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Inspired by nature's redox management in bioinorganic systems, we developed various Zn-complexes to catalyze a radical-mediated borrowing hydrogen process for producing β-disubstituted ketones. A diverse range of secondary alcohols, including fatty alcohols, terpenoids and steroid analogs, were successfully utilized for the chemoselective functionalization of ketones. Several organometallic and control studies suggest that coordinatively unsaturated radical species operate as active catalysts to promote alcohol activation and initiate the HAT process. [ABSTRACT FROM AUTHOR]

Spin filtering is a fundamental operation in spintronics, enabling the generation and detection of spin-polarized carriers. Here, we proposed and theoretically demonstrated that a 3d transition metal (TM) doped hydrogenated silicon quantum dot (TM:H-SiQD) is a suitable candidate for spin-filter devices. Using density functional theory, we investigate the structure, electronic properties, and magnetic behavior of TM:H-SiQD. Our calculations demonstrate that Mn:H-SiQD exhibits the highest stability. The designed spin-filter device using Mn:H-SiQD shows a spin-filtering efficiency of 99.9% at 300 K electrode temperature along with very high conductance. This remarkable efficiency positions it as a promising candidate for spintronic devices. [ABSTRACT FROM AUTHOR]

Donor‐atom‐based nano‐devices in silicon represent a breakthrough for individual control of electrons at atomic scale. Here, a finite‐bias characterization of electrical transport through such a device, fabricated on a silicon‐on‐insulator (SOI) wafer with low phosphorus (P) doping, is presented. In this device, multiple quasi‐periodic current peaks are observed at low temperatures in the electrical transfer characteristics. Such behavior of the transport characteristics is generally observed in devices having high doping concentration or with selective doping in the channel region to form a multi‐donor cluster quantum dot. However, in the present device donor–cluster formation is highly improbable owing to low doping concentration. The observed electrical transport characteristics of the device are explained with a model of two non‐interacting donors coupled in series with an unintentionally larger quantum dot, likely formed within the channel due to roughness. Theoretical simulation is also presented here for such a circuit supporting the experimental observations. [ABSTRACT FROM AUTHOR]

Thin silicon solar cells can be a low‐cost effective photo‐conversion device, if the device can efficiently absorb the solar spectrum. Herein, a new lithography‐free technique is developed for the fabrication of quasiperiodic silicon inverted‐pyramids arrays (SiIPAs), which show a high‐light‐trapping phenomenon in the ultraviolet–visible—near‐infrared (300–2000 nm). Fabricated SiIPA samples show a significant reduction of reflectance (3%) in the silicon absorption band (300–1000 nm). A unique additional absorption of 33–44% compared to the planar silicon is observed in the sub‐bandgap region of silicon (1100–2000 nm) for these samples. Photocurrent response measurement confirms the generation of additional electron–hole pairs in the sub‐bandgap region of silicon for the SiIPA samples in comparison with planar sample. In these results, the effect of field confinement and the creation of optical resonance modes within these structures, qualitatively supported by numerical simulation, are signified. The estimated short‐circuit current density using the experimental absorption spectrum of SiIPAs is 55.46 mA cm−2, which is far higher than the Lambertian limit of ≈43 mA cm−2. The theoretical efficiency of the solar cell can be achieved up to 35.22%, which surpasses the Shockley–Queisser limit of 33.7%. [ABSTRACT FROM AUTHOR]

The manuscript theoretically discusses various important aspects for donor atom based single qubit operations in silicon (Si) quantum computer architecture at room temperature using a single nitrogen (N) deep‐donor close to the Si/SiO2 interface. Quantitative investigation of room temperature single electron shuttling between a single N‐donor atom and the interface is the focus of attention under the influence of externally applied electric and magnetic field. To apprehend the realistic experimental configurations, central cell correction along with effective mass approach is adopted throughout the study. Furthermore, a detailed discussion currently explores the significant time scales implicated in the process and their suitability for experimental purposes. Theoretical estimates are also provided for all the external fields required to successfully achieve coherent single electron shuttling and their stable maintenance at the interface as required. The results presented in this work offer practical guidance for quantum electron control using N‐donor atoms in Si at room temperature. [ABSTRACT FROM AUTHOR]

The study was conducted to investigate the pathology of naturally occurring co-contamination of mycotoxins in poultry farms and the role of local management practices in the overall scenario. During the investigation, different chicken farms (n=73) in the Aizawl district of Mizoram state (India) were surveyed and monitored for management practices, the occurrence of disease and mortality. The feed samples collected from affected farms were tested for the presence of Aflatoxin and Ochratoxin by ELISA kits. The dead birds were subjected to necropsy. Liver and kidneys from the dead birds were processed for histopathological studies. Ten feed samples out of 49 tested (20.4%) were found affected by co-contamination with Aflatoxin and Ochratoxin. In this study, the mean level of Aflatoxin and Ochratoxin was 13.302 ppb and1.822 ppb, and the median level 12.143 ppb and1.674, ppb, respectively. Clinical signs were ruffled feathers, depression, dullness, huddling, poor growth and, anorexia. Necropsy revealed pathological lesions in visceral and lymphoid organs. Histopathological findings were inflammations, degenerative, and necrotic lesions in liver and kidneys. Poor management practices were observed in affected farms. A perusal of available literature did not reveal any study on the presence of co-contamination of Mycotoxicosis in poultry and poultry feed in Aizawl, Mizoram. [ABSTRACT FROM AUTHOR]

Designing well-defined Zn-complexes for sustainable dehydrogenative catalysis overcoming the difficulties associated with activating Zn2+(d10)-metal species is considered paramount goal in catalysis. Herein, we explore the plausibility of β-alkylation of secondary alcohols with primary alcohols by well-defined 3d10 Zn-complexes. Detailed organometallic and catalytic investigations, in conjunction with computational analyses, were conducted to ascertain the potential involvement of the catalyst at various stages of the catalytic process. [ABSTRACT FROM AUTHOR]

Single-electron transistor (SET) has an advanced feature that can be exploited in quantum devices. For practical utilization of such devices, the room-temperature operation is highly essential. Dopant-based single-electron devices are well studied at low temperatures although a few devices are developed for high-temperature operation with certain limitations. Here, we propose and theoretically exhibit that nitrogen (N) donor in silicon is an important candidate for the effective designing of quantum devices. Theoretical calculation of the density of states using the semi-empirical density functional theory method indicates that N-donor in silicon has a deep ground state compared to a phosphorus (P) donor. The N-donor spectrum is explored in nano-silicon structure along with the P-donor. A comparative study of the Bohr radius of N-donor and P-donor is also reported. The simulated current–voltage characteristics confirm that the N-doped device is better suited for SET operation at room temperature. [ABSTRACT FROM AUTHOR]

Hydrogen-saturated silicon nanowires (H-SiNWs) are the most attractive materials for nanoelectronics due to their special tunable electronic properties. The incorporation of magnetism in H-SiNWs can be extremely beneficial for a wide range of emerging spintronic devices, which can offer a more effective way to control spin. Here, we investigate the energetic stability, electronic properties, and magnetic properties of transition metal (TM), i.e., Fe and Mn doped Hydrogen-saturated silicon nanowires (TM:H-SiNWs) that have a diameter of 1 nm directed in (100), (110), and (111) facets using spin-polarized density functional theory (DFT). The calculations showed that the TM-doped H-SiNWs (TM:H-SiNWs) convince the electronic and magnetic alterations of H-SiNWs semiconductors. It can be ascertained that the total magnetization of the studied configurations is contributed by the hybridization between a localized p orbital of Si and a d orbital of the TM atoms. In addition, we report the Curie temperature of the TM:H-SiNWs using a mean-field approximation and a Monte Carlo simulation based on the Ising model. We obtain the above room temperature ferromagnetism in the (100) and (111) direction-oriented Mn:H-SiNWs. This study provides an in-depth knowledge of the properties of TM-doped H-SiNWs and can be used as a reference in silicon-based spintronic devices. [ABSTRACT FROM AUTHOR]

We report finite-bias characteristics of electrical transport through phosphorus donors in silicon nanoscale transistors, in which we observe inelastic-cotunneling current in the Coulomb-blockade region. The cotunneling current appears like a resonant-tunneling current peak emerging from the excited state and sustain within the blockade regions. These cotunneling features are unique, since the inelastic-cotunneling currents have so far been reported either as a broader hump or as a continuous increment of current. This finding is ascribed purely due to excitation-related inelastic cotunneling involving the ground and excited states. Theoretical calculations were performed for a two-level quantum dot, supporting our experimental observation. [ABSTRACT FROM AUTHOR]

Current–voltage characteristics of a quantum dot in double-barrier configuration, as formed in the nanoscale channel of silicon transistors, were analyzed both experimentally and theoretically. Single electron transistors (SET) made in a SOI-FET configuration using silicon quantum dot as well as phosphorus donor quantum dots were experimentally investigated. These devices exhibited a quantum Coulomb blockade phenomenon along with a detectable effect of variable tunnel barriers. To replicate the experimental results, we developed a generalized formalism for the tunnel-barrier dependent quantum Coulomb blockade by modifying the rate-equation approach. We qualitatively replicate the experimental results with numerical calculation using this formalism for two and three energy levels participated in the tunneling transport. The new formalism supports the features of most of the small-scaled SET devices. [ABSTRACT FROM AUTHOR]

The "borrowing hydrogen" (BH) method for C‐alkylation reactions using alcohol as alkylating agents is an important synthetic transformation. In this respect, designing cheap and bench stable earth abundant metal catalyst for borrowing hydrogen transformation is a key challenge to be witnessed. Herein we have presented a synthesis of non‐phosphine, easily accessible and bench stable SNS−Ni complexes. The Ni‐catalyst was successfully applied for the C‐alkylation of ketone enolates to α‐alkylated ketones. Primary alcohol with different functional groups and various heteroaromatic alcohols are well tolerated. The present catalyst system was efficiently applied to gram scale synthesis and also the green chemistry metrics of the reaction were calculated. The present protocol was also extended successfully for the synthesis of biologically important quinoline moieties. Finally, various control experiments and deuterium labelled experiments suggest that the reaction proceeds via borrowing hydrogen pathway. [ABSTRACT FROM AUTHOR]

In silicon nanoscale transistors, dopant atoms can significantly affect the transport characteristics, in particular at low temperatures. Investigation of coupling between neighboring dopants in such devices is essential in defining the properties for transport. In this work, we present an overview of different regimes of inter-dopant coupling, controlled by doping concentration and a selective doping process. Tunneling-transport spectroscopy can reveal the fundamental physics of isolated dopants in comparison with strongly-coupled dopants. In addition, observations of surface potential for Si nano-transistors can provide direct access to understanding the behavior of coupled dopants. [ABSTRACT FROM AUTHOR]

Following the rapid development of the electronics industry and technology, it is expected that future electronic devices will operate based on functional units at the level of electrically active molecules or even atoms. One pathway to observe and characterize such fundamental operation is to focus on identifying isolated or coupled dopants in nanoscale silicon transistors, the building blocks of present electronics. Here, we review some of the recent progress in the research along this direction, with a focus on devices fabricated with simple and CMOS-compatible-processing technology. We present results from a scanning probe method (Kelvin probe force microscopy) which show direct observation of dopant-induced potential modulations. We also discuss tunneling transport behavior based on the analysis of low-temperature I- V characteristics for devices representative for different regimes of doping concentration, i.e., different inter-dopant coupling strengths. This overview outlines the present status of the field, opening also directions toward practical implementation of dopant-atom devices. [ABSTRACT FROM AUTHOR]

Quantum confinement effects on optical transitions in ensembles of nc-Si QDs in an a-SiOx matrix has become evident by simultaneously considering the dielectric function dispersions obtained by optical modeling with spectroscopic ellipsometry, the absorption edge, and the photoluminescence peak. Diminution of the peak amplitude in the ε2-spectra for reducing the diameter of nc-Si QDs could arise due to the disappearance of excitonic effects in the E1 transition, while the peak broadening indicates an amplification of disorder in Si QDs. An energy blue shift happens to take place in an analogous fashion for all the characteristic parameters, upon decreasing the size of the nc-Si QDs for diameters in the range 6.5 ＜ d ＜ 2.0 nm. The band gap widening with the reduction of QD size is well supported by the first-principles calculations based on quantum confinement, while studies on the Stokes shift in the optical gap from the PL data could provide an understanding of the imperfect passivation of the surface defects on tiny nc-Si QDs. Low dimensional nc-Si QDs (∼2 nm in diameter) assembled in a large density (∼2.3 × 1012 cm−2) embedded in an a-SiOx matrix synthesized by spontaneous and low-temperature (300 °C) RF plasma processing, compatible to CMOS technology, are highly conducive for device applications. Systematic changes in composition and characteristics, including the thickness, of the individual sub-layers of the nc-Si QD thin films can be comprehensively pursued through a nondestructive process by ellipsometric simulation which could, thereby, enormously contribute to the precise optimization of the deposition parameters suitable for specific device fabrication e.g., all-silicon tandem solar cells and light emitting diodes, using silicon nanotechnology. [ABSTRACT FROM AUTHOR]

The impact of dopant atoms in transistor functionality has significantly changed over the past few decades. In downscaled transistors, discrete dopants with uncontrolled positions and number induce fluctuations in device operation. On the other hand, by gaining access to tunneling through individual dopants, a new type of devices is developed: dopant-atom-based transistors. So far, most studies report transport through dopants randomly located in the channel. However, for practical applications, it is critical to control the location of the donors with simple techniques. Here, we fabricate silicon transistors with selectively nanoscale-doped channels using nano-lithography and thermal-diffusion doping processes. Coupled phosphorus donors form a quantum dot with the ground state split into a number of levels practically equal to the number of coupled donors, when the number of donors is small. Tunneling-transport spectroscopy reveals fine features which can be correlated with the different numbers of donors inside the quantum dot, as also suggested by first-principles simulation results. [ABSTRACT FROM AUTHOR]

We report a very simple method for the fabrication of amorphous silicon rich oxide nanowires (a-SiOx NWs) with intrinsic nanocrystalline silicon quantum dots (nC-Si QDs) with a high density and controlled size, by thermally annealing thin films of nC-Si quantum dots embedded in the a-SiOx matrix, overcoated by an ultra-thin Au catalyst layer. The size and density of the Si-QDs in the basic matrix are controllable by changing the plasma parameters during the growth of the nC-Si/a-SiOx thin films. The diameter of the grown SiOx nanowires is controlled by merely varying the thickness of the Au-coating. The formation of the 1D NWs with rigid boundaries influences a shrinkage in the size of the intrinsic 0D QDs; the size-reduction of the QDs is more prominent in narrower NWs obtained from thinner catalyst layers. This unique quantum-dot/nanowire composite system demonstrates a significantly improved optical absorption and reduced reflection in the entire UV-visible range of the solar spectrum compared to its thin film structure, and those are again pronounced by reducing the dimension of the nanowires. The photoluminescence properties of this composite system demonstrate a strong room temperature emission band in the range of 400–600 nm with a peak at ∼519 nm. The PL peak of the NW film undergoes a large blue shift by 150 nm from that of the annealed QD films which has been attributed to the reduction in the average size of the intrinsic nC-Si QDs during the growth of the a-SiOx NWs. These novel a-SiOx NWs with intrinsic nC-Si QDs, produced by a simple synthesis technique involving a solid–liquid–solid (SLS) growth process, deserve enough promise in the field of photovoltaics and light emitting devices. [ABSTRACT FROM AUTHOR]

Abstract: Electronic transport in silicon quantum dots (Si-QDs) in core/shell configuration was studied. The nC–Si cores encapsulated by protective SiO x shells embedded in a-Si matrix were obtained from one-step and spontaneous plasma processing, at low substrate temperature (300°C) compatible for device fabrication. The size, density and distribution of nC–Si QDs were controlled by optimizing the plasma parameters. Very high electrical conductivity, σ ∼4×10−2 Scm−1, was achieved at a total number density of Si-QDs, N ∼4.8×1011 cm−2, corresponding to the lowering in its average core size, d ∼3.7nm, to the order of the bulk Si exciton Bohr radius and the associated quantum confinement effects. The electrical conductivity was demonstrated to exhibit quantum size (3< d (nm)<10) effect in zero dimensional quantum dots. The underlying electronic transport was explained using heteroquantum-dot model, the nC–SiO x :H QDs possess hetero-junction like band structure in the interface regions, due to their different band gaps. [Copyright &y& Elsevier]

Abstract: Detail structural characterizations of the nC-Si/SiO x :H films prepared from low temperature (300°C) SiH4 plasma, have been performed using various spectroscopic and microscopic probes, e.g., IR spectroscopy, ellipsometry, scanning electron microscopy and atomic force microscopy. The growth structure has been probed by Bruggeman effective medium approximation fitting to the ellipsometry data, considering a three-layer growth model, which has been identified by FESEM studies. It has been observed that with the reduction in pressure (p) the overall crystallinity improves along with the lowering in the incubation layer thickness, and the reduction of void fraction in the bulk as well as in the growth zone and surface layer. The maximum crystallinity in the bulk has been identified at p =0.6Torr, corresponding to the lowest roughness on the surface. Oxygen incorporation has been found to be favored at lower gas pressure in the plasma, along with simultaneous dehydrogenation of the silicon network which remains the key criteria for attaining enhanced nanocrystallinity. Plausible formation mechanism of the nC-Si/SiO x :H structure, activated by chemical reactions occurring in the He diluted (SiH4 +CO2) plasma has been investigated. [Copyright &y& Elsevier]

The nC-SiOx:H films have been produced from He diluted SiH4 plasma in RF glow discharge. Systematic oxygen incorporation in Si:H identifies a dehydrogenation process, demonstrating a reduced solubility of hydrogen in the SiOx:H network. The dark-conductivity varies from 1.6 × 10−2 S cm−1 to 3.1 × 10−6 S cm−1 as the O-content (CO) changes from 0 to 15 at% and shows, in general, dual activation energies across ~310 K. The notable observation includes an irregular optical gap variation of the Si-network with the increasing oxygenation. A prominent narrowing of the optical gap has been demonstrated till the crystallinity in the material sustains, corresponding to an O-content of 2.2 at%. For CO > 2.2 at% the optical gap of the amorphous SiOx:H network spontaneously widens. This opposite nature of optical gap variations and temperature dependent conduction mechanism exhibiting dual activation energy are explained in the frame work of three phase model of the network. [ABSTRACT FROM AUTHOR]

Abstract: A comprehensive report on the structural studies on SiO:H films prepared at high growth rate from He-diluted (SiH4+CO2) plasma has been presented and extraction of some intriguing ideas that deserve high relevance for the potential development of nano-crystalline hydrogenated silicon oxide (nc-SiO:H) films has been tried. Poly-hydrogenation has been found as inherent to increasing alloying of the network; however, the bonded H-content reduces linearly with the degree of oxygen incorporation, i.e., the solubility of H in the SiO:H network decreases as the O-content increases in the presence of He. This result happens to be opposite to the conventional H2-diluted plasma condition and appears to be attractive as well. In addition, He-dilution contributes to a high growth rate of the material. Dynamic interaction of He* in the formation of activated oxygen atoms in the plasma and their efficient mobilization on the surface reaction process at the growing network induces abstraction of H from the SiH n groups and the terminal H atoms are replaced by bridging O atoms to form the SiO:H network. Abstraction of H from the network being an essential criteria for developing nanocrystallinity and it being inherent to oxygenation in Si network when prepared from He-diluted (SiH4+CO2) plasma in PECVD, the process could provide an appropriate pathway for preparing nc-SiO:H structures for solar cells, from such plasma in suitable parametric conditions. [Copyright &y& Elsevier]

Quantum confinement in zero-dimensional silicon nanocrystals (nC) in the quantum dot (QD) configuration has triggered a tremendous interest in nanostructured device technology. However, the formation of Si-QDs eventually proceeds through multi-step routes and involves high temperature processing that impedes preferred device configuration. The present work demonstrates the formation of nC-Si QDs of controlled size, density and distribution through one-step and spontaneous plasma processing, at a low substrate temperature (300 °C) compatible for device fabrication. Direct growth of nC-Si/SiOx core/shell quantum dots embedded in the a-Si matrix, 6.4–3.7 nm in diameter and with number density in the range ∼ 6 × 109–1 × 1011 cm − 2 has been accomplished, following a novel route where He dilution to SiH4 in RF plasma CVD has been found instrumental. On gradual reduction in the size of QDs, splitting of the energy bands widens the optical band gap and induces visible photoluminescence that appears controllable by tuning the size and density of the dots. This low temperature and spontaneous plasma processing of nC-Si/SiOx core/shell QDs that exhibit the quantum size effect in photoluminescence is being reported for the first time. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the effect of three essential oils with different main chemical structures, i.e., cinnamon bark oil (CNO), clove bud oil (CLO) and ajwain seed oil (AJO) as an alternative to antibiotic growth promoter (AGP) on intestinal health, immune response and antioxidant status in broiler chickens. Four hundred one-day-old broiler chicks were randomly divided into five dietary groups comprising of eight replicates (n = 8) in each group. Each replicate contained ten chicks. Five dietary groups consisted of: 1) a basal diet (control; without any antibiotic and essential oils); 2) the basal diet + bacitracin methylene disalicylate added at a dose of 50 mg/kg diet (AGP); 3) the basal diet + CNO at 300 mg/kg diet (CNO); 4) the basal diet + CLO at 600 mg/kg diet (CLO); and 5) the basal diet + AJO at 400 mg/kg diet (AJO). Both AGP and CNO significantly increased the villi height in duodenum ( P = 0.004), jejunum ( P = 0.008) or ileuim ( P = 0.003) compared with the control. The counts of Escherichia coli in pre-caecal contents decreased ( P = 0.006) in the groups receiving AGP and CNO and the counts of Clostridium spp. decreased ( P = 0.029) in the AGP group compared with the control. Population of Lactobacilli spp. was not affected ( P = 0.39) by any diets. Antibody titers against Newcastle disease virus increased with CNO, CLO and AJO supplementation ( P < 0.001) compared with the control and AGP. The concentrations of cholesterol in serum reduced ( P = 0.030) in CNO, CLO and AJO groups compared with the control and AGP groups. Supplementation of CNO and CLO increased ( P = 0.001) the superoxide dismutase activity in serum compared with the AGP. In conclusion, supplementation of CNO could be more advantageous than the AGPs in diets due to its combined beneficial effects on immune response, gut health, antioxidant status and blood cholesterol in broiler chickens. [ABSTRACT FROM AUTHOR]