Detection of deposition rate of plasma-polymerized acrylate and methacrylate derivatives using quartz crystal microbalance

The deposition rates of plasma-polymerized (pp-)films of 12 acrylate derivatives (CH₂CHCOOR: substitution R is H, CH₃, CHCH₂, CH₂CH₃, CH₂CH₂CH₃, (CH₂)₃CH₃, C(CH₃)₃, CH₂CH(CH₃)₂, CH₂(CH₂)₄CH₃, CH₂CF₃, CH₂CF₂CF₃, CH₂(CF₂)₂CF₃), and 12 methacrylate derivatives (CH₂CCH₃COOR′: substitution R′ is H, CH₃, CHCH₂, CH₂CH₃, CH₂CH₂CH₃, (CH₂)₃CH₃, C(CH₃)₃, CH₂CH(CH₃)₂, CH₂(CH₂)₄CH₃, CH₂CF₃, CH₂CF₂CF₃, CH₂(CF₂)₂CF₃) are determined by the quartz crystal microbalance technique. Using the same polymerization conditions (100 W RF and 100 Pa vapor pressure) for the various monomers, it is found that the deposition rates were proportional to the polymerization time. The average deposition rate of pp-acrylate derivatives is larger than that of pp-methacrylate derivatives without pp-hexylacrylate. The average deposition rate of pp-fluoroalkylacrylates was higher than 7-25 times that of pp-alkylacrylate, and the average deposition rate of pp-fluoroalkylmethacrylates was higher than 10-31 times that of pp-alkylmethacrylates, respectively. The average deposition rate of pp-film depends on the chemical structure of the monomer suggesting different mechanisms under plasma-polymerization.     

Theoretical assessment of the nonlinear optical properties of substituted oligoacenes

The β and γ nonlinear optical coefficients of substituted oligoacenes (1–10 rings) with the donors (D) groups –CH₃, –CH₂CH₃, –CH₂CH₂CH₃, –CH₂CH₂CH₂CH₃, –C(CH₃)₃, –CH₃CHN(CH₃)₂, –N(CH₃)₂, –OCH₃, –OCH₂CH₃, –OCH₂CH₂CH₃, –OCH₂CH₂CH₂CH₃, –OC(CH₃)₃, and –OCHCH₃N(CH₃)₂ and the acceptor (R) group –CHC(CN)₂ is calculated by the AM1/TDHF method. A partial least squares regression analysis of electronic and structural parameters is performed to investigate their correlation with β and γ hyperpolarizabilities. It is found that the dipole moment, the HOMO–LUMO energy gap, the ionization potential, the number of π-electrons, and the number of rings in the bridge are parameters that significantly affect β and γ magnitudes. The dipole moment and the number of π-electrons are positively correlated with β values, while the HOMO–LUMO energy gap and the ionization potential are negatively correlated. Calculations indicate that the hyperpolarizabilities increase with the number of rings in the bridge and that the dimethylamine/dicyanoethenyl pair leads to the highest hyperpolarizabilities values. Optimization of β and γ is obtained through several substitution patterns of the oligoacenes. The present methodology shows that more extended systems containing two D/R pairs have high values of β and γ coefficients, which indicates that these systems can be employed in manufacturing nonlinear optics devices.     

Hydrothermal synthesis of highly pure brookite-type titanium oxide powder from aqueous sols of titanate nanosheets

Hydrothermal synthesis of brookite-type titanium dioxide was examined using aqueous sols of titanate nanosheets, which were prepared with Ti[OCH(CH₃)₂]₄ and N(CH₃)₄OH by a bottom-up process in aqueous solutions. Highly pure brookite powders were yielded at hydrothermal temperatures as low as 120 °C and N(CH₃)₄OH/Ti[OCH(CH₃)₂]₄ molar ratios greater than 2. Although titanate nanosheets are formed at N(CH₃)₄OH/Ti[OCH(CH₃)₂]₄ ≥ 0.4, the addition of excess N(CH₃)₄OH was critical in forming highly pure brookite powders. Excess N(CH₃)₄⁺ caused the precipitation of layered titanates, which were formed by stacking titanate nanosheets. Additionally, the crystal nucleation of brookite occurred in the precipitates. Then, the adsorption of titanate nanosheets on brookite particles caused the particles to transform into rod-like shapes elongated along the c-axis. The adsorbed titanate nanosheets were structurally converted into brookite under the influence of the underlying brookite crystal. Despite having a rough surface, the resulting brookite particles were single crystal-like. Moreover, the use of any tetraalkylammonium hydroxides other than N(CH₃)₄OH did not yield brookite. The addition of N(CH₃)₄OH to the reaction sols yielded precipitates of small titanate nanosheets. The morphology of the titanate nanosheets could have a significant influence on brookite crystallization.     

Formation and properties of ZnO nano-particles from gas phase synthesis processes

ZnO nano-particles have been synthesized in low pressure flow reactors utilizing Zn(CH₃)₂ as precursor. Two different synthesis routes have been employed. A low pressure flame reactor and a microwave reactor were used for synthesis of ZnO particle in Zn(CH₃)₂ doped H₂/O₂/Ar flames and Zn(CH₃)₂ doped Ar/O₂ plasmas, respectively. The particle formation process has been investigated in situ by a particle mass spectrometer. Also, sampled powders have been investigated ex situ by means of FT-IR, XRD, TEM, and UV-VIS. For both synthesis routes nanometer sized ZnO particles were found with particle diameters in the range between 4 to 8 nm. In cases of the flame reactor the results suggest a strong influence of water on the particle formation process.     

The effect of solution chemistry on the preparation of MgAl2O4 by hydrothermal-assisted sol-gel processing

Preparation of magnesium aluminate spinel powder by hydrothermal-assisted sol-gel processing from MgAl₂(OCH₂CH₂OR)₈, RCH₃ (1), CH₂CH₂OCH₃ (2), MgAl₂[OCH(CH₃)₂]₈ (3) and MgAl₂(O-^sBu)₈ (4) in toluene and parent alcohol has been investigated. Coordination status of aluminum atom in precursors was determined by ²⁷Al NMR and correlation between coordination number of aluminum and development of spinel phase in hydrothermal-assisted sol-gel processing has been studied. The gels obtained from hydrothermal-assisted hydrolysis of magnesium-aluminum alkoxides that contain six-coordinated aluminum atoms in solution (1 and 2) after calcination at 700 °C resulted in the formation of pure spinel phase, whereas in similar hydrolysis and calcination processes of precursors that contain four-coordinated aluminum (3 and 4) spinel phase forms along with some Al₂O₃ and MgO. Selected powders obtained from hydrothermal-assisted sol-gel processing were characterized by thermal analysis (TGA/DSC), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Results indicate that the coordination status of aluminum in the precursor is very crucial for the formation of pure phase spinel. The morphology of prepared spinels was studied by SEM and the results showed that the solvent in hydrothermal-assisted sol-gel processing has a marked effect on the morphology of the resulting MgAl₂O₄. In hydrothermal-assisted sol-gel processing of aluminum-magnesium alkoxides in hydrophobic solvent, spherical particles are formed, while in the parent alcohol, non-spherical powders are formed.     

Novel inclusion compounds consolidated by host-host and host-guest hydrogen bonding: Complexes of thiourea with (2-hydroxyethyl)trimethylammonium carbonate and oxalate

New inclusion complexes [(CH₃)₃N⁺CH₂CH₂OH]₂CO₃^2-·6(NH₂)₂CS (1) and [(CH₃)₃N⁺CH₂CH₂OH]₂C₂O₄^2-·2(NH₂)₂CS (2) have been prepared and characterized by X-ray crystallography. In the crystal structure of 1, the choline ions are accommodated within an open channel-type host lattice built of urea molecules and carbonate ions. In complex 2, the choline ions are sandwiched between pleated sheets constructed from the parallel arrangement of thiourea-oxalate ribbons. In both inclusion compounds the guest choline ions form O-H⋯O donor hydrogen bonds with anionic O atoms in the host lattices.     

Sorption of CH<Subscript>3</Subscript><Superscript>131</Superscript>I from water vapor-air medium on porous inorganic sorbents containing triethylenediamine and <Emphasis Type="Italic">d</Emphasis> element nitrates

Sorption of CH₃ ¹³¹I from a water vapor-air medium on porous inorganic sorbents based on silica gel of KSKG grade and containing triethylenediamine (CH₂-CH₂)₃N₂ and d element nitrates was studied. The sorbents prepared by impregnation with (CH₂-CH₂)₃N₂ and Zn, Ni, and Cu nitrates from aqueous solution recover CH₃ ¹³¹I from a water vapor-air flow poorly (degree of recovery <10%). Calcination of the sorbents at temperatures exceeding 250°C does not noticeably affect their sorption power. Heating of the complex Ag(NO₃)(OH)·(CH₂-CH₂)₃N₂H to 160°C causes its exothermic decomposition with a large heat release and formation of metallic silver. Thermal decomposition of the complex of Cu²⁺ with (CH₂-CH₂)₃N₂, synthesized from an aqueous solution at the molar ratio Cu(NO₃)₂: (CH₂-CH₂)₃N₂ = 1: 2, occurs similarly.     

INCORPORATED C70 IN SOL AND GEL

C₇₀ is incorporated in gel by a sol-gel process with using 3-amino-propyltriethoxysilane (NH₂(CH₂)₃Si(OC₂H₅)₃, APTS) and 3-glycidoxypropltrimethoxysilane (CH₂OCHCH₂O(CH₂)₃Si(OCH₃)₃, GPTMS) as precursors. C₇₀ is firstly mixed with APTS to form C₇₀-NH₂(CH₂)₃Si(OC₂H₅)₃ compound by the reaction between C₇₀ and amino-group of APTS, and then the compound is hybridized with GPTMS to form solid gel. The linkage of C₇₀ and APTS is estimated and confirmed with FT-IR spectra, and the UV/Visible spectra of the sol and gel are measured.     

Diffusion of self-assembled monolayers of thiols on the gold surfaces covered with polydimethylsiloxane stamps

Thiols can diffuse and form self-assembled monolayers (SAMs) on the gold surfaces covered with polydimethylsiloxane (PDMS) stamps. For the first time, with cells as the indicator of how far alkanethiols had diffused to form SAM, we studied the growth dynamics of SAMs of HS(CH₂)₁₁(OCH₂CH₂)₃OH (EG₃) and HS(CH₂)₁₁(OCH₂CH₂)₆OH (EG₆) on the gold surfaces covered with PDMS stamps. The growth of SAMs is well described by one-dimensional diffusion from a line source of concentration, with surface diffusion coefficient of 193.4 ± 19.2 μm²/min (EG₃) and 95.8 ± 18.9 μm²/min (EG₆).     

Solubility Diagram of the System Uranyl Sulfate-Dimethylurea-Water

The system UO₂SO₄-NH₂CON(CH₃)₂-H₂O was studied by the isothermal solubility method at 25°C. The congruently soluble complex UO₂SO₄·2NH₂CON(CH₃)₂ (I) and incongruently soluble complex UO₂SO₄·3NH₂CON(CH₃)₂ (II) were revealed. Complexes I and II were studied by X-ray diffraction, IR spectroscopy, and thermal analysis.     

Effect of aluminium alkoxide with donor-functionalized group on texture and morphology of the alumina prepared by sol-gel processing

A new aluminium alkoxide, Al(OCH₂CH₂OCH₂CH₂OCH₃)₃, with donor-functionalized group was prepared and characterized by elemental analysis, mass spectrometry, and ¹H, ¹³C and ²⁷Al NMR spectroscopy. The prepared aluminium alkoxide was used as a precursor for the synthesis of alumina by the sol-gel processing. The physiochemical properties of alumina that were obtained from hydrolysis of Al(OCH₂CH₂OCH₂CH₂OCH₃)₃ were investigated and compared with that of alumina synthesized from aluminium 2-butoxide. Utilizing Al(OCH₂CH₂OCH₂CH₂OCH₃)₃ as a precursor in sol-gel processing resulted in formation of alumina with significantly lower surface area, smaller pore volume, and pore size in comparison with alumina obtained from aluminium 2-butoxide. A novel morphology was observed for the alumina prepared from aluminium alkoxide with donor-functionalized group.     

A theoretical study on initial growth mechanism of ZrO2 film using cyclopentadienyl-type precursor

The initial growth reaction of atomic layer deposition (ALD) of ZrO₂ using Cp₂Zr(CH₃)₂ (CpC₅H₅, cyclopentadienyl) as metal precursor on the hydroxylated silicon surface is investigated by using density functional theory (DFT). The ALD cycle is achieved through two types of ligand elimination reactions (i.e., CH₄ and CpH elimination reactions). The possible reaction pathways are proposed in order to find the dominant initial reaction during the Cp₂Zr(CH₃)₂ precursor pulse. DFT calculations show that the CH₄ elimination reaction is energetically more favorable than CpH elimination reaction. As a result, the two CH₃ ligands of Cp₂Zr(CH₃)₂ may be dissociated prior to the two Cp rings during the metal precursor pulse. In addition, one CpH elimination may occurs sequentially following the first CH4 elimination reaction according to activation barrier analysis during the Cp₂Zr(CH₃)₂ pulse. All the calculated results are in agreement with the experimental findings.     

Exploring the Interplay Between Ligand Derivatisation and Cation Type in the Assembly of Hybrid Polyoxometalate Mn‐Andersons

Herein a library of hybrid Mn‐Anderson polyoxometalates anions are presented: 1 , [(MnMo₆O₁₈)((OCH₂)₃‐C‐(CH₂)₇CHCH₂)₂]^3?; compound 2 , [(MnMo₆O₁₈)((OCH₂)₃C‐NHCH₂C₁₆H₉)₂]^3?; compound 3 , [(MnMo₆O₁₈)((OCH₂)₃C‐(CH₂)₇CHCH₂)₁((OCH₂)₃C‐NHCH₂C₁₆H₉)₁]^3?; compound 4 , [(MnMo₆O₁₈)((OCH₂)₃C‐NHC(O)CH₂CHCH₂)₂]^3? and compounds 5 – 9 , [(MnMo₆O₁₈)((OCH₂)₃C‐NHC(O)(CH₂)_xCH₃)₂]), where x = 4, 10, 12, 14, and 18 respectively. The compounds resulting from the cation exchange of the anions 1 – 9 to give TBA ( a ) and DMDOA ( b ) salts, and additionally for compounds 1 , 2 and 3 , tetraphenylphosphonium (PPh₄) ( c ) salts, are explored at the air/water interface using scanning force microscopy, showing a range of architectures including hexagonal structures, nanofibers and other supramolecular forms. Additionally the solid‐state structures for compounds 1c , 2c , 4a , 6a , 9a , are presented for the first time and these investigations demonstrate the delicate interplay between the structure of the covalently derivatised hybrid organo‐clusters as well as the ion‐exchange cation types.     

Adsorption and decomposition of 1,3-disilabutane on Si (111)-7×7

The adsorption and decomposition of 1,3-disilabutane (DSB) was studied on Si (111)-7×7 in the temperature range 100-1200 K by Cs⁺ reactive ion scattering and X-ray photoelectron spectroscopy (XPS). By combining the results of these two techniques, adspecies in the intermediate states during the decomposition of DSB were qualitatively identified and an adsorption model was proposed. At 100-150 K, DSB was found to adsorb on the surface as the C₂H₈Si₂ species as well as CH₄Si and to condense molecularly on a monolayer of C₂H₈Si₂ adspecies. XPS indicates that the molecular species desorbs mostly at 200 K and completely at 300 K. Up to 600 K, the C₂H₈Si₂ adspecies are converted to CH₄Si with increasing temperature and then above this temperature the CH₄Si species decomposes to form the SiC film. The intensity variations of Si (2p) and total C (1s) peaks and the analysis by curve fitting of the C (1s) peaks suggest that one CH₄Si species leaves the system by cleavage of C-Si bonds in C₂H₈Si₂ adspecies rather than to form two CH₄Si adspecies, and the breakage probably occurs within the extremity ones in accordance with the double-bonded chemisorption character.     

Synthesis of co-ordination networks from flexible bis-(4-pyridyl) ligands and cadmium salts.

Crystallisation of flexible dipyridyl ligands with Cd(NO₃)₂·4H₂O, Cd(ClO₄)₂·xH₂O or Cd(NO₃)₂·4H₂O and KSCN gives co-ordination networks of composition [Cd(ClO₄)₂(Py₂C₃H₆)₂(H₂O)₂]·Py₂C₃H₆ 1 (Py₂C₃H₆ =1,3-bis(4-pyridyl)propane); [Cd(ClO₄)₂(Py₂C₂H₄)₃] 2 (Py₂C₂H₄ =1,2-bis(4-pyridyl)ethane); [Cd(NCS)₂(Py₂C₃H₆)] 3; [Cd₂(NO₃)₄(o-C₆H₄(CH₂CH₂4-Py)₂)₄] 4 (o-C₆H₄(CH₂CH₂Py)₂ =1,2-bis[2-(4-pyridyl)ethyl] benzene and [Cd(NO₃)₂(PyCH₂CH₂CH=CHCH₂CH₂Py)₃] 5 (PyCH₂CH₂CH=CHCH₂CH₂Py =1,6-bis(4-pyridyl)hex-3-ene). The compounds were characterised by X-ray single crystal diffraction studies which revealed the presence of different polymeric motifs. Structures 1 and 5 consist of 1-D polymeric chains, structure 4 consists of a 2-D polymeric network and structure 3 is a 3-D polymeric network. None of these exhibit lattice interpenetration. However structure 2 consists of three identical but independent interpenetrating 3-D lattice networks.     

A survey of ABX3 halides for optical second harmonic generation

A group of ABX₃ halides have been searched for nonlinear optical character by testing each for second harmonic generation in powdered samples using the method of Kurtz and Perry. It was found that most simple ternary halides do not produce second harmonic light and apparently have centrosymmetric structures. (CH₃)₄NHgCl₃, (CH₃)₄NHgI₃, (CH₃)₄NHgBr₃, KHgI₃·H₂O, and RbHgI₃·H₂O were found to produce SHG and the first two of these compounds were found to be phase-matchable.     

Importance of H2 gas for growth of hot-wire CVD nanocrystalline 3C-SiC from SiH4/CH4/H2

Silicon carbide (SiC) thin films were prepared by hot-wire chemical vapor deposition from SiH₄/CH₄/H₂ and the influence of H₂ gas flow rate (F(H₂)) on the film properties was investigated. The SiH₄ gas flow rate was 1 sccm. At the CH₄ gas flow rate (F(CH₄)) of 1 sccm, nanocrystalline cubic SiC (nc-3C-SiC) grew even without H₂. On the other hand, at F(CH₄) = 2 sccm, amorphous SiC grew without H₂ and nc-3C-SiC grew above F(H₂) = 50 sccm. As F(H₂) was increased, the crystallinity improved both at F(CH₄) = 1 and 2 sccm. However, the mean crystallite size decreased at F(CH₄) = 1 sccm and increased at F(CH₄) = 2 sccm. We discuss growth mechanisms of nc-3C-SiC.     

Unusual Pressure-Driven Phase Transformation and Band Renormalization in 2D vdW Hybrid Lead Halide Perovskites

The application of high pressure allows control over the unit cell and interatomic spacing of materials without any need for new growth methods or processing while accessing their materials properties in situ. Under these extreme pressures, materials may assume new structural phases and reveal novel properties. Here, unusual phase transition and band renormalization effects in 2D van der Waals Ruddlesden−Popper hybrid lead halide perovskites, which have shown extraordinary optical properties and immense potential in light emission and conversion technologies, are reported. The results show that (CH₃(CH₂)₃NH₃)₂(CH₃NH₃)Pb₂Br₇ (n = 2) layers undergo two distinct phase transitions related to PbBr₆ octahedra, butylammonium (BA), and methylammonium (MA) molecule tilting motion that leads to rather unique/anomalous bandgap variation with pressure. In contrast, (CH₃(CH₂)₃NH₃)PbBr₄ (n = 1) lacks MA molecules and possesses only one pressure-induced phase transition related to PbBr₆ octahedra and BA tilting. In this range, the bandgap reduces monotonically, much similar to other inorganic semiconductors and display surprisingly large redshift from 3 to 2.4 eV. Together with theoretical calculations, this study offers unique insights into these pressure-induced changes and extends the understanding of these highly anisotropic layered soft organic perovskite materials under extreme conditions.     

Fabrication of Nb-doped bismuth titanate thin films using nonionic block copolymer: Enhanced ferroelectric properties

Crack-free Nb-doped Bi₄Ti₃O₁₂ (Nb-BIT-p) ferroelectric thin films were fabricated utilizing nonionic block copolymer, HO(CH₂CH₂O)₂₀(CH(CH₃)CH₂O)₇₀(CH₂CH₂O)₂₀H (EO₂₀PO₇₀EO₂₀), on Pt/Ti/SiO₂/Si substrates by a processing route of metalorganic solution deposition. The Nb-BIT-p films after calcination showed only a Bi₄Ti₃O₁₂-type crystalline phase with a random orientation and small grains (< 0.4 μm). The remanent polarization (2P_r) and the coercive field (E_c) values of Nb-BIT-p capacitors were unusually high, such as 42 ± 3 μC/cm² and 72 ± 5 kV/cm, respectively, at a maximum applied field of 160 kV/cm. After 1.5 × 10¹⁰ read/write cycles with ± 8 V amplitude (160 kV/cm) at 1 MHz frequency, the 2P_r value was partially reduced, but recoverable close to the original one by repeated switching at a high field.     

A vapor phase deposition of self-assembled monolayers: Vinyl-terminated films of volatile silanes on silicon oxide substrates

Vinyl-terminated self-assembled monolayers (SAMs) offer significant flexibility for further chemical modification and can serve as a versatile starting point for a tailoring of surface properties. A vapor phase deposition of such films would offer advantages in cases where the preparation from solution is not an option or not desired, for example in connection with silicon microstructures such as micro-electromechanical systems. We show that SAMs of 9-decenyltrichlorosilane (CH₂CH(CH₂)₈SiCl₃), 10-undecenyltrichlorosilane (CH₂CH(CH₂)₉SiCl₃), 14-pentadecenyltrichlorosilane (CH₂CH(CH₂)₁₃SiCl₃), decyltrichlorosilane (CH₃(CH₂)₉SiCl₃), and octadecanetrichlorosilane (CH₃(CH₂)₁₇SiCl₃) can be prepared both from solution and from the vapor phase. The resulting layers were compared by static contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy to determine their surface wettability, the film thickness, the smoothness and homogeneity of the respective films, and their chemical composition and each method gave films of comparable quality. Deposition of functionalized SAMs from the vapor phase is rare. Here we report the parameters for the preparation of well-ordered vinyl-terminated SAMs from the vapor phase.