Kinetic study of atom transfer radical homo- and copolymerization of styrene and methyl methacrylate initiated with trichloromethyl-terminated poly(vinyl acetate) macroinitiator

Atom transfer radical bulk copolymerization of styrene (St) and methyl methacrylate (MMA) was performed in the presence of CuCl/PMDETA as a catalyst system and trichloromethyl-terminated poly(vinyl acetate) telomer as a macroinitiator at 90 °C. The overall monomer conversion was followed gravimetrically and the cumulative average copolymer composition at moderate to high conversion was determined by ¹H NMR spectroscopy. Reactivity ratios of St and MMA were calculated by the extended Kelen–Tudos (KT) and Mao–Huglin (MH) methods to be r_St = 0.605 ± 0.058, r_MMA = 0.429 ± 0.042 and r_St = 0.602 ± 0.043, r_MMA = 0.430 ± 0.032, respectively, which are in good agreement with those reported for the conventional free-radical copolymerization of St and MMA. The 95% joint confidence limit was used to evaluate accuracy of the estimated reactivity ratios. Results showed that in the controlled/living radical polymerization systems such as ATRP, more reliable reactivity ratios are obtained when copolymer composition at moderate to high conversion is used. Good agreement between the theoretical and experimental composition drifts in the comonomer mixture and copolymer as a function of the overall monomer conversion was observed, indicating the accuracy of reactivity ratios calculated by copolymer composition at the moderate to high conversion. Instantaneous copolymer composition curve and number-average sequence length of comonomers in the copolymer indicated that the copolymerization system tends to produce a random copolymer.     

Residence time distribution analysis and optimization of photocatalysis of phenazopyridine using immobilized TiO2 nanoparticles in a rectangular photoreactor

Optimization of photocatalytic degradation of phenazopyridine (PhP) under UV light irradiation using immobilized TiO₂ nanoparticles was studied. The effect of operational parameters was investigated using response surface methodology (RSM). Maximum removal efficiency was achieved at the optimum conditions: initial drug concentration of 10 mg/L, UV light intensity of 47 W/m², flow rate of 200 mL/min, and reaction time of 150 min. The residence time distribution (RTD) analysis was studied to find the effect of flow rate on the drug removal efficiency. The tracer (PhP) pulse injection response was studied with UV–vis measurements and was used to prepare RTD curves.     

Process intensification approach for preparation of curcumin nanoparticles via solvent–nonsolvent nanoprecipitation using spinning disc reactor

Continuous preparation of curcumin nanoparticles via solvent–nonsolvent (S-NS) precipitation by using spinning disc reactor was investigated. The process intensification by spinning disc reactor (SDR) along with the comparative study of conventional mechanical agitated contactor was carried out. Solvent used for curcumin precipitation in this study was ethanol whereas non-solvent deionised water. Influences of various operating parameters for spinning disc process; such as flow rate of S-NS, S-NS ratio, concentration of curcumin, disc characteristics, concentration of protecting agent and rotating disc speed were examined on the nanoparticles size. The average optimum curcumin particles size was obtained in the range 180–220 nm in consideration with particles size distribution at a flow rate of 200 mL min⁻¹; curcumin concentration of 0.5 g L⁻¹ in ethanol; polyvinylpyrilodine (PVP) concentration of 1 g L⁻¹ in deionised water; S:NS ratio 1:4 and operating disc speed of 1500 rpm. Particles were characterized by using XRD, FT-IR, DSC and SEM which showed decrease in the crystallinity after the nanoprecipitation of curcumin. The dissolution rates of the fabricated curcumin nanoparticle were found drastically higher than original curcumin.     

The effects of pulse repetition rate on the structural,surface morphological and UV photodetection properties of pulsed laser deposited Mg-doped ZnO nanorods

The Mg_0.05Zn_0.95O (MZO) nanorod array (NRA) films have been successfully grown onto SiO₂/ n-Si substrates by pulsed laser deposition (PLD) without any template or seed layer and the influence of pulse repetition rate (3 to 15 Hz) of a 248 nm KrF excimer laser on their crystallinity, surface morphology and UV photodetection properties were systematically investigated. All the samples show the hexagonal wurtzite phase with a preferential c-axis orientation and the optimum crystallization of the MZO NRAs occurs at 5 Hz. FE-SEM analysis revealed that the growth of MZO NRAs is strongly influenced by the pulse repetition rate. It was observed that the average film thickness increases almost linearly with the pulse repetition rate and the MZO nanorod arrays grown at 5 Hz exhibits best surface area. Moreover, the room temperature UV photodetection properties of the samples were investigated in metal–semiconductor–metal (MSM) planar configurations and are found to be strongly driven by the pulse repetition rate dependent crystalline and surface morphological features. The device current–voltage (I–V) characteristics were measured under dark and UV light conditions. Then, the photocurrent and responsivity were measured with the variation of optical power density and applied voltage, respectively. Transient photoresponse studies show an exceedingly stable and fast switching UV photoresponse for the photodetector having MZO nanorods grown at 5 Hz, which demonstrates highest responsivity of 17 mA/W upon 2 mW/cm² UV illumination (365 nm), at 5 V bias.     

Electrochemical synthesis and characterization of a novel thiazole-based copolymer and its application in biosensor

A novel copolymer based on 2-aminothiazole (AT) and 2-amino-4-thiazoleacetic acid (ATA) is electrochemically synthesized and then characterized using UV–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and electrochemical techniques. The results confirmed that the obtained polymer was a copolymer rather than a blend or a composite of the respective homopolymers and could improve the electrochemical response of both positively and negatively charged analytes. Therefore, the copolythiazole film was applied to determine ascorbic acid (AA), dopamine (DA) and uric acid (UA). It is found that the peak separating degrees and peak currents of AA, DA and UA at copolythiazole modified electrode were much better than those at bare GCE. Under the optimum conditions, the linear calibration curves were obtained in the range of 10–2000 μM for AA, 1–150 μM for DA, 1–180 μM for UA. The detection limits of AA, DA and UA were 2, 0.04 and 0.4 μM, respectively (S/N = 3). The practical application of the modified electrode was demonstrated by the determination of UA in urine sample.     

Newer dynamic electrochromic nanorods of poly(o-anisidine-co-ethyl 4-aminobenzoate) synthesized by electrochemical polymerization

Electrochemical copolymerization of o-anisidine with ethyl 4-aminobenzoate was carried out in aqueous 0.1 M HClO₄ by employing cyclic voltammetry. Copolymer films were grown for different molar concentration ratios of ethyl 4-aminobenzoate. Electrochemical homopolymerizations of o-anisidine and ethyl 4-aminobenzoate were carried out independently under similar conditions. The copolymers exhibited high solubility in many polar solvents. The scan rate exerted good influence on the polymer effect on this glassy carbon electrode copolymer film, revealing electroactive film's excellent adherent properties. Spectroelectrochemical studies of the copolymer film were carried out on indium tin oxide plates. The copolymer was characterized by FTIR spectral data. The surface morphology was studied using SEM and TEM analysis. The electrical conductivity of copolymer was measured by four-probe conductivity meter.     

Photocatalytic reduction of CO2 to energy products using Cu–TiO2/ZSM-5 and Co–TiO2/ZSM-5 under low energy irradiation

Copper or cobalt incorporated TiO₂ supported ZSM-5 catalysts were prepared by a sol–gel method, and then were characterized by XRD, BET, XPS and UV–vis diffuse reflectance spectroscopy. Ti^3 + was the main titanium specie in TiO₂/ZSM-5 and Cu–TiO₂/ZSM-5, which will be oxide to Ti^4 + after Co was doped. With the deposition of Cu or Co, the efficiency of the CO₂ conversion to CH₃OH was increased under low energy irradiation. The peak production rate of CH₃OH reached 50.05 and 35.12 μmol g^− 1 h^− 1, respectively. High photo energy efficiency (PEE) and quantum yield (φ) were also reached. The mechanism was discussed in our study.     

All-solid-state quantum-dot-sensitized solar cells with compact PbS quantum-dot thin films and TiO2 nanorod arrays

To improve the electron injection efficiency from PbS quantum dots to TiO₂ nanorods and prevent the direct contact of spiro-OMeTAD and TiO₂ nanorods, a compact PbS quantum-dot thin film can be successfully obtained on TiO₂ nanorod arrays 360 nm in length by repeated spin coating of Pb(Ac)₂, Na₂S and 1,2-ethanedithiol solution in a step-by-step process. The corresponding solid-state quantum-dot-sensitized solar cells are fabricated using a novel structured FTO/compact PbS quantum-dot thin film sensitized TiO₂ nanorod array/spiro-OMeTAD/Au that achieves a photoelectric conversion efficiency of 3.57% under AM 1.5 G illumination (100 mW cm⁻²), which represents a high value among all-solid-state PbS quantum-dot-sensitized TiO₂ nanorod array solar cells.     

Photoreversible crosslinking of poly-(ethylene-butyl-acrylate) copolymers functionalized with coumarin chromophores using microwave methodology

Coumarin chromophores were successfully bonded onto ethylene-co-butyl acrylate (EBA) with a butyl ester content of 17% under mild conditions in solution via microwave irradiation. The synthesis consisted of three steps: partial conversion of butyl esters into carboxylic acid groups, conversion of carboxylic acid functionalities into acid chloride groups and esterification using 7-(3-hydroxy-propoxy) coumarin. The EBA modified with coumarin groups was characterized using FTIR, NMR, UV spectroscopy and thermal methods. The EBA modified with coumarin moieties (EBA-g-coum) was crosslinked by irradiating at 365 nm, and the coumarin photodimers were cleaved by irradiating at 280 nm. The reversibility of the photoreactions in the solid state was monitored using UV spectroscopy. Additionally, the mechanical properties of the materials were determined.     

Photocatalytic and adsorptive treatment of 2,4-dinitrophenol using a TiO2 film covering activated carbon surface

Anatase titanium dioxide (TiO₂) in particle sizes of roughly 0.5–20 μm was prepared from amorphous TiO₂ in an aqueous H₂O₂ solution by heating at 90 °C for 9 h and directly deposited on a PET film. On the other hand, granular activated carbon (AC) particles in sizes of 1–2 mm in diameter were adhesively deposited on a PET film, and their surfaces were also coated with TiO₂. The resulting three preparations (TiO₂-, AC-, and TiO₂/AC-PET films) were set up in an annular-flow reactor to treat aqueous solutions of 2,4-dinitrophenol (DNP) in a batch-recirculation mode. The rate of DNP adsorption onto the TiO₂/AC-PET film without UV irradiation was almost the same as that onto the AC-PET film, indicating that the attraction of DNP to AC was not lowered in the presence of TiO₂ film. Observation of SEM photographs suggests that this result is attributed to the porous structure of the thin TiO₂ film covering AC particles. The rate of DNP removal by the TiO₂-AC PET film under UV irradiation was 2.9 times higher than that by the TiO₂-PET film under UV irradiation, and was 1.1 times higher than the rate of DNP adsorption onto the AC-PET film. The rate of DNP removal by the AC-PET film decreased by 40% after six runs, while that by the TiO₂/AC-PET film decreased by 22%. Durable experiments using the TiO₂/AC-PET and AC-PET films clarified that the lifetime of the TiO₂/AC-PET film is at least two times longer than that of the AC-PET film. This result suggests that DNP molecules are photocatalytically decomposed when passing through the porous TiO₂-PET film, which lessens a burden of DNP adsorption on AC. Moreover, the DNP treatments in the batch-recirculation flow system suggested that the TiO₂/AC-PET film saturated with DNP can be successfully regenerated at 60 °C.     

High-quality diamond film deposition on a titanium substrate using the hot-filament chemical vapor deposition method

Diamond film on titanium substrate has become extremely attractive because of the combined properties of these two unique materials. Diamond film can effectively improve the properties of Ti for applications as aerospace and biomedical materials, as well as electrodes. This study focuses on the effects of process parameters, including gas composition, substrate temperature, gas flow rate and reactor pressure on diamond growth on Ti substrates using the hot-filament chemical vapor deposition (HFCVD) method. The nucleation density, nuclei size as well as the diamond purity and growth tendency indices were used to quantify these effects. The crystal morphology of the material was examined with scanning electron microscopy (SEM). Micro-Raman spectroscopy provided information on the quality of the diamond films. The growth tendency of TiC and diamond film was determined by X-ray diffraction analysis. The optimal conditions were found to be: CH₄:H₂ = 1%, gas flow rate = 300 sccm, substrate temperature T_sub = 750 °C, reaction pressure = 40 mbar. Under these conditions, high-quality diamond film was deposited on Ti with a growth rate of 0.4 μm/h and sp² carbon impurity content of 1.6%.     

Simulation of airflow and aerosol deposition in the nasal cavity of a 5-year-old child

As a human grows from birth to adulthood, both airway anatomy and breathing conditions vary that alter the deposition rate and pattern of inhaled aerosols. However, deposition studies have typically focused on adult subjects, results of which may not be readily extrapolated to children. Furthermore, because of greater ventilation rate per body weight, children receive a greater dose than adults and therefore are more susceptible to respiratory risks. This study is to evaluate the transport and deposition of respiratory aerosols in a nasal-laryngeal airway model based on MRI head images of a 5-year-old boy. Differences between this child and adults in nasal physiology and aerosol filtering efficiency will be emphasized. A validated low Reynolds number (LRN) k?ω turbulence model was employed to simulate laminar, transitional, and fully turbulent flow regimes within the nasal airways. Particle trajectories and deposition in the spectrum of 0.5–32 μm were evaluated using a well-tested Lagrangian tracking approach for inhalation flow rates ranging from sedentary (3 L/min) to heavily active (30 L/min) conditions. Simulation results of the inhalation pressure drop and particle deposition rate provided a reasonable match with existing experimental results in nasal airway casts of children. Much higher breathing resistance was observed in the 5-year-old child compared to adults. Furthermore, deposition patterns were sensitive to inhalation flow rate under low activity conditions. An empirical correlation of child nasal filtering efficiency was proposed for micrometer particles based on a wide range of test conditions. Results of this study demonstrate that significant child–adult difference exists in inhaled aerosol depositions, which should be taken into account for risk assessment of airborne toxicants on infants and children.     

New heteroleptic benzimidazole functionalized Ru-sensitizer showing the highest efficiency for dye-sensitized solar cells

We designed and synthesized a new ruthenium complex using terpyridine as an anchoring ligand and BOC (tert-butyloxycarbonyl) protected bidentate benzimidazole derivative as an ancillary ligand, coded as GS7. The complex was characterized using ¹H NMR, FTIR, elemental analysis, UV–vis spectrophotometer, and cyclic voltammetry. We also tested photovoltaic performance of this complex for dye-sensitized solar cell (DSSCs). GS7 when used as a sensitizer for DSSCs with iodine triiodide electrolyte, showed a J_sc of 15.25 mA cm^− 2, a V_oc of 0.576 V, a FF of 0.691 and overall power conversion efficiency of (η) 6.07%.     

Controlled radical copolymerization of β-pinene and n-butyl acrylate

The feasibility of the radical copolymerization of β-pinene and n-butyl acrylate (n-BA) was clarified for the first time. β-pinene was found to undergo degradative chain transfer during the copolymerization. This degradative chain transfer became less competitive with the copolymerization by the addition of EtAlCl₂, and the copolymer yield, β-pinene incorporation and molecular weight of the copolymer increased remarkably compared with the case in the absence of EtAlCl₂. The monomer reactivity ratios evaluated by the nonlinear least-squares method were r_β-pinene ∼ 0 and r_n-BA ∼ 2.2 in the absence of EtAlCl₂, r_β-pinene ∼ 0 and r_n-BA ∼ 0.86 in the presence of EtAlCl₂ in bulk at 70 ˚C. Furthermore, the possible controlled copolymerization of β-pinene and n-butyl acrylate was then attempted via the reversible addition-fragmentation transfer (RAFT) technique. The copolymerization (f_β-pinene = 0.20) using 2-cyanopropyl-2-yl dithiobenzoate as the RAFT agent displayed the typical features of a controlled system, such as the first-order kinetics and the linear increase in molecular weight with the overall conversion. The livingness of the copolymer chains was further proved by using them as the macroinitiator for the chain extension with styrene by RAFT process.     

Effect of oxygen flow rate on the ultraviolet sensing properties of zinc oxide nanocolumn arrays grown by radio frequency magnetron sputtering

Highly transparent metal–semiconductor–metal ultraviolet (UV) photoconductive sensors were fabricated using thin (less than 100 nm in thickness), dense, small-diameter ZnO nanocolumn arrays prepared via low-power, catalyst-free radio frequency (RF) magnetron sputtering at different oxygen flow rates ranging from 0 to 25 sccm. The FESEM images revealed the average nanocolumn diameter decreased with increasing oxygen flow rate. The transmittance spectra show that with the introduction of oxygen, the transmittance of the nanocolumn arrays in the visible region improves relative to that of a film prepared in the absence of oxygen with values greater than 95%. The UV responsivity and sensitivity were significantly improved for sputtered ZnO nanocolumn arrays prepared at oxygen flow rates up to 10 sccm, with the highest values of 9.70 mA/W and 2.20×10⁴. Furthermore, the responsivity and sensitivity decreased at oxygen flow rates greater than 10 sccm, which can be attributed to the increased electrical resistance of the nanocolumn arrays. Our findings indicate that a high-performance UV photoconductive sensor can be realised using very thin sputtered ZnO nanocolumn arrays and that such a sensor would exhibit high sensitivity.     

Quality of diamond wafers grown by microwave plasma CVD: effects of gas flow rate

We found a strong impact of gas flow rate on diamond growth process in a 5 kW microwave plasma chemical vapour deposition reactor operated on CH₄-H₂ gas mixtures. Diamond films of 0.1–1.2 mm thickness and 2.25 in. in diameter were produced at H₂ flow rates varied systematically from 60 sccm to 1000 sccm at 2.5% CH₄. The highest growth rate, 5 μm h⁻¹, was observed at intermediate F values (≈300 sccm). Carbon conversion coefficient (the number of C atoms going from gas to diamond) increases monotonically up to 57% with flow rate decrease, however, this is accompanied with a degradation of diamond quality revealed from Raman spectra, thermal properties and surface morphology. High flow rates were necessary to produce uniform films with thermal conductivity >18 W cm⁻¹ K⁻¹. Diamond disks with very low optical absorption (loss tangent tgδ<10⁻⁵) in millimetre wave range (170 GHz) have been grown at optimized deposition conditions for use as windows for high-power gyrotrons.     

Simulation of supercritical water–hydrocarbon mixing in a cylindrical tee at intermediate Reynolds number: Impact of temperature difference between streams

The objective of this work is to study the impact of the temperature difference between the streams on the flow dynamics and mixing of supercritical water (SCW) and a model hydrocarbon (n-decane), under fully miscible conditions, in a small-scale cylindrical tee mixer (pipe ID = 2.4 mm), at an intermediate inlet Reynolds number of 500 using 3-D CFD simulations. When the water and n-decane streams enter the mixer at inlet temperatures of 800 K and 700 K respectively (ΔT = 100 K), the flow remains laminar and the variations of density and viscosity with temperature do not have a significant impact on the flow and mixing dynamics. However, when the water inlet temperature is 1000 K (ΔT = 300 K), the water–HC shear layer becomes unstable close to x = 5D downstream of the mixing joint followed by shear-layer rollup and transition to turbulence. This leads to significant enhancement in the mixing rate. However, in a simulation of SCW n-decane mixing with the same inlet conditions but with the physical properties held fixed at the inlet values (no variation with temperature), the shear layer remains stable and steady state is reached. It was found that, the large variation of temperature of 300 K within the mixing layer leads to an increase in the local fluid density and a decrease in the local fluid viscosity within the mixing layer attributed mainly to the cooling of water and the heating of n-decane respectively. These physical property variations result in an increase in the local Reynolds number within the shear layer rendering it unstable to perturbations in the flow. Thus, the variations in mixture density and viscosity with temperature under near-critical conditions were found to have a significant impact on the flow and mixing dynamics in the tee mixer.     

Photocatalysed selective oxidation of cyclohexane to benzene on MoOx/TiO2

Heterogeneous oxidative dehydrogenation of cyclohexane to benzene was found to occur under photocatalytic conditions on MoO_x/TiO₂. Initial cyclohexane conversion of 15% and maximum selectivity to benzene of 65% were achieved at 308 K on 8 wt.% MoO_x/TiO₂ under irradiation with a continuous flow reactor. The main by-product was carbon dioxide. Catalyst deactivation was observed. Titania exhibited high activity of total oxidation to carbon dioxide but was not selective for conversion to benzene. Polymolybdate species seem to be responsible for changing the selectivity of titania, favouring the formation of benzene. Nevertheless, when supported on α- or γ-alumina they promote only the formation of carbon dioxide.     

New prototype for the treatment of falling film liquid effluents by gliding arc discharge part I: Application to the discoloration and degradation of anthraquinonic Acid Green 25

Gliding arc discharge (GAD) reactors are continuously in progress in order to improve the treatment efficiency of recalcitrant compounds. However, up to now, they remain difficult to transfer to industrial applications because of some technical constraints in their design. In this study, a new efficient prototype is proposed for the treatment of gravity falling film shaped of liquid effluents. The liquid flow rate is now continuous as the tank containing the solution to be treated is replaced by an inclined plate along which flows the liquid. The various working parameters are optimized and the new prototype efficiency is tested on discolouration and degradation of the anthraquinonique Acid Green 25. The optimized values obtained are: the liquid flow rate ω = 1 L h⁻¹, the plate tilt angle α = 45° and the channel width Δ = 3 mm. The rates of discolouration and degradation reach 95% and 90% respectively after 12 cycles (180 min) of plasma exposition. The GAD in the presence of humid air generates highly oxidizing radical species such as ^•OH with a standard potential E°[(^•OH/H₂O) = 2.85 V/SHE] and its reducer agent H₂O₂ [E°(H₂O₂/H₂O) = 1.68 V/SHE.     

Enhanced efficiency of dye-sensitized solar cells with counter electrodes consisting of platinum nanoparticles and nanographites

The effect of a counter electrode (CE), fabricated by hybridizing the platinum nanoparticle (PtNP) and the nanographite (NG) on a dye-sensitized solar cell (DSSC), has been studied in this work. The catalytic PtNP/NG composite film for a CE is prepared using aniline (ANI) monomers as a dispersing medium, followed by spin-coating and annealing processes. The PtNP/NG composite film owns a high catalytic ability of converting tri-iodide to iodide due to the large surface roughness of the film. Thus, the DSSC assembled with the corresponding CE gives enhanced short-circuit current density (J_SC) and power-conversion efficiency (η) of 17.57 mA cm^?2 and 7.07%, respectively, while the corresponding values are 14.57 mA cm^?2 and 6.65% for a DSSC with a bare PtNP CE. Lower loading amounts of PtNPs for the PtNP/NG CE than those for the bare PtNP CE is demonstrated. Transmission electron microscopy (TEM) and UV/Vis absorption measurements are used to observe the dispersion of NGs in the solutions. X-ray diffraction (XRD) and Raman analyses are used to confirm the PtNP/NG composite film. The results are also substantiated by the characterizations of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM), and atomic force microscopy (AFM).