N-Iodosaccharin (NISac): a new reusable catalyst for formal [2+4] cycloaddition of imines and enones

The first example of N-iodosaccharin (NISac)-catalyzed step, pot and atom economic synthesis of 1,3-oxazines via formal [2+4] cycloaddition of imines and enones has been reported. No by-product formation, operational simplicity, ambient temperature and high yields (85-95%) are the salient features of the present synthetic protocol. After isolation of the product, the catalyst NISac can be easily recovered and reused without any loss of efficiency.     

Lasing without population inversion in molecules

We have described here the physical basis for lasing without population inversion (LWOPI). This type of amplification is obtained basically by two mechanisms: (i) one is based on atomic interference and (ii) the other is based on Fano-type interference. We have shown here, in H₂ molecules, amplification without population inversion is feasible by considering both the mechanisms.     

A novel carbocatalytic hydride transfer strategy for efficient reduction of structurally different aldehydes and ketones in water

Reduced graphene oxide (rGO)–NaBH₄ is reported as mild and efficient catalyst-system for chemo-/regioselective reduction of structurally different aliphatic, aromatic as well as α,β-unsaturated aldehydes and ketones in water. The rGO was prepared by reducing graphene oxide using Tulsi leaf extract as bio-reductant. Operational simplicity, ambient reaction condition, high yield of pure products (80–97%), no by-product formation, no use of column chromatography for purification are the salient features of the envisaged protocol. Furthermore, the recovered TRGO was recycled and reused for subsequent reductions up to five times without any loss in activity.     

Influence of Rare Earth Ho3+ Doping on Structural,Microstructure and Magnetic Properties of ZnO Bulk and Thin Film Systems

We have investigated the doping behavior of rare earth element holmium (Ho³⁺) in ZnO semiconductor. The structural, microstructure, and magnetic properties of Zn_1-xHo_xO (x=0.0, 0.04, and 0.05) thin films deposited on Si(100) substrate by thermal evaporation technique were studied. The ceramic targets were prepared by conventional solid state ceramic technique. The pallets used as target were final sintered at 900 oC in the presence of N2 atmosphere. The experimental results of X-ray diffraction (XRD) spectra, surface morphology, and magnetic properties show that the Ho³⁺ doped ZnO thin films has a strong influence on the materials properties. The higher angle shift in peak position and most preferred (101) orientation were observed in XRD pattern. These spectra confirmed the substitution of Ho3+ in ZnO lattice. The surface morphology and stoichiometry for both bulk and thin films were analyzed by scanning electron microscopy and energy dispersive spectroscopy. It was observed that grain size decreases with the increase of Ho³⁺. Room temperature ferromagnetism was observed for Zn_0.95Ho_0.05O films. The ferromagnetism might be attributed to the substitution of Ho ions for Zn²⁺ in ZnO lattices.     

Improved cell viability and hydroxyapatite growth on nitrogen ion-implanted surfaces

Stainless steel 306 is implanted with various doses of nitrogen ions using a 2?MV pelletron accelerator for the improvement of its surface biomedical properties. Raman spectroscopy reveals incubation of hydroxyapatite (HA) on all the samples and it is found that the growth of incubated HA is greater in higher ion dose samples. SEM profiles depict uniform growth and greater spread of HA with higher ion implantation. Human oral fibroblast response is also found consistent with Raman spectroscopy and SEM results; the cell viability is found maximum in samples treated with the highest (more than 300%) dose. XRD profiles signified greater peak intensity of HA with ion implantation; a contact angle study revealed hydrophilic behavior of all the samples but the treated samples were found to be lesser hydrophilic compared to the control samples. Nitrogen implantation yields greater bioactivity, improved surface affinity for HA incubation and improved hardness of the surface.     

Step-wise laser excitation of the 4snf 3F Rydberg states of neutral zinc

The new experimental results on the effective quantum numbers and term energies of the highly excited odd-parity 4s4d ³D_1,2,3 →4snf ³F_2,3,4 Rydberg transitions of zinc have been presented. The experiment was performed using the three dye lasers simultaneously pumped by the second harmonic (532?nm) of the Q-switched Nd:YAG laser. The new observation includes the 4snf ³F₃ (12?≤n?≤?50) series excited from the 4s4d ³D₂ intermediate level. In addition, the 4snf ³F₂ (12?≤n?≤?28) and 4snf³F₄ (12?≤n?≤?33) series are observed from the thermally populated 4s4d ³D_1,3 fine structure components. The ionization potential of zinc has been determined from the unperturbed 4snf ³F₃ series as 75769.31?±?0.15?cm^?1, which is in excellent agreement with the previously reported value.     

Optoelectronic and thermoelectric properties of Zintl YLi3X2(X=Sb,Bi) compounds through modified Becke—Johnson potential

In the present work, we investigate the structural, optoelectronic and thermoelectric properties of the YLi₃X₂(X=Sb, Bi) compounds using the full potential augmented plane wave plus local orbital (FP-APW+lo) method. The exchange-correlation potential is treated with the generalized gradient approximation/local density approximation (GGA/LDA) and with the modified Becke-Johnson potential (TB-mBJ) in order to improve the electronic band structure calculations. In addition, the estimated ground state properties such as the lattice constants, external parameters, and bulk moduli agree well with the available experimental data. Our band structure calculations with GGA and LDA predict that both compounds have semimetallic behaviors. However, the band structure calculations with the GGA/TB-mBJ approximation indicate that the ground state of the YLi₃Sb₂ compound is semiconducting and has an estimated indirect band gap (Γ-L) of about 0.036 eV while the ground state of YLi₃Bi₂ compound is semimetallic. Conversely the LDA/TB-mBJ calculations indicate that both compounds exhibit semiconducting characters and have an indirect band gap (Γ-L) of about 0.15 eV and 0.081 eV for YLi₃Sb and YLi₃Bi₂ respectively. Additionally, the optical properties reveal strong responses of the herein materials in the energy range between the IR and extreme UV regions. Thermoelectric properties such as thermal conductivity, electrical conductivity, Seebeck coefficient, and thermo power factors are also calculated.     

A Critical Review on Pulsed Electric Field: A Novel Technology for the Extraction of Phytoconstituents

Different parts of a plant (seeds, fruits, flower, leaves, stem, and roots) contain numerous biologically active compounds called “phytoconstituents” that consist of phenolics, minerals, amino acids, and vitamins. The conventional techniques applied to extract these phytoconstituents have several drawbacks including poor performance, low yields, more solvent use, long processing time, and thermally degrading by-products. In contrast, modern and advanced extraction nonthermal technologies such as pulsed electric field (PEF) assist in easier and efficient identification, characterization, and analysis of bioactive ingredients. Other advantages of PEF include cost-efficacy, less time, and solvent consumption with improved yields. This review covers the applications of PEF to obtain bioactive components, essential oils, proteins, pectin, and other important materials from various parts of the plant. Numerous studies compiled in the current evaluation concluded PEF as the best solution to extract phytoconstituents used in the food and pharmaceutical industries. PEF-assisted extraction leads to a higher yield, utilizes less solvents and energy, and it saves a lot of time compared to traditional extraction methods. PEF extraction design should be safe and efficient enough to prevent the degradation of phytoconstituents and oils.     

The effect of replacing pnictogen elements on the physical properties of SrMg_2X_2(X=N,P,As,Sb,Bi) Zintl compounds

The effect of replacing the anion from N to Bi down the group in the periodic table is investigated on SrMg_2X_2(X = N,P,As,Sb,Bi).A full potential linearized augmented plane wave plus local orbitals method is used along with different exchange–correlation potentials to obtain the lattice constants,phonons,electronic,and optical properties of the Sr Mg_2X_2(X = N,P,As,Sb,Bi) Zintl compounds.A good agreement is achieved and our calculations are validated by previous experimental and theoretical data.All compounds have shown stable dynamical behavior with gamma centered longitudinal response having no imaginary frequencies.Electronic band structures reveal the semiconducting nature of the compounds.The Pnictogen(X)-p state contributed mainly in the valence band and the Sr-d state forms the conduction of the compounds.Relative charge transfer and low overlapping of the atomic densities indicates the preferable ionic bonding character of these materials.In the optical properties,real and imaginary parts of dielectric function,complex refractive index,birefringence,reflectivity,and optical conductivity are calculated.These compounds can be utilized in the optical and optoelectronic devices.