2D Silicon-Based Semiconductor Si2 Te3 toward Broadband Photodetection.

Silicon-based semiconductor materials dominate modern technology for more than half a century with extraordinary electrical-optical performance and mutual processing compatibility. Now, 2D materials have rapidly established themselves as prospective candidates for the next-generation semiconductor industry because of their novel properties. Considering chemical and processing compatibility, silicon-based 2D materials possess significant advantages in integrating with silicon. Here, a systematic study is reported on the structural, electrical, and optical performance of silicon telluride (Si2 Te3 ) 2D material, a IV-VI silicon-based semiconductor with a layered structure. The ultrawide photoluminescence (PL) spectra in the range of 550-1050 nm reveals the intrinsic defects in Si2 Te3 . The Si2 Te3 -based field-effect transistors (FETs) and photodetectors show a typical p-type behavior and a remarkable broadband spectral response in the range of 405-1064 nm. Notably, the photoresponsivity and detectivity of the photodetector device with 13.5 nm in thickness and upon 405 nm illumination can reach up to 65 A W-1 and 2.81 × 1012 Jones, respectively, outperforming many traditional broadband photodetectors. It is believed this work will excite interests in further exploring the practical application of 2D silicon-based materials in the field of optoelectronics.

Trap state passivation and photoactivation in wide band gap inorganic perovskite semiconductors.

CsPbCl3 is a promising material to construct future short wavelength optoelectronic devices based on inorganic perovskite semiconductors. In this study, CsPbCl3 microcrystals were synthesized by a solution phase process. It was found that the photoluminescence (PL) intensities of the CsPbCl3 microcrystals can increase by up to five times under persistent irradiation of UV light without peak shifting, accompanied with an increased absorption coefficient above the band gap and decreased PL lifetime. This PL enhancement is a reversible process with excitation light switching on and off. The photoactivation process of the CsPbCl3 microcrystals is attributed to the passivation of the trap states.

Synthesis and luminescence properties of cubic-shaped Ca1-x TiO3 :Eu3+ particles.

In this article Ca1-x TiO3 :xEu3+ single crystalline particles with a cubic morphology and average size of 248 to 815 nm were synthesized by a solvothermal method. The structural and optical properties of the Ca1-x TiO3 :xEu3+ cubes were investigated, the formation mechanism of the cubes were analyzed and discussed, and the influence of Eu doping content and cubic size on the photoluminescence were examined. The differences in the photoluminescence between Ca1-x TiO3 :xEu3+ cubic crystals and nanoparticles was analyzed. It was found that an addition of a small amount of water can substantially reduce the size of the cubes. An obvious red emission band centered at 615 nm was observed under the excitation at 395 nm for the cubes. Our results demonstrate CaTiO3 cubes are good host materials for designing red phosphors.

Metal oxide semiconductor SERS-active substrates by defect engineering.

A general route to transform metal oxide semiconductors from non-SERS active to SERS-active substrates based on defect engineering is reported. The SERS enhancement factor (EF) of metal oxide semiconductors like α-MoO3 and V2O5 can be greatly enhanced and the SERS performance can be optimized according to the detecting analyte and activating laser wavelength by introducing oxygen vacancy defects. The EF of R6G on α-MoO3-x nanobelts can be as high as 1.8 × 107 with a detection limit of 10-8 M, which is the best among metal oxide semiconductors and comparable to noble metals without a "hot spot". A model, named "effective electric current model", was proposed to describe the photo-induced charge transfer process between the absorbed molecules and semiconductor substrates. The EF of 4-MBA, R6G and MB on α-MoO3-x nanobelts with different oxygen vacancy concentrations calculated based on the model matches very well with experimental results. As an extension, some potential metal oxide semiconductor SERS-active substrates were predicted based on the model. Our results clearly demonstrate that, through defect engineering, the metal oxide semiconductors can be made SERS-active substrates with high stability and high biocompatibility.

Microwave-Assisted Solvothermal Synthesis of VO2 Hollow Spheres and Their Conversion into V2O5 Hollow Spheres with Improved Lithium Storage Capability.

Monodispersed hierarchically structured V2O5 hollow spheres were successfully obtained from orthorhombic VO2 hollow spheres, which are in turn synthesized by a simple template-free microwave-assisted solvothermal method. The structural evolution of VO2 hollow spheres has been studied and explained by a chemically induced self-transformation process. The reaction time and water content in the reaction solution have a great influence on the morphology and phase structure of the resulting products in the solvothermal reaction. The diameter of the VO2 hollow spheres can be regulated simply by changing vanadium ion content in the reaction solution. The VO2 hollow spheres can be transformed into V2O5 hollow spheres with nearly no morphological change by annealing in air. The nanorods composed of V2O5 hollow spheres have an average length of about 70 nm and width of about 19 nm. When used as a cathode material for lithium-ion batteries, the V2O5 hollow spheres display a diameter-dependent electrochemical performance, and the 440 nm hollow spheres show the highest specific discharge capacity of 377.5 mAhg(-1) at a current density of 50 mAg(-1) , and are better than the corresponding solid spheres and nanorod assemblies.

TiO(2) nanospheres: a facile size-tunable synthesis and effective light-harvesting layer for dye-sensitized solar cells.

A facile route to synthesize amorphous TiO2 nanospheres by a controlled oxidation and hydrolysis process without any structure-directing agents or templates is presented. The size of the amorphous TiO2 nanospheres can be easily turned from 20 to 1500 nm by adjusting either the Ti species or ethanol content in the reaction solution. The phase structure of nanospheres can be controlled by hydrothermal treatment. The TiO2 nanospheres show excellent size-dependent light-scattering effects and can be structured into a light-harvesting layer for dye-sensitized solar cells with a quite high power conversion efficiency of 9.25 %.

Thermal conductivity of a single Bi0.5Sb1.5Te3 single-crystalline nanowire.

Single-crystalline Bi0.5Sb1.5Te3 nanowires were fabricated by a template-assisted pulsed electrodeposition technique; the thermal conductivity of a single Bi0.5Sb1.5Te3 nanowire of different diameters was characterized through a self-heating 3 ω method. The temperature-dependent resistance measurements prove the semiconductor behavior of the nanowires. The extremely low thermal conductivity of the nanowires was found compared with the corresponding bulk, and the Umklapp peaks shift to a higher temperature as the decreasing nanowire's diameter decreases, which qualitatively agrees with the theoretical calculations based on the Callaway model. The boundary scattering plays an important role in the reduction of the thermal conductivity and in the shift of the Umklapp peak of the Bi0.5Sb1.5Te3 nanowires.

Comparison of the effectiveness of two adjustable negative pressure ureteral access sheaths combined with flex ureteroscopy for ≤ 2 cm renal stones.

To compare the safety and effectiveness of the combination of intelligent intrarenal pressure control platforms (IPCP) and flexible ureteral access sheath (FUAS) combined with retrograde intrarenal surgery (RIRS) for the treatment of renal stones less than 2 cm. We retrospectively collected 383 patients with renal stones who underwent RIRS in our department from June 2022 to October 2023. Inclusion criteria: stone length or the sum of multiple stone lengths ≤ 2 cm. Finally, 99 cases were included and divided into an IPCP group (n = 40) and FUAS group (n = 59) based on surgical methods. The main endpoint was the stone-free rate (SFR) at third months after surgery, with no residual stones or stone fragments less than 2 mm defined as stone clearance. The secondary endpoints were surgical time and perioperative complications, including fever, sepsis, septic shock, and perirenal hematoma. There was no statistically significant difference in general information between the two groups, including age, gender, body mass index, comorbidities, stone side, stone location, stone length, urine bacterial culture, and hydronephrosis. The operation time for IPCP group and FUAS group was 56.83 ± 21.33 vs 55.47 ± 19.69 min (p = 0.747). The SFR of IPCP group and FUAS group on the first postoperative day was 75.00% vs 91.50% (p = 0.024). The SFR was 90.00% vs 94.90% in the third month (p = 0.349).In IPCP group, there were 11 cases with stones located in the lower renal calyces and 17 cases in FUAS group. The SFR of the two groups on the first day and third months after surgery were 45.50% vs 88.20% (p = 0.014) and 63.60% vs 94.10% (p = 0.040), respectively, with statistical differences. For kidney stones ≤ 2 cm, there was no difference in SFR and the incidence of infection-related complications between IPCP and FUAS combined with RIRS, both of which were superior to T-RIRS. For lower renal caliceal stones, FUAS has a higher SFR compared to IPCP.

Kirkendall effect induced ultrafine VOOH nanoparticles and their transformation into VO2(M) for energy-efficient smart windows.

Vanadium dioxide (VO2) has received widespread attention for application in energy-efficient smart windows because of its distinct thermochromic property in the near-infrared region during the reversible metal-insulator phase transition. In this study, lepidocrocite VOOH ultrafine nanoparticles (NPs) with a diameter less than 30 nm were prepared by a mild and efficient hydrothermal method, and the Kirkendall effect played a vital role in the growth of the VOOH NPs. It was found that VOOH could be transformed into VO2via a subsequent annealing treatment during which the size and morphology of VOOH are well preserved even though the annealing temperature is up to 500 °C. The ultrafine VO2 NPs are crucial for achieving excellent nanothermochromic performance with a luminous transmittance (Tlum) up to 56.45% and solar modulation ability (ΔTsol) up to 14.95%. The environmental durability is well improved by coating VO2 NPs with an SiO2 shell as confirmed via progressive oxidation and acid corrosion experiments. Meanwhile, the Tlum of the VO2@SiO2 film is further increased from 56.45% to 62.29% while the ΔTsol remained unchanged. This integrated thermochromic performance presents great potential for the development of VO2-based smart windows.

A Submicrosecond-Response Ultraviolet-Visible-Near-Infrared Broadband Photodetector Based on 2D Tellurosilicate InSiTe3.

2D material (2DM) based photodetectors with broadband photoresponse are of great value for a vast number of applications such as multiwavelength photodetection, imaging, and night vision. However, compared with traditional photodetectors based on bulk material, the relatively slow speed performance of 2DM based photodetectors hinders their practical applications. Herein, a submicrosecond-response photodetector based on ternary telluride InSiTe3 with trigonal symmetry and layered structure was demonstrated in this study. The InSiTe3 based photodetectors exhibit an ultrafast photoresponse (545-576 ns) and broadband detection capabilities from the ultraviolet (UV) to the near-infrared (NIR) optical communication region (365-1310 nm). Besides, the photodetector presents an outstanding reversible and stable photoresponse in which the response performance remains consistent within 200 000 cycles of switch operation. These significant findings suggest that InSiTe3 can be a promising candidate for constructing fast response broadband 2DM based optoelectronic devices.

High-temperature anisotropic silicon-etching steered synthesis of horizontally aligned silicon-based Zn(2)SiO(4) nanowires.

A high-temperature anisotropic silicon-etching strategy is demonstrated to steer the growth of the horizontally localized parallel Zn(2)SiO(4) nanowires.

The hydrothermal synthesis of ultra-high aspect ratio Ag nanoflakes and their performance as conductive fillers in heaters and pastes.

Ag nanoflakes with a size ranging from 5 to 60 µm, a thickness of several tens of nanometers and an aspect ratio of up to 800 have been synthesized via a hydrothermal method. PVP was used as both a surfactant, inducing anisotropic growth of the Ag nanoflakes, and as a reductant, reducing Ag+ to Ag. An Ag-oxalate complex was used as a precursor, allowing effective control of the kinetic growth of the Ag nanoflakes. Influences on the size and morphology of the Ag nanoflakes, such as H+ concentration and reaction time, were discussed and analyzed. Our method can be easily scaled up for mass production. A large interfacial contact area between the Ag nanoflakes with more electrical channels makes the Ag nanoflakes excellent conductive fillers.

Lower Ionized Calcium Predicts Hematoma Expansion and Poor Outcome in Patients with Hypertensive Intracerebral Hemorrhage.

BACKGROUND AND OBJECTIVE: We tested the hypothesis that ionized calcium levels at admission are associated with early hematoma expansion and functional outcome in patients with hypertensive intracerebral hemorrhage (HICH). METHODS: Patients presenting with HICH were enrolled in the observational cohort study that prospectively collected age, sex, blood pressure, history of diabetes and smoking, time from symptom onset to initial computed tomography (CT), admission ionized calcium (iCa) and total calcium (tCa), coagulation function, Glasgow Coma Scale (GCS), and postoperative modified Rankin Scale score. Hematoma reconstruction on CT was performed to measure hematoma volumes. Hematoma expansion (HE) was defined as an increase of more than 30% or 6 mL in HICH volume. We performed univariate and multivariate analyses to assess for association of iCa level with early HE and functional outcome. RESULTS: We included 111 patients with HICH for analysis. Admission serum iCa was 1.10 mmol/L in patients with HE and 1.17 in patients without HE. Univariate analysis indicated significant difference of GCS, initial HICH volume, iCa, and tCa between the HE and non-HE groups (P < 0.05). Lower admission iCa (less than 1.12 mmol/L) was associated with HE (odds ratio [OR] 0.300, 95% confidence interval [CI] 0.095-0.951, P = 0.041) after adjustment for age, blood pressure, GCS score, time to initial CT scan, baseline HICH volume, prothrombin time, and tCa. Furthermore, predictive factors of poor outcome included iCa (OR 0.192, 95% CI 0.067-0.554, P = 0.002) and GCS score (OR 0.832, 95% CI 0.722-0.959, P = 0.011). CONCLUSIONS: These data support the hypothesis that lower ionized calcium is associated with early hematoma expansion and poor outcome in patients with hypertensive intracerebral hemorrhage.

Ultrahigh Detectivity and Wide Dynamic Range Ultraviolet Photodetectors Based on BixSn1-xO2 Intermediate Band Semiconductor.

The ultraviolet (UV) photodetectors have significant applications different fields. High detectivity, high responsivity and wide active area are required to probe a weak UV light in actual ambient. Unfortunately, most practical UV photoconductors based on wide bandgap semiconductor films can hardly have both a high responsivity and a low dark current density. In this study, the intermediate band engineering in semiconductor has been proposed try to solve this problem. The intermediate band UV photodetectors based on BixSn1-xO2 (0.017 < x < 0.041) films show a detectivity of 6.1 × 1015 Jones at 280 nm and a quantum efficiency of 2.9 × 104 %. The dynamic range is 195 dB, which is much higher than other UV photodetector. The recovery time is about 1 s after exposing device into ethanol steam. Our results demonstrate that the intermediate band semiconductor BixSn1-xO2 films can serve as a high performance UV photodetector.

Conversion of a Bi nanowire array to an array of Bi-Bi2O3 core-shell nanowires and Bi2O3 nanotubes.

A template-based heat-treatment method has been developed to convert metal nanowire arrays into arrays of metal-metal oxide core-shell nanowires and single-crystalline metal oxide nanotubes. This process is demonstrated by kinetically controlling the conversion of single-crystalline Bi nanowires to Bi-Bi(2)O(3) core-shell nanowires via a multistep, slow oxidation method, and then controlling their further conversion to a single-crystalline Bi(2)O(3) nanotube array via fast oxidation. This process can conveniently be extended to fabricate a free-standing, easily oxidized metal-metal oxide nanowire and metal oxide nanotube array, which may have future applications in nanoscale optics, electronics, and magnetics.

Thermal properties of bi nanowire arrays with different orientations and diameters.

The thermal properties of single-crystalline Bi nanowire arrays with different orientations and diameters were studied by differential scanning calorimeter and in situ high-temperature X-ray diffraction. Bi nanowires were fabricated by a pulsed electrodeposition technique within the porous anodic alumina membrane. The relationships between the orientation and diameter of Bi nanowires and the corresponding thermal properties are deduced solely from experimental results. It is shown that the melting point decreases with decreasing nanowire diameter, and there is an anisotropic thermal expansion property of Bi nanowires with different orientations and diameters. The transition of the thermal expansion coefficient from positive at low temperature to negative at high temperature for Bi nanowire arrays was analyzed and discussed.

Effective deposition potential induced size-dependent orientation growth of Bi-Sb alloy nanowire arrays.

The influence of effective deposition potential on the orientation and diameter of Bi(1-x)Sbx alloy nanowire arrays by pulsed electrodeposition technique was reported. X-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy analysis show that the orientation of the Bi(1-x)Sbx nanowires can be turned from the [110] to the [202] direction by increasing the effective deposition potential, and the nanowires fully fill in the pores of the AAM in the lower potential region, while in the higher potential region the nanowires partly fill the pores of the AAM. The origin of those phenomena and the growth mechanism of the nanowire are discussed together with composition analysis.

The formation of mesoporous TiO2 spheres via a facile chemical process.

The mesoporous TiO(2) solid and hollow spheres have been synthesized via a controllable and simple chemical route. Structural characterization indicates that these TiO(2) mesoporous spheres after calcined at 500 degrees C have an obvious mesoporous structure with the diameters of 200-300 nm for solid spheres and 200-500 nm for hollow spheres. The average pore sizes and BET surface areas of the mesoporous TiO(2) solid and hollow spheres are 6.8, 7.0 nm and 162, 90 m(2)/g, respectively. Optical adsorption investigation shows that TiO(2) solid and hollow spheres possess a direct band gap structure with the optical band gap of 3.68 and 3.75 eV, respectively. A possible formation mechanism for TiO(2) solid and hollow spheres is discussed.

Fabrication and characterization of single-crystalline ZnTe nanowire arrays.

Semiconductor ZnTe nanowire arrays have been synthesized by the pulsed electrochemical deposition from aqueous solutions into porous anodic alumina membranes. X-ray diffraction analyses show that the as-synthesized nanowires have a highly preferential orientation. Scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy indicate that high-filling, ordered, and single-crystalline nanowire arrays have been obtained. The optical absorption spectra of the nanowire arrays show that the optical absorption band edge of the ZnTe nanowire array exhibits a blue shift compared with that of bulk ZnTe. The growth mechanism and the electrochemical deposition process are discussed together with the chemical compositions analysis.

Citric acid modulated electrochemical synthesis and photocatalytic behavior of BiOCl nanoplates with exposed {001} facets.

Well-crystallized BiOCl nanoplates with exposed {001} facets were synthesized by a facile electrochemical anodic oxidation method. The thickness of the nanoplates decreases with increasing citric acid content in the electrolyte. The optical absorption edge of the BiOCl nanoplates shifts to a longer wavelength with citric acid. The BiOCl nanoplates obtained with citric acid show a high photocatalytic activity for degrading rhodamine B (RhB) as compared with that without citric acid. The photocatalytic activity of BiOCl nanoplates is higher in degrading RhB dyes than in degrading rhodamine 6G, methyl orange and methyl blue dyes. The superoxide radical and holes are the two major active species in photocatalytic degradation of RhB by BiOCl nanoplates. Citric acid can decrease the overlap in the layered structure of BiOCl and reduce the nanoplates thickness, leading to the increase in the exposure of {001} facets and the enhanced photocatalytic activity.