Green synthesis of nanocomposites consisting of silver and protease alpha chymotrypsin

The synergy of ultrasonication and the exposure to light radiation was found to be necessary in the formation of nanocomposites of silver and a protease alpha chymotrypsin. The reaction was carried out in aqueous medium and the process took just less than 35 min. Ultrasonication alone formed very negligible number of nanoparticles of <100 nm size whereas light alone produced enough number but the size of the particles was >100 nm.The effects of pH (in the range of 3–5, 9–10), ultrasonication time periods (0–30 min), ultrasonication intensity (33–83 W cm^?2), energy of light radiation (short UV, long UV and Fluorescent light) and time period of exposure (5–60 min) to different light radiations were studied.The formation of nanocomposites under these effects was followed by surface plasmon resonance (SPR) spectra, dynamic light scattering (DLS), transmission electron microscopy (TEM). Ag–chymotrypsin nanocomposites of sizes ranging from 13 to 72 nm were formed using the synergy of ultrasonication and exposure to short UV radiation. Results show that ultrasonication promoted nuclei formation, growth and reduction of polydispersity by Ostwald ripening.     

Influence of Cu doping on the microstructure,optical properties and photoluminescence features of Cd0.9Zn0.1S nanoparticles

Cd_0.9−xZn_0.1Cu_xS (0≤x≤0.06) nanoparticles were successfully synthesized by a conventional chemical co-precipitation method at room temperature. Crystalline phases and optical absorption of the nanoparticles have been studied by X-ray diffraction (XRD) and UV–visible spectrophotometer. XRD confirms the phase singularity of the synthesized material, which also confirmed the formation of Cd–Zn–Cu–S alloy nanocrystals rather than separate nucleation or phase formation. Elemental composition was examined by the energy dispersive X-ray analysis and the microstructure was examined by scanning electron microscope. The blue shift of absorption edge below Cu=2% is responsible for dominance of Cu⁺ while at higher Cu concentration dominated Cu²⁺, d–d transition may exist. It is suggested that the addition of third metal ion (Cu²⁺/Cu⁺) is an effective way to improve the optical property and stability of the Cd_0.9Zn_0.1S solid solutions. When Cu is introduced, stretching of Cd–Zn–Cu–S bond is shifted lower wave number side from 678 cm⁻¹ (Cu=0%) to 671 cm⁻¹ (Cu=6%) due to the presence of Cu in Cd–Zn–S lattice and also the size effect. The variation in blue band emission peak from 456 nm (∼2.72 eV) to 482 nm (∼2.58 eV) by Cu-doping is corresponding to the inter-band radiation combination of photo-generated electrons and holes. Intensity of red band emission centered at 656 nm significantly increased up to Cu=4%; beyond 4% it is decreased due to the quenching of Cu concentration.     

Structural investigation of Te-based chalcogenide glasses using Raman spectroscopy

Structural changes of metals (Zn, Sb, In, Ga) and metal halides (AgI, ZnI₂, CdI₂, PbI₂, BiI₃) modified GeTe₄ glasses were investigated with the aid of Raman spectroscopy. The Raman spectra of these glasses in the frequency region between 100 cm^?1 and 300 cm^?1 display four main bands at about 124, 140, 159 and 275 cm^?1 which are contributed by Ge–Te, Te–Te, Te–Te and Ge–Ge vibration modes. The intensity of 159 cm^?1 and 275 cm^?1 bands vary with the addition of different glass modifiers. While the relative intensity of the 124 cm^?1 and 140 cm^?1 bands are insensitive to composition changes. Glass modifiers like Zn, In and Sb act as glass network unstabilizer which will disorganize the glass network by opening up the chain structures of Ge–Te and Te–Te. In the case of Ga and metal halides, Ga can open up Ge–(Te–Te)_4/2 tetrahedra and form Ga–(Te–Te)_3/2 triangle. Iodine can form covalent bonds with tellurium and decrease the tendency of microcrystal formation. Thus both Ga and iodine ultimately act as glass network stabilizer.     

In situ characterization of transport properties of superconducting (Cu, C)-system thin films

Transport properties of (Cu, C)Ba₂CuO_x [(Cu, C)-1201] thin films have been characterized by in situ temperature dependence of resistivity, without breaking vacuum from the deposition to the measurement. In in situ transport properties measurements, the obtained results reveal that (Cu, C)Ba₂CuO_x films exhibit T_c > 20 K on the cased of conductivity at 290 K (σ_[290 K]) > 4 × 10² S/cm and temperature coefficient of resistivity (TCR) > 1.5 × 10^?3 K^?1, and doping level of them should be in between under-doped and optimally-doped states. Their results suggest that there would be possible to further increases of T_c, and XPS data suggest that (Cu, C)-system should have the excellent dopability in their charge reservoir and the possibility of low anisotropy.     

Qualitative observation of chemical change rate for quercetin in basic medium characterized by time resolved UV–vis spectroscopy

Time resolved spectroscopy was applied to a real time investigation of chemical reaction of quercetin (5.0 × 10^? 5 mol L^? 1) with various concentrations of sodium hydroxide (from 5.0 × 10^? 3 to 1.0 mol L^? 1). The UV–vis absorption spectra acquired first reveal that there was an intermediate product with an absorption band centered at 427 nm formed during the reaction. The rates of chemical changes for quercetin in basic medium are also first obtained by the present work. The transient spectral information obtained is valuable for understanding the molecular mechanism of the reaction between quercetin and sodium hydroxide.     

Luminescence and evaluation of trapping parameters in NaMgSO4Cl: X (X=Cu or Ce) phosphor

Thermoluminescence (TL) characteristics of recently developed high sensitive mixed halosulphate phosphors, NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce were studied in comparison with CaSO₄: Dy in order to assess the possibility of their use in personal monitoring and TLD phosphors at very low dose of 5 Gy. It was found that NaMgSO₄Cl: Cu is 5.59 times and NaMgSO₄Cl: Ce is 6.18 times more sensitive as compared to standard CaSO₄: Dy. UV photo-excited luminescence from Cu to Ce doped NaMgSO₄Cl halosulphate phosphors has been investigated. The intense emission of the spectrum is assigned to electronic transitions 3d⁹4s¹→3d¹⁰ in monovalent copper ion and 5d→4f in Ce³⁺ ions. Increase in PL peak intensity suggesting that Cu and Ce play an important role in PL emission in the present matrix. These phosphors were synthesized by the wet chemical method. XRD, photoluminescence (PL) and thermoluminescence (TL) characterization of phosphors has been reported in this paper. The preparation of an inexpensive and high sensitive NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce with TL glow peaks for different concentrations are observed between 160 and 195 °C and between 200 and 225 °C, respectively, exposed to gamma-rays of ⁶⁰Co for their thermoluminescence (TL) properties. The glow curves have been recorded at a heating rate of 2 K s^?1 and irradiated at a dose rate of 0.995 kGy h^?1 for 5 Gy. In present study the trapping parameters such as order of kinetics (b), activation energy (E) and frequency factors (s) have been calculated for the 195 and 200 °C glow peaks of NaMgSO₄Cl: Cu and NaMgSO₄Cl: Ce, respectively by using Chen's method. The paper discusses the luminescence of Cu⁺ and Ce³⁺ by simple method of incorporation in NaMgSO₄Cl host.     

Effect of oxygen partial pressure on the structure and properties of Cu–Al–O thin films

We have studied the electrical and optical properties of Cu–Al–O films deposited on silicon and quartz substrates by using radio frequency (RF) magnetron sputtering method under varied oxygen partial pressure P_O. The results indicate that P_O plays a critical role in the final phase constitution and microstructure of the films, and thus affects the electrical resistivity and optical transmittance significantly. The electrical resistivity increases with the increase of P_O from 2.4 × 10^?4 mbar to 7.5 × 10^?4 mbar and afterwards it decreases with further increasing P_O up to 1.7 × 10^?3 mbar. The optical transmittance in visible region increases with the increase of P_O and obtains the maximum of 65% when P_O is 1.7 × 10^?3 mbar. The corresponding direct band gap is 3.45 eV.     

Electrical and structural investigations of perovskite structure reactively sputter deposited coatings

Sr(Zr_0.84Y_0.16)_0.91O_3 ? δ (SZY) and Ba(Zr_0.84Y_0.16)_0.96O_3 ? δ (BZY) protonic conductor coatings were co-sputter deposited from metallic targets in argon–oxygen reactive gas mixtures. The chemical and structural features were investigated by energy dispersive X-ray spectroscopy and X-ray diffraction, and their morphology was assessed by scanning electron microscopy of the surface and of brittle fracture cross sections. The electrical properties of the coating were determined by complex impedance spectroscopy as a function of temperature in air. Relationships are established between the electrical properties and the morphology of the coatings. The SZY as deposited coatings is amorphous and crystallises under the convenient perovskite structure after annealing treatment at 873 K under air. The BZY as deposited coatings is crystallised at 523 K in situ under perovskite structure and a further annealing treatment increases the grain size. Conductivities and activation energies of crystallised coatings were 3.1 · 10^? 5 S cm^? 1/2 · 10^? 5 S cm^? 1 and 0.65 eV/0.71 eV after stabilization at 773 K for strontium and barium zirconate, respectively.     

Hydrolytic enzymes in activated sludge: Extraction of protease and lipase by stirring and ultrasonication

Hydrolytic enzymes released by the microorganisms in activated sludge are responsible for the organic matter degradation; however, the optimal extraction procedure of this valuable resource has not been well established until now. The present study evaluates the recovery of protease and lipase from the activated sludge by using stirring and ultrasonication, varying different parameters such as extraction time, concentration of additives (Triton X100, Cation Exchange Resin and Tris buffer), stirring velocity, ultrasonic power and sludge source. Sludge was collected from two urban wastewater treatment plants located in Prague (Czech Republic) and Reus (Spain). It was found that stirring using 2% v/v Triton X100 for 1 h was enough to extract 57.4 protease units/g VSS, and that the same method using a combination of 10 mM Tris pH 7.5 + 0.48 g/mL CER + 0.5% TX100 as an additive allowed to extract 15.5 lipase units/g VSS from sludge collected from Reus Wastewater Treatment Plant. Ultrasonication allowed reducing the extraction time to 10 min for protease (using 2% v/v Triton X100 yielding 52.9 units/g VSS) and to 20 min for lipase (without any additive yielding nearly 21.4 units/g VSS), which makes this method appropriate for the extraction of enzymes from the activated sludge, and suitable to be scaled up for its application in the industry.     

Synthesis and characterization of nanostructural CuS–ZnS binary compound thin films prepared by spray pyrolysis

We have investigated the effect of zinc concentration ([Zn]/[Cu]=0–100 at%) on nanostructural, optical and electrical properties of CuS–ZnS binary thin films grown on glass substrate by the spray pyrolysis technique. X-ray diffraction analysis showed that the films were crystallized with mixed structures of CuS hexagonal and ZnS cubic structure. UV–vis optical measurements analysis showed that these binary films have a relatively high absorption coefficient (～10⁵ cm^?1) in the visible spectrum with a direct band gap in the range of 2.57–2.45 eV in agreement with the corresponding room temperature PL spectra. The electrical studies showed that all these samples have a p-type conductivity and the free hole density decreases with increasing [Zn]/[Cu] molar ratio, in agreement with the reflectance spectra of the layers, originating from plasma oscillations.     

Evaluation on the air-borne ultrasound-assisted hot air convection thin-layer drying performance of municipal sewage sludge

The thin-layer drying behavior of the municipal sewage sludge in a laboratory-scale hot air forced convective dryer assisted with air-borne ultrasound was investigated in between 70 and 130 °C hot air temperatures. The drying kinetics in the convective process alone were compared to that for ultrasound-assist process at three ultrasound powers (30, 90, 150 W). The average drying rates within whole drying temperature range at ultrasound powers of 30, 90 and 150 W increased by about 22.6%, 27.8% and 32.2% compared with the convective drying alone (without ultrasound). As the temperature increasing from 70 °C to 130 °C, there were maximum increasing ratios for the effective moisture diffusivities of the sewage sludge in both falling rate periods at ultrasonic power of 30 W in comparison with other two high powers. In between the ultrasound powers of 0 and 30 W, the effect of the power on the drying rate was significant, while its effect was not obvious over 30 W. Therefore, the low ultrasonic power can be just set in the drying process. The values of the apparent activation energy in the first falling rate period were down from 13.52 to 12.78 kJ mol⁻¹, and from 17.21 to 15.10 kJ mol⁻¹ for the second falling rate period with increasing the ultrasonic power from 30 to 150 W. The values of the apparent activation energy in two falling rate periods with the ultrasound-assist were less than that for the hot air convective drying alone.     

Improvement of Cu–CeO2 anodes for SOFCs running on ethanol fuels

Ethanol is considered to be an attractive green fuel for solid oxide fuel cells (SOFCs) due to several advantages. In this paper, we presented recent progress of our group in Cu–CeO₂ anodes for SOFCs with ethanol steam as a fuel. Cu–CeO₂–ScSZ (scandia stabilized zirconia)anodes with different ratios of copper versus ceria were fabricated and the impedance spectra of symmetric cells were measured to optimize the anode composition. Area specific resistance (ASR) of these anodes was examined to prove the thermal stability of them, and possible reasons for degradation were analyzed. Furthermore, a Ni–ScSZ interlayer was added between Cu–CeO₂–YSZ (yttria stabilized zirconia) anode and ScSZ electrolyte to improve the anode performance, and the three-layer structure was fabricated by acid leaching of nickel and wet impregnation method. The maximum power density of the single cell reached 604 mW cm^? 2 and 408 mW cm^? 2 at 800 °C in hydrogen and ethanol steam respectively, and the cell obtained stable output in ethanol steam over an operation period of 50 h.     

Investigation of properties of Cu containing DLC films produced by PECVD process

Copper containing diamond like carbon (Cu-DLC) thin films were deposited on various substrates at a base pressure of 1×10^?3 Torr using a hybrid system involving DC-sputtering and radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) techniques. The compressive residual stresses of these films were found to be considerably lower, varying between 0.7 and 0.94 GPa and Cu incorporation in these films improve their conductivity significantly. Their structural properties were studied by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction techniques that clearly revealed the presence of Cu in the DLC structure. Raman analysis yields that Cu incorporation in DLC enhances the graphite-like sp² bonding. However, the sp² bonding was found to continuously reduce with the increasing C₂H₂ gas pressure, this may be due to reduction of Cu nanocrystal at the higher pressure. FTIR results inferred various bonding states of carbon with carbon, hydrogen and oxygen. In addition, hydrogen content and sp³ and sp² fractions in different Cu-DLC films were also estimated by FTIR spectra and were correlated with stress, electrical, optical and nano-mechanical properties of Cu-DLC films. The effect of indentation load (4–10 mN) on nano-mechanical properties of these films was also explored.     

Sonochemical synthesis of hierarchical ZnO nanostructures

This work is about fabrication of ZnO nanostructures (ZnO-NS) via a simple sonochemical method. The chemicals used for the synthesis of various shaped ZnO are Zn salt, sodium hydroxide and ammonia solution without other structure directing agent or surfactant needed. This method is feasible and green, as it does not require high temperature and/or highly toxic chemicals. The shape of the ZnO-NS can be tuned by adjusting the ultrasound energy dissipated via varying the ultrasonication time from 5 to 60 min. It was found that uniform ZnO nanorods with diameter around 50 nm were formed after 15 min of ultrasonication while flowerlike ZnO-NS was formed after 30 min. This method produces high quality ZnO-NS with controllable shapes, uniformity, and purity.     

Modification of B-site doping of perovskite LaxSr1 − xFe1 − y−zCoyCrzO3 − δ oxide by Mg2+ ion

Co-doping B-site of perovskite oxide La_xSr_1 ? xCo_yFe_1 ? yO_3 ? δ (LSCFO) with Cr⁶⁺ and Mg²⁺ ions has been attempted in this research for revamping chemical stability and oxygen ionic conductivity of this mixed conducting oxide. It is known that partial substitution for B-site cations of LSCFO by Cr gives rise to a significant improvement on chemical and thermal stability of the perovskite oxide. On the basis of this doped structure, introduction of an immaterial dose of Mg²⁺ ion into its B-site results in a microstructure consisting of smaller grains with higher density than its precursor. Furthermore, the resulting perovskite oxide La_0.19Sr_0.8Fe_0.69Co_0.1Cr_0.2 Mg_0.01O_3 ? δ (LSFCCMO) displays higher O^2? conductivity than the solely Cr-doped LSCFO besides the improved chemical stability against reduction in 5% CH₄/He stream at 850 °C. A detailed examination of the oxidation states of B-site transition metal ions by XPS has also been conducted as a part of structural characterizations of LSFCCMO. The assessment of relative O^2? conductivity shows that the grain boundary area plays a more important role than the bulk phase in facilitating ion transport, but with comparable boundary areas the higher densification level is favorable.     

Sono-thermal pre-treatment of waste activated sludge before anaerobic digestion

Sonication and thermalization can be applied successfully to disrupt the complex waste activated sludge (WAS) floc structure and to release extra and intra cellular polymeric substances into soluble phase along with solubilization of particulate organic matters, before sludge digestion. In this study, sonication has been combined with thermalization to improve its disintegration efficiency. It was aimed that rise in temperature occurring during the sonication of sludge was used to be as an advantage for the following thermalization in the combined pre-treatment. Thus, the effects of sonication, thermalization and sono-thermalization on physical and chemical properties of sludge were investigated separately under different pre-treatment conditions. The disintegration efficiencies of these methods were in the following descending order: sono-thermalization > sonication > thermalization. The optimum operating conditions for sono-thermalization were determined as the combination of 1-min sonication at 1.0 W/mL and thermalization at 80 °C for 1 h. The influences of sludge pre-treatment on biodegradability of WAS were experienced with biochemical methane potential assay in batch anaerobic reactors. Relative to the control reactor, total methane production in the sono-thermalized reactor increased by 13.6% and it was more than the sum of relative increases achieved in the sonicated and thermalized reactors. Besides, the volatile solids and total chemical oxygen demand reductions in the sono-thermalized reactor were enhanced as well. However, it was determined that sludge pre-treatment techniques applied in this study was not feasible due to their high energy requirements.     

High resolution emission spectroscopy of the E2Π–X2Σ+ transition of SrH and SrD

Emission spectra of SrH and SrD have been studied at high resolution using a Fourier transform spectrometer. The molecules have been produced in a high temperature furnace from the reaction of strontium metal vapor with H₂/D₂ in the presence of a slow flow of Ar gas. The spectra observed in the 18 000–19 500 cm^?1 region consist of the 0–0 and 1–1 bands of the E²Π–X²Σ⁺ transition of the two isotopologues. A rotational analysis of these bands has been obtained by combining the present measurements with previously available pure rotation and vibration–rotation measurements for the ground state, and improved spectroscopic constants have been obtained for the E²Π state. The present analysis provides spectroscopic constants for the E²Π state as ΔG(½) = 1166.1011(15) cm^?1, B_e = 3.805503(32) cm^?1, α_e = 0.098880(47) cm^?1, r_e = 2.1083727(89) Å for SrH, and ΔG(½) = 839.1283(23) cm^?1, B_e = 1.918564(15) cm^?1, α_e = 0.034719(23) cm^?1, r_e = 2.1121943(83) Å for SrD.     

Rechargeability improvement of δ-type chemical manganese dioxide with the co-doping of Bi and Ni in alkaline electrolyte

δ-MnO₂ with the doping of Ni and Bi was prepared through a simple chemical precipitation/oxidation method. Its structure was confirmed by the X-ray diffraction tests. The results of cyclic voltammetry and galvanostatic charge–discharge tests showed that both the doping of Bi and Ni benefited the electrochemical activity of the MnO₂ electrode. Compared to the un-doped electrode, the Bi-doped one showed larger discharge capacity and the Ni-doped one showed higher discharge potential and better cycleability. With the co-doping of 5 wt% Bi and 10 wt% Ni, the discharge capacity of the MnO₂ electrode reached 252 mA h g^?1 at a 0.2C rate and 116 mA h g^?1 at a 1C rate, respectively. Its capacity remained in 105 mA h g^?1 after 50 cycles at a 1C rate, but the capacity of a commercial electrolytic MnO₂ electrode was only 37 mA h g^?1.     

Third-order nonlinear optical response of newly synthesized accepter/donor substituted propylidene aryloxy acet hydrazide

A class of organic compounds namely propylidene aryloxy acet hydrazide derivatives were synthesized. The third-order nonlinear optical properties and optical limiting studies of the compounds were investigated using the single beam Z-scan technique at 532 nm. The Z-scan study reveals that the compounds exhibit a self-defocusing effect at 532 nm. The calculated values of nonlinear refractive index, third-order nonlinear optical susceptibility and second order molecular hyperpolarizability are of the order of 10^?11 esu, 10^?13 esu and 10^?31 esu, respectively. The compounds exhibit good optical limiting properties at the wavelength used.     

Lipase catalyzed ultrasonic synthesis of poly-4-hydroxybutyrate-co-6-hydroxyhexanoate

Four different lipases were compared for ultrasound-mediated synthesis of the biodegradable copolymer poly-4-hydroxybutyrate-co-6-hydroxyhexanoate. The copolymerization was carried out in chloroform. Of the enzymes tested, Novozym 435 exhibited the highest copolymerization rate, in fact the reaction rate was observed to increase with about 26-fold from 30 to 50 °C (7.9 × 10^?3 M s^?1), sonic power intensity of 2.6 × 10³ W m^?2 and dissipated energy of 130.4 J ml^?1. Copolymerization rates with the Candida antarctica lipase A, Candida rugosa lipase, and Lecitase Ultra? were lower at 2.4 × 10^?4, 1.3 × 10^?4 and 3.5 × 10^?4 M s^?1, respectively. The catalytic efficiency depended on the enzyme. The efficiency ranged from 4.15 × 10^?3 s^?1 M^?1 for Novozym 435–1.48 × 10^?3 s^?1 M^?1 for C. rugosa lipase. Depending on the enzyme and sonication intensity, the monomer conversion ranged from 8.2% to 48.5%. The sonication power, time and temperature were found to affect the rate of copolymerization. Increasing sonication power intensity from 1.9 × 10³ to 4.5 × 10³ W m^?2 resulted in an increased in acoustic pressure (P_a) from 3.7 × 10⁸ to 5.7 × 10⁸ N m^?2 almost 2.4–3.7 times greater than the acoustic pressure (1.5 × 10⁸ N m^?2) that is required to cause cavitation in water. A corresponding acoustic particle acceleration (a) of 9.6 × 10³–1.5 × 10⁴ m s^?2 was calculated i.e. approximately 984–1500 times greater than under the action of gravity.