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This study examines a boreal peatland (the Sagnes peatland, Fanay, Limousin, France) with a depth of 1 m. This peatland is currently in the late stages of organic deposition, as evidenced by the growth of Carex species, along with Sphagnum mosses, in the uppermost level. To gain molecular insights, we conducted an analysis of the lignin and polyphenolic counterparts using HMDS (hexamethyldisilazane) thermochemolysis, enabling the identification of lignin degradation proxies. The goal was to develop characteristic indicators for the state of lignin degradation based on the relative distribution of lignin phenols, measured by gas chromatography coupled with mass spectrometry (GC-MS) after the HMDS thermochemolysis. For that purpose, the singular contribution of the 11 aromatic moieties yielded, along with SGC (sum of lignin moieties) and the most lignin degradation proxies, were applied. It has been shown that HMDS thermochemolysis exhibited the capacity to reveal oxidized and degraded lignin fractions, following the increasing trend yielded for most moieties and SGC proxy, in the mesotelm and catotelm layers. In addition, the C/G (Cinnamyl/Guaiacyl) and S/G (Syringyl/Guaiacyl) ratios showed their highest input in the upper half of the core. This bias in the aforementioned ratios could indicate that HMDS thermochemolysis is to be applied for geological samples, where low G-compounds exist. For the sake of validating HMDS thermochemolysis' application, Principal Component Analysis (PCA) was then applied to the molecular fingerprint. For ratios and proxies of aromatic moieties of HMDS thermochemolysis, the PCA approach exhibited a higher contribution (79%). This indicates the efficiency of these ratios in describing the molecular fingerprint of peat depth records. In addition, a higher separation between the contributions of the investigated variables (molecular proxies) along the first two PCs was noticed. In other words, the variables that showed a high contribution towards PC1 exhibited a low contribution towards PC2, and vice versa. These findings indicate the high reliance of applying the ratios and proxies of HMDS thermochemolysis. [ABSTRACT FROM AUTHOR]

SiBCN films are synthesized by plasma-enhanced chemical vapor deposition at a reduced pressure and 500-600 °C. Organoelement silicon and boron compounds are selected as precursors, namely, hexamethyldisilazane HN(SiMe3)2 and triethylaminoborane Et3N·BH3 that were not used previously in the synthesis of SiBCN films. Vapor flows of initial compounds and additional gas (ammonia) were separately supplied to the reactor without premixing. The chemical bonding structure, elemental composition, surface morphology, and film deposition rate are studied by FTIR, XPS, wave dispersive X-ray spectroscopy, SEM, and Raman spectroscopy techniques. The surface morphology analysis of the samples shows that the films are smooth, homogeneous, and uniform without features. Variation of precursor concentrations in the initial mixture allows changes in the film composition in a wide range. The boron concentration in four-component coatings reaches 45 at.%. The study of chemical bonding structures of the films reveals the occurrence of Si–C, Si–N, B–N, C–H bonds along with the hybrid BCnN3–n bond. [ABSTRACT FROM AUTHOR]

Pollen is becoming an increasingly important subject for molecular researchers in genetic engineering, plant breeding, and environmental monitoring. To broaden the scope of these studies, it is essential to develop accessible methods for scientists who are not specialized in palynology. The article presents a simplified technical procedure for preparing pollen grains for scanning electron microscopy (SEM). The protocol is convenient for any molecular laboratory due to its small set of reagents, ease of execution, low cost, does not require special equipment, and takes only one hour to complete. The high penetrating ability of formaldehyde and the final delicate dehydration using hexamethyldisilazane (HMDS) instead of critical point drying allow for sufficient preservation of the architecture of the aperture, which is considered a gateway for the passage of biomolecules. The method was successfully applied to pollen grains of representatives of dicotyledons (beetroot, petunia, radish, tomato and tobacco) and monocotyledons (lily, onion, corn, rye and wheat). Species studied included insect-pollinated (entomophilous) and wind-pollinated (anemophilous) species. A comparative analysis of the sizes of fresh living pollen grains under a light microscope and those prepared for SEM showed some shrinkage. Quantitative analysis of the degree of pollen grain shrinkage showed that this process depends on the initial shape of dry pollen grains, and the number and structure of apertures. The results support the theoretical model of the folding/unfolding pathways of pollen grains. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the modification of glass surfaces by the synergistic combination of cold plasma and chemical surface modification techniques. Glass surface hydrophobicity was obtained as a result of various plasma and deposition operational conditions. The mechanisms governing the hydrophobization process were also studied. Glass plates were activated with plasma using different gases (oxygen and argon) at different treatment times, ranging from 30 to 1800 s. Then, the plasma-treated surfaces were exposed to hexamethyldisilazane vapors at different temperatures, i.e., 25, 60, and 100 °C. Complete characterization, including contact angle measurements, surface free energy calculations, 3D profilometry, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy, was accomplished. It was found that the extent of the hydrophobicity effect depends on both the plasma pre-treatment and the specific conditions of the hexamethyldisilazane deposition process. Plasma activation led to the formation of active sites on the glass surface, which promoted the adsorption and reaction of hexamethyldisilazane species, thereby inducing surface chemical modification. Longer plasma pre-treatment resulted in stronger modification on the glass surface, resulting in changes in the surface roughness. The largest water contact angle of ≈100° was obtained for the surface activated by argon plasma for 1800 s and exposed to hexamethyldisilazane vapors at 25 °C. The changes in the surface properties were caused by the introduction of the hydrophobic trimethylsilyl groups onto the glass surface as well as roughness development. [ABSTRACT FROM AUTHOR]

This paper presents a amidinyl transfer reagent for the synthesis of nitrogen‐containing compounds, wherein N,N‐dimethylformamide is used as the C1 source to react with hexamethyldisilazane, generating the N,N‐dimethylformimidamide intermediate. This intermediate is then reacted with amines to induce amidinyl transfer. This protocol can be applied for the synthesis of N‐formamide, benzimidazole and quinazolinone, for which amine derivatives used as substrates under optimized conditions. The advantages of this method are its operational simplicity, high efficiency, structural diversity in products with favorable yields, and applicability in gram‐scale operations. [ABSTRACT FROM AUTHOR]

This study reports the surface coating of fluorine-free hexamethyldisilazane (HMDS) on non-porous silica particles (SPs) and mesoporous silica particles (MSPs), with nanopores arranged in the straight channels, and compares the degree of superhydrophobicity by coating them on biodegradable PLA film by gravure process. The particle sizes of SPs and MSPs are 50 nm and 800 nm, and the amount of HMDS grafted onto SPs and MSPs is 0.5% and 9.5%, respectively. The superhydrophobicity of these particles is confirmed by the measurement of water contact angle (WCA) as a function of HMDS concentration for SPs and MSPs from 0 to 1.6 M, respectively. The WCA of HMDS@SPs and HMDS@MSPs grafted with 1.6 M of HMDS is 152° and 151° (WCA of unmodified SPs and MSPs is 13.85° and 27.65°). To apply superhydrophobic PLA film coating, 5 wt% of HMDS@SPs and HMDS@MSPs were mixed with gravure solution and then coated on biodegradable polylactic acid (PLA) film. The results showed that the WCA of PLA film with HMDS@SPs and HMDS@MSPs were 98.40° and 152.31°, respectively. This remarkable difference in WCA is due to the dissociation of HMDS molecules grafted on the surface of SPs and MSPs, which are easily separated by the gravure solvent. For MSPs materials composed of many nanopores, the dissociated HMDS molecules are initially released into the solution but are retained within the nanopores. Therefore, the residual amount of HMDS molecules dissociated by the gravure solution is much higher in HMDS@MSPs than in HMDS@SPs.

Pollen is becoming an increasingly important subject for molecular researchers in genetic engineering, plant breeding, and environmental monitoring. To broaden the scope of these studies, it is essential to develop accessible methods for scientists who are not specialized in palynology. The article presents a simplified technical procedure for preparing pollen grains for scanning electron microscopy (SEM). The protocol is convenient for any molecular laboratory due to its small set of reagents, ease of execution, low cost, does not require special equipment, and takes only one hour to complete. The high penetrating ability of formaldehyde and the final delicate dehydration using hexamethyldisilazane (HMDS) instead of critical point drying allow for sufficient preservation of the architecture of the aperture, which is considered a gateway for the passage of biomolecules. The method was successfully applied to pollen grains of representatives of dicotyledons (beetroot, petunia, radish, tomato and tobacco) and monocotyledons (lily, onion, corn, rye and wheat). Species studied included insect-pollinated (entomophilous) and wind-pollinated (anemophilous) species. A comparative analysis of the sizes of fresh living pollen grains under a light microscope and those prepared for SEM showed some shrinkage. Quantitative analysis of the degree of pollen grain shrinkage showed that this process depends on the initial shape of dry pollen grains, and the number and structure of apertures. The results support the theoretical model of the folding/unfolding pathways of pollen grains.

SiO 2 aerogels have an inherent optical transparency, but there is a hydrophilic defect and high transparency and hydrophobicity seem impossible to achieve at the same time. In order to realize the practical application value of highly transparent aerogel, our study used hexamethyldisilazane (HMDS) as the hydrophobic agent to improve the hydrophobicity of the prepared highly transparent SiO 2 aerogels. We investigated the effects of HMDS concentration and modification duration on SiO 2 aerogels through the chemical liquid method. Results showed that the concentration and modification time of HMDS have no significant effect on the microstructure and properties of highly transparent SiO 2 aerogels, which maintained uniform microstructure, low thermal conductivity, good thermal stability and contact angles were all above 136°. Hydrophobic and highly transparent SiO 2 aerogels hold great potential for use as observation windows in the aerospace applications, building thermal management, and transparent coating. [ABSTRACT FROM AUTHOR]

Trimethylsilyl esters of P(III) acids were synthesized in high yields (89–94%) by the reaction of hydrophosphoryl compounds with hexamethyldisilazane at 20°C in the presence of ZnSO4 and diethylamine. The reaction is complete in 4 h, it does not require specially prepared solvents or an inert atmosphere, and can be proposed as a new synthetically useful and easy-to-perform method for the synthesis of trimethylsilyl esters of P(III) acids. [ABSTRACT FROM AUTHOR]

The collagen network is the highly organized backbone of articular cartilage providing tissue tensile stiffness and restricting proteoglycan bleaching out of the tissue. Osteoarthritis (OA) diminishes proper collagen network adaptation. Our aim was to provide quantitative three-dimensional (3D) information of the cartilage collagen network adaptation in early osteoarthritis using high resolution micro-computed tomography (µCT)-imaging. Osteochondral samples from the femoral condyles were collected from healthy (N = 8, both legs) and experimental OA rabbit model with anterior cruciate ligament transection (N = 14, single leg). Samples were processed for cartilage µCT-imaging and histological evaluation with polarized light microscopy (PLM). Structure tensor analysis was used to analyse the collagen fibre orientation and anisotropy of the µCT-images, and PLM was used as a validation for structural changes. Depth-wise comparison of collagen fibre orientation acquired with µCT-imaging and PLM correlated well, but the values obtained with PLM were systematically greater than those measured with µCT-imaging. Structure tensor analysis allowed for 3D quantification of collagen network anisotropy. Finally, µCT-imaging revealed only minor differences between the control and experimental groups. [ABSTRACT FROM AUTHOR]

Hexamethyldisilazane (HMDS) has been widely used in photolithography and coating process, film preparation, electrochemistry, organic synthesis and other fields. The research progress of HMDS in organic synthesis was reviewed, and its development trend was predicted. [ABSTRACT FROM AUTHOR]

The one-pot synthesis of N-substituted α,β-dehydrotyrosyl dipeptides was carried out by the azlactone method. The target dipeptides were obtained in good yields (53–79%). From the latter, 2,3,5-trisubstituted 4-imidazolones were obtained using 1,1,1,3,3,3-hexamethyldisilazane as a dehydrating agent. It was found that in the case of β-alanine-containing peptides, abstraction of the methyl ester of acrylic acid and the formation of 2,5-disubstituted 4-imidazoline were observed. Antiradical and anticholinesterase properties of the synthesized compounds were studied. Docking analysis was carried out for both some dipeptides and imidazole-4-ones. [ABSTRACT FROM AUTHOR]

Ambient pressure drying (APD) can prospectively reduce the costs of aerogel fabrication and processing. APD relies solely on preventing shrinkage or making it reversible. The latter, i.e., the aerogel re-expansion after drying (so-called springback effect—SBE), needs to be controlled for reproducible aerogel fabrication by APD. This can be achieved by an appropriate surface functionalization of aerogel materials (e.g., SiO2). This work addresses the fabrication of monolithic SiO2 aerogels and xerogels by APD. The effect of several silylation agents, i.e., trimethylchlorosilane, triethylchlorosilane, and hexamethyldisilazane on the SBE is studied in detail, applying several complementary experimental techniques, allowing the evaluation of the macroscopic and microscopic morphology as well as the composition of SiO2 aerogels. Here, we show that some physical properties, e.g., the bulk density, the macroscopic structure, and pore sizes/volumes, were significantly affected by the re-expansion. However, silylation did not necessarily lead to full re-expansion. Therefore, similarities in the molecular composition could not be equated to similarities in the SBE. The influences of steric hindrance and reactivity are discussed. The impact of silylation is crucial in tailoring the SBE and, as a result, the APD of monolithic aerogels. [ABSTRACT FROM AUTHOR]

Reactions of isonicotinic acid hydrazide and its trimethylsilyl derivatives with hexamethyldisilazane, organic, and organosilicon isocyanates were studied. The possibility of synthesizing previously unknown isoniazid derivatives by preliminary introduction of a trimethylsilyl substituent to the nitrogen atom was established. [ABSTRACT FROM AUTHOR]

Metal nitrides are intensely investigated because they can offer high melting points, excellent corrosion resistance, high hardness, electronic and magnetic properties superior to the corresponding metals/metal oxides. Thus, they are used in diverse applications including refractory materials, semiconductors, electronic devices, and energy storage/conversion systems. Here, we present a simple, novel, scalable and general route to metal nitride precursors by reactions of metal chlorides with hexamethyldisilazane [HMDS, (Me3Si)2NH] in tetrahydrofuran or acetonitrile at low temperatures (ambient to 60°C/N2). Such reactions have received scant attention in the literature. The work reported here focuses primarily on the Al‐HMDS precursor produced from the reaction of AlCl3 with HMDS (mole ratio = 1:3) characterized by matrix‐assisted laser desorption/ionization‐time of flight, Fourier‐transform infrared spectroscopy, thermogravimetric analysis‐differential thermal analysis, and multinuclear nuclear magnetic resonance spectroscopy (NMRs) for chemical and structural analyses. The Al‐HMDS precursor heated to 1600°C/4 h/N2 produces aluminum nitride, characterized by X‐ray powder diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, and magic‐angle spinning NMR. On heating to 800–1200°C/4 h/N2, the precursor transforms to an amorphous, oxygen‐sensitive powder with very high surface areas (>200 m2/g) indicating nanosized particles, which can be used as additives to polymer matrices to modify their thermal stabilities. Al2O3 is also presented in the final product after heating, due to its high susceptibility to oxidation. This approach was extended via proof‐of‐concept studies to other metal chloride systems, including Zn‐HMDS, Cu‐HMDS, Fe‐HMDS, and Bi‐HMDS. The formed precursors are volatile, offering the potential utility as gas‐phase deposition precursors for their corresponding metal nitrides. [ABSTRACT FROM AUTHOR]

Abstract Sample preparation including dehydration and drying of samples is the most intricate part of scanning electron microscopy. Most current sample preparation protocols use critical-point drying with liquid carbon dioxide. Very few studies have reported samples that were dried using chemical reagents. In this study, we used hexamethyldisilazane, a chemical drying reagent, to prepare plant samples. As glandular trichomes are among the most fragile and sensitive surface structures found on plants, we used Millingtonia hortensis leaf samples as our study materials because they contain abundant glandular trichomes. The results obtained using this new method are identical to those produced via critical-point drying.

[Display omitted] 'Technical' tris(trimethylsilyl) phosphite, (Me 3 SiO) 3 P, as a mixture with (Me 3 SiO) 2 P(O)H and (Me 3 SiO) 3 P(O) (71 : 20 : 9) was obtained upon the action of (Me Si) NH on phosphorous acid H 3 PO 3 in the presence of catalytic amount of Me 3 SiCl. The action of this material on acid chlorides RC(O)Cl affords (hydroxymethylene)bis(phosphonic) acids RC(OH)[P(O)(OH) 2 ] 2 in preparative yields. [ABSTRACT FROM AUTHOR]

N-phenethylquinazolin-4-amines have emerged as potential Mycobacterium tuberculosis cytochrome bd oxidase inhibitors and attractive scaffolds in tuberculosis drug discovery programs. The classical two-step strategy of chlorination-amination to synthesize such structures presents several operational issues accompanied by variable results. This work reports an efficient one-pot protocol to access N-phenethylquinazolin-4-amines via silylation-amination mediated by hexamethyldisilazane. The products were obtained with excellent yields (84–99%) under one-pot solvent-free conditions.

In this paper, we focus on fabrication and physicochemical properties investigations of silica–multiwalled carbon nanotubes/poly(dimethylsiloxane) composite coatings deposited on the glass supports activated by cold plasma. Air or argon was used as the carrier gas in the plasma process. Multiwalled carbon nanotubes were modified with poly(dimethylsiloxane) in order to impart their hydrophobicity. The silica–multiwalled carbon nanotubes/poly(dimethylsiloxane) nanocomposite was synthesized using the sol–gel technique with acid-assisted tetraethyl orthosilicate hydrolysis. The stability and the zeta potential of the obtained suspension were evaluated. Then, the product was dried and used as a filler in another sol–gel process, which led to the coating application via the dip-coating method. The substrates were exposed to the hexamethyldisilazane vapors in order to improve their hydrophobicity. The obtained surfaces were characterized by the wettability measurements and surface free energy determination as well as optical profilometry, scanning electron microscopy, and transmittance measurements. In addition, the thermal analyses of the carbon nanotubes as well as coatings were made. It was found that rough and hydrophobic coatings were obtained with a high transmittance in the visible range. They are characterized by the water contact angle larger than 90 degrees and the transmission at the level of 95%. The X-ray diffraction studies as well as scanning electron microscopy images confirmed the chemical and structural compositions of the coatings. They are thermally stable at the temperature up to 250 °C. Moreover, the thermal analysis showed that the obtained composite material has greater thermal resistance than the pure nanotubes. [ABSTRACT FROM AUTHOR]

Borazine rings act as a pivotal part in siliconboroncarbonitride ceramics (SiBCN) for high-temperature stability and great resistance to crystallization. A detailed investigation of the ring formation mechanism will guide the design and synthesis of SiBCN to meet application requirements under extreme conditions. Boron trichloride (BCl 3) and hexamethyldisilazane (HN(SiMe 3) 2) are common raw materials for the synthesis of precursors for SiBCN. In this paper, quantum chemical calculation was used to study the cyclization reaction mechanism between BCl 3 and HN(SiMe 3) 2 to form trichloroborazine (TCBZ) at the MP2/6-31G (d,p) level of theory. We discussed the structure properties, reaction pathways, energy barriers, reaction rates, and other aspects in detail. The results show that BCl 3 and HN(SiMe 3) 2 alternately participate in the reaction process, accompanied by the release of trimethylchlorosilane (TMCS), and that the entire reaction shows an absolute advantage in terms of energy. In the Step by step reaction, lower reaction barriers are formed due to the introduction of BCl 3 with more heat released compared to that for the introduction of HN(SiMe 3) 2. The final single-molecule cyclization and TMCS elimination steps are found to be faster compared to all previous bimolecular reactions. [ABSTRACT FROM AUTHOR]

Hydrogenated silicon carbonitride thin films have been deposited on silicon substrates in a plasma enhanced chemical vapor deposition (PECVD) system using hexamethyldisilazane (HMDSN: C6H19Si2N) as an organosilicon monomer precursor, the plasma polymerized HMDSN (pp-HMDSN) films surfaces have been subsequently nanostructured via SF6 plasma surface etching for different etching times of 0.5 min, 1 min and 3 min. The plasma etching of pp-HMDSN thin film surface affected its surface morphology, chemical structure, wettability property, optical anti-reflectance characteristics and photoluminescence (PL) emission property. It is found that with etching time increase, the refractive index decreases and the PL energy bandgap increases as the silicon content and chemical bond Si-C intensity in thin film decrease, the optical reflectance spectrum changed in shape and position of minimum reflectance and the surface is converted from hydrophilic to hydrophobic one as surface porosity is enhanced. [ABSTRACT FROM AUTHOR]

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We demonstrated the way to improve the characteristics of quantum dot light emitting diodes (QD-LEDs) by adding a simple step to the conventional fabrication process. For instance, we can effectively deactivate the surface defects of quantum dot (QD) (e.g., CdSe/ZnS core-shell QDs in the current work) with the SiO bonds by simply mixing QDs with hexamethyldisilazane (HMDS) under atmospheric conditions. We observed the substantial improvement of device characteristics such that the current efficiency, the maximum luminance, and the QD lifetime were improved by 1.7–1.8 times, 15–18%, and nine times, respectively, by employing this process. Based on the experimental data (e.g., energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS)), we estimated that the growth of the SiOx on the surface of QDs is self-limited: the SiOx are effective to passivate the surface defects of QDs without deteriorating the intrinsic properties including the color-purity of QDs. Second, we proposed that the emission profiling study can lead us to the fundamental understanding of charge flow in each layer of QD-LEDs. Interestingly enough, many problems related to the charge-imbalance phenomenon were simply solved by selecting the combination of thicknesses of the hole transport layer (HTL) and the electron transport layer (ETL). [ABSTRACT FROM AUTHOR]

Sample preparation including dehydration and drying of samples is the most intricate part of scanning electron microscopy. Most current sample preparation protocols use critical-point drying with liquid carbon dioxide. Very few studies have reported samples that were dried using chemical reagents. In this study, we used hexamethyldisilazane, a chemical drying reagent, to prepare plant samples. As glandular trichomes are among the most fragile and sensitive surface structures found on plants, we used Millingtonia hortensis leaf samples as our study materials because they contain abundant glandular trichomes. The results obtained using this new method are identical to those produced via critical-point drying. [ABSTRACT FROM AUTHOR]

The technique was developed, the installation was done, and the conditions for the production of Si3N4 and Si2N2O by the method of gas-phase pyrolysis of hexamethyldisilazane (CH3)3-Si-NH-Si-(CH3)3 (HMDS) were experimentally studied. In the experiments, two different methods of inputting the raw material were used—the input of a vapor–gas mixture (bubbling feeder with heating to supply the HMDS vapor in a stream of carrier gases) and input as a gas-droplet stream (pneumatic nozzle). The effect of gas-dynamic synthesis conditions at temperatures up to 1100°C on the properties of silicon oxonitride and silicon nitride nanopowders was studied. The influence of the conditions of mixing the reactants, the volume ratio of nitrogen/ammonia, and the content of HMDS in the vapor–gas mixture on the yield of products was shown. The dependences of the degree of conversion of the feedstock on the gas flow rate and the concentration of ammonia in the gas phase were obtained. The optimal conditions for the pyrolysis process were found: temperature, the ratio of the components of the gas mixture, the conditions of mixing, and the contact times of the phases. X-ray amorphous Si3N4 and Si2N2O powders with particle sizes of 50–200 nm and a specific surface area of up to 15 m2/g and powders of alpha modification of silicon nitride Si3N4 in the form of threadlike crystals with a particle diameter of 50–200 nm were obtained. [ABSTRACT FROM AUTHOR]

In this report, a synthetic protocol for the preparation of phosphinic dipeptides of type 5 is presented. These compounds serve as valuable building blocks for the development of highly potent phosphinopeptidic inhibitors of medicinally relevant Zn-metalloproteases and aspartyl proteases. The proposed method is based on the tandem esterification of α-aminophosphinic and acrylic acids under silylating conditions in order to subsequently participate in a P-Michael reaction. The scope of the transformation was investigated by using a diverse set of readily available acrylic acids and (R)-α-aminophosphinic acids, and high yields were achieved in all cases. In most examples reported herein, the isolation of biologically relevant (R,S)-diastereoisomers became possible by simple crystallization from the crude products, thus enhancing the operational simplicity of the proposed method. Finally, functional groups corresponding to acidic or basic natural amino acids are also compatible with the reaction conditions. Based on the above, we expect that the practicality of the proposed protocol will facilitate the discovery of pharmacologically useful bioactive phosphinic peptides.

In this paper, we focus on fabrication and physicochemical properties investigations of silica–multiwalled carbon nanotubes/poly(dimethylsiloxane) composite coatings deposited on the glass supports activated by cold plasma. Air or argon was used as the carrier gas in the plasma process. Multiwalled carbon nanotubes were modified with poly(dimethylsiloxane) in order to impart their hydrophobicity. The silica–multiwalled carbon nanotubes/poly(dimethylsiloxane) nanocomposite was synthesized using the sol–gel technique with acid-assisted tetraethyl orthosilicate hydrolysis. The stability and the zeta potential of the obtained suspension were evaluated. Then, the product was dried and used as a filler in another sol–gel process, which led to the coating application via the dip-coating method. The substrates were exposed to the hexamethyldisilazane vapors in order to improve their hydrophobicity. The obtained surfaces were characterized by the wettability measurements and surface free energy determination as well as optical profilometry, scanning electron microscopy, and transmittance measurements. In addition, the thermal analyses of the carbon nanotubes as well as coatings were made. It was found that rough and hydrophobic coatings were obtained with a high transmittance in the visible range. They are characterized by the water contact angle larger than 90 degrees and the transmission at the level of 95%. The X-ray diffraction studies as well as scanning electron microscopy images confirmed the chemical and structural compositions of the coatings. They are thermally stable at the temperature up to 250 °C. Moreover, the thermal analysis showed that the obtained composite material has greater thermal resistance than the pure nanotubes.

Hexamethyldisilazane tunes morphology and enhances stability of the perovskite nanocrystals by surface modification with hydrophobic CH 3 groups. A novel facile room-temperature, hexamethyldisilazane (HMDS)-mediated strategy is demonstrated for the synthesis of all-inorganic perovskite colloidal nanocrystals (NCs). As a unique reaction-triggering and morphology-directing agent, HMDS is introduced for the first time to trigger the room-temperature reaction for generating perovskite NCs with controlled morphology and optical properties. Particularly, the stability of the resulting NCs is greatly enhanced due to the surface modification by hydrophobic -CH 3 groups from HMDS. The typical CsPbBr 3 perovskite NCs films are highly stable without significant decrease in photoluminesence (PL) intensity after being exposed to 60% relative humidity for 720 h. Moreover, no noticeable change of phase and morphology occurs even after 100 days of exposure. The representative CsPbBr 3 NCs are employed in a prototype white-light-emitting diodes (WLEDs) on 365 nm commercial GaN chip. The present strategy provides a facile and versatile route not only to control the morphology and optical properties of perovskites nanomaterials at room temperature but also enhance their stability, which will bring promising potential application for optoelectronics. [ABSTRACT FROM AUTHOR]

Drying is a critical step in preparing cell samples for examination with scanning electron microscopy (SEM). The two commonly used drying procedures are the critical point drying (CPD) and the chemical drying using hexamethyldisilazane (HMDS drying). Here we compared the application of these procedures for the drying of HaCaT human keratinocyte cells grown on electrospun nylon mats. Both drying procedures allowed us to obtain images of the cells and characterize the microvilli on the cell surface. After HMDS drying the membrane was less damaged than after CPD. Both drying procedures could be used to investigate contact guidance–the substrate‐induced changes in cell shape. The aspect ratio of HaCaT cells grown on the aligned and random mats was 4.2 ± 2.8 and 1.5 ± 0.3, respectively. HaCaT keratinocyte cells were grown on electrospun nylon mats and prepared for SEM imaging. Two sample preparation procedures were compared—CPD and chemical drying using HMDS. The membrane was less damaged after HMDS drying than after CPD drying. [ABSTRACT FROM AUTHOR]

We demonstrated the way to improve the characteristics of quantum dot light emitting diodes (QD-LEDs) by adding a simple step to the conventional fabrication process. For instance, we can effectively deactivate the surface defects of quantum dot (QD) (e.g., CdSe/ZnS core-shell QDs in the current work) with the SiO bonds by simply mixing QDs with hexamethyldisilazane (HMDS) under atmospheric conditions. We observed the substantial improvement of device characteristics such that the current efficiency, the maximum luminance, and the QD lifetime were improved by 1.7–1.8 times, 15–18%, and nine times, respectively, by employing this process. Based on the experimental data (e.g., energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS)), we estimated that the growth of the SiOx on the surface of QDs is self-limited: the SiOx are effective to passivate the surface defects of QDs without deteriorating the intrinsic properties including the color-purity of QDs. Second, we proposed that the emission profiling study can lead us to the fundamental understanding of charge flow in each layer of QD-LEDs. Interestingly enough, many problems related to the charge-imbalance phenomenon were simply solved by selecting the combination of thicknesses of the hole transport layer (HTL) and the electron transport layer (ETL).

Fragment ions produced from hexamethyldisilazane (HMDS) with a hot tungsten wire in a Freeman-type ion source were assayed using a low-energy mass-selected ion beam system. The possible candidates of chemical formulae for these ions are C + , N + , CH 3 + , CH 4 + , Si + , SiCH 5 + , SiC 2 H 6 + , SiC 3 H 9 + , Si 2 NCH 4 + , Si 2 NC 2 H 7 + , Si 2 NC 3 H 10 + , Si 2 NC 4 H 12 + , and Si 2 NC 5 H 16 + . The ion production strongly depended on the tungsten temperature. Among the HMDS derived fragment ions, SiCH 5 + ions were mass-selected. The ion energy was 100 eV. Then, the SiCH 5 + ions were irradiated to a Si substrate. It was inferred from the analysis of resulting deposited film that silicon carbide films containing a small amount of nitrogen atoms were deposited following the irradiation. [ABSTRACT FROM AUTHOR]

Bilayer composite membranes (CMs) are prepared by depositing a polymer layer onto track-etched polypropylene (PP) membrane by using plasma polymerization of hexamethyldisilazane (HMDSN). The chemical structure, wetting properties, and morphological characteristics of the prepared CMs are investigated. By depositing the plasma-polymerized polymer, we obtain CMs with two hydrophobic layers, of which one is the initial PP membrane, serving as a matrix. This layer has a water contact angle of 120°. The other layer, which was formed during plasma polymerization of HMDSN, contains nitrogen-containing functional groups, along with minor amounts of oxygen-containing, mainly carboxylic, groups. The water contact angle of this layer is ~98°. Deposition of a polymer film by plasma-assisted polymerization results in smoothing surface asperities of the initial (matrix) membrane, a considerable decrease in pore diameter, and alteration of pore shape; namely, the pores acquire an asymmetric (conical) profile. [ABSTRACT FROM AUTHOR]

Objective: The aims of this study were: to 1) develop a novel sample processing protocol to visualize human articular cartilage (AC) chondrons using micro-computed tomography (μCT), 2) develop and validate an algorithm to quantify the chondron morphology in 3D, and 3) compare the differences in chondron morphology between intact and osteoarthritic AC.Method: The developed protocol is based on the dehydration of samples with hexamethyldisilazane (HMDS), followed by imaging with a desktop μCT. Chondron density and depth, as well as volume and sphericity, were calculated in 3D with a custom-made and validated algorithm employing semi-automatic chondron selection and segmentation. The quantitative parameters were analyzed at three AC depth zones (zone 1: 0-10%; zone 2: 10-40%; zone 3: 40-100%) and grouped by the OARSI histological grades (OARSI grades 0-1.0, n = 6; OARSI grades 3.0-3.5, n = 6).Results: After semi-automatic chondron selection and segmentation, 1510 chondrons were approved for 3D morphometric analyses. The chondrons especially in the deeper tissue (zones 2 and 3) were significantly larger (P < 0.001) and less spherical (P < 0.001), respectively, in the OARSI grade 3-3.5 group compared to the OARSI grade 0-1.0 group. No statistically significant difference in chondron density between the OARSI grade groups was observed at different depths.Conclusion: We have developed a novel sample processing protocol for chondron imaging in 3D, as well as a high-throughput algorithm to semi-automatically quantify chondron/chondrocyte 3D morphology in AC. Our results also suggest that 3D chondron morphology is affected by the progression of osteoarthritis (OA). [ABSTRACT FROM AUTHOR]

Bis-thiourea complexes of cobalt, nickel, copper and zinc chlorides were used efficiently for rapid and efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) in CH3CN. All reactions were carried out at room temperature within immediate-120 min timeframe to afford trimethylsilyl ether derivatives in high to excellent yields. Investigation of the results exhibited that the prepared bis-thiourea metal complexes show the activity as Co(tu)2Cl2> Ni(tu)2Cl2> Cu(tu)2Cl2> Zn(tu)2Cl2in their silylation reactions. [ABSTRACT FROM AUTHOR]

In this paper we present a new analytical GC/MS method for the analysis of mixtures of free fatty acids and metal soaps in paint samples. This approach is based on the use of two different silylating agents: N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1,1,1,3,3,3-hexamethyldisilazane (HMDS). Our experimentation demonstrated that HMDS does not silylate fatty acid carboxylates, so it can be used for the selective derivatization and GC/MS quantitative analysis of free fatty acids. On the other hand BSTFA is able to silylate both free fatty acids and fatty acids carboxylates. The reaction conditions for the derivatization of carboxylates with BSTFA were thus optimized with a full factorial 3 2 experimental design using lead stearate and lead palmitate as model systems. The analytical method was validated following the ICH guidelines. The method allows the qualitative and quantitative analysis of fatty acid carboxylates of sodium, calcium, magnesium, aluminium, manganese, cobalt, copper, zinc, cadmium, and lead and of lead azelate. In order to exploit the performances of the new analytical method, samples collected from two reference paint layers, from a gilded 16th century marble sculpture, and from a paint tube belonging to the atelier of Edvard Munch, used in the last period of his life (1916–1944), were characterized. [ABSTRACT FROM AUTHOR]

A practical and highly efficient silylation of alcohol and phenol derivatives with hexamethyldisilazane (HMDS) using acidic ionic liquids under mild reaction conditions is described. A series of Brønsted as well as Brønsted-Lewis acidic ionic liquids were prepared and their performance investigated for the silylation of a wide variety of alcohols and phenols with HMDS. Imidazole- as well as N-methyl-2-pyrrolidone-based acidic ionic liquids have a higher catalytic activity for the protection of sensitive, hindered alcohols and phenols, thus providing an environmentally begin and versatile alternative to current acid catalysts. In addition, the acidic ionic liquids are reusable, being recovered easily and reused several times without significant deterioration in catalytic activity. [ABSTRACT FROM AUTHOR]

A green and highly efficient silylation of hydroxyl groups with hexamethyldisilazane using biodegradable thiamine-functionalized FeO@SiO magnetic nanoparticles is described. The thiamine-functionalized silica-supported magnetic (FeO@SiO@VB) nanocatalyst was characterized successfully by infrared spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy, powder X-ray diffraction and thermogravimetric analysis. Thiamine hydrochloride as well as anchored thiamine on the surface of magnetic nanoparticles has a higher catalytic activity for the protection of alcohols and phenols under mild reaction condition and short reaction times. Furthermore, the nanocatalyst could be recovered using an external magnet and reused with almost consistent activity. [ABSTRACT FROM AUTHOR]

In this work, the role of the number of free silanol groups at the nanosilica surface (specific surface area SBET = 250 m2/g, initial amount of silanols αOH = 0.60-0.62 mmol/g) was analyzed in interaction with poly(vinyl pyrrolidone) (PVP) vs. the degree (QTMS) of silica hydrophobization by hexamethyldisilazane at 100°C. The values of QTMS were found 0.07, 0.42, 0.67, 0.81, 0.82, and 1.0. Adsorption of PVP onto the nanosilica surface was carried out from water and water-ethanol (1:1) solutions of the polymer. It was found that free silanol groups play a crucial role in the adsorption of poly(vinyl pyrrolidone). The value of the maximal adsorption (monolayer capacity) on completely hydrophobic nanosilica surface is approximately lower than that for unmodified nanosilica by a factor of about 6.5. [ABSTRACT FROM AUTHOR]

The main products of the reaction of 1,3-dichloro-1,3-dimethyl-1,3-diorganyldisiloxanes with hexamethyldisilazane (molar ratio 1 : 1, 20 °C) are the earlier unknown linear 1-chloro-1,3-dimethyl-1,3-diorganyl-3-(trimethylsilylamino)disiloxanes of the general formula ClMeRSiOSiMeRNHSiMe ( 1) (R = ClCH ( a), Me ( b), Vin ( c), Ph ( d)) obtained in up to 53-72% yield and 1,3-dimethyl-1,3-diorganyl-1,3-bis(trimethylsilylamino)disiloxanes of the general formula (MeSiNH)MeRSiOSiMeR(NHSiMe) ( 2a- d) (7-12% yield). Thermolysis of compounds 1a- d leads to the formation of cyclic silazaoxanes. A plausible scheme for their formation was suggested. [ABSTRACT FROM AUTHOR]

The thermal stability of ZrO-SiO aerogels was significantly improved by inorganic-organic synergetic surface modifications: inorganic ions [Fe(III)] surface modification and hexamethyldisilazane gas phase modification. The replacement of Hs from surface hydroxyl groups on the aerogel by Fe(III) ions and silyl groups played a critical role in isolating the hydrous particles of ZrO-SiO aerogels. So the particle growth caused by the condensation of hydroxyl groups upon firing was inhibited. Meanwhile, the decomposition of the silyl groups upon heat treatment produced SiO particles, which could serve as pining particle to inhibit the crystallization of ZrO. Hence, the porous microstructure of the modified aerogels was still well preserved up to 1000 °C, with a high specific surface area of 203.5 m/g, and a considerable pore volume of 0.721 cc/g. These characteristics of the modified aerogels suggest that it has great potential on ultrahigh-temperature applications in the fields of thermal insulation, catalysis, and catalyst support, etc. [ABSTRACT FROM AUTHOR]

Reaction of 2-formylbenzoates with hexamethyldisilazane and diethyl phosphite in the presence of Yb(OTf) 3 proceeded smoothly at room temperature to afford addition adducts, which were readily cyclized to 3-phosphonate phthalides by adding trifluoroacetic acid (TFA). The reactions employing Sc(OTf) 3 instead of Yb(OTf) 3 produced 3-phosphonate isoindolinones without addition of TFA. [ABSTRACT FROM AUTHOR]

A novel one-flask synthetic method was developed in which 5-aminopyrazoles were reacted with N,N-substituted amides in the presence of PBr3. Hexamethyldisilazane was then added to perform heterocyclization to produce the corresponding pyrazolo[3,4-d]pyrimidines in suitable yields. These one-flask reactions thus involved Vilsmeier amidination, imination reactions, and the sequential intermolecular heterocyclization. To study the reaction mechanism, a series of 4-formyl-1,3-diphenyl-1H-pyrazol-5-yl-N,N-disubstituted formamidines, which were conceived as the chemical equivalent of 4-(iminomethyl)-1,3-diphenyl-1H-pyrazol-5-yl-formamidine, were prepared and successfully converted into pyrazolo[3,4-d]pyrimidines. The experiments demonstrated that the reaction intermediates were the chemical equivalents of 4-(iminomethyl)-1,3-diphenyl-1H-pyrazol-5-yl)formamidines. The rate of the reaction could be described as being proportional to the reactivity of amine reactants during intermolecular heterocyclization, especially when hexamethyldisilazane was used. [ABSTRACT FROM AUTHOR]

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Heterogeneously catalyzed oxidative desulfurization (ODS) offers a mild pathway to remove refractory sulfur compounds from liquid hydrocarbon fuels. However, adsorption of polar oxidation byproducts on the catalyst surface decreases desulfurization efficiency at the low ODS reaction temperature. Here, we report that high-performance surface-silylated titania-silica catalysts can be prepared by a silylation method using hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMCS) as the silane reagents. The bulk structure and surface properties of the catalysts before and after surface silylation were characterized by N 2 adsorption–desorption, XRD, FTIR, TGA, UV–vis DRS, FESEM, EDS, and water contact angle measurement to establish the structure–function relationship. The effects of silyl groups loading, reaction temperature, type of oxidant, and inhibiting compounds on the ODS performance of the catalysts were systematically evaluated. The results revealed that TS-H-2 catalyst with the optimum loading of silyl groups was an excellent catalyst capable of ultra-fast oxidizing ∼100 % of DBT, after only 5 min, which was due to increased surface hydrophobicity and decreased accumulation of poisoning polar byproducts on the active sites. The ODS performance of TS-H-2 was better preserved compared to unmodified TS-nonsil catalyst in the presence of inhibiting compounds such as cyclohexene (CH), indole (IND), and quinoline (QU), while it increased in the presence of p -xylene (PX). The negative effects of the three former inhibiting compounds were resulted from their competition with the sulfur compound for the oxidant and poisoning of the active sites. The positive effect of PX on the ODS rate was due to solubilization of the strongly adsorbed molecules on the surface of catalyst. [ABSTRACT FROM AUTHOR]