene, is one of the most potential alternative routes. In the present work, a series of mesoporous materials with different pore structures, namely SBA-15, MCF, KIT-6, and microporous materials of Silicalite-1 were synthesized via the hydrothermal method. These supports were further impregnated with 5 wt% GaN and applied in the CO 2 -ODHP. The effects of the support, especially the pore structure, acidic and basic properties, Si–OH species, redox characteristic, etc . on catalytic performance of GaN/SiO 2 were studied. The 5GaN/Silicalite-1 catalyst (5 means 5 wt%) with a microporous structure, was vigorously disturbed by the extra-granular and intra-granular diffusion limitations, resulting in a low propylene selectivity. However, the Si–OH species in the Silicalite-1 could react with GaN to create more active sites of the Si–O–GaN species, resulting in the improvement of the propane conversion. The 3D interconnected mesopores of the KIT-6 are favorable to eliminate the extra-granular diffusion limitation, and no intra-granular diffusion limitation exists during the reaction. The combination of active sites and mass transfer properties of the catalysts could reduce the apparent activation energy of the reaction, offering an excellent catalytic activity. The present work gains insight into how to reasonably design an efficient GaN-based catalyst in the CO 2 -ODHP reaction, especially with microporous/mesoporous structures.

How dissociated fragments of multiatomic molecules saturate all active surface sites—H2O adsorption on the Si(100) surface

A fundamental question for the adsorption of any gas molecule on surfaces is its saturation coverage, whose value can provide a comprehensive examination for the adsorption mechanisms, dynamic and kinetic processes involved in the adsorption processes. This investigation utilizes scanning tunneling microscopy to visualize the H2O adsorption processes on the Si(100) surface with a sub-monolayers (<0.05 ML) of chemically-reactive dangling bonds remaining after exposure to (1) a hydrogen atomic beam, (2) H2O, and (3) Cl2 gases at room temperature. In all three cases, each of the remaining isolated single dangling bonds (sDB) adsorb and is passivated by either of the two dissociation fragments, the H or OH radical, to form a surface Si–H and Si–OH species. A new adsorption mechanism, termed ‘dissociative and asynchronous chemisorption’, is proposed for the observation presented herein. Upon approaching a sDB site, the H2O molecule breaks apart into two fragments. One is chemisorbed to the sDB. The other attaches to the same or the neighboring passivated dimer to form a transition state of surface diffusion, which then diffuses on the mostly passivated surface and is eventually chemisorbed to another reactive site. In other words, the chemisorption reactions of the two fragments after dissociation occur at different and uncorrelated time and places. This adsorption mechanism suggests that a diffusion transition state can be an adsorption product in the first step of the dissociative adsorption processes.

Functional Janus-SiO2 Nanoparticles Prepared by a Novel "Cut the Gordian Knot" Method and Their Potential Application for Enhanced Oil Recovery.

Currently available methods (e.g., interfacial protection and phase separation) for preparing Janus nanoparticles are often complex and expensive. Furthermore, the preparation of Janus nanoparticles with a particle size below 10 nm is challenging. In this work, we combine an in situ surface-modification route with a chemical etching route to establish a novel "cut the Gordian knot" method for the preparation of functional Janus-SiO2 nanoparticles. Hydrophobic SiO2 nanoparticles with a three-dimensional network structure prepared via an in situ surface-modification route were dispersed in NaOH solution containing surfactant or ethanol to enable corrosion close to the modifier-nanoparticle interface with a relatively low content of surface modifiers. Thus, amphipathic Janus-SiO2 nanoparticles with a hydrophilic surface containing Si-OH species and a hydrophobic surface containing -CH3 fragments were generated. The as-prepared Janus-SiO2 nanoparticles with a size of 4-9 nm and a specific surface area of up to 612.9 m2/g can be easily dispersed in water, and they also can transfer from the water phase to the oil phase by tuning the surface polarity. Moreover, they can be tuned to achieve bidirectional regulation of surface wettability plus a reduction of the oil/water interface tension. Hence, a significant reduction (by 33∼50%) of water injection pressure and an enhanced oil recovery (EOR) (by 21.1% ∼ 26.6%) can be achieved. Apart from that, Janus-SiO2 nanoparticles are able to increase the viscosity of partially hydrolyzed polyacrylamide by 282.9% and significantly decrease its viscosity loss ratio in brine, causing an EOR of about 36.6%. With simple, low-cost, and scalable procedures, the following approach could be well applicable to fabricating Janus-SiO2 nanoparticles with a high potential for augmented water injection as well as EOR of low-permeability reservoirs.

Structure of water in hybrid cellulose acetate-silica ultrafiltration membranes and permeation properties

Hybrid cellulose acetate (CA) silica (SiO2) (CA/SiO2) membranes were synthesized by promoting the in situ condensation between silanols from the SiO2 precursor and the COH or acetate groups from the CA polymer.For all the CA/SiO2 membranes, the ATR-FTIR peak assigned to (SiOC) proves the hybrid condensation reaction and confirms the synthesis of monophasic hybrid membranes.ATR-FTIR shows the presence of uncondensed highly reactive SiOH species, in membranes with silica contents higher than 20 mol%. Together with RMN studies, results show molecular water strongly hydrogen-bonded with SiOH groups, yielding a drastic decrease in the membrane hydraulic permeability, from 57 to 10 kg/h/m2/bar.The incorporation of 5 and 10 mol% of silica increased the hydraulic permeability from 32 to 82 kg/h/m2/bar when compared to the CA membrane.

Revealing long- and short-range structural modifications within phosphorus-treated HZSM-5 zeolites by atom probe tomography, nuclear magnetic resonance and powder X-ray diffraction.

The average and the local structure of phosphorus-treated HZSM-5 zeolites were investigated by means of atom probe tomography, powder X-ray diffraction (at ambient and cryogenic temperatures) and 1H, 29Si, 27Al, and 31P magic angle spinning (MAS) solid state nuclear magnetic resonance (NMR) spectroscopy. Phosphatation to yield a product with P/Al ≤ 1 followed by thermal treatment leads to breaking of the Si-OH-Al bridging groups, and subsequent partial dealumination of the zeolite framework, as shown by the contraction of the orthorhombic unit-cell volume and by the loss of tetrahedral framework Al, as observed in the 27Al Multiple Quantum (MQ) MAS NMR spectrum. Most of the framework Al is present in an electronic environment distorted by the presence of phosphorus and appears not to be involved in classic Si-OH-Al Brønsted acid sites. The 31P MAS NMR signals indicate that phosphorus interacts with the zeolitic framework to locally form silico-aluminophosphate (SAPO) domains and the presence of a new kind of acidic site was confirmed by the resonance at ∼8.6 ppm in the 1H MAS NMR spectra, attributed to P-OH groups. Increasing the phosphorus loading (P/Al ≫ 1) promotes further dealumination of the framework and cross-dehydroxylation between P-OH and Si-OH species, leading to the formation of a crystalline silicon orthophosphate phase. With decreasing Al content, the monoclinic HZSM-5 structure becomes preferred, especially at 85 K where the strain relaxation is higher. However, the presence of a higher amount of silicophosphate impurities hinders the low-temperature strain release of the framework, indicating that some of these species are localized in the zeolite pores and contribute to the strain build up.

Carbon ceramic electrodes modified with mixed oxides SiO2/SnO2 for determination of levofloxacin

The preparation of a carbon ceramic electrode modified with SnO2 (CCE/SnO2) using tin dibutyl diacetate as precursor was optimized by a 23 factorial design. The factors analyzed were catalyst (HCl), graphite/organic precursor ratio, and inorganic precursor (dibutyltin diacetate). The statistical treatment of the data showed that only the second-order interaction effect, catalyst × inorganic precursor, was significant at 95% confidence level, for the electrochemical response of the system. The obtained material was characterized by scanning electron microscopy (MEV), X-ray diffraction (XRD), RAMAN spectroscopy, XPS spectra, and voltammetric techniques. From the XPS spectra, it was confirmed the formation of the Si–O–Sn bond by the shift in the binding energy values referred to Sn 3d3/2 due to the interaction of Sn with SiOH species. The incorporation of SnO2 provided an increment of the electrode response for levofloxacin, with Ipa = 147.0 μA for the ECC and Ipa = 228.8 μA for ECC/SnO2, indicating that SnO2 when incorporated into the silica network enhances the electron transfer process. Under the optimized working conditions, the peak current increased linearly with the levofloxacin concentration in the range from 6.21×10−5 to 6.97×10−4 mol L−1 with quantification and detection limits of 3.80×10−5 mol L−1 (14.07 mg L−1) and 1.13×10−5 mol L−1 (4.18 mg L−1), respectively.

Effects of fictive temperature on the leaching of soda lime silica glass surfaces

AbstractThe fictive temperature of glass characterizes the glass network structure and its thermal history, and thereby can influence ion and water transport in the glass surface. In this study, IR specular reflectance (SR), refractive index, and density measurements were used to characterize and confirm the effects of glass sample processing, especially the fictive temperature/thermal‐history variations. The subsequent acid leaching of these glasses created leached surface layers due to interdiffusion and reaction of hydrous species in the surface; the hydrogen depth profiles obtained with secondary ion mass spectrometry (SIMS) confirmed enhanced leaching with increasing fictive temperature. Attenuated total reflectance (ATR) in the mid‐ and near‐IR indicated increases in both SiOH and H2O species with increasing fictive temperature. The relative intensities and shapes of the ATR peaks were found to vary between the samples suggesting that speciation of the hydrous reaction products (eg, strong and weakly hydrogen‐bonded OH) is also influenced by the original fictive temperature of the glass, but could not be quantitatively determined.

Control of the Surface Chemistry of Magnetron-Deposited Silicon Nitride Etched with Various Wet Treatments

Silicon nitride is a common material in the microelectronic industry, thanks to its dielectric, chemical and mechanical properties. However, when exposed to atmosphere, the silicon nitride layer tends to oxidize. This work presents several efficient ways to remove this native oxide layer while controlling the resulting surface chemistry. Achieving such a control may provide a reliable starting point for further surface functionalization by organic molecules. The silicon nitride thin films are deposited by magnetron sputtering. The silicon nitride stoichiometry can be tuned by varying the gas fluxes (Ar, N2) during deposition. Three wet treatments are studied and optimized: hydrofluoric acid (HF), ammonium fluoride (NH4F) and potassium hydroxide (KOH). The treatment efficiency is controlled by X-ray Photoelectron Spectroscopy measurements (XPS). The surface chemistry is investigated by combining Attenuated Total Reflection InfraRed (ATR-IR) and XPS measurements. All of the three chemical treatments yield the removal of the native oxide, albeit at different rates. HF solution is an efficient and fast etching treatment of silicon nitride. On the resulting surface, fluorine is detected by XPS, suggesting the presence of Si-F bonds. No Si-H bonds are detected on the etched surface by ATR-IR, in agreement with the literature results. NH4F solution is as efficient as HF in etching the silicon nitride surface, although much slower. This also leads to Si-F bonds, but in a lesser amount than after a HF treatment. KOH can also etch the native oxide of the silicon nitride layer. In this case, the resulting surface contains more oxygen than with the two previous solutions, a likely fingerprint of the presence of surface Si-OH species. Interestingly, the etching rate of the bulk silicon nitride appears much reduced upon etching with KOH as compared to HF. The formation of Si-H bonds can be forced thanks to a H2plasma treatment performed after the wet native oxide stripping. As shown in the figure, a broad SiH stretching vibration builds up in the infrared spectra upon submitting the silicon nitride film to such a plasma treatment at room temperature. The detailed analysis of XPS signals of samples submitted to various treatment durations shows that the initial surface Si-F bonds are not broken by the plasma, but that the silicon nitride film is progressively etched during the treatment. The film roughens during its dry etching, accounting for the large increase of the SiH signal. An important parameter we also investigated is the silicon-nitrogen ratio. The chemistry of the etched surface is highly dependent on this ratio. As shown in the figure, with a silicon-rich silicon nitride layer, a HF treatment leads to the formation of some Si-H bonds on surface. Figure 1

Analysis of Water and Hydroxyl Species in Soda Lime Glass Surfaces Using Attenuated Total Reflection (ATR)‐IR Spectroscopy

ATR‐IR spectroscopy is a useful and convenient method for evaluation of local structure and concentration of water and hydroxyl species in glass because it can be more surface sensitive than reflection or transmission IR analysis. In this work, a semiquantitative analysis of the ATR spectra of OH groups and interstitial molecular water species in glass surfaces after various surface treatments is presented. Both hydroxyl groups and interstitial molecular water exist in the hydrated surfaces but the relative water speciation varies with surface treatment. The SiOH and H2O species in the glass surface showed a wide range of hydrogen bonding interactions and their distributions varied with the SO2, polishing, acid leaching, thermal tempering, and chemical strengthening treatments. SIMS analysis of the hydrogen concentration — depth profiles for the acid‐leached samples was used to provide independent information to validate and quantify the ATR signal.

Sexithiophene ultrathin films on passivated Si(0 0 1) surfaces: Growth and electronic structure

We investigated the electronic states of α-sexithiophene (α-6T) on three passivated Si(001) surfaces, oxidized Si(001), water-adsorbed Si(001), and ethylene-adsorbed Si(001), by means of high-resolution photoelectron spectroscopy using synchrotron radiation. The main purpose of the present study was to identify the origin of the marked difference in molecular orientation on these substrates. We found that the interaction of α-6T molecules with Si–OH species should be the dominant reason for the in-plane orientation. On the other hand, the predominance of the in-plane orientation on ethylene-adsorbed Si(001) could not be simply explained by the chemical interaction but was ascribed to the geometrical effect of the surface corrugation. We investigated changes in the core levels upon α-6T deposition on passivated Si(001) surfaces and interpreted the results based on the charge transfer scheme.

ChemInform Abstract: Crossed and Linked Histories of Tetrapyrrolic Macrocycles and Their Use for Engineering Pores Within Sol—Gel Matrices

AbstractReview: 454 refs.

High CO2Capture in Sodium Metasilicate (Na2SiO3) at Low Temperatures (30–60 °C) through the CO2–H2O Chemisorption Process

Na2SiO3 was synthesized by two different routes: solid-state reaction and combustion method. It was determined that Na2SiO3 sample prepared by the combustion method presented a surface area 3 times larger than the solid-state reaction sample. Different water vapor sorption experiments were performed using N2 or CO2 as carrier gases. If N2 was used as carrier gas, it was evidenced that Na2SiO3 is able to trap water in two different ways: physically and chemically producing Na–OH and Si–OH species. Moreover, when CO2 was used, Na2SiO3 continued trapping water, as in the previous case, but in this case CO2 was trapped, forming Na2CO3 and NaHCO3 phases. Additionally, as it could be expected, the surface area resulted to be a very important factor controlling the CO2 capture efficiency. The Na2SiO3 sample prepared by the combustion method captured up to 8.5 mmol of CO2 per gram of ceramic (efficiency of 52%), a considerably high CO2 amount among different materials. Therefore, the presence of water vapor stron...

Modes of Interaction of Simazine with the Surface of Model Amorphous Silicas in Water

Simazine (2-chloro-4,6-bis(ethylamino)-s-triazine) was adsorbed from aqueous solutions on three types of amorphous silica, one commercial nonporous and two sol–gel with different porosity. Adsorption takes place on both types of solids in a narrow pH interval around 5.5. This fact, pH changes along adsorption, and IR spectroscopic data concerning dried samples provide evidence that adsorption involves proton transfer from acidic SiOH species to N atoms at ethylamino chains, those at the ring being practically not basic. Two adsorbate species are involved with markedly different interaction enthalpy, causing the presence of two regions in the pseudoisotherms, one irreversibly held, the other partially reversible. Possibilities for the occurrence of two species are discussed. The most likely explanation seems to be a two steps process, in which first a protonated molecule is formed, onto which a second molecule may anchor so forming a dimer, held together by either sharing of the positive charge or hydrophobic interactions. The available surface appears to have basically the same properties in all three cases. Microporosity, however, introduces diffusional constraints and limits the extent of surface available to adsorption.

Crossed and linked histories of tetrapyrrolic macrocycles and their use for engineering pores within sol-gel matrices.

The crossed and linked histories of tetrapyrrolic macrocycles, interwoven with new research discoveries, suggest that Nature has found in these structures a way to ensure the continuity of life. For diverse applications porphyrins or phthalocyanines must be trapped inside solid networks, but due to their nature, these compounds cannot be introduced by thermal diffusion; the sol-gel method makes possible this insertion through a soft chemical process. The methodologies for trapping or bonding macrocycles inside pristine or organo-modified silica or inside ZrO2 xerogels were developed by using phthalocyanines and porphyrins as molecular probes. The sizes of the pores formed depend on the structure, the cation nature, and the identities and positions of peripheral substituents of the macrocycle. The interactions of the macrocyclic molecule and surface Si-OH groups inhibit the efficient displaying of the macrocycle properties and to avoid this undesirable event, strategies such as situating the macrocycle far from the pore walls or to exchange the Si-OH species by alkyl or aryl groups have been proposed. Spectroscopic properties are better preserved when long unions are established between the macrocycle and the pore walls, or when oligomeric macrocyclic species are trapped inside each pore. When macrocycles are trapped inside organo-modified silica, their properties result similar to those displayed in solution and their intensities depend on the length of the alkyl chain attached to the matrix. These results support the prospect of tuning up the pore size, surface area, and polarity inside the pore cavities in order to prepare efficient catalytic, optical, sensoring, and medical systems. The most important feature is that research would confirm again that tetrapyrrolic macrocycles can help in the development of the authentic pore engineering in materials science.

General Intercalation of Poly(oxyalkylene)−Amidoacids for Anionic and Cationic Layered Clays

The same poly(oxyalkylene)−amidoacids (POA−amidoacid) were incorporated into two different types of ionic clays, anionic layered-double-hydroxides (Mg−Al LDH), and cationic montmorillonite (MMT). Conventionally, the intercalation is an ionic exchange reaction, i.e. anionic organic salts for LDH and cationic salts for MMT. The successful intercalation using the neutral species of POA−amidoacid implies the existence of a new mechanism for clay intercalation. We prepared the POA−amidoacid from the reaction of maleic anhydride and poly(oxyalkylene)−diamine (POA−amine) with different hydrophobic and hydrophilic POA-backbones of 600−4200 molecular weight. The intercalation has resulted in the expansion of the clay basal spacing from 7.8 to 63 Å for LDH and from 12.4 to 51 Å for MMT, with a high Bragg’s regularity of XRD analyses. It appears that the driving force for the intercalation and organic incorporation into the silicate interlayer galleries is dissimilar to the counterion exchange but involving noncovalent bonding between amidoacid functionalities and ≡SiOH species in clay. The intercalation without ionic exchange reaction is effective for generating new clay hybrids with thermal responsiveness in water.

Vapor-phase silanization of oxidized porous silicon for stabilizing composition and photoluminescence

A vapor-phase deposition approach to the silanization modification of the oxidized porous silicon (PSi) surface using (CH3O)3Si(CH2)3NH2 has been exploited. Standard clean (SC)-1 (NH3H2O/H2O2/H2O, 1:1:5,v/v) and SC-2 [HCl/H2O2/H2O (1:1:6,v/v)] solutions are utilized for the first time to obtain oxidized PSi and have been proved to be a very efficient combination for creating Si–OH species on the PSi surface. After the modification, an amine group terminated surface was successfully created as demonstrated by the contact angle with water, the x-ray photoelectron spectroscopy, and the Fourier transform infrared (FTIR) spectra. The influences of the surface derivatives on the composition stability of the PSi layer and on its photoluminescence properties were investigated by means of FTIR spectra, photoluminescence spectra, and time-resolved photoluminescence measurements.