Magnetic nanoparticles: a versatile carrier for enzymes in bio-processing sectors.

Many industrial processes experience the advantages of enzymes which evolved the demand for enzymatic technologies. The enzyme immobilisation technology using different carriers has trustworthy applications in industrial biotechnology as these techniques encompass varied advantages such as enhanced stability, activity along with reusability. Immobilisation onto nanomaterial is highly favourable as it includes almost all aspects of science. Among the various techniques of immobilisation, the uses of nanoparticles are remarkably well perceived as these possess high-specific surface area leading to high enzyme loadings. The magnetic nanoparticles (MNPs) are burgeoning in the field of immobilisation as it possess some of the unique properties such as high surface area to volume ratio, uniform particle size, biocompatibility and particularly the recovery of enzymes with the application of an external magnetic field. Immobilisation of industrially important enzymes onto nanoparticles offers overall combined benefits. In this review, the authors here focus on the current scenario in synthesis and functionalisation of MNPs which makes it more compatible for the enzyme immobilisation and its application in the biotechnological industries.

Analysis of Laser Injection Condition and Electrical Properties in Local BSF for Laser Fired Contact c-Si Solar Cell Applications.

A crystalline silicon (c-Si) local-back-contact (LBC) solar cell for which a laser-condition-optimized surface-recombination velocity (SRV), a contact resistance (Rc), and local back surface fields (LBSFs) were utilized is reported. The effect of the laser condition on the rear-side electrical properties of the laser-fired LBC solar cell was studied. The Nd:YAG-laser (1064-nm wavelength) power and frequency were varied to obtain LBSF values with a lower contact resistance. A 10-kHz laser power of 44 mW resulted in an Rc of 0.125 ohms with an LBSF thickness of 2.09 µm and a higher open-circuit voltage (VOC) of 642 mV.

Reversed-Phase UHPLC Enantiomeric Separation of Rasagiline Salts Using a Chiralpak® AGP Column.

We report the first rapid ultra-high performance liquid chromatographic (UHPLC) enantiomeric reversed-phase separation of rasagiline mesylate and its tartrate salts using a Chiralpak® AGP column (50 mm × 2.1 mm, 5 µm) as a stationary phase. This method was developed as an alternative to the usage of previously reported normal-phase chiral LC columns for isomer separation. Our method is based on an isocratic approach using a mixture of ammonium acetate and isopropyl alcohol (90:10, v/v) as the mobile phase (0.6 mL/min flow rate). The detection limit (at a detection wavelength of 210 nm) and quantification limit for the rasagiline enantiomers were 0.06 and 0.2 µg/mL, respectively. This method is compatible with the UHPLC-MS technique. The successful separation of rasagiline and its enantiomer was confirmed by determining the corresponding specific optical rotation values. Our method will be applicable for detecting rasagiline enantiomers during the control of manufacturing processes, and for use in rapid analysis for quality control in pharmaceutical industry to obtain optically pure pharmaceutical substances. This method was validated in terms of its precision, limit of detection, limit of quantification, linearity, accuracy, robustness, ruggedness, specificity, forced degradation, and solution stability, according to International Council on Harmonization Validation Guidelines Q2 (R1).

Effects of Low Temperature Anneal on the Interface Properties of Thermal Silicon Oxide for Silicon Surface Passivation.

High quality surface passivation has gained a significant importance in photovoltaic industry for reducing the surface recombination and hence fabricating low cost and high efficiency solar cells using thinner wafers. The formation of good-quality SiO2 films and SiO2/Si interfaces at low processing temperatures is a prerequisite for improving the conversion efficiency of industrial solar cells with better passivation. High-temperature annealing in inert ambient is promising to improve the SiO2/Si interface. However, annealing treatments could cause negative effects on SiO2/Si interfaces due to its chemical at high temperatures. Low temperature post oxidation annealing has been carried out to investigate the structural and interface properties of Si-SiO2 system. Quasi Steady State Photo Conductance measurements shows a promising effective carrier lifetime of 420 µs, surface recombination velocity of 22 cm/s and a low interface trap density (D(it)) of 4 x 10(11) states/cm2/eV after annealing. The fixed oxide charge density was reduced to 1 x 10(11)/cm2 due to the annealing at 500 degrees C. The FWHM and the Si-O peak wavenumber corresponding to the samples annealed at 500 degrees C reveals that the Si dangling bonds in the SiO2 films due to the oxygen defects was reduced by the low temperature post oxidation annealing.

Boron Oxygen Pair Effect in p+ Emitter and Nanosized Boron Rich Layer by Fold Coordination Analysis for Crystalline Silicon Solar Cell Applications.

N-type substrates possess better material characteristics than p-type substrates for high efficiency mass producible Si solar cells with HIT, IBC structures. The major drawbacks of these structures are a complicated fabrication process and an expensive unit cost. In this paper, the boron emitter doping profile of a nanosized boron rich layer (BRL), for which the boron and oxygen concentrations are correlated, is optimized to fabricate high efficiency solar cells on an n-type substrate. Boron doping was carried out using a BBr3 furnace with varying oxygen gas ratios and the surface was treated with acid etching. The effect of the oxygen on the nanosized BRL was analyzed using both FTIR spectroscopy and XPS, where by conductivity and the Si-B bond were observed for the three-fold and four-fold coordinated borons, respectively. The results showed that the oxygen quantities in the boron doped emitter and the nanosized BRL affected the characteristics of the solar cell. Regarding the solar cells that were fabricated using the boron emitter and shallow emitter (90 ohm/sq) processes, the open-circuit voltage increased by 54 mV and the short circuit current (J(sc)) increased by 3.7 mA/cm2. The J(sc) increase was due to an increased quantum efficiency in the short wavelength range. The shallow emitter etch back process minimized the boron-oxygen defects in the doping profile.

Enhanced Haze Ratio on Glass by Novel Vapor Texturing Method.

State-of-the-art optical trapping designs are required to enhance the light trapping capabilities of tandem thin film silicon solar cells. The wet etch process is used to texture the glass surface by dipping in diluted acidic solutions such as HNO3 (nitric acid) and HF (hydrofluoric acid). For vapor texturing, the vapor was generated by adding silicon to HF:HNO3 acidic solution. The anisotropic etching of vapor textured wafers resulted in an etching depth of about 2.78 µm with reduced reflectance of 5%. We achieved a high haze value of 74.6% at a 540 nm wavelength by increasing the etching time and HF concentration.

Low Surface Recombination Velocity on P-Type Cz-Si Surface by Sol-Gel Deposition of Al2O3 Films for Solar Cell Applications.

High quality surface passivation has gained a significant importance in photovoltaic industry for fabricating low cost and high efficiency solar cells using thinner and lower cost wafers. The passivation property of spin coated Al2O3 films with a thickness of about 50 nm on p-type Cz-Si wafers has been investigated as a function of annealing temperatures. An effective surface recombination velocity of 55 cm/s was obtained for the films annealed at 500 °C. The chemical and field effect passivation was analyzed by C-V measurements. A high density of negative fixed charges (Qf) in the order of 9 x 10(11) cm(-2) was detected in Al2O3 films and its impact on the level of surface passivation was demonstrated experimentally. The C-V curves show density of the interface state (Dit) of 1 x 10(12) eV(-1)cm(-2) at annealing temperature of 500 °C. During annealing, a thin interfacial SiOx is formed, and this interfacial layer is supposed to play a vital role in the origin of negative QF and Dit. The homogeneous SiOx interlayer result in higher passivation performance due to both the increase of negative Qf and the decrease of Dit.

Boron Doped Nanocrystalline Film with Improved Work Function as a Buffer Layer in Thin Film Silicon Solar Cells.

We investigated thin film silicon solar cells with boron doped hydrogenated nanocrystalline silicon/ hydrogenated amorphous silicon oxide [p-type nc-Si:H/a-SiOx:H] layer. First, we researched the bandgap engineering of diborane (B2H6) doped wide bandgap hydrogenated nanocryslline silicon (p-type nc-Si:H) films, which have excellent electrical properties of high dark conductivity, and low activation energy. The films prepared with lower doping ratio and higher hydrogen dilution ratio had higher optical gap (Eg), with higher dark conductivity (σ(d)), and lower activation energy (Ea). We controlled Eg from 2.10 eV to 1.75 eV, with σ(d) from 1.1 S/cm to 7.59 x 10(-3) S/cm, and Ea from 0.040 eV to 0.128 eV. Next, we focused on the fabrication of thin film silicon solar cells. By inserting p-type nc-Si:H film into the thin film silicon solar cells, we achieved a remarkable increase in the built-in potential from 0.803 eV to 0.901 eV. By forming p-type nc-Si:H film between SnO2:F/ZnO:Al (30 nm) and p-type a-SiOx:H layer, the solar cell properties of open circuit voltage (Voc), short circuit current density (Jsc), and efficiency (η) were improved by 3.7%, 9.2%, and 9.8%, respectively.

Crystalline Fraction and Doping Concentration Effect on Heterojunction Solar Cells n-Doped µc-Si:H Back Surface Field Layer.

The back surface field (BSF) plays a vital role for high efficiency in the Heterojunction Intrinsic Thin (HIT) film solar cell. This paper investigated the effect of crystalline volume fraction (Xc) and 1% hydrogen diluted phosphine (PH3) gas doping concentration of the n-type µc-Si:H back surface file (BSF) layer. Initially, the thickness of the n-type µc-Si:H BSF layer was optimized. With increase in Xc from 6% to 59%, the open circuit voltage (Voc) increased from 573 mV to 696 mV, and the fill factor (FF) also increased from 59% to 71%. In the long wavelengths region (≥ 950 nm), the QE of the solar cells decreased over the optimized Xc of the n-doped micro BSF layer, due to the defects of a film. In the second part of this paper, the effect of high conductivity n-type µc-Si:H BSF layer with optimized thickness on the performance of HIT solar cells was investigated, by doping gas ratio variation. Even though Xc decreased, conductivity was increased, with increasing PH3 doping concentration. Under the optimized condition, a n-µc-Si:H BSF layer has a dark conductivity of 2.59 S/cm, activation energy of 0.0519 eV, and X, of 52%. The conversion efficiency of 18.9% was achieved with a Voc of 706 mV, fill factor of 72%, and short circuit current density of 37.1 mW·cm(-2).

Analysis of Resistance and Surface Recombination Velocities by Contact Coverage for Optimizing Electrical Loss in c-Si Local Back Contact.

Recently, the importance of solar cell research has emerged due to emerging social issues such as environmental pollution problems and rising oil prices. Accordingly, each company is studying to make solar cell of high efficiency. In order to fabricate high-efficiency solar cells, the two major techniques have to be applied on the rear. One is complete passivation of the surface using a thermal oxide and the other one is the part that comes in contact with the electrode doped partially LBSF (Local BSF) formation. In this paper, LBC technology which is usually applied for high efficiency crystalline silicon solar cell, applied to mass productive solar cell to achieve high open circuit voltage and short circuit current with low surface recombination from rear side. Thermal SiO2/SiN(x) double layer which has superior thermal stability is formed on rear surface as passivation layer, then 1% of the whole rear surface area is locally contacted with aluminum. Finally, the cell has been fired at high temperature and the cell process has complete. The fabricated LBC cells conversion efficiency was 18.0% with 625 mV of open-circuit voltage (V(oc)), 37.58 mA/cm2 of current density (J(sc)), 76.3% of fillfactor (FF) at 5% contact coverage, respectively.

Advanced Passivation Technology and Loss Factor Minimization for High Efficiency Solar Cells.

High-efficiency Si solar cells have attracted great attention from researchers, scientists, photovoltaic (PV) industry engineers for the past few decades. With thin wafers, surface passivation becomes necessary to increase the solar cells efficiency by overcoming several induced effects due to associated crystal defects and impurities of c-Si. This paper discusses suitable passivation schemes and optimization techniques to achieve high efficiency at low cost. SiNx film was optimized with higher transmittance and reduced recombination for using as an effective antireflection and passivation layer to attain higher solar cell efficiencies. The higher band gap increased the transmittance with reduced defect states that persisted at 1.68 and 1.80 eV in SiNx films. The thermal stability of SiN (Si-rich)/SiN (N-rich) stacks was also studied. Si-rich SiN with a refractive index of 2.7 was used as a passivation layer and N-rich SiN with a refractive index of 2.1 was used for thermal stability. An implied Voc of 720 mV with a stable lifetime of 1.5 ms was obtained for the stack layer after firing. Si-N and Si-H bonding concentration was analyzed by FTIR for the correlation of thermally stable passivation mechanism. The passivation property of spin coated Al2O3 films was also investigated. An effective surface recombination velocity of 55 cm/s with a high density of negative fixed charges (Qf) on the order of 9 x 10(11) cm(-2) was detected in Al2O3 films.

Statistical optimization of process parameters for exopolysaccharide production by Aureobasidium pullulans using sweet potato based medium.

Statistical experimental designs were applied to optimize the fermentation medium for exopolysaccharide (EPS) production. Plackett-Burman design was applied to identify the significance of seven medium variables, in which sweet potato and yeast extract were found to be the significant variables for EPS production. Central composite design was applied to evaluate the optimum condition of the selected variables. Maximum EPS production of 9.3 g/L was obtained with the predicted optimal level of sweet potato 10 %, yeast extract 0.75 %, 5.5 pH, and time 100 h. The determined (R 2) value was 0.97, indicating a good fitted model for EPS production. Results of this study showed that sweet potato can be utilized as a low-cost effective substrate for pullulan production in submerged fermentation.

Aminoguanidine inhibits ventricular fibrosis and remodeling process in isoproterenol-induced hypertrophied rat hearts by suppressing ROS and MMPs.

AIM: Aminoguanidine (AG), a well known inhibitor of advanced glycation end products, has been reported to attenuate cardiac hypertrophy and fibrosis. However, the underlying mechanism by which AG exerts its anti-fibrotic activity is not well understood. Reactive oxygen species (ROS) and matrix metalloproteinases (MMPs) are implicated as playing a major role in the development of cardiac fibrosis. Hence, the present study was designed to investigate the effect of AG on ROS generation and MMPs during the progress of hypertrophic growth. MAIN METHODS: Isoproterenol (ISO) (7 mg/kg/day, s.c., for 15 days) was used to induce cardiac hypertrophy in experimental adult Wistar rats. ISO-treated rats were co-treated with AG (50 mg/kg/day, i.p., for 15 days). Ventricular collagen deposition, gelatinase activity of MMP-2 and MMP-9, and the level of tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) were investigated. In addition, in silico docking of MMP-2 and MMP-9 proteins, ROS generation, and nuclear translocation of NF-κB-p65 were also studied. KEY FINDINGS: AG co-treatment markedly attenuated the ISO-induced hypertrophic growth and fibrosis. Heart-weight-to-body weight ratio and ventricular collagen levels were normalized upon AG co-treatment. A significantly decreased level of ventricular ROS generation (p < 0.001) and NF-κB-p65 nuclear translocation was observed in the rat hearts co-treated with AG. Furthermore, in silico docking analysis revealed that AG interacts at the active site of MMP-2 and MMP-9. SIGNIFICANCE: Anti-fibrotic and anti-hypertrophic activities of AG were mainly attributed to its ROS quenching efficacy and its direct interaction with MMP-2 and MMP-9.

Characterization, analysis, and application of fabricated Fe3O4-chitosan-pectinase nanobiocatalyst.

The investigation on fabrication of Fe3O4-chitosan-pectinase nanobiocatalyst was performed by covalently binding the pectinase onto carboxyl group activated chitosan-coated magnetic nanoparticles (CMNPs). The morphological and size distribution analysis of the different magnetic nanoparticles (MNPs) was done using transmission electron microscopy (TEM), and the average diameter was 11.07 ± 3.04, 11.55 ± 3.16, and 11.59 ± 3.16 nm for MNPs, CMNPs, and fabricated nanobiocatalyst, respectively, suggesting that there was no significant change in the size of MNPs after coating and binding. The characteristic peaks occurred at 2θ of 30.39, 35.43, 43.37, 57.22, and 62.9, and their corresponding indices 220, 311, 400, 520, and 441 for different MNPs from the X-ray diffraction (XRD) studies confirmed the presence of Fe3O4 with the spinel structure, and there was no phase change even after coating and binding. The various required characteristic absorption peaks (575, 585, 1,563, 1,614, 1,651, and 1,653 cm(-1)) from Fourier transform infrared (FT-IR) spectroscopy confirmed the surface modifications and binding of pectinase onto the MNPs. At the weight ratio of about 19.8 × 10(-3) mg bound pectinase/mg activated CMNPs, the activity of fabricated nanobiocatalyst was found to be maximum. In order to monitor their improved activity, the pH, temperature, reusability, storage ability, and kinetic studies were established.

Influence of n-doped µc-Si:H back surface field layer with micro growth in crystalline-amorphous silicon heterojunction solar cells.

The back surface field (BSF) plays an important role for the efficiency of the heterojunction intrinsic thin-film (HIT) solar cell. In this paper, the effect of thickness variation in n-type micro crystalline BSF layer was investigated by Raman and spectroscopy ellipsometry. As we increase the crystalline volume fraction (X(c)) from 6% to 59%, the open circuit voltage (V(oc)) increases from 573 to 696 mV with increase in fill factor from 59% to 71%. However, we observed that V(oc) and FF are decreased over 59% X(c) of n-type µc-Si:H BSF layer. It seems that higher X(c) micro layer include lots of defects. The quantum efficiency (QE) measurements were demonstrated on optimized thickness of n-doped micro BSF layer. In the long wavelengths region, the QE slightly increases with increasing the n-type µc-Si:H BSF layer thickness from 10 to 40 nm because of BSF effect, whereas the QE decreases when n-type µc-Si:H BSF layer thickness increases from 40 to 120 nm due to defects in the layer. The performance of heterojunction solar cell device was improved with the optimized thickness on n-doped micro BSF layer the best photo voltage parameters of the device were found to be V(oc) of 696 mV, short-circuit current density of 36.09 mA/cm2 and efficiency of 18.06% at n-doped micro BSF layer thickness of 40 nm.

Reduction of tail state on boron doped hydrogenated amorphous silicon oxide films prepared at high hydrogen dilution.

In this report, we have investigated on the defect state of diborane (B2H6) doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiO:H) films prepared using silane (SiH4), hydrogen (H2) and nitrous oxide (N2O) in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system with different hydrogen dilutions. The films prepared with higher hydrogen dilution show lower Urbach energy (Eu), lower microstructure (R*), lower short and medium range disorder (omegaTO, Gamma(TO), I(TA)/I(TO), I(LA)/I(TO)), higher dark conductivity (sigma d) and higher refractive index (n) with high optical gap (Eg). Eu decreases from 248 meV to 153 meV, and R* decreases from 0.46 to 0.26, Raman peak omegaTO-TO mode position shifts from 480.24 to 483.28, GammaTO-full width half maximum of omegaTO decreases from 78.16 to 63.87, I(TA)/I(TO)-the ratio of integrated area of TA and TO mode decreases from 0.624 to 0.474, I(LA)/I(TO)-the ratio of integrated area of LA and TO mode deceases from 0.272 to 0.151, sigma d increases from 4.6 x 10(-7) S/cm to 1.1 x 10(-6) S/cm, n increases from 3.70 to 3.86. Reduced Nd, Eu and R* at wide Eg indicates that the films are more useful for solar cell window layer. Applying this layer to a single junction solar cell shows open circuit voltage (Voc) = 0.80 V, short circuit current density (Jsc) = 16.3 mA/cm2, fill factor (FF) = 72%, efficiency (eta) = 9.4%.

Fabrication, characterization and application of pectin degrading Fe3O4-SiO2 nanobiocatalyst.

The covalent binding of pectinase onto amino functionalized silica-coated magnetic nanoparticles (CSMNPs) through glutaraldehyde activation was investigated for nanobiocatalyst fabrication. The average particle size and morphology of the nanoparticles were characterized using transmission electron microscopy (TEM). The statistical analysis for TEM image suggests that the coating and binding process did not cause any significant change in size of MNPs. The morphological and phase change of the magnetic nanoparticles (MNPs) after various coatings and immobilization were characterized by X-ray diffraction (XRD) studies. The various surface modifications and pectinase binding onto nanoparticles were confirmed by Fourier transform infrared (FT-IR) spectroscopy. The maximum activity of immobilized pectinase was obtained at its weight ratio of 19.0×10(-3) mg bound pectinase/mg CSMNPs. The pH, temperature, reusability, storage ability and kinetic studies were established to monitor their improved stability and activity of the fabricated nanobiocatalyst. Furthermore, the application was extended in the clarification of Malus domestica juice.

Selective emitter using a screen printed etch barrier in crystalline silicon solar cell.

The low level doping of a selective emitter by etch back is an easy and low cost process to obtain a better blue response from a solar cell. This work suggests that the contact resistance of the selective emitter can be controlled by wet etching with the commercial acid barrier paste that is commonly applied in screen printing. Wet etching conditions such as acid barrier curing time, etchant concentration, and etching time have been optimized for the process, which is controllable as well as fast. The acid barrier formed by screen printing was etched with HF and HNO3 (1:200) solution for 15 s, resulting in high sheet contact resistance of 90 Ω/sq. Doping concentrations of the electrode contact portion were 2 × 1021 cm-3 in the low sheet resistance (Rs) region and 7 × 1019 cm-3 in the high Rs region. Solar cells of 12.5 × 12.5 cm2 in dimensions with a wet etch back selective emitter Jsc of 37 mAcm-2, open circuit voltage (Voc) of 638.3 mV and efficiency of 18.13% were fabricated. The result showed an improvement of about 13 mV on Voc compared to those of the reference solar cell fabricated with the reactive-ion etching back selective emitter and with Jsc of 36.90 mAcm-2, Voc of 625.7 mV, and efficiency of 17.60%.

Molecular docking studies of protein-nucleotide complexes using MOLSDOCK (mutually orthogonal Latin squares DOCK).

Understanding the principles of protein receptor recognition, interaction, and association with molecular substrates and inhibitors is of principal importance in the drug discovery process. MOLSDOCK is a molecular docking method that we have recently developed. It uses mutually orthogonal Latin square sampling (together with a variant of the mean field technique) to identify the optimal docking conformation and pose of a small molecule ligand in the appropriate receptor site. Here we report the application of this method to simultaneously identify both the low energy conformation and the one with the best pose in the case of 62 protein-bound nucleotide ligands. The experimental structures of all these complexes are known. We have compared our results with those obtained from two other well-known molecular docking software, viz. AutoDock 4.2.3 and GOLD 5.1. The results show that the MOLSDOCK method was able to sample a wide range of binding modes for these ligands and also scores them well.

Stability of SiNX/SiNX double stack antireflection coating for single crystalline silicon solar cells.

Double stack antireflection coatings have significant advantages over single-layer antireflection coatings due to their broad-range coverage of the solar spectrum. A solar cell with 60-nm/20-nm SiNX:H double stack coatings has 17.8% efficiency, while that with a 80-nm SiNX:H single coating has 17.2% efficiency. The improvement of the efficiency is due to the effect of better passivation and better antireflection of the double stack antireflection coating. It is important that SiNX:H films have strong resistance against stress factors since they are used as antireflective coating for solar cells. However, the tolerance of SiNX:H films to external stresses has never been studied. In this paper, the stability of SiNX:H films prepared by a plasma-enhanced chemical vapor deposition system is studied. The stability tests are conducted using various forms of stress, such as prolonged thermal cycle, humidity, and UV exposure. The heat and damp test was conducted for 100 h, maintaining humidity at 85% and applying thermal cycles of rapidly changing temperatures from -20°C to 85°C over 5 h. UV exposure was conducted for 50 h using a 180-W UV lamp. This confirmed that the double stack antireflection coating is stable against external stress.