Structural,surface, optical,and antimicrobial characterization of I2/Polymethyl methacrylate and CuS/I2/polymethyl methacrylate thin films

In this study, I₂/PMMA and CuS/I₂/PMMA thin films were produced by Chemical Bath Deposition (CBD) on polymethyl methacrylate (PMMA) substrates, and their physicochemical and antimicrobial properties were analyzed. The film's surface tensions were characterized by KSV instruments, and the surface tensions for plain PMMA, I₂/PMMA, and CuS/I₂/PMMA thin films were 30.27, 28.77, and 31.86 mN/m, respectively. The I₂ and CuS/I₂ structures in the XRD patterns are amorphous. After coating CuS, the long rod-like extension structures are formed; spherical shapes form some agglomeration in some regions to SEM images. Chemical analysis was performed with an EDX spectrometer attached to SEM. The thicknesses and surface roughnesses of I₂/PMMA and CuS/I₂/PMMA thin films were determined to be 50.34 nm, 1126 nm; 62.03 nm and 204.99 nm via AFM, respectively. The optical spectra of the films were recorded in the range of 300–1100 nm with a UV-VIS spectrophotometer. The antibacterial and antifungal properties of I₂ and CuS coating were evaluated against facultative gram-negative E. Coli and C. Albicans. The coated films exhibited excellent antimicrobial performance.     

Optical and physical properties of iridescent photonic crystals obtained by self‐assembled polymethyl methacrylate nanospheres within graphene oxide nanoplatelets

Opal photonic crystals prepared by vertical templating of polymethyl methacrylate (PMMA) nanospheres in aqueous graphene oxide (GO) solutions were successfully obtained. The results show that increasing the PMMA nanospheres' size leads to the modification of the d‐spacing in GO nanoplatelets, inducing brilliant iridescence colors that span the entire visible electromagnetic spectrum. Scanning electron microscopy study shows a uniform distribution of GO nanoplatelets on the surface and the bulk of the opal photonic crystals. The reflectance spectra exhibit a significant red shift from 385 to 660 nm when the nanospheres' size increases from 160 to 306 nm, respctively. The Raman spectra show a systematic decrease in the intensity ratio of the D to G bands of GO (I_D/I_G), suggesting a partial reduction of graphene oxide with decrasing the extent of defects in the partially reduced GO nanoplatelets. This finding is confirmed by the significant decrease observed in the intensity of the hydroxyl band in the attenuated total reflectance mode‐Fourier transform infrared spectra of the photonic crystals. The results provide the first demonstrated example of intercalated assemblies of polymer nanospheres within GO nanosheets, leading to photonic crystals with brilliant iridescence colors that span the entire visible electromagnetic spectrum and can be tuned only by varying the size of the PMMA nanospheres.     

Novel optical oxygen sensing material: metalloporphyrin dispersed in fluorinated poly(aryl ether ketone) films

A series of new fluorine-containing poly(aryl ether ketone)s (8F-PEKEK(Ar); Ar: 2-2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (6FBA), 2,2-bis(4-hydroxyphenyl)propane (BA), 2-(4-hydroxyphenyl)-2-(3-hydroxyphenyl)propane (3,4^′-BA) or 9,9^′-bis(4-hydroxyphenyl)fluorine (HF)) are synthesized and applied to the matrix of optical oxygen sensing using phosphorescence quenching of metalloporphyrins, platinum and palladium octaethylporphyrin, (PtOEP and PdOEP) by oxygen. The phosphorescence intensity of PtOEP and PdOEP in 8F-PEKEK(Ar) films decreased with increase of oxygen concentration. The ratio I₀/I₁₀₀ is used as a sensitivity of the sensing film, where I₀ and I₁₀₀ represent the detected phosphorescence intensities from a film exposed to 100% argon and 100% oxygen, respectively. For PtOEP in 8F-PEKEK(Ar) film, I₀/I₁₀₀ values are more than 20.0 and large Stern-Volmer constants more than 0.19%⁻¹ are obtained compared with PtOEP in polystyrene film. For PdOEP in 8F-PEKEK(Ar) film, on the other hand, the large I₀/I₁₀₀ values more than 143 are obtained. However, the Stern-Volmer plots of PdOEP in 8F-PEKEK(Ar) films exhibit considerable linearity at lower oxygen concentration range between 0% and 20%. These results indicate that PtOEP and PdOEP films are useful optical oxygen sensor at the oxygen concentration range between 0% and 100% and between 0% and 20%, respectively. The response times of PtOEP and PdOEP dispersed in 8F-PEKEK(Ar) films are 5.6 and 3.0 s on going from argon to oxygen and 110.1 and 160.0 s from oxygen to argon, respectively.     

Luminescence studies in polymers—II : Temperature effect on polyvinylcarbazole fluorescence

Polyvinylcarbazole (PVCa) films and solutions emit normal and excimer fluorescence between 77 and 425 K. The absolute (I_M and I_D) and relative (I_M/I_D) intensities emitted strongly depend on temperature. The usual U-shaped curve is obtained for log I_M/I_D as a function of 1/T in the case of polymer films. In solution, two minima corresponding to two different excimers are observed. The formation and dissociation of PVCa excimers in films and solutions have been interpreted according to the usual kinetic scheme. The binding energies for the excimer in films and for the high temperature excimer in solutions are respectively 4 and 2·8 kcal mole⁻¹.     

Electrodeposition of PbO2 onto Au and Ti substrates

The electrodeposition of lead dioxide (PbO₂) onto Au and Ti substrates was anodically executed at 65°C and the electrochemical characteristics and the mechanism in the PbO₂ films deposition were investigated by the using an in-situ electrochemical quartz crystal microbalance, cyclic voltammogram, and chronoamperometry experiments. An X-ray diffractometer and scanning electron microscope were also used for investigation of the formed lead dioxide films onto both substrates. Considering the experimental and theoretical mass/charge ratios, PbO₂ deposition on Au by applying constant potential was in excellent agreement with the theoretical value, while relatively higher values of the mass/charge ratio due to film hydration were found when Ti was used as substrate. Analysis of X-ray diffractometer and scanning electron microscope show different film structures on each substrate, especially the additional hydration of the lead dioxide film deposited on Ti leads to some structural effects, identified as Sky-Lotus PbO₂.     

Crystallization of titania ultra-fine particles from peroxotitanic acid in aqueous solution in the present of polymer and incorporation into poly(methyl methacylate) via dispersion in organic solvent

We report a novel strategy for incorporation of titanium dioxide (TiO₂) particles, which were crystallized from peroxotitanic acid in the presence of hydrophilic polymer by hydrothermal treatment in aqueous solution, into poly(methyl methacrylate) (PMMA) via dispersion into chloroform. Dispersion of TiO₂ particles into chloroform was achieved by solvent change from water to chloroform in aid of amphiphilic polymer dispersant, poly(N-vinyl pyrrolidone) (PVP), poly(N-vinyl pyrrolidone-co-methyl methacrylate) (PVP-co-PMMA), poly(N-vinyl pyrrolidone-block-methyl methacrylate) (PVP-b-PMMA) through azeotropical removal of water. Incorporation of TiO₂ particles into PMMA was carried out by a casting process of a mixture of TiO₂ particles dispersed with PVP₁₅₄-b-PMMA₁₅₆ in chloroform and PMMA on a glass substrate. Resultant hybrid film containing TiO₂ less than 10 wt.% showed high transparency in visible region attributable to homogeneous dispersion into PMMA matrix. The refractive index of the hybrid films increased with TiO₂ content and agreed with the calculated values.     

Growth and characterization of ultrathin carbon films on electrodeposited Cu and Ni

Ultrathin carbon films were grown on different types of metallic substrates. Free‐standing foils of Cu and Ni were prepared by electroforming, and a pure Ni film was obtained by galvanic displacement on a Si wafer. Commercial foil of Ni 99.95% was used as a reference substrate. Carbon films were grown on these substrates by chemical vapour deposition in a CH₄‐H₂ atmosphere. Obtained films were characterized by Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and ultraviolet photoemission spectroscopy. The XPS at grazing collection angle was used to determine the thickness of carbon films. Depending on the deposition parameters, the films of graphene or graphite were obtained on the different substrates. The uniformity of graphene and its distribution over the sample area were investigated from Raman data, optical images, and XPS chemical maps. The presence of graphene or graphite in the films was determined from the Raman spectra and Auger peak of C KVV. For this purpose, the D parameter, which is a fingerprint of carbon allotropes, was determined from C KVV spectra acquired by using X‐rays and electron beam. A formation of an intermediate layer of metal hydroxide was revealed in the samples with graphene overlayer.     

Dispersion of carbon nanotubes by the branched block copolymer Tetronic 1107 in an alcohol–water solution

The dispersion of carbon nanotubes (CNTs) by the branched block copolymer Tetronic 1107 was investigated in mixed solvents consisting of water and one of the following alcohols: ethanol, n-propanol, ethylene glycol (EG), or glycerol (GLY). The maximum concentration of dispersed CNTs (C _limit) and the optimum T1107 concentration (C _opt) to disperse the maximum amount of CNTs in different solvents were obtained from UV–vis–NIR absorbance spectra. The addition of ethanol or n-propanol to water dramatically increases the C _limit. The value of C _opt follows the order: n-propanol–water?>?ethanol–water?>?EG–water?≈?GLY–water mixtures. I _D/I _G was used to characterize the defect density of CNTs dispersed in the mixed solvents, which was investigated by Raman spectroscopy. The I _D/I _G values in n-propanol–water and ethanol–water mixtures are higher than those in EG–water and GLY–water mixtures. High-resolution transmission electron microscopy is used to confirm a favorable dispersion in the presence of different alcohols.     

Water Miscible Mono Alcohols’ Effect on the Proteolytic Performance of Bacillus clausii Serine Alkaline Protease

In this study, our investigations showed that the increasing concentrations of all examined mono alcohols caused a decrease in the V _m, k _cat and k _cat/K _m values of Bacillus clausii GMBE 42 serine alkaline protease for casein hydrolysis. However, the K _m value of the enzyme remained almost the same, which was an indicator of non-competitive inhibition. Whereas inhibition by methanol was partial non-competitive, inhibition by the rest of the alcohols tested was simple non-competitive. The inhibition constants (K _I) were in the range of 1.32–3.10 M, and the order of the inhibitory effect was 1-propanol>2-propanol>methanol>ethanol. The ΔG ^≠ and ΔG ^≠ _E???T values of the enzyme increased at increasing concentrations of all alcohols examined, but the ΔG ^≠ _ES value of the enzyme remained almost the same. The constant K _m and ΔG ^≠ _ES values in the presence and absence of mono alcohols indicated the existence of different binding sites for mono alcohols and casein on enzyme the molecule. The k _cat of the enzyme decreased linearly by increasing log P and decreasing dielectric constant (D) values, but the ΔG ^≠ and ΔG ^≠ _E???T values of the enzyme increased by increasing log P and decreasing D values of the reaction medium containing mono alcohols.     

Intensity autocorrelation function for a flexible polymer

An exact expression for the autocorrelation function of the intensity of light scattered from a solution of large, flexible polymers is obtained using a simple “mean-force” model. A Q² dependence of the reciprocal relaxation time is found for both small values of QR_G and also very large values of QR_G. At small QR_G the relaxation time is proportional to the translational diffusion coefficient D of the entire polymer, while at large QR_G the relaxation time is proportional to the sum of D and an effective segment diffusion coefficient kt/f.     

Gas transport properties of annealed polyimide films

Sorption and permeation of CO₂ in various annealed polyimide (PI) films were investigated. Dual-mode sorption and partial immobilization models were used to analyze the data. Sorption of CO₂ in PI film quenched from above the glass transition temperature (T_g) is greater than in film as received. In fact, sorption is decreased over the entire pressure range by cooling the film slowly. These changes in sorption of CO₂ can be attributed to a change in the Langmuir sorption capacity C′_H by annealing, since the other dual-mode sorption parameters, k_D and b, are almost independent of annealing. The value of C′_H is increased by quenching, and decreased by slow cooling from above T_g. The two diffusion coefficients D_D and D_H according to the Henry and Langmuir modes, respectively, for CO₂ also depend markedly on annealing. Diffusion coefficients of quenched PI films are increased and those of film cooled slowly are decreased compared with values for PI film as received. The change in D_H is larger than that in D_D. The permeability coefficient of quenched PI films at 100 cmH_g is about 1.7 times that of PI film as received. The film structure formed by quenching can enhance permselectivity.     

Influence of deposition pressure on hydrogenated amorphous carbon films prepared by d.c.‐pulse plasma chemical vapor deposition

Hydrogenated amorphous carbon films (a‐C : H) were prepared by d.c.‐pulse plasma chemical vapor deposition using CH₄ and H₂ gases. The microstructure and hardness of the resulting films were investigated at different deposition pressures (6, 8, 11, 15, and 20 Pa). The growth rate increased sharply from 3.2 to 10.3 nm/min with increasing the pressure from 6 to 20 Pa. According to Raman spectra, XPS, and Fourier transform infrared analysis, the films deposited at the pressure of 6 and 8 Pa have high sp³ content and show typical diamond‐like character. However, the microstructures and bond configuration of the films deposited at 11, 15, and 20 Pa have high sp² content and favored fullerene‐like nanostructure. The hardness and sp² content were shown to reach their minimum values simultaneously at a deposition pressure of 8 Pa and then increased continuously. The film with fullerene‐like nanostructure obtained at 20 Pa displays a high Raman I_D/I_G ratio (~1.6), and low XPS C 1s binding energy (284.4 eV). The microstructural analysis indicates that the films are composed of a hard and locally dense fullerene‐like network, i.e. a predominantly sp²‐bonded material. The rigidity of the films is basically provided by a matrix of dispersed cross‐linked sp² sites. Copyright © 2012 John Wiley & Sons, Ltd.     

Untersuchungen an molekülkomplexen von n-σ-TYP MITT. I. über freie enthalpie—kraftkonstantenkorrelationen von molekülkomplexen des jods m

Linear correlations have been found between the ΔG⁰ values of the molecular complexes R₁R₂R₃PO/I₂, R₁R₂SO/I₂ and R₁R₂SeO/I₂ and the PO, SO and SeO valence force constants, respectively. The nature of the correlation is determined by the ZO donor bond and not by the donor atom, where Z is P, S or Se. The change on ΔG⁰ values for an equal change in the ZO valence force constants increases in the order R₁R₂SO/I₂?R₁R₂R₃PO/I₂ < R₁ R₂SeO/I₂. Seleninyl complexes with I₂ are more stable than the analogous thionyl complexes. From ΔG⁰—f_zo correlation deductions can be made about the nature of the ZO donor bond and ΔG⁰ values can be evaluated from vibrational spectra. A linear correlation exists between the ΔG⁰ values of corresponding thionyl and seleninyl complexes which is of the same form as the correlation between the valence force constants of analogous thionyl and seleninyl compounds.     

DFT,AIM, and NBO study of the interaction of simple and sulfur-doped graphenes with molecular halogens,CH3OH,CH3SH,H2O,and H2S

Graphene is an important material in adsorption processes because of its high surface. In this work, the interactions between graphene (G), S-doped graphene (SG), and 2S-doped graphene (2SG) with eight small molecules including molecular halogens, CH₃OH, CH₃SH, H₂O, and H₂S were studied using density functional theory calculations. The adsorption energies showed that the SG was the best adsorbent, fluorine was the best adsorbate, and all molecular halogens were adsorbed on graphenes better than the other molecules. Most adsorption processes in the gas phase were exothermic with small positive ΔG _ads. Moreover, the solvent effect on the adsorption process was examined and all ΔH _ads and ΔG _ads values for adsorption processes tended to be more negative in all solvents. Therefore, most adsorption processes in the solvents were thermodynamically favorable. The second order perturbation energies obtained from NBO calculations confirmed that the interactions between molecular halogens and our molecules had more strength than those of other molecules. The Laplacian of ρ values obtained from the AIM calculations indicated that the type of interaction in all our complexes was one of closed shell interaction. The MO results and DOS plots also revealed that sulfur doping could increase the conductivity of graphene and this conductivity was enhanced more when they interacted with molecular halogens.     

Synthesis of Polymer Films by an Electron Emission CVD Technique

A low-pressure chemical vapor deposition (CVD) technique based on the formation of reactive film precursors by dissociation of gas-phase reactants by electron impact is described. The electrons are emitted by a hot filament and a positive bias voltage applied to the substrate provides control of the emission current. The emitted electrons are primarily responsible for the gas dissociation, but secondary electrons resulting from electron-impact ionization of the gas molecules also produce reactive species, contributing to the deposition process. This technique was used to synthesize polymer films from C₂H₂–N₂ mixtures at pressures ranging from 1–10 Pa. The dependencies of the current collected by the substrate, I_S, on the substrate bias voltage, V_S, and on the gas pressure were determined. The film deposition rate was measured as a function of several deposition variables such as I_S, V_S, and the N₂ to C₂H₂ flow rate ratio. Oxygen was present in the films as a contaminant. Analyses by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) provided insight into the film molecular structure, allowing identification of various functional groups and binding states of the C- and N–atoms. From the XPS spectra, the N/C and O/C ratios were determined.     

A procedure for studying the sorption of ethanol vapor on a monomolecular Langmuir-Blodgett arachic acid film

The paper presents the results of studies of the sorption of ethanol from the gas phase by a monomolecular arachic acid layer deposited by the Langmuir-Blodgett method onto the surface of a nickel substrate. Studies were performed using a working model based on a field-effect transistor. Sorption was accompanied by changes in the potential of the nickel substrate. The dependence of transistor current I _D on time t was related to the conditions of Langmuir-Blodgett film deposition. The value and characteristic time of signal variations as the atmosphere changed depended on the pressure of monolayer deposition and, therefore, monolayer phase state on the surface of water when it was transferred to the solid substrate. The experimental I _D (t) dependence was compared with the time dependence of arachic monolayer surface coverage with sorbent molecules calculated by the Langmuir model. The conclusion was drawn that the model was capable of describing the sorption of ethanol vapor by the Langmuir-Blodgett arachic acid monolayer at low partial pressures p ≤ 0.05p ₀, where p ₀ is the saturated vapor pressure.     

Probing interfacial interactions of nafion ionomer: Thermal expansion of nafion thin films on substrates of different hydrophilicity/hydrophobicity

Interfacial interactions of Nafion ionomer with superhydrophilic (Pt, Au), hydrophilic (SiO₂), and hydrophobic (graphene, octyltrichlorosilane [OTS]‐modified SiO₂) is investigated, using in situ thermal ellipsometry, by quantification of substrate‐ and thickness‐dependent thermal properties of the ultrathin Nafion films of nominal thickness ranging 25–135 nm. For sub‐50 nm thin Nafion films, the thermal expansion coefficient of films decreased in the order of most hydrophobic to most hydrophilic substrate: OTS > graphene > SiO₂ > Au > Pt, implying weaker interpolymer and polymer–substrate interactions for films on hydrophobic substrates. Expansion coefficient of films on SiO₂, graphene, and OTS‐modified SiO₂ decreased with thickness whereas that of films on Au and Pt substrates increased with thickness. Above ~100 nm of thickness, films on all substrates converged toward a common value representative of bulk Nafion. Thermal transition temperature was found to be higher for films on hydrophilic SiO₂ than that for films on hydrophobic graphene and OTS‐modified SiO₂ but was not discernible for films on Au and Pt substrates. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 343–352     

Ring-disk electrode studies of the open-circuit dissolution of iodine films formed during the anodic oxidation of iodide on platinum

The open-circuit behavior of iodine films formed on platinum by electrooxidation of iodide was studied at rotating disk and rotating ring-disk electrodes. The potential transient and ring current transient at open circuit for c_I^?>0.012 M can be explained by assuming: (1) convective-diffusion controlled dissolution of the film; (2) establishment of the I₂+I^?→ I₃^? equilibrium; (3) establishment of the I₂ (solid) →I₂ (solution) equilibrium. The behavior at lower concentrations of c_I^? suggests that convective-diffusion control is absent.     

The chemical composition and bonding structure of amorphous hydrogenated carbon nitride film on aluminum surface deposited by electrodeposition

Amorphous hydrogenated carbon nitride films with excellent adhesion to the substrates were deposited on the surfaces of aluminum plates by electrodeposition with acetonitrile as carbon source. The as‐obtained films were detailed characterized by Raman, XPS and FTIR. The results show that the as‐obtained films are mainly made up of sp2 C, sp3 C, C? N, C?N bonds and a spot of sp3? CH₂, sp3? CH₃, sp3? CH and sp2? CH bonds. The atomic ratio of N/C is evaluated to be about 2.98 at.% by XPS. Raman analysis indicated that I_D/I_G ratios decreased from 0.827 to 0.675 when the deposition time increased from 10 to 20 h. At the end, on the basis of the detailed analysis, results of Raman, FTIR and XPS, the possible deposition mechanism was discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectra of carriers in ionic-liquid-gated transistors fabricated with poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene)

We observed the Raman spectra of carriers, positive polarons and bipolarons, generated in a poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C14) film by FeCl₃ vapor doping. Electrical conductivity and Raman measurements indicate that the dominant carriers in the conducting state were bipolarons. We identified positive polarons and bipolarons generated in an ionic-liquid-gated transistor (ILGT) fabricated with PBTTT-C14 as an active semiconductor and an ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [BMIM][TFSI] as a gate dielectric using Raman spectroscopy. The relationship between the source−drain current (I_D) at a constant source−drain voltage (V_D) and the gate voltage (V_G) was measured. I_D increased above −V_G = 1.1 V and showed a maximum at −V_G = 2.0 V. Positive polarons were formed at the initial stage of electrochemical doping (−V_G = 0.8 V). As I_D increased, positive bipolarons were formed. Above V_G = −2.0 V, bipolarons were dominant. The charge density (n), the doping level (x), and the mobility of the bipolarons were calculated from the electrochemical measurements. The highest mobility (μ) of bipolarons was 0.72 cm² V⁻¹ s⁻¹ at x = 110 mol%/repeating unit (−V_G = 2.0 V), whereas the highest μ of polarons was 4.6 × 10⁻⁴ cm² V⁻¹ s⁻¹ at x = 10 mol%.