Adjustment methods of Schottky barrier height in one- and two-dimensional semiconductor devices.

The Schottky contact which is a crucial interface between semiconductors and metals is becoming increasingly significant in nano-semiconductor devices. A Schottky barrier, also known as the energy barrier, controls the depletion width and carrier transport across the metal-semiconductor interface. Controlling or adjusting Schottky barrier height (SBH) has always been a vital issue in the successful operation of any semiconductor device. This review provides a comprehensive overview of the static and dynamic adjustment methods of SBH, with a particular focus on the recent advancements in nano-semiconductor devices. These methods encompass the work function of the metals, interface gap states, surface modification, image-lowering effect, external electric field, light illumination, and piezotronic effect. We also discuss strategies to overcome the Fermi-level pinning effect caused by interface gap states, including van der Waals contact and 1D edge metal contact. Finally, this review concludes with future perspectives in this field.

A Surface Matrix of Au NPs Decorated Graphdiyne for Multifunctional Laser Desorption/Ionization Mass Spectrometry.

The development of the valid strategy to enhance laser desorption/ionization efficiency gives rise to widespread concern in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) technology. Herein, a hybrid of Au NP-decorated graphdiyne (Au/GDY) was fabricated and employed as the SALDI-MS matrix for the first time, and a mechanism based on photothermal and photochemical energy conversions was proposed to understand LDI processes. Given theoretical simulations and microstructure characterizations, it was revealed that the formation of a coupled thermal field and internal electric field endow the as-prepared Au/GDY matrix with superior desorption and ionization efficiency, respectively. Moreover, laser-induced matrix ablation introduced strain and defect level into the Au/GDY hybrid, suppressing the recombination of charge carriers and thereby facilitating analyte ionization. The optimized Au/GDY matrix allowed for reliable detection of trace sulfacetamide and visualization of exogenous/endogenous components in biological tissues. This work offers an integrated solution to promote LDI efficiency based on collaborative photothermal conversion and internal electric field, and may inspire the design of novel semiconductor-based surface matrices.

Tunable Schottky barrier height of a Pt-CuO junction via a triboelectric nanogenerator.

Tuning Schottky barrier height is crucial to optimize the performance of Schottky junction devices. Here, we demonstrate that the Schottky barrier height can be tuned with the voltage from a triboelectric nanogenerator (TENG). Schottky barrier heights at both ends are increased after the treatment with the voltage generated by the TENG. The electric field generated by the impulse voltage of the TENG drives the diffusion of the ionized oxygen vacancy in a CuO nanowire, which induces the nonuniform distribution of the ionized oxygen vacancy. The positively charged oxygen vacancy accumulates at the contacted interface of Pt and the CuO nanowire, and it impels the conduction and valence bands to bend downwards. The Schottky barrier height is raised. A theoretical model based on the energy band diagram is proposed to explain this phenomenon. This method offers a simple and effective avenue to tune the Schottky barrier height. It opens up the possibility to develop a high-performance Schottky sensor by tuning the Schottky barrier height.

Combining triboelectric nanogenerator with piezoelectric effect for optimizing Schottky barrier height modulation.

Schottky-contacted sensors have been demonstrated to show high sensitivity and fast response time in various sensing systems. In order to improve their sensing performance, the Schottky barriers height (SBH) at the interface of semiconductor and metal electrode should be adjusted to appropriate range to avoid low output or low sensitivity, which was induced by excessively high or low SBH, respectively. In this work, a simple and effective SBH tuning method by triboelectric generator (TENG) is proposed, the SBH can be effectively lowered by voltage pulses generated by TENG and gradually recover over time after withdrawing the TENG. Through combining the TENG treatment with piezotronic effect, a synergistic effect on lowering SBH was achieved. The change of SBH is increased by 3.8 to 12.8 times, compared with dependent TENG treatment and piezotronic effect, respectively. Furthermore, the recovery time of the TENG-lowered SBH can be greatly shortened from 1.5 h to 40 s by piezotronic effect. This work demonstrated a flexible and feasible SBH tuning method, which can be used to effectively improve the sensitivity of Schottky-contact sensor and sensing system. Our study also shows great potential in broadening the application scenarios of Schottky-contacted electronic devices.

Synthetic methods for compounds containing fluoro-lactam units.

In recent years, considerable attention has been devoted to the exploration of novel synthetic methods for fluoro-lactams due to their significant biological and pharmaceutical activities. This review summarizes recently established strategies for synthesizing fluorine-substituted lactams, including fluoro-ß-lactams, fluoro-γ-lactams, and fluoro-δ-lactams. Additionally, the reaction scopes, limitations, and mechanisms are discussed.

Schottky-Contacted Nanowire Sensors.

The progress of the Internet-of-Things in the past few years has necessitated the support of high-performance sensors. Schottky-contacted nanowire sensors have attracted considerable attention owing to their high sensitivity and fast response time. Their progress is reviewed here, based on several kinds of important nanowires, for applications such as bio/chemical sensors, gas sensors, photodetectors, and strain sensors. Although Schottky-contacted nanowire sensors deliver excellent performance in these fields, they can be further improved by various methods, including defect engineering, surface modification, the piezotronic effect, and the piezophototronic effect, all of which are discussed here. With regard to practical applications, further efforts are required to address challenges such as the stability, selectivity, ultrafast response, multifunctionality, flexibility, distributed energy supply, and sustainability of Schottky-contacted nanowire sensors. Finally, future perspectives and solutions are discussed.

Triboelectric Nanogenerator Enhanced Schottky Nanowire Sensor for Highly Sensitive Ethanol Detection.

Highly sensitive ethanol sensors are important for environmental and industrial monitoring. In our work, we demonstrate a method to enhance the response of a Schottky sensor based on a ZnO nano/microwire (NMW) by triboelectric nanogenerator (TENG). Via lowering the Schottky barrier height (SBH) via the high voltage from TENG, the response of the sensor is enhanced by 139% for 100 ppm ethanol. This method accelerates the recovery process. The high voltage from TENG produces a high intensity electric field to drive diffusion of the oxygen vacancies in ZnO NMW toward to the junction area around the interface. It is equivalent to applying the reverse voltage on the Schottky junction, which leads to the increase of depletion width. More chemisorbed oxygen on the depletion region is consumed once the ethanol gas is injected into the chamber, which improves the response of the ethanol sensor. This study provides a new, simple, and effective method to improve the sensor response.

Body-Integrated Self-Powered System for Wearable and Implantable Applications.

The human body has an abundance of available energy from the mechanical movements of walking, jumping, and running. Many devices such as electromagnetic, piezoelectric, and triboelectric energy harvesting devices have been demonstrated to convert body mechanical energy into electricity, which can be used to power various wearable and implantable electronics. However, the complicated structure, high cost of production/maintenance, and limitation of wearing and implantation sites restrict the development and commercialization of the body energy harvesters. Here, we present a body-integrated self-powered system (BISS) that is a succinct, highly efficient, and cost-effective method to scavenge energy from human motions. The biomechanical energy of the moving human body can be harvested through a piece of electrode attached to skin. The basic principle of the BISS is inspired by the comprehensive effect of triboelectrification between soles and floor and electrification of the human body. We have proven the feasibility of powering electronics using the BISS in vitro and in vivo. Our investigation of the BISS exhibits an extraordinarily simple, economical, and applicable strategy to harvest energy from human body movements, which has great potential for practical applications of self-powered wearable and implantable electronics in the future.

Fully Bioabsorbable Capacitor as an Energy Storage Unit for Implantable Medical Electronics.

Implantable medical electronic devices are usually powered by batteries or capacitors, which have to be removed from the body after completing their function due to their non-biodegradable property. Here, a fully bioabsorbable capacitor (BC) is developed for life-time implantation. The BC has a symmetrical layer-by-layer structure, including polylactic acid (PLA) supporting substrate, PLA nanopillar arrays, self-assembled zinc oxide nanoporous layer, and polyvinyl alcohol/phosphate buffer solution (PVA/PBS) hydrogel. The as-fabricated BC can not only work normally in air but also in a liquid environment, including PBS and the animal body. Long-term normal work time is achieved to 30 days in PBS and 50 days in Sprague-Dawley (SD) rats. The work time of BC in the liquid environment is tunable from days to weeks by adopting different encapsulations along BC edges. Capacitance retention of 70% is achieved after 3000 cycles. Three BCs in series can light up 15 green light-emitting diodes (LEDs) in vivo. Additionally, after completing its mission, the BC can be fully degraded in vivo and reabsorbed by a SD rat. Considering its performance, the developed BC has a great potential as a fully bioabsorbable power source for transient electronics and implantable medical devices.

Lattice Boltzmann modeling of fluid-particle interaction based on a two-phase mixture representation.

In this work, we derive a lattice Boltzmann model for fluid-particle interaction by considering the system as a two-phase mixture. A partially saturated type scheme is achieved rigorously without any viscosity-dependent weight parameter. The scheme is of second-order accuracy in both space and time including the body-force term. Moreover, we devise a scheme suitable for the scenario where two or more particles intersect a single computational cell, typically occurring for particles in contact or close to contact. Good performance is found when the present scheme is validated against three classic problems, namely the flow past a stationary cylinder, a cylindrical particle settling in a channel under gravity, and the flow around two impacting cylinders.

Highly Corrosion Resistant and Sandwich-like Si3N4/Cr-CrNx/Si3N4 Coatings Used for Solar Selective Absorbing Applications.

Highly corrosion resistant, layer-by-layer nanostructured Si3N4/Cr-CrNx/Si3N4 coatings were deposited on aluminum substrate by DC/RF magnetron sputtering. Corrosion resistance experiments were performed in 0.5, 1.0, 3.0, and 5.0 wt % NaCl salt spray at 35 °C for 168 h. Properties of the coatings were comprehensively investigated in terms of optical property, surface morphology, microstructure, elemental valence state, element distribution, and potentiodynamic polarization. UV-vis-near-IR spectrophotometer and FTIR measurements show that the change process in optical properties of Si3N4/Cr-CrNx/Si3N4/Al coatings can be divided into three stages: a rapid active degradation stage, a steady passivation stage, and a transpassivation degradation stage. With the increase in the concentration of NaCl salt spray, solar absorptance and thermal emittance experienced a slight degradation. SEM images reveal that there is an increase in surface defects, such as microcracks and holes and -cracks. XRD and TEM measurements indicate that the phase structure changed partially and the content of CrOx and Al2O3 has increased. Auger electron spectroscopy shows that the elements of Cr, N, and O have undergone a minor diffusion. Electrochemical polarization curves show that the as-deposited Si3N4/Cr-CrNx/Si3N4/Al coatings have excellent corrosion resistance of 3633.858 kΩ, while after corroding in 5.0 wt % NaCl salt spray for 168 h the corrosion resistance dropped to 13.759 kΩ. However, these coatings still have an outstanding performance of high solar absorptance of 0.924 and low thermal emittance of 0.090 after corroding in 3.0 wt % NaCl salt spray for 120 h. Thus, the Si3N4/Cr-CrNx/Si3N4/Al coating is a good choice for solar absorber coatings applied in the high-saline environment.

Breakdown parameter for kinetic modeling of multiscale gas flows.

Multiscale methods built purely on the kinetic theory of gases provide information about the molecular velocity distribution function. It is therefore both important and feasible to establish new breakdown parameters for assessing the appropriateness of a fluid description at the continuum level by utilizing kinetic information rather than macroscopic flow quantities alone. We propose a new kinetic criterion to indirectly assess the errors introduced by a continuum-level description of the gas flow. The analysis, which includes numerical demonstrations, focuses on the validity of the Navier-Stokes-Fourier equations and corresponding kinetic models and reveals that the new criterion can consistently indicate the validity of continuum-level modeling in both low-speed and high-speed flows at different Knudsen numbers.

[Isolation, identification and naringin biotransforming properties of naringinase producing bacteria isolated from human intestinal microflora].

OBJECTIVE: Isolation of specific bacteria from human intestinal microflora to convert naringin to naringenin efficiently. METHODS: Fresh human feces from healthy individual was cultured in an anaerobic chamber for 24 h before being diluted and spread on agar medium. We cultured and incubated each single colony with the substrate naringin. The biotransformation of naringin by each single colony was detected by high-performance liquid chromatography (HPLC). We identified the isolated bacteria based on the analyses of 16S rDNA sequence and biochemical traits. We also studied the bioconversion kinetics of the bacteria. RESULTS: Four bacterial strains, named AUH-JLD3, AUH-JLD7, AUH-JLD104 and AUH-JLD109, capable of biotransforming naringin to naringenin, were isolated and identified as Blautia sp. AUH-JLD3, Enterococcus sp. AUH-JLD7, Bacteroides sp. AUH-JLD104 and Streptococcus pasteurianus subsp. AUH-JLD109 respectively based on the 16S rDNA sequence analysis, bacterial cell morphology, and biochemical traits. Study on biotransforming kinetics showed that all the four isolated bacterial strains were able to convert naringin (0.2 mmol/L) to naringenin within 12 h. The maximal concentration of the substrate naringin that strain AUH-JLD3, strain AUH-JLD7, strain AUH-JLD104 and strain AUH-JLD109 could biotransform efficiently were 0. 2 mmol/L (the average biotransforming rate was 66. 67%), 0.8 mmol/L (the average biotransforming rate was 86.49%), 0. 2 mmol/L (the average biotransforming rate was 73.68%) and 1.6 mmol/L (the average biotransforming rate was 93.20%), respectively. CONCLUSION: The four bacterial strains were capable of biotransforming naringin to naringenin, among which Streptococcus pasteurianus subsp. AUH-JLD109 has the highest naringin biotransforming capacity.

Multiscale lattice Boltzmann approach to modeling gas flows.

For multiscale gas flows, the kinetic-continuum hybrid method is usually used to balance the computational accuracy and efficiency. However, the kinetic-continuum coupling is not straightforward since the coupled methods are based on different theoretical frameworks. In particular, it is not easy to recover the nonequilibrium information required by the kinetic method, which is lost by the continuum model at the coupling interface. Therefore, we present a multiscale lattice Boltzmann (LB) method that deploys high-order LB models in highly rarefied flow regions and low-order ones in less rarefied regions. Since this multiscale approach is based on the same theoretical framework, the coupling precess becomes simple. The nonequilibrium information will not be lost at the interface as low-order LB models can also retain this information. The simulation results confirm that the present method can achieve modeling accuracy with reduced computational cost.

Gauss-Hermite quadratures and accuracy of lattice Boltzmann models for nonequilibrium gas flows.

Recently, kinetic theory-based lattice Boltzmann (LB) models have been developed to model nonequilibrium gas flows. Depending on the order of quadratures, a hierarchy of LB models can be constructed which we have previously shown to capture rarefaction effects in the standing-shear wave problems. Here, we further examine the capability of high-order LB models in modeling nonequilibrium flows considering gas and surface interactions and their effect on the bulk flow. The Maxwellian gas and surface interaction model, which has been commonly used in other kinetic methods including the direct simulation Monte Carlo method, is used in the LB simulations. In general, the LB models with high-order Gauss-Hermite quadratures can capture flow characteristics in the Knudsen layer and higher order quadratures give more accurate prediction. However, for the Gauss-Hermite quadratures, the present simulation results show that the LB models with the quadratures obtained from the even-order Hermite polynomials perform significantly better than those from the odd-order polynomials. This may be attributed to the zero-velocity component in the odd-order discrete set, which does not participate in wall and gas collisions, and thus underestimates the wall effect.

[Influence of lysozyme-like protein on virulence and capsular polysaccharide synthesis of Streptococcus pneumoniae].

OBJECTIVE: To study the biological character and pathogenic effect of a lysozyme-like protein in Streptococcus pneumoniae. METHODS: The gene knockout mutant was constructed by the long flanking homology polymerase chain reaction. The mutant containing rescue plasmid to complement the lysozyme-like gene was also constructed. The differences in biology and pathogenicity in D39 wild strain, gene knockout mutant and gene knockout mutant containing rescue plasmid were observed to identify the functions of the lysozyme-like gene. RESULTS: Compared with the wild strain, the gene knockout mutant had the characteristics of slower growth, declining virulence, and obviously reduced capsule polysaccharide synthesis. Complement experiment showed when the rescue plasmid was transformed into the mutant strain, the mRNA level of hypothetical lysozyme-like gene in the gene knockout mutant containing rescue plasmid was higher than that of the wild strain. Although the levels of virulence and capsule polysaccharide synthesis could be partly complemented compared with those of the gene knockout mutant, but not reached the levels in the wild strain. CONCLUSIONS: The lysozyme-like protein, a new Streptococcus pneumoniae virulence factor, may regulate the proliferation and the capsular polysaccharides synthesis of Streptococcus pneumoniae to affect expression of virulence.

Lattice Boltzmann model for traffic flow.

Mesoscopic models for traffic flows are usually difficult to be employed because of the appearance of integro-differential terms in the models. In this work, a lattice Boltzmann model for traffic flow is introduced on the basis of the existing kinetics models by using the Bhatnagar-Gross-Krook-type approximation interaction term in the Boltzmann equation and discretizing it in time and phase space. The so-obtained model is simple while the relevant parameters are physically meaningful. Together with its discrete feature, the model can be easily used to investigate numerically the behavior of traffic flows. In consequence, the macroscopic dynamics of the model is derived using the Taylor and Chapman-Enskog expansions. For validating the model, numerical simulations are conducted under the periodic boundary conditions. It is found that the model could reasonably reproduce the fundamental diagram. Moreover, certain interesting physical phenomena can be captured by the model, such as the metastability and stop-and-go phenomena.

Decreased glucagon responsiveness by bile acids: a role for protein kinase Calpha and glucagon receptor phosphorylation.

Dihydroxy bile acids like chenodeoxycholic acid (CDCA) induce heterologous glucagon receptor desensitization. We previously demonstrated that protein kinase C (PKC) was activated by certain bile acids and mediated the CDCA-induced decrease in glucagon responsiveness. The aim of the present study was to explore the role of PKC in the phosphorylation and desensitization of the glucagon receptor by CDCA. Desensitization was evaluated by measuring adenylyl cyclase activity. Receptor phosphorylation was assayed by metabolic labeling with [gamma-(32)P] ATP. Protein kinase C (PKC) translocation and activation was visualized by fluorescence microscopy. CDCA decreased cAMP production induced by glucagon in a dose-dependent manner without affecting cAMP synthesis through stimulation of either stimulatory GTP-binding protein (Gs) by NaF or adenylyl cyclase by forskolin. The CDCA-induced inhibition of adenylyl cyclase activity was potentiated by the phosphatase inhibitor, okadaic acid. The desensitizing effect of CDCA was bile acid-specific and was significantly reduced in the presence of PKC inhibitors and after PKC down-regulation by phorbol 12-myristate 13-acetate. CDCA increased glucagon receptor phosphorylation more than 3-fold at concentrations as low as 25 mum. Furthermore, CDCA significantly stimulated human recombinant PKCalpha autophosphorylation in vitro, as well as PKCalpha translocation to the plasma membrane and phosphorylation in vivo at concentrations as low as 25 mum. CDCA also stimulated PKCdelta translocation to the perinuclear region. Activated PKCalpha, PKCzeta, and to a lesser extent, PKCdelta, phosphorylated the glucagon receptor in vitro. This study demonstrates that certain bile acids, such as CDCA, stimulate phosphorylation and heterologous desensitization of the glucagon receptor, involving at least PKCalpha activation.

Bile acids stimulate PKCalpha autophosphorylation and activation: role in the attenuation of prostaglandin E1-induced cAMP production in human dermal fibroblasts.

The aim was to identify the specific PKC isoform(s) and their mechanism of activation responsible for the modulation of cAMP production by bile acids in human dermal fibroblasts. Stimulation of fibroblasts with 25-100 microM of chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA) led to YFP-PKCalpha and YFP-PKCdelta translocation in 30-60 min followed by a transient 24- to 48-h downregulation of the total PKCalpha, PKCdelta, and PKCepsilon protein expression by 30-50%, without affecting that of PKCzeta. Increased plasma membrane translocation of PKCalpha was associated with an increased PKCalpha phosphorylation, whereas increased PKCdelta translocation to the perinuclear domain was associated with an increased accumulation of phospho-PKCdelta Thr505 and Tyr311 in the nucleus. The PKCalpha specificity on the attenuation of cAMP production by CDCA was demonstrated with PKC downregulation or inhibition, as well as PKC isoform dominant-negative mutants. Under these same conditions, neither phosphatidylinositol 3-kinase, p38 MAP kinase, p42/44 MAP kinase, nor PKA inhibitors had any significant effect on the CDCA-induced cAMP production attenuation. CDCA concentrations as low as 10 microM stimulated PKCalpha autophosphorylation in vitro. This bile acid effect required phosphatidylserine and was completely abolished by the presence of Gö6976. CDCA at concentrations less than 50 microM enhanced the PKCalpha activation induced by PMA, whereas greater CDCA concentrations reduced the PMA-induced PKCalpha activation. CDCA alone did not affect PKCalpha activity in vitro. In conclusion, although CDCA and UDCA activate different PKC isoforms, PKCalpha plays a major role in the bile acid-induced inhibition of cAMP synthesis in fibroblasts. This study emphasizes potential consequences of increased systemic bile acid concentrations and cellular bile acid accumulation in extrahepatic tissues during cholestatic liver diseases.

Human prolactin receptor variants in breast cancer: low ratio of short forms to the long-form human prolactin receptor associated with mammary carcinoma.

Prolactin plays an essential role in the development of rodent mammary tumors and is a potent mitogen in human normal and cancerous breast tissues/cells. In this study, we have analyzed the expression of prolactin receptors, including the long receptor form (LF; stimulatory) and two novel short forms (SFs; S1a and S1b) derived from alternative splicing that are inhibitory of the activation induced by prolactin through the LF. Southern analysis of breast cancer profiling arrays revealed that 29 patients (group I) expressed an elevated LF, 10 patients (group II) showed decreased LF, and 8 patients (group III) had no change relative to the adjacent normal tissue. Their respective SF expression was increased in 21 patients of group I and generally decreased in groups II and III. However, the ratio of SF to LF was significantly decreased in 76% of the breast tumors and distributed evenly among the groups. Quantification of differential expression of prolactin receptor variants by real-time PCR in 15 pairs of human normal and tumor breast-matched tissues revealed a similar significant decrease in the ratio of SF to LF in the tumor tissue. Consistent lower ratio of SFs to LFs was confirmed in 8 of ten different breast cancer cell lines compared with normal mammary Hs578Bst and MCF10A cells. Because SFs act as dominant negative regulators of the stimulatory actions of the LF in vitro, their relatively reduced expression in cancer could cause gradations of unopposed prolactin-mediated LF stimulatory function and contribute to breast tumor development/progression.