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These days, textile industries pose a more significant threat to surface water and groundwater sources directly or indirectly by discharging wastewater containing various dyes and organic pollutants to these water sources. The phase-junction-engineered heterogeneous photocatalysis carried out by visible-light-driven semiconductor photocatalysts is opening a new window for the degradation of environmental organic pollutants. In this work, we have reported a one-step bottom-up hydrothermal synthesis of biphasic tungsten oxide (o/h-WO3) and performed a photodegradation experiment under visible light irradiation for the efficient degradation of organic pollutants such as Methylene blue (MB) methyl violet (MV), respectively. The XRD, RAMAN, TEM, and UV-vis characterization techniques were used to investigate the structural, morphological, and optical properties of the as-synthesized o/h-WO3. Moreover, the low calculated band gap ( ̴ 2.8 eV) and the anionic nature of o/h-WO3 suggest it as an efficient visible-light-driven photocatalyst suitable for heterogeneous photocatalysis. The photodegradation experiment performed under visible light using o/h-WO3 photocatalyst showed better degradation efficiency of 71% and 89% for MB and MV, respectively, in 100 min. The dyes followed first-order kinetics, and their kinetic rate constants were calculated using the Langmuir-Hinshelwood model. Furthermore, the recyclability study of the photocatalyst was also performed and discussed the underlying mechanism for the photodegradation of the organic dyes.

Er3+–Yb3+ co-doped NaGd(MoO4)2 phosphors with different concentrations of Er3+ and Yb3+ ions have been successfully synthesized via a high-temperature solid-state reaction method.

Spring-water sources mapping was carried out in eight wards of Dhulikhel and four wards of Melamchi Municipality and forest area dynamics in Roshi and Melamchi Watersheds. Ward number 9 and 10 of Dhulikhel Municipality were rich in water sources. Whereas ward number 6 of Melamchi Municipality has a good amount of water sources compared to other wards. The major spring types were depression, fractured, and contact in both the Municipalities.The percentage of forest areas in the Roshi and Melamchi watersheds seems to be fluctuating with the data compared in 2010 and 2020. There is an increase in forest areas in both municipalities in 2020. Also, the perennial spring sourceswith good discharge are prominent in having a good forest area and large watershed recharge area.

Wastewater produced by the textile industry contains various dyes and organic compounds that directly or indirectly affect surface water or groundwater pollution. Visible-light-driven semiconductor photocatalysis is the leading pathway for the degradation of environmental pollutants. Herein we report the bottom-up hydrothermal growth of 2D tin disulfide nanostructures (SnS2 NSs) for the efficient photodegradation of organic pollutants such as Rhodamine B (Rh.B) and Methyl Violet (M.V) in an aqueous medium under visible light (λ > 400 nm) irradiation. The as-synthesized SnS2 NSs were characterized by various structural, morphological, and optical techniques such as XRD, RAMAN, TEM, UV–Vis, Brunauer–Emmett–Teller, etc. Furthermore, the low bandgap (∼1.6 eV), the high surface area (56 m2/g), and the anionic nature of SnS2 NSs attribute to it as an efficient photocatalyst for photocatalytic applications. The photocatalytic properties of SnS2 NSs showed good degradation efficiency of 94 and 99.6% for Rh. B and M.V, respectively, in 25 min. The kinetic rate constant of these dyes was estimated by using the Langmuir–Hinshelwood model. Here we also performed the recyclability test of the photocatalyst and discussed the plausible mechanism for the photocatalytic degradation of organic pollutants. The XPS spectra of SnS2 NSs were studied before and after the photodegradation of Rh.B and M.V, indicating the high stability of the photocatalyst. Moreover, in vitro cytotoxicity was also evaluated against human cervical cancer cell lines (HeLa cells) with different concentrations (0–1,000 μg/ml) of as-synthesized SnS2 NSs. This intended work provides a possible treatment for the degradation of organic pollutants under visible light to balance the aquatic ecosystems.

Bismuth Selenide and associated compounds inheriting stacked layered structure represent a unique class of materials where bulks are insulating with conducting surfaces, best known as thermoelectric materials. The bottom-up solution-based approach is a convenient alternative producing ultrathin high quality two-dimensional Bi2Se3 nanosheets. The present investigation deals with glycol mediated synthesis of highly crystalline ultrathin Bi2Se3 nanosheets. The as-synthesized Bi2Se3 nanosheets exhibit a rhombohedral crystal structure with a substantial surface-to-volume ratio that can possess several potential applications. Besides, the ultrathin Bi2Se3 nanosheets produced herein, found to be n-type with robust spatial confinement of charge carriers advantageous for thermoelectric applications, delivering a high-power factor of 1.55 μW/cmK2 at 150 °C. The method demonstrates the generic feature of the solution phase technique for the synthesis of highly crystalline nanosheets allowing mass production of identical ultra-thin nanosheets that can be easily integrated into devices for several promising applications, including spintronics, energy storage, and topological quantum computation.

In the present study, we report a systematic study of doping/ admixing of carbon nanotubes (CNTs) in different concentrations in MgB2. The composite material corresponding to MgB2+ x at.%CNTs (35 at.% > x > 0 at.%) have been prepared by solid-state reaction at ambient pressure. All the samples in the present investigation have been subjected to structural/ microstructural characterization employing XRD, SEM and TEM techniques. The magnetization measurements were performed by PPMS and Tc & Jct measurements have been done by the four-probe technique. The microstructural investigations reveal the formation of MgB2-CNTs composites. A CNT connecting the MgB2 grains may enhance critical current density due to its size (~ 5-20 nm diameter) compatible with coherence length of MgB2 (~ 5-6 nm) and ballistic transport current carrying capability along the tube axis. The Jct of MgB2 samples with varying CNTs concentration have been found to vary significantly e.g. Jct of the MgB2 sample with 10 at.% CNT addition is ~2.3 x 10^3 A/cm2 and its value for MgB2 sample without CNT addition is ~7.2x10^2 A/cm2 at 20K. The optimum result on Jc is obtained for 10 at.% CNTs admixed MgB2 sample at 5K, the Jc reaches ~5.2 x10^6 A/cm2 in self field, ~1.6 x 10^6 A/cm2 at 1T, ~2.9 x 10^5 A/cm2 at 2.6T and \~3.9 x 10^4 A/cm2 at 4T. The high value of intragrain Jc in 10 at.% CNTs admixed MgB2 superconductor has been attributed to the incorporation of CNTs into the crystal matrix of MgB2, which are capable of providing effective flux pinning centres. A feasible correlation between microstructural features and superconducting properties has been put forward., 8 pages, 6 figures. To be published in J. Nanoscience and Nanotechnology

We report systematic studies of structural, microstructural and transport properties of (Hg_0.80 Sb_0.2-x Pb_x)Ba_2 Ca_2 Cu_3O_8+\delta (where x = 0.0, 0.05, 0.1, 0.15, 0.2) compounds. Bulk polycrystalline samples have been prepared by two-step solid-state reaction route at ambient pressure. It has been observed that simultaneous substitution of Sb and Pb at Hg site in oxygen deficient HgO_\delta layer of HgBa2Ca2Cu3O8+\delta cuprate high-Tc superconductor leads to the formation of Hg-1223 as the dominant phase. Microstructural investigations of the as grown samples employing scanning electron microscopy reveal single crystal like large grains embodying spiral like features. Superconducting properties particularly transport current density (Jct) have been found to be sensitive to these microstructural features. As for example (Hg0.80Sb0.05Pb0.15)Ba2Ca2Cu3O8+\delta compound which exhibits single crystal like large grains (~ 50 micrometer) and appears to result through spiral growth mechanism, shows highest Jct (~ 1.85 x 103 A/cm2) at 77K. A possible mechanism for the generation of spiral like features and correlation between microstructural features and superconducting properties have been put forward., Comment: 16 pages, 6 figures. Accepted in Physica C

Samples of series Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3-x Zn x O 10-δ with x = 0.0, 0.015, 0.03, 0.06, 0.09 and 0.12 are synthesized by solid-state reaction route. All the samples crystallize in tetragonal structure with majority (> 90%) of Bi -2223( Bi 2 Sr 2 Ca 2 Cu 3 O 10) phase (c-lattice parameter ~ 36 Å). The proportion of Bi -2223 phase decreases slightly with an increase in x. The lattice parameters a and c of main phase ( Bi -2223) do not change significantly with increasing x. Superconducting critical transition temperature (Tc) decreases with x as evidenced by both resistivity [ρ(T)] and ac magnetic susceptibility [χ(T)] measurements. Interestingly the decrement of Tc is not monotonic and the same saturates at around 96 K for x > 0.06. In fact Tc decreases fast (~ 10 K/at%) for x = 0.015 and 0.03 samples and later nearly saturates for higher x values. Present results of Zn doping in Bi -2223 system are compared with other Zn -doped HTSC (high temperature superconducting) systems, namely the RE -123 ( REBa 2 Cu 3 O 7) and La -214 (( La, Sr )2 CuO 4).

We report systematic studies of structural, microstructural and transport properties of Y1-xCaxBa2Cu3O7-d bulk samples with 0.20 x 0.0. The partial substitution of Ca2+ at Y3+ site in YBa2Cu3O7-d leads towards slightly overdoped regime, which along with disorder in CuO2 planes is responsible for decrease in superconducting transition temperature (Tc) of the doped system. The microstructural variants being studied by transmission electron microscopy (TEM) technique in imaging and selected area diffraction modes revealed an increase in the density of twins with increase in Ca concentration despite the fact that there is slight decrease in the orthorhombicity. This is against the general conviction of decrease in twin density with decreasing orthorhombicity. An increase in twin density results in sharpening of twin boundaries with increasing Ca concentration. These sharpened twin boundaries may work as effective pinning centers. A possible correlation between microstructural features and superconducting properties has been put forward and discussed in the present investigation., Comment: 21 pages of TEXT and Figs. To appear in Physica C (2005)

We report the synthesis of La doped MgB 2 superconductors with nominal compositions Mg 1 - x La x B 2 (with x=0.01, 0.03, 0.05, 0.07) by solid state reaction at ambient pressure. A special encapsulation technique has been used by us to prepare high quality superconducting MgB 2 samples. The bulk polycrystalline samples possess superconducting transition temperature T c ( R = 0 ) ranging between 36-39K. It has been found that transport critical current density J c of the samples change significantly with the doping level of La. A high transport (J c ) value ∼1.9 x 10 3 A/cm 2 at 15K has been achieved for Mg 0 . 9 7 La 0 . 0 3 B 2 sample. The XRD and TEM investigations indicate that the samples prepared by encapsulation method are devoid of MgO, which is generally found when synthesis of MgB 2 is done through sintering of Mg and B powders. The detailed microstructural investigations of Mg 0 . 9 7 La 0 . 0 3 B 2 specimens by transmission electron microscopy (TEM) reveal the presence of partial dislocation network, moire fringes and superlattice structure in the as synthesized samples. The higher transport critical current density observed in Mg 0 . 9 7 La 0 . 0 3 B 2 superconductor has been attributed to the partial dislocations which are capable of providing pinning centres.

In the present study, we have investigated the effect of Bi doping at the Hg site in the oxygen deficient HgO δ layer of HgBa 2 Ca 2 Cu 3 O 8+ δ cuprate superconductor in relation to the occurrence of substructures in the form of long period polytypoid (LPP), defect matrix substructures, stacking faults and their influence on superconducting properties, particularly the critical current density. Bulk polycrystalline samples have been prepared by solid state reaction process through precursor route. It has been observed that the as grown Hg 1− x Bi x Ba 2 Ca 2 Cu 3 O 8+ δ variants (with x =0.05, 0.10, 0.15, 0.20, 0.25) correspond to the Hg(Bi):1223 phase. Transmission electron microscopic (TEM) observations reveal the presence of long period polytypoid-like structures, associated defect matrix substructure and stacking faults. A correlation between the details of defect substructures associated with LPP and the transport critical current density has been found to exist. It is suggested that this correlation arises due to defect matrix substructure and stacking faults providing effective flux pinning sites. The optimum transport critical current density J ct of ∼1.05×10 3 A/cm 2 at 77 K has been observed for the composition Hg 0.85 Bi 0.15 Ba 2 Ca 2 Cu 3 O 8+ δ . TEM studies reveal that the phase with this composition has the highest density of ordered LPP structures and associated defect matrix substructures. Such an observation bringing out a correlation between transport critical current density and LPP together with defect matrix substructure appears to be the first of its type. Evaluation of intra-grain critical current density through magnetic measurements for the optimum phase Hg 0.85 Bi 0.15 Ba 2 Ca 2 Cu 3 O 8+ δ revealed that this phase also has corresponding highest J c (intra-grain) ∼4.7×10 4 A/cm 2 at 77 K.

It has been found that simultaneous doping of Tl and Bi at Hg site of HgBa2Ca2Cu3O8+δ HTSC phase induces interesting microstructural variants in the form of long period polytypoid (LPP) like structure embodying native defect substructures. It has been observed that the as synthesized (HgTl0.2−xBix)Ba2Ca2Cu3O8+δ (with x = 0.05, 0.10, 0.15) phases have superconducting onset transition temperature (Tc) of about ∼133 K. However, the intragrain critical current density (Jc) for the various materials with different compositions varies significantly. It varies from 6.2 × 106 A/cm2 to 2.9 × 106 A/cm2 at 5 K and 1 T for (HgTl0.10Bi10)Ba2Ca2Cu3O8+δ and (HgTl0.15Bi0.05)Ba2Ca2Cu3O8+δ HTSC phase respectively. A correlation between the intragrain Jc and the defect substructures has been found to be present. This correlation has been described and disscussed. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report here the improvement of superconducting properties of MgB2 bulk samples by sintering at ambient pressure, employing RF induction heating. It has been found that Tc (R = 0) transition temperature of the sintered sample gets enhanced to ~40.00 K as compared to Tc (R = 0) ~25 K for the unsintered MgB2 sample. A high critical current density of ~5.45×104 A cm−2 (20 K) has been achieved for a sintered MgB2 sample whereas for an unsintered sample, the Jc is found to be ~1.20×103 A cm2 (20 K). Detailed microstrucural investigations by transmission electron microscope (TEM) reveal that most of the intergrain interfaces correspond to low angle grain boundaries. Based on TEM explorations, these boundaries have been recognized to be dominantly low angle tilt boundaries. Surface microstructural features of the MgB2 sample as investigated by scanning electron microscopy reveal a well-connected uniform grain structure for the sintered samples.

In this paper we have reported investigations on the effect of simultaneous substitution of Bi and Tl at the Hg site in the oxygen deficient HgOδ layer of HgBa2Ca2Cu3O8+δ cuprate superconductor. Bulk polycrystalline samples have been prepared by the two-step solid state reaction process (precursor route). It has been observed that the as grown HgBi0.2−xTIxBa2Ca2Cu3O8+δ (withx = 0.00, 0.05, 0.10, 0.15, 0.20) corresponds to the 1223 phase. It has been found that the Tc varies with the average cationic size of the dopant cations. The optimumTc of ∼ 131 K has been found for the composition HgBi0.15TI0.05Ba2Ca2Cu3O8+δ This composition leads to the average dopant cation size of ∼1.108 a which is very close to the size of Hg2+ (∼ 111 a). The microstructure for HgBi0.15TI0.05Ba2Ca2Cu3O8+δ has been found to be most dense and this phase exhibits the highest stability. The Jc of the optimum material HgBi0.15TI0.05Ba2Ca2Cu3O8+δ is found to be ∼ 1.29 × 103 A/cm2 at 77 K.

The extensive use of silver nanoparticles needs a synthesis process that is greener without compromising their properties. The present study describes a novel green synthesis of silver nanoparticles using Guava (Psidium guajava) leaf extract. In order to compare with the conventionally synthesized ones, we also prepared Ag-NPs by chemical reduction. Their optical and morphological characteristics were thoroughly investigated and tested for their antibacterial properties on Escherichia coli. The green synthesized silver nanoparticles showed better antibacterial properties than their chemical counterparts even though there was not much difference between their morphologies. Fourier transform infrared (FTIR) spectroscopic analysis of the used extract and as-synthesized silver nanoparticles suggests the possible reduction of Ag(+) by the water-soluble ingredients of the guava leaf like tannins, eugenol and flavonoids. The possible reaction mechanism for the reduction of Ag(+) has been proposed and discussed. The time-dependent electron micrographs and the simulation studies indicated that a physical interaction between the silver nanoparticles and the bacterial cell membrane may be responsible for this effect. Based on the findings, it seems very reasonable to believe that this greener way of synthesizing silver nanoparticles is not just an environmentally viable technique but it also opens up scope to improve their antibacterial properties.

We report the synthesis and characterization of graphite (C) doped MgB2-xCx (x = 0.0, 0.1, 0.2 and 0.3) samples. The crystal structure and microstructural characterization have been investigated by x-ray diffractometer and transmission electron microscopic (TEM) analysis. The superconducting properties especially Jc and Hc2 have been measured by employing physical property measurement system. We found that the graphite doping affects the lattice parameters as well as the microstructure of MgB2 superconductor. In case of optimally doped (x=0.1) sample, the critical current density at 5K corresponds to 1.1 x 10^6 and 5.3 x 10^4 A/cm^2 for 3T and 5T fields respectively. The upper critical field has been enhanced nearly two times after doping. The flux pinning behavior has been investigated by flux pinning force density curve and it reveals that the flux pinning behaviour has improved significantly by doping. TEM micrographs show the graphite nanoparticles of size ~5-10 nm which are invariably present in MgB2 grains. These nanoparticles act as flux pinning centre and are responsible for enhancement of superconducting properties of MgB2., Comment: Accepted in "Journal of Applied Physics"

In the present study, La-doped MgB_2 superconductors with different doping level (Mg1-xLaxB2; x=0.00, 0.01, 0.03 & 0.05) have been synthesized by solid-state reaction route at ambient pressure. Effect of La doping have been investigated in relation to microstructural characteristics and superconducting properties, particularly intragrain critical current density (Jc). The microstructural characteristics of the as synthesized Mg(La)B2 compounds were studied employing transmission electron microscopic (TEM) technique. The TEM investigations reveal inclusion of LaB6 nanoparticles within the MgB2 grains which provide effective flux pinning centres. The evaluation of intragrain Jc through magnetic measurements on the fine powdered version of the as synthesized samples reveal that Jc of the samples change significantly with the doping level. The optimum result on Jc is obtained for Mg0.97La0.03B2 at 5K, the Jc reaches ~1.4x107A/cm2 in self field, ~2.1 x 106A/cm2 at 1T, ~2.5 x 105A/cm2 at 2.5T and ~1.8 x 104 A/cm2 at 4.5T. The highest value of intragrain Jc in Mg0.97La0.03B2 superconductor has been attributed to the inclusion of LaB6 nanoparticles which are capable of providing effective flux pinning centres.

In the present work, methanol oxidation reaction was investigated on Pt particles of various diameters on carbon-nanofibers and carbon-black supports with different surface-oxygen concentrations, aiming for a better understanding of the relationship between the catalyst properties and the electrochemical performance. The pre-synthesized Pt nanoparticles in ethylene glycol, prepared by the polyol method without using any capping agents, were deposited on different carbon supports. Removal of oxygen-groups from the carbon supports had profound positive effects on not only the Pt dispersion but also the specific activity. The edge structures on the stacked graphene sheets in the platelet carbon-nanofibers provided a strong interaction with the Pt particles, significantly reconstructing them in the process. Such reconstruction resulted in the formation of more plated Pt particles on the CNF than on the carbon-black and exposure of more Pt atoms with relatively high co-ordination numbers, and thereby higher specific activity. Owing to the combined advantages of optimum Pt particle diameter, an oxygen-free surface and the unique properties of CNFs, Pt supported on heat-treated CNFs exhibited a higher mass activity twice of that of its commercial counterpart.

In the present investigation, we report a systematic study of Ag admixing in MgB2 prepared by solid-state reaction at ambient pressure. All the samples in the present investigation have been subjected to structural/ microstructural characterization employing x-rays diffraction (XRD) and transmission electron microscopic (TEM) techniques. The magnetization measurements were performed by physical property measurement system (PPMS). The TEM investigations reveal the formation of MgAg nanoparticles in Ag admixed samples. These nanoparticles may enhance critical current density due to their size (~5-20 nm) compatible with coherence length of MgB2 (~5-6 nm). In order to study the flux pinning effect of Ag admixing in MgB2, the evaluation of intragrain critical current density (Jc) has been carried out through magnetic measurements on the fine powdered version of the as synthesized samples. The optimum result on intragrain Jc is obtained for 10 at.% Ag admixed sample at 5K. This corresponds to 9.23x10^7 A/cm^2 in self-field,5.82x10^7 A/cm^2 at 1T,4.24 x10^6 A/cm^2 at 3.6T and 1.52x10^5 A/cm^2 at 5T. However, intragrain Jc values for MgB2 sample without Ag admixing are 2.59x10^6 A/cm^2,1.09x10^6A/cm^2,4.53x10^4 A/cm^2 and 2.91x10^3A/cm^2 at 5 K in self field, 1T, 3.6T and 5T respectively.. The high value of intragrain Jc for Ag admixed MgB2 superconductor has been attributed to the inclusion of MgAg nanoparticles into the crystal matrix of MgB2, which are capable of providing effective flux pinning centres. A feasible correlation between microstructural features and superconducting properties has been put forward., 5pages,6figures