Preparation of n-ZnO/p-Si solar cells by oxidation of zinc nanoparticles: effect of oxidation temperature on the photovoltaic properties

In this study, n-ZnO/p-Si solar cells were fabricated by spraying ZnO nanoparticles (NPs) film synthesised by dissolving of high purity zinc in hydrogen peroxide H₂O₂ followed by thermal oxidation in air on p-type silicon substrates. The oxidation was carried out at different temperatures (200–500) °C. The crystalline structure of the ZnO NPs films was investigated by X-ray diffraction which indicated wurtzite structure films along (100) plane. The morphology of the NPs was studied by atomic force microscopy and scanning electron microscopy. The result showed an average grain size of ZnO NPs in the range of (72.7–95.8) nm and the surface roughness increasing with oxidation temperature. Three peaks located at ultraviolet, violet and green emission regions were noticed in the photoluminescence spectra of ZnO NPs. From optical studies, it was shown that the direct optical band gap is found to be in the range of (3.85–3.96) eV depended on the oxidation temperature. The synthesised ZnO films have n-type conductivity, and the mobility was in the range of (7–24) cm² V^?1 s^?1. Current–voltage I–V and capacitance–voltage C–V of ZnO NPs/Si heterojunction solar cell were investigated as function of oxidation temperature. The spectral response of n-ZnO NPs/p-Si solar cell showed two peaks of response and its maximum value approaching 0.62 mA W^?1 at λ = 800 nm. Solar cell oxidized at 500 °C gave open circuit voltage V _OC of 375 mV, short circuit current density J _SC of 25 mA cm^?2, a fill factor FF of 0.72, and conversion efficiency η of 6.79 % under illumination of 100 mW cm^?2.     

Observation of Conformational Exchange in Cyclosporin in Media of Varying Polarity by NMR Spectroscopy

The molecule of peptide cyclosporin A experiences chemical exchange in polar solvents. In apolar media, such as chloroform or benzene, this transformation is suppressed, but still leads to formation of a small fraction of a minor conformer. To elucidate the nature of this phenomenon, the peptide was dissolved in mixed solvents chloroform–DMSO and water–DMSO. Analysis of ¹H nuclear magnetic resonance and two-dimensional exchange spectroscopy spectra showed that the conformational exchange proceeds at a low rate of \(\sim\) 10^?1 s^?1 at the room temperature and involves passing over a high free energy barrier. Thus the situation resembles the exchange process in chloroform, associated with cis–trans isomerization of peptide bonds, but in the presence of DMSO transformation occurs at several sites independently, and the energy difference between arising conformers is small, 10²–10³ kJ/mol.     

Moderately deformed bands in the continuum of144Gd

The lifetimes of the gamma-ray continuum in¹⁴⁴Gd were measured up to spin ～ 50? via the DSAM technique following the⁷⁴Ge(⁷²Ge, 2n) reaction at 270 MeV beam energy. The average Doppler Shift of theE2 bump corresponds mostly to a structure with a deformation (β～0.2–0.3), consistent with the triaxial structure predicted to lie close to the yrast line at spins 30–50? in this nucleus.     

A comparative study on the effects of salt and filler on transport and structural properties of organic–inorganic hybrid electrolytes

Organic–inorganic hybrid electrolytes based on the reaction of tri-block copolymer poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether), poly(ethylene glycol diglycidyl ether, and (3-glycidyloxypropyl)trimethoxysilane doped with LiClO₄ and SiO₂ nanoparticles were synthesized by a sol–gel process. The structural and dynamic properties of the materials thus obtained were systematically investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, alternate current impedance, and ¹³C solid-state NMR measurements. A maximum ionic conductivity of 3.2?×?10^?5 S cm^?1 was obtained at 30 °C for the solid hybrid electrolyte with a [O]/[Li] ratio of 16 and 7 wt% of SiO₂ nanoparticles. A Vogel–Tamman–Fulcher-like temperature dependence of ionic conductivity was observed for the hybrid electrolytes, implying that the diffusion of charge carriers was assisted by the segmental motions of the polymer chains.     

Isotopic shift of the ground state of neon from the experimental results concerning the absorption of 0.63-μm laser radiation

Isotopic shifts of the 3s[3/2] ₁ ⁰ –2р ⁶(¹ S ₀) and 3s'–2р ⁶(¹ S ₀) transitions, equal, respectively, to 417 ± 20 and–98 ± 20 MHz, have been measured using the 0.63-μm radiation of a helium–neon laser and opto-magnetic resonances induced by the interference of the reactive components of fields in overlapping areas of the emissions of isotopic atoms. Combining these results with the absolute specific mass shift of the 3p[5/2]₂ level (–647 MHz), the isotopic mass shift of the ground state of neon equal to 3223 ± 30 MHz, and its specific mass shift equal to–9782 ± 30 MHz have been determined.     

Study of very thin oxide layers by conversion and Auger electrons

Oxidic layers as thin as 20–30 Å on α-Fe and stainless steel are studied by⁵⁷Fe-DCEMS with K-conversion electrons and ICEMS. No indication of a vanishingf-factor could be found. Mössbauer spectra, recorded by use of LMM-Auger electrons (AEMS) and by electrons emitted with energies below 15 eV (LEEMS), contain information on the surface layer as well as on the bulk material, showing that part of these electrons are due to secondary effects and the high escape depths of K-conversion electrons.     

Heat capacity of oxides in the Bi2O3-SiO2 system

The high-temperature heat capacity of Bi₄Si₃O₁₂, Bi₂SiO₅, and Bi₁₂SiO₂₀ has been investigated. It has been found that there is a correlation between the specific heat C _p ⁰ (298 K) and the composition of oxides in the Bi₂O₃-SiO₂ system.     

Probing PM2.5 with terahertz wave

The goal of continuous ambient participate monitoring has been accomplished by the use of terahertz(THz)wave.The frequency-dependent spectrum and absorbance of the particulate matter(PM2.5)were measured in the range of 0–10 THz.The PM2.5 concentration was calculated according to the sampling time and air flow.With the increase of,the THz wave amplitude gradually decreased and the absorbance A of PM2.5 increased.The relationship between and A can be described mathematically through A0.5.Our results demonstrate that the terahertz wave could be a valuable tool to monitor and inspect the PM2.5 concentration.     

Preparation and ionic conductivity of composite polymer electrolytes based on hyperbranched star polymer

Hyperbranched star polymer HBPS-(PPEGMA) _x was synthesized by atom transfer radical polymerization (ATRP) using hyperbranched polystyrene (HBPS) as macroinitiator and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as monomer. The structure of the prepared hyperbranched star polymer was characterized by ¹H NMR, ATR-FTIR, and GPC. Polymer electrolytes based on HBPS-(PPEGMA) _x , lithium salt, and/or nano-TiO₂ were prepared. The influences of lithium salt concentration and type, nano-TiO₂ content, and size on ionic conductivity of the obtained polymer electrolytes were investigated. The results showed that the low crystallinity of the prepared polymer electrolyte was caused by the interaction between lithium salt and polymer. The addition of TiO₂ into HBPS-(PPEGMA) _x /LiTFSI improved the ionic conductivity at low temperature. The prepared composite polymer electrolyte showed the highest ionic conductivity of 9?×?10^?5 S cm^?1 at 30 °C when the content of TiO₂ was 15 wt% and the size of TiO₂ was 20 nm.     

Magnetic characteristics of MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles obtained by glycine–nitrate synthesis

The magnetic properties of magnesium–iron spinel (MgFe₂O₄) powdered nanoparticles obtained by glycine–nitrate synthesis are investigated by X-ray phase analysis and the NMR method. According to the results of X-ray phase analysis, the average size of the crystalline part of nanoparticles of the powder under investigation is 45 ± 4 nm. Magnetization J is determined using the formula J = (B/μ0)–H, where B and H are the induction and strength of the magnetic field in the sample, which are measured by the NMR method. The magnetic characteristics of MgFe₂O₄ are as follows: specific saturation magnetization J_sat = 17.52 A m²/kg, specific residual magnetization J_r = 5.73 A m2/kg, coercive force H_c = 4600 A/m, and magnetic moment P_sat = 371 × 10^–20 A m² in the magnetic saturation state and P_r = 121 × 10^–20 A m² in the residual magnetization state.     

VUV emission of Xe III levels excited by electron impact viaN 4,5 00 Auger transitions

Optical excitation functions were measured for Xenon emission lines. The Xe III 5s 5p ⁵ levels are excited in two different processes, by a direct two electron ejection and by a 4d ionization followed by an Auger decay. An emission line found at 1089.0 Å is excited by 4d ionization. This line is assigned to the Xe III transition 5s5p ^{5 1} P ⁰ —5s ⁰ 5p ^{6 1} S. The¹ S energy level amounts to 26.14 eV.     

Measurement of the Lamb shift 42S1/2-42P1/2 of the helium ion

Helium ions were produced in then=4 states by electron collisions with ground state atoms, resulting in simultaneous ionization and excitation. Dipole transitions between the Zeeman levels of the states 4² S _1/2 and 4² P _1/2 were induced by a microwave electric field. The intensity of the emitted Fowlerα line 4686 Å, corresponding to transitions from then=4 to then=3 states was then reduced by about 3%. From the measurements, a value of the Lamb shiftδ=1751±25 MHz was obtained, compared with the theoretical valueδ=1768.23±0.55 MHz, and the results ofLea, Leventhal andLamb ofδ=1765±20 MHz.     

Double photoionization of C2+

The time-dependent close-coupling method is used to study the single photon double ionization of C²⁺ in support of possible experiments at FLASH/DESY using an EBIT. Energy and angle differential cross sections are calculated to fully investigate the correlated motion of the two photoelectrons. Single energy differential as well as total cross sections are calculated for different incident photon energies in the range of 125–225 eV. Good agreement is found between our results and available R-matrix results for the double ionization of C²⁺. The study is also extended to the double photoionization along the Be-like isoelectronic sequence (Be-F⁵⁺), where good agreement is found when compared with available theoretical calculations and experimental measurements.     

Experimental study of the isomeric states101mRu,103mRu and101mTc

In natural Ruthenium isomeric states were produced by photonuclear reactions with LINAC Bremsstrahlung of 26 MeV. They were identified as: 526.6±0.7 keVT _1/2=22.5±0.5 μsec in¹⁰¹Ru 192.0±0.2 keVT _1/2=760±50 μsec in¹⁰¹Tc 210.9±0.2 keVT _1/2=1560±50 μsec in¹⁰³Ru The experimental techniques are described.     

Conductivities and ion association constants of ferric chloride and chromic chloride in DMF and DMSO as a function of temperature

The equivalent conductivities of anhydrous ferric chloride (FeCl₃) and anhydrous chromic chloride (CrCl₃) were measured in nonaqueous aprotic solvents such as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at temperatures between 278.15 and 318.15 K. In both DMF and DMSO, conductivity values for FeCl₃ were found to be higher than those for CrCl₃. In addition, the conductivity values for both FeCl₃ and CrCl₃ in DMF were higher than those in DMSO at all temperatures. The conductivity data were analyzed by the Robinson–Stokes equations. The limiting equivalent ionic conductivities for ferric ion (Fe³⁺) and chromic ion (Cr³⁺) and the ion association constants (K _A ) for FeCl₃ and CrCl₃ were determined in DMF and DMSO. The K _A values calculated for both FeCl₃ and CrCl₃ in DMF were higher than those in DMSO. This can be ascribed to an increase of the ion association constants with a decrease of the relative permittivity of solvents used in this study. The K _A values increased with the increase in temperature in the studied solvents. Thermodynamic functions (Gibbs’ free energy, entropy, and enthalpy of ion association) were estimated from the temperature dependence of the ion association constant. The positive values of entropy and enthalpy found for FeCl₃ and CrCl₃ at all temperatures indicate that the association process in DMF and DMSO is endothermic.     

On the determination of collision cross sections by nuclear Doppler shift

We report on measurements of the energy loss of ions in matter by “Inverted Doppler Shift Attenuation” (IDSA). This new method is an inversion of the “Doppler Shift Attenuation” (DSA) method for the determination of lifetimes of nuclear states. While in DSA the exact knowledge of the velocity dependent energy loss functiondE/ds is required, it is shown that in IDSA this function or the absolute collision cross section, respectively, can be determined from the Doppler spectrum of an excited nuclear fragment recoiling in matter, whose lifetime is known. No corrections or assumptions concerning the collision processes are necessary. ⁷Li^* fragments (E _γ=478 keV) from the¹⁰B(n, α)⁷Li^* reaction produce an easily observable and analysable Doppler spectrum. Here boron must be a constituent or an implanted impurity of the material to be investigated. The experimental set-up is described. An exact relativistic analysis of the Doppler spectrum is given. The measured collision cross sections turn out (a) to be proportional tov within the range 1.5 · 10⁸≦v≦4.8 · 10⁸ cm/sec, (b) are thus only due to pure “electronic” collisions, and (c) sensitively dependent on the charge distributions of the target atoms.     

A sensitive amperometric detection of dopamine agonist drug pramipexole at functionalized multi-walled carbon nanotubes (f-MWCNTs) modified electrode

The electrochemical detection of dopaminergic agonist drug pramipexole dihydrochloride monohydrate (PPX) has been investigated by cyclic voltammetric (CV) and amperometric i–t techniques at functionalized multi-walled carbon nanotubes-modified glassy carbon electrode. For the first time, a sensitive and rapid electrochemical method was developed for the determination of PPX. The surface morphological characteristics of the proposed electrode have been studied by using transmission electron microscopy (TEM); further, electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR) have been employed. PPX shows an irreversible anodic peak, which may be ascribed to the oxidation of the –NH groups of PPX. The proposed method was showing good sensitivity of 0.993 μA μM^?1 cm^?2 with a linear range of 5 to 340 μM by amperometric i–t and CV technique shows a linear range of 12.5 to 313 μM with a sensitivity of 1.92 μA μM^?1 cm^?2. The recovery of PPX from blood serum samples was found 100.6 and 98.9 %, respectively. Furthermore, the proposed method has been demonstrated for the determination of PPX in commercially available pharmaceutical samples and good agreement of results obtained.     

Structural properties of Zinc Lithium borate glass

Zinc Lithium Borate glasses of different composition were prepared with the aim of using it for thermoluminescence dosimetry. Melt quenching method was adopted in this process. Fourier transform Infrared (FTIR) spectroscopy and UV-vis-NIR spectroscopy techniques were employed to investigate the infrared spectra and energy band gap of different composition of Zinc Lithium Borate glasses. X-ray diffraction analysis was used to confirm the amorphous nature of the glass samples. Glass forming ability and stability of the glass was checked using Differential thermal analysis (DTA). Density, molar volume, refractive index parameters have been analyzed in the light of different concentration of the modifier. The active vibrational modes of 1200–1600 cm^?1 for B-O stretching of BO₃ units, 800–1200 cm^?1 for B-O stretching of BO₄ units and 400–800 cm^?1 for bending vibration of various borate segments were detected. Addition of ZnO to lithium borate shows its influence in converting the dominant BO₃ group to BO₄ group. BO₄ are known for creating complex defects, a situation that established deep and stable traps good for thermoluminescence phenomena. From optical data, direct and indirect energy band gap has been calculated using the data obtained from UV-vis-NIR spectroscopy. Both direct and indirect band gaps decrease with the increase of modifier Li₂CO₃.     

Luminescent properties of Eu2+ ions in AlN at low and high intensity of excitation

Luminescent properties of powder AlN∶Eu²⁺ phosphors were studied by excitation of 2-nd harmonic of ruby laser (hv=3·56 eV). It was shown that emission spectra of AlN∶Eu²⁺ phosphors consist of five or two overlapping bands according to the concentration of europium and the intensity of excitation. Decay times of luminescence of Eu²⁺ centres in different peaks lie between 0·9 and 1·5 μsec which is in agreement with the value of decay time of 4f⁶ 5d→47⁷ transition of Eu²⁺ ions. It is evident from the decomposition of emission spectra of Eu²⁺ centres that there exist several types of Eu²⁺ centres in AlN as was already demonstrated in the case of oxygen centres in AlN.