Thermal Oxidation Etching Research Articles

Surface modification of titanium foams for modulated and targeted release of drug-loaded biocompatible hydrogel. Proof of concept

Bone-tissue replacement surgeries usually need medication to mitigate implant rejections or prevent local infections. In this study, a modulated and targeted tetracycline (TC) loaded gelatine type A hydrogel is release from Ti foams as a proof of concept for an innovative and intelligent drug release system. The drugs are released in a localized and controlled manner. The Ti foams fabricated by the space holder technique were surface modified by two different techniques of surface modification, i.e., thermal oxidation and acid etching, to assess their influence on TC release. The characterization carried out after the surface modification indicated that samples modified with acid etching have produced a rougher surface, increasing the diameter of pores (from 500 μm to 700 μm, approximately) due to coalescence of pores. The increase of pore roughness has demonstrated the delaying of the TC release due to the greater adhesion between the surface roughness and the hydrogel. In addition, the increase of pore size improves the possibility to infiltrate high amount of drug-loaded biocompatible hydrogel. Opposite, oxidized surface samples have generated a rutile type TiO2 layer that, because of its hydrophilic nature facilitate the degradation of the hydrogel, and consequently, the TC release from the Ti foams. Therefore, both methods show opposite behaviour, available to increase (acid etching) or decrease (thermal oxidation) the TC release thanks to the different kinetic degradation of hydrogel, as a potential way for drug-release from metallic implants. Thus, while acid-etched samples showed maximum TC release value of 35 wt%, after 120 min, the oxidized samples surpassed the 40 % of TC release after same 120 min of release time treatment.

Facile synthesis of ZnO/Ag/g-C3N4 nanocomposites for multiple applications in photocatalytic degradation and photoactivated NO2 sensing

It is important to seek effective strategies to fabricate nanomaterials with multi-functionalities in noxious gas detection and poisonous waste treatment. Herein, Ag nanoparticles and g-C3N4 nanosheets co-modified ZnO heterostructure was synthesized via a one-step polymer-network gel method, which is used as both photocatalyst and sensing material. Being a visible-light-driven photocatalyst, the ternary ZnO/Ag/g-C3N4 composite produced 100 % Rhodamine B degradation within 30 min with good cycling stability. Besides, the gas sensor based on ZnO/Ag/g-C3N4 exhibited superb room-temperature sensing performance under neutral light excitation, with a response value of 15.3–5 ppm NO2 and a lower detection limitation. The excellent performance was mainly attributed to the significantly enhanced visible-light absorption as well as effectively suppressed charge recombination because of the synergism between the individual components. Moreover, the formation of g-C3N4 nanosheets during thermal oxidation etching plays a critical role in improving the surface area and enriching the surface oxygen vacancies. Thus, this work provides novel insights for the synthesis and multi-applications of ZnO/Ag/g-C3N4 heterostructure with high performance.

Two-dimensional boron nanosheets for selective enrichment and detection of cis-diol compounds by surface-assisted laser desorption/ionization time-of-flight mass spectrometry

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) is an effective method for detecting of low-mass molecules. In this study, two-dimensional boron nanosheets (2DBs) were fabricated through thermal oxidation etching and coupling liquid exfoliation technologies, and applied as a matrix and selective sorbent for detecting cis-diol compounds by SALDI-TOF MS. The outstanding nanostructure and boric acid active sites of 2DBs endow them with sensitivity for cis-diol compound detection, excellent selectivity, and low background interference for complex samples. The specific in-situ enrichment faculty of the 2DBs as a matrix was investigated by SALDI-TOF MS using glucose, arabinose, and lactose as model analytes. In the presence of 100 -fold more interfering substances, the 2DBs showed high selectivity against cis-diol compounds, and exhibited a better sensitivity and a reduced limit of detection through enrichment treatment than graphene oxide matrices. The linearity, limit of detection (LOD), reproducibility, and accuracy of the method were evaluated under optimized conditions. The results showed that the linear relationships of six saccharides remained in the range of 0.05–0.6 mM with a correlation coefficient r ≥0.98. The LODs of six saccharides were 1 nM (glucose, lactose, mannose, fructose) and 10 nM (galactose, arabinose). Sample-to-sample (n = 6) with relative standard deviations (RSDs) of 3.2% to 8.1% were observed. Recoveries (n = 5) of 87.9–104.6% were obtained at three spiked levels in the milk samples. The proposed strategy promoted the development of a matrix for use with SALDI-TOF MS detection, in which the UV absorption properties and enrichment capabilities of 2DBs were combined.

Process Optimization and Performance Evaluation of TSV Arrays for High Voltage Application.

In order to obtain high-quality through-silicon via (TSV) arrays for high voltage applications, we optimized the fabrication processes of the Si holes, evaluated the dielectric layers, carried out hole filling by Cu plating, and detected the final structure and electric properties of the TSVs. The Si through-hole array was fabricated in an 8-inch Si substrate as follows: First, a blind Si hole array was formed by the Si deep reactive etching (DRIE) technique using the Bosch process, but with the largest width of the top scallops reduced to 540 nm and the largest notch elimidiameternated by backside grinding, which also opens the bottom ends of the Si blind holes and forms 500-μm-deep Si through holes. Then, the sidewalls of the Si holes were further smoothed by a combination of thermal oxidation and wet etching of the thermal oxide. The insulating capability of the dielectric layers was evaluated prior to metal filling by using a test kit. The metal filling of the through holes was carried out by bottom-up Cu electroplating and followed by annealing at 300 °C for 1 h to release the electroplating stress and to prevent possible large metal thermal expansion in subsequent high-temperature processes. The TSV arrays with different hole diameters and spacing were detected: no visible defects or structure peeling was found by scanning electron microscopy (SEM) observations, and no detectable interdiffusion between Cu and the dielectric layers was detected by energy dispersive X-ray (EDX) analyses. Electric tests indicated that the leakage currents between two adjacent TSVs were as low as 6.80 × 10-10 A when a DC voltage was ramped up from 0 to 350 V, and 2.86 × 10-9 A after a DC voltage was kept at 100 V for 200 s.

Phosphorous and Aluminum Implantation for MOSFET Manufacturing: Revisiting Implantation Dose Rate and Subsequent Surface Morphology

In this work, we study the impact of the dose rate on the electrical properties of aluminum (p-body, p+-body-contact) and phosphorous (n-source/drain) implanted 4H-SiC. We find no significant differences for dose rates ranging from 1×1011 cm-2s-1 to 2−7×1012 cm-2s-1. AFM scans across implanted and non-implanted regions after thermal oxidation and subsequent oxide etching reveal a clear dependence of the oxidation rate on the conduction type and doping concentration. In addition, we observe an increasing (decreasing) oxidation rate for increasing doping concentrations of the n-type (p-type) ion implanted areas.

Photocatalytic Degradation of Bisphenol A (BPA) Present in Aqueous Solution Using g-C3N4 Nanosheets Under Solar Light Irradiation

A graphite-like carbon nitride (g-C3N4) nanosheet sample was synthesized from a melamine precursor by a method of simple direct heating in a semi-closed system followed by thermal oxidation etching at 550 °C for 12 h. The sample was labelled as (g-C3N412h) and was systematically characterized. Moreover, the results were then compared with a pristine g-C3N4 sample for the degradation of Bisphenol A (BPA) present in water. Bisphenol A (BPA) is an endocrine disruptor. It is known that the BPA is one of the most harmful organic materials and that it does not degrade easily in the environment. It was therefore selected as a target to test the photocatalytic activity of prepared carbon nitride nanosheets under direct solar irradiation. The results showed the structure of the g-C3N4 nanosheets when the sample had been treated for a longer time compared to the regular treatment time. The optical band gap results remained the same, indicating the existence of a g-C3N4 backbone structure. However, the XPS and FTIR spectra showed some modification on g-C3N4 after longer etching treatment time such as the C-H, CO and N pyridinic structure. The photocatalytic degradation of Bisphenol A by the g-C3N4 nanosheets under solar irradiation was much better (around 60%) than that with the g-C3N43h bulk sample (around 30%). This enhanced photocatalytic activity can be attributed to multiple factors such as the smaller particle size, rich carbon surface and high surface area exhibited by the g-C3N4 nanosheets. This further indicates that g-C3N4 can be used with solar irradiation to treat wastewater containing endocrine disruptor chemicals.

Metal-free four-in-one modification of g-C3N4 for superior photocatalytic CO2 reduction and H2 evolution

Utilization of g-C3N4 as a single photocatalyst material without combination with other semiconductor remains challenging. Herein, we report a facile green method for synthesizing a metal free modified g-C3N4 photocatalyst. The modification process combines four different strategies in a one-pot thermal reaction: non-metal doping, porosity generation, functionalization with amino groups, and thermal oxidation etching. The as-prepared amino-functionalized ultrathin nanoporous boron-doped g-C3N4 exhibited a high specific surface area of 143.2 m2 g−1 which resulted in abundant adsorption sites for CO2 and water molecules. The surface amino groups act as Lewis basic sites to adsorb acidic CO2 molecules, which can also serve as active sites to facilitate hydrogen generation. Besides, the simultaneous use of ammonium chloride as a dynamic gas bubble template along with thermal oxidation etching efficiently boosts the delamination of the g-C3N4 layers to produce ultrathin sheets; this leads to stronger light–matter interactions and efficient charge generation. Consequently, the newly modified g-C3N4 achieved selective gas-phase CO2 reduction into CO with a production yield of 21.95 µmol g−1, in the absence of any cocatalyst. Moreover, a high hydrogen generation rate of 3800 µmol g-1h−1 and prominent apparent quantum yield of 10.6% were recorded. This work opens up a new avenue to explore different rational modifications of g-C3N4 nanosheets for the efficient production of clean energy.

Effects of various alcohol sacrificial agents on hydrogen evolution based on CoS2@SCN nanomaterials and its mechanism

Visible light induced photocatalysis converted solar energy to chemical energy in the form of hydrogen. g-C3N4 modified by thermal oxidation etching, doped S, and nonprecious metal cocatalyst CoS2 (CoS2@SCN) were used for photocatalytic hydrogen production. And then the charge transfer behavior and mechanism of various alcohol sacrificial agents on hydrogen evolution was analyzed by optical characterization, impedance analysis, Mott-Schottky, and photocurrent tests. The relationship between the structure and catalytic performance was also explored using characterization methods. The results showed that CoS2 significantly improved the light absorption of g-C3N4, and carrier migration and separation. And when the sacrificial agent was triethanolamine, the nanocomposite CoS2@SCN exhibited best catalytic performance with the highest hydrogen activity of 223.6 μmol g−1 h−1, the minimum volume in-phase charge transfer resistance with 55.19 Ω and the maximum photocurrent and photocurrent density with 5.5 μA cm−2 and 0.63 mA cm−2. The more negatively charged surface of organic alcohols were, the easier they were to react with holes, thus enhanced charge transfer and hydrogen production efficiency. This report provides guidance for the selection of hydrogen producing sacrificial agents and preparation of highly charge-efficient catalysts. And it also provides a theoretical basis for hydrogen production from wastewater and environmental remediation.

Oriented thermal etching of hollow carbon spheres with delicate heat management for efficient solar steam generation

Hollow carbon spheres (HCSs) with controllable morphology and structure have received considerable attention in the field of energy conversion and storage. Herein, monodispersed HCSs with cavity sizes tuned from 100 nm to 800 nm and shell thickness from 450 nm to 50 nm were successfully synthesized through a unique template-free thermal-etching method. It was evidenced that the dynamically controllable synthesis of HCSs was attributed to the “inside-out” oriented thermal oxidation etching of carbon spheres (CSs) induced by the differentiated “core-shell” chemical structures. Comparing to CSs, the obtained HCSs exhibited much increased efficiency for solar-driven interfacial steam generation (SISG), reaching as high as 88.9%, which outperforms most of the previously reported carbon-based materials. It was then demonstrated that the rational heat management for both photothermal and thermal-evaporation conversion is essential to achieve satisfying SISG efficiency. Depending on the increasing cavity sizes, HCSs presented gradual increases in both photothermal conversion and thermal-evaporation performances, mainly attributed to the improved light absorption and the delicate heat management, respectively. However, the further increase in cavity size resulted in excessive heat loss and presented decreased thermal-evaporation performance. This work provides an alternative and promising approach to the reasonable design of hollow nanostructures with delicate heat management for efficient SISG as well as other solar energy conversion applications.

2D Graphitic Carbon Nitride for Energy Conversion and Storage

AbstractGraphitic carbon nitride (g‐C3N4) have attracted great attention in the field of energy conversion and storage due to its unique layered structure, tunable bandgap, metal‐free characteristic, high physicochemical stability, and easy accessibility. 2D g‐C3N4 nanosheets have the features of short charge/mass transfer path, abundant reactive sites and easy functionalization, which are beneficial to optimizing their performance in different fields. However, the reviews of the comprehensive applications of 2D g‐C3N4 for energy conversion and storage are rare. Herein, this review first introduces the physicochemical properties of bulk g‐C3N4 and g‐C3N4 nanosheets, and then summarizes the synthetic strategies of 2D g‐C3N4 nanosheets in detail, such as thermal oxidation etching, chemical exfoliation, ultrasonication‐assisted liquid phase exfoliation, chemical vapor deposition, and others. Emphasis is focused on the rational design and development of 2D g‐C3N4 nanosheets for the diversified applications in energy conversion and storage, including photocatalytic H2 evolution, CO2 reduction, electrocatalytic H2 evolution, O2 evolution, O2 reduction, alkali‐metal ion batteries, lithium‐metal batteries, lithium–sulfur batteries, metal‐air batteries, and supercapacitors. Finally, the current challenges and perspectives of 2D g‐C3N4 nanosheets for energy conversion and storage applications are discussed.

Sulfur doping and structure defect functionalized carbon nitride nanosheets with enhanced photocatalytic degradation activity

Carbon nitride (C3N4) is a promising semiconductor photocatalytic material to treat residual pollutants in water. However, the limited visible light absorption and severe recombination of photoinduced carriers restrict the further development of C3N4 photocatalyst. Herein, sulfur doping and structure defect simultaneous functionalized C3N4 nanosheets (SCN-T) were prepared by convenient copolymerization of dicyandiamide and thioacetamide followed by thermal oxidation etching process. The SCN-T can not only harvest more visible light due to sulfur doping by lifting the valence band and conduction band, but also exhibit stronger reduction ability originated from combined effect of doping and exfoliation, higher separation and transfer efficiency and prolonged average lifetime of photoinduced carriers than pristine bulk C3N4 because of defect and sheet structures. The photocatalytic activity of the SCN-T was evaluated by performing the degradation experiments of Rhodamine B (RhB) and tetracycline hydrochloride (TC-HCl), and the results show that SCN-T exhibits a significant enhanced photocatalytic degradation activity. The degradation rate constants for RhB and TC-HCl over the SCN-T are 4.95 times and 2.07 times that of pristine bulk C3N4, respectively. The work provides valuable information for the activity optimization on the basis of composition and structural properties.

Preparation of g‐C3N4 Nanosheets/CuO with Enhanced Catalytic Activity on the Thermal Decomposition of Ammonium Perchlorate

AbstractThe thermal oxidation etching assisted g‐C3N4 nanosheets/CuO was prepared through a facile co‐precipitation strategy. In this work, the structure, morphology, and composition of g‐C3N4 (UCN, prepared by urea), g‐C3N4 nanosheets (TCN, prepared by thermal oxidation etching of UCN), g‐C3N4/CuO (UCN/CuO), g‐C3N4 nanosheets/CuO (TCN/CuO) were characterized via X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Furthermore, the catalytic effect of the obtained samples on the thermal decomposition of ammonium perchlorate (AP) was examined by thermal gravimetric analysis (TGA). As a result, in the case of 5 wt% TCN/CuO, the high decomposition temperature of AP decreased by 120.6 °C, which is much lower than that of UCN, TCN, CuO and UCN/CuO. In addition, the exothermic heat released from the decomposition of AP increased from 430.64 J g−1 to 2856.08 J g−1. This evident catalytic activity may be related to the synergistic effect of CuO and TCN. This work provides a novel strategy for the construction of composite catalyst for the thermal decomposition of AP, which is supposed to possess significant potential in the solid propellant field.

Selective, Catalytic Oxidations of C–H Bonds in Polyethylenes Produce Functional Materials with Enhanced Adhesion

Summary The synthesis of functional and processable polyethylenes from simple vinyl monomers with controlled molecular weights and architectures has been a grand challenge of polymer chemistry. Post-polymerization modification of the homopolymers of ethylene is attractive for this purpose but has been hampered by the lack of efficient methods for the selective functionalization of C–H bonds in polyolefins. We report the selective, catalytic oxidation of C–H bonds in commodity polyethylenes with varying molecular weights and architectures. Remarkably, the functionalized materials, even at low levels of functionalization, exhibit physical properties that are absent in unmodified polyolefins, such as strong adhesion and the ability to be painted with common waterborne latex paint. Such observations indicate that selectively modified polyethylenes as described here may help to transform existing commodity plastics into more valuable and potentially more sustainable materials.

Visible light-driven oxidant-free dehydrogenation of alcohols in water using porous ultrathin g-C3N4 nanosheets

Graphitic carbon nitride (g-C3N4) is a fascinating photocatalyst for solar energy utilization in photo-catalysis. Nevertheless, it often suffers from moderate photo-catalytic activity due to its low specific surface area and fast recombination rate of photogenerated electrons upon photo-excitation. Herein, we overcome the bottlenecks by constructing a porous g-C3N4 nanosheet (PCNS) through a simple thermal oxidation etching method. Benefited from its porous layer structure, the obtained PCNS exhibits large specific surface area, efficient separation of photogenerated charge carriers, as well as high exposure of active sites. As a result, it is robust and universal in visible light-driven dehydrogenation of alcohols in water under oxidant-free condition. Almost quantitative yields (> 99%) of various valuable carbonyl compounds were obtained over PCNS, while bulk g-C3N4 was far less efficient. Moreover, the photo-catalyst was highly stable and could be facilely recovered from the aqueous system for efficient reuse. The easy preparation and excellent performance made PCNS a promising and competitive photocatalyst for the solar applications.

Enhanced photocatalytic degradation of sulfadiazine via g-C3N4/carbon dots nanosheets under nanoconfinement: Synthesis, Biocompatibility and Mechanism

A metal-free environmentally-friendly and highly efficient photocatalyst is always desirable for photocatalytic remediation of antibiotic contamination. Herein, we firstly reported a novel g-C3N4/carbon dots nanosheets (C-CN-NS) nanocomposite photocatalyst which was prepared through a simple thermal oxidation etching process to remove a representative antibiotic sulfadiazine (SDZ). The degradation rate of SDZ by C-CN-NS500 (calcination temperature at 500 °C) was around 2.4 times larger than that of g-C3N4/carbon dots (C-CN) under visible light (λ > 420 nm) irradiation. The valence band of C-CN-NS500 increased by 0.42 eV under the quantum confinement effect, which promoted the oxidation potential, in favor of the degradation of SDZ. Increased specific surface area, improved separation efficiency and prolonged contact time for C-CN-NS500 can also facilitate the degradation of SDZ. Experiments demonstrated that photo-induced hole (h+) has the strongest effect in photocatalytic degradation process, followed by O2−, and OH. The toxicity assessment showed that C-CN-NS500 nanocomposite has high biocompatibility and low toxicity. This work may provide a promising green photocatalyst for photocatalytic degradation of antibiotic contaminant.

G-C3N4 nanosheets with tunable affinity and sieving effect endowing polymeric membranes with enhanced CO2 capture property

Two-dimensional (2D) materials have emerged as excellent nano-building blocks for high performance membranes. Among them, graphitic carbon nitride (g-C3N4) nanosheets possess intrinsic nanopores in plane and CO2-philic property from the rich amine groups, which are in favor of selective transport of CO2 molecules. Herein, for the first time, g-C3N4 nanosheets with tunable CO2 adsorption properties and nanostructures were synthesized and incorporated into polyether block amide (Pebax) membrane for CO2 separation. The g-C3N4 nanosheets with variable adsorption properties were produced from two monomers, dicyandiamide and melamine, and the variation of nanostructures was controlled by thermal oxidation etching process. The effects of CO2-philic and molecular sieving properties of g-C3N4 nanosheets on solubility and diffusivity of gas molecules in the as-prepared membranes were systematically investigated. The results demonstrated that the g-C3N4 nanosheets produced from dicyandiamide and undergoing 4 h thermal etching (DCN-4 nanosheets) showed the optimal CO2 sorption and sieving property. The membrane with 0.25 wt% DCN-4 nanosheets exhibited simultaneous enhancement in CO2 permeance and CO2/N2 selectivity compared with pure Pebax membrane. Moreover, the membrane maintained its separation performance during long-term operation test, showing great potential for CO2 capture.

Graphitic Carbon Nitride Q-Switched Tm:CNNGG Laser at 2 Micrometer Wavelength Region

The Q-switching performance of graphitic carbon nitride (g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) based on saturated absorption is demonstrated in 2 micrometer wavelength region for the first time. The g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> saturable absorbers, processed by thermal oxidation etching, are employed for passive Q-switching in a Tm:CNNGG laser. With a 5 hours long thermal oxidation etched g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> saturable absorber, the Q-switched Tm:CNNGG laser generates a shortest pulse duration of 132 ns with a repetition frequency of 16 kHz and a peak power of 98.5 W. The experimental results indicate that g-C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> is an excellent saturable absorber for passive Q-switching in 2 micrometer wavelength region.

Rapid photocatalytic degradation of acetaminophen and levofloxacin using g-C3N4 nanosheets under solar light irradiation

Rapid photocatalytic performance was targeted through modifying the graphite-like carbon nitride (g-C3N4) bulk materials to nanosheet structure via thermal oxidation etching process. Simple thermal oxidation etching treatment was used in order to reduce multilayer g-C3N4 structure to nanosheet material. The differences in the obtained sample of g-C3N4 nanosheets and pristine g-C3N4 were characterised via scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Photoluminescence (PL), Fourier-transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Brunauer–Emmett–Teller (BET) analysis and particle size analysis. The photocatalytic efficiency was tested for the degradation of acetaminophen and levofloxacin under direct solar irradiation. The results showed some variation in XRD, particle size and BET results indicating that etching process was evolved in reducing the particles size and lowering the layers number in g-C3N4 bulk sample. The optical and band gap properties results noticed some variation where the XPS and FTIR spectra showed some modification on g-C3N4 nanosheet motif such as the C–H, CO and N pyridinic structure. Accordingly, the photocatalytic degradation of acetaminophen by the g-C3N4 nanosheets under solar irradiation was much faster and reached 99% in one hour where in the case of g-C3N4 bulk sample the degradation reached only 38% in 4 h. Similarly, levofloxacin degradation with nanosheet sample reached 99% in one hour compare to 16% in presence of the bulk sample. This enhancement can be attributed to multiple factors such as smaller particle size, rich carbon surface and lower band gap exhibited by the g-C3N4 nanosheets. This further indicates that the performance of g-C3N4 can be further enhanced via this method and can used to treat wastewater contaminated by pharmaceuticals under solar irradiation.

Light transmission and internal scattering in pulsed laser-etched partially-transparent silicon wafers

Continuing trend in silicon wafer thickness directed at cost reduction approaches basic boundaries created by: (a) mismatch between Al paste and Si wafer thermal expansion and (b) incomplete optical absorption. With its symmetrical front and back electrical contacts, the bifacial solar cell setup reduces stress due to mismatch thermal expansion, decreases metal use and increases high temperature efficiency. Efficiency improvement is accomplished in bifacial solar cells by capturing light from the back surface. Partially transparent wafers provide an option to improve near-infrared radiation absorption within Si wafer. To fully absorb optical radiation, three-dimensional texture of these kinds of wafers is essential. Pulsed laser interactions, thermal oxidation, and wet chemical etching are included in this research. A feature of its energy and pattern setup is the interaction of pulsed laser with Si, running at 1.064 μm wavelength and micro-second length. Two experimental settings were explored: (a) post-laser chemical etching with potassium hydro-oxide etching with thermal oxide as etching mask and (b) post-laser heat Si surface oxidation. Due to fast melting and recrystallization, laser pulsed processing inherently produces its own texture. Some of these spherically-shaped, randomly focused characteristics improve inner scattering and boost near-infrared absorption within the wafer. These characteristics are separated during chemical etching with the thermally-grown oxide layer as an etch mask. Comparison of optical absorption in both surfaces shows almost a rise in the magnitude of absorption in non-etched surfaces. Detailed optical (optical microscope and IR absorption), morphological (field emission scanning electron microscope) and heat imaging (far IR camera) analyses were performed to comprehend physical processes that contribute to near-IR absorption improvement. Such kinds of partially-transparent, three-dimensional textured Si wafers are anticipated to discover applications for bifacial solar cells as substrates.

Enhancing the Thermal, Mechanical and Swelling Properties of PVA/Starch Nanocomposite Membranes Incorporating g-C3N4

A ground-breaking and soft nanomaterial, namely graphitic carbon nitride (g-C3N4) has gained importance as two-dimensional filler in polymeric membranes. In this research, g-C3N4 was synthesized by “thermal oxidation etching process”, employing melamine as a precursor. The porous nanosheets were characterized by SEM, XRD and FTIR. g-C3N4 nanosheets showed remarkable thermal stability up to 620 °C. The PVA starch nanocomposite membranes were fabricated with varying amounts of g-C3N4. Owing to strong interactions between g-C3N4, and polymers, the composite membranes showed exceptional thermal and mechanical stability and resist to degrade in various mediums including water, saline and blood. The hybrid membranes showed remarkable swelling abilities up to 96 h. Moreover, g-C3N4 enhanced the hydrophilicity, consequently, moisture retention capability and water vapor transmission were improved. XRD and SEM results revealed the proper dispersion of g-C3N4 into the polymeric matrix. The results suggested that prepared hybrid PVA/St/g-C3N4 membranes could be used as wound dressings.