Charge transport mechanisms of PbSnSe2 and observation of transition from direct to Fowler-Nordheim tunneling

In this study, we report the observation of various conduction mechanisms in mechanically exfoliated PbSnSe2 based on temperature-dependent current and voltage characteristics. A transition from direct tunneling to Fowler-Nordheim tunneling in PbSnSe2 was observed at 2.63 V. At lower temperatures, the 3D Mott variable range hopping model fits the data, yielding a density of states of ∼8.80 × 1020 eV-1 cm-3 at 2 V. The values of Whop and Rhop were 64 meV and 22.7 nm, respectively, at 250 K. The Poole-Frenkel conduction was observed in the Au/PbSnSe2/Au device and the dielectric constant of PbSnSe2 was calculated to be 1.4. At intermediate voltages, a space charge limited current with an exponential distribution of traps was observed and a trap density of ∼9.53 × 1013 cm-3 and a trap characteristic temperature of 430 K were calculated for the Au/PbSnSe2/Au device.

Solution combustion synthesis: the relevant metrics for producing advanced and nanostructured photocatalysts

The current developments and progress in energy and environment-related areas pay special attention to the fabrication of advanced nanomaterials via green and sustainable paths to accomplish chemical circularity. The design and preparation methods of photocatalysts play a prime role in determining the structural, surface characteristics and optoelectronic properties of the final products. The solution combustion synthesis (SCS) technique is a relatively novel, cost-effective, and efficient method for the bulk production of nanostructured materials. SCS-fabricated metal oxides are of great technological importance in photocatalytic, environmental and energy applications. To date, the SCS route has been employed to produce a large variety of solid materials such as metals, sulfides, carbides, nitrides and single or complex metal oxides. This review intends to provide a holistic perspective of the different steps involved in the chemistry of SCS of advanced photocatalysts, and pursues several SCS metrics that influence their photocatalytic performances to establish a feasible approach to design advanced photocatalysts. The study highlights the fundamentals of SCS and the importance of various combustion parameters in the characteristics of the fabricated photocatalysts. Consequently, this work deals with the design of a concise framework to link the fine adjustment of SCS parameters for the development of efficient metal oxide photocatalysts for energy and environmental applications.

Sustainable chemical processing of flowing wastewater through microwave energy

Iron oxide nanostructured catalysts have emerged as potential candidates for efficient energy conversion and electrochemical energy storage devices. However, synthesis and design of nanomaterial plays a key role in its performance and efficiency. Herein, we describe a one-pot solution combustion synthesis (SCS) of α-Fe₂O₃ with glycine as a fuel, and a subsequent reduction step to produce iron-containing catalysts (i.e., Fe₃O₄, Fe-Fe₃O₄, and Fe⁰). The synthesized iron-based nanoparticles were investigated for methyl orange (MO) degradation through Microwave (MW) energy under continuous flow conditions. Fe-Fe₃O₄ showed higher MO degradation efficiency than α-Fe₂O₃, Fe₃O₄ and Fe⁰ at low absorbed MW power (i.e. 5-80 W). The enhanced degradation efficiency is associated to the combination of higher availability of electron density and higher heating effect under MW energy. Investigation of dielectric properties showed relative dielectric loss of Fe₃O₄, Fe-Fe₃O₄, and Fe⁰ as 3847, 2010, and 1952, respectively. The calculated average local temperature by the comparative analysis of MW treatment with conventional thermal (CT) treatment showed a marked thermal effect of MW-initiated MO degradation. This work highlights the potential of microwave-driven water depollution under continuous-flow processing conditions and demonstrates the positive impact that earth-abundant Fe catalyst synthesized by green SCS method can have over the treatment of wastewater.

Development of High-Performance Bismuth Sulfide Nanobelts Humidity Sensor and Effect of Humid Environment on its Transport Properties

Orthorhombic phase bismuth sulfide (Bi₂S₃) nanobelts were prepared via  liquid-solid phase reaction method. Bi₂S₃ nanobelts were observed to be preferentially oriented along the (101) plane. Direct band gap (2.95 eV) and characteristic wavelength (λ_max = 342 nm) were extracted through UV-visible spectroscopy. Specific surface area (9.8 m²/g) and pore size (2.5-120 nm) were evaluated through Brunauer-Emmett-Teller (BET) analysis. Relative humidity (RH) sensing properties were studied in the range of 11-97% RH at ambient conditions. The response of the sensor increases linearly with increase in RH. Fast response time (8-10 s) and recovery time (15 s) were observed. Reproducible and large response was also observed between 11 and 97% RH. Small hysteresis (<5%) and long-term stability during 30 days were confirmed. As a function of frequency, capacitance, alternating current conductivity, and electrical complex modulus in the frequency range of 20-2 MHz were studied at 11-97% RH. The sensing mechanism was also studied.

Pressure-induced changes in the electronic structure and enhancement of the thermoelectric performance of SnS2: a first principles study

Hydrostatic pressure reduces the band gap and increases the ZT value of SnS₂.

Two-dimensional SnS nanoflakes: synthesis and application to acetone and alcohol sensors

SnS nanoflakes were synthesized using a solid state reaction method at 600 °C and their gas sensing properties were investigated.

Investigation of change in surface area and grain size of cadmium titanate nanofibers upon annealing and their effect on oxygen sensing

We have investigated the phase changes in CdTiO3 nanofibers as the annealing temperature of nanofibers was increased from 600 to 1200 °C. The nanofibers annealed at 600 °C were ilmenite with a very small amount of CdO. Upon annealing at 950 °C, CdO was completely removed. Annealing at 1000 °C yielded pure perovskite nanofibers, and at temperatures above 1100 °C rutile TiO2 nanofibers were obtained. Brunauer-Emmett-Teller (BET) analysis showed that with increase in annealing temperature the surface area of nanofibers was decreased. The nanofibers annealed at 600 °C have the higher surface area of ∼9.41 m(2)/g. Then oxygen sensors using CdTiO3 nanofibers annealed at 600 °C (ilmenite) and 1000 °C (perovskite) were fabricated. The sensitivity of the ilmenite nanofibers sensor was 2 times than that of the perovskite nanofibers sensor. The response and recovery times were 120 and 23 s, respectively, for the ilmenite nanofibers sensor, whereas response and recovery times were 156 and 50 s, respectively, for the perovskite nanofibers sensor. Better oxygen characteristics of ilmenite nanofibers are attributed to their large surface area and porosity. Therefore, we believe that ilmenite CdTiO3 nanofibers are potential candidates to develop practical oxygen sensors.

Aposthia: a birth defect or normal quantitative recessive human genetic trait?

Aposthia (natural circumcision) is the condition of being born without a prepuce. Usually sporadic cases are reported in the medical literature. In this paper for the first time we present the genetic profile of 3 families with aposthia trait and discuss the possible genetics.

Localization of a novel locus for hereditary nail dysplasia to chromosome 17q25.1-17q25.3

We report on a six-generation Pakistani consanguineous family with autosomal recessive transmission of a form of hereditary nail dysplasia. Affected individuals presented with onycholysis of fingernails and anonychia of toenails. Associated abnormalities of ectodermal appendages were not observed in any of the affected individuals. Linkage has been established to chromosome 17q. A maximum multipoint analysis logarithm of the odds ratio score of 4.85 was obtained at marker D17S1301. Due to the consanguineous nature of this kindred, the gene for nail dysplasia is probably contained within a 5.0-cM (3 MB on the sequence-based physical map) region of homozygosity flanked by markers D17S1807 and D17S937.

Linkage mapping of a nonspecific form of X-linked mental retardation (MRX53) in a large Pakistani family

Nonspecific X-linked mental retardation is a nonprogressive, genetically heterogeneous condition that affects cognitive function in the absence of other distinctive clinical manifestations. We report here linkage data on a large Pakistani family affected by a form of X-linked nonspecific mental retardation. X chromosome genotyping of family members and linkage analysis allowed the identification of a new disease locus, MRX53. The defined critical region spans approximately 15 cM between DXS1210 and DXS1047 in Xq22.2-26. A LOD score value of 3.34 at no recombination was obtained with markers DXS1072 and DXS8081.