Search Results (299)

Nanostructured semiconductors have emerged as transformative materials for enhancing the efficiency of waste heat-to-electricity conversion through thermoelectric (TE) processes. By altering structural features at the nanoscale, these materials can simultaneously reduce lattice thermal conductivity and optimize electronic transport properties, thereby significantly improving the thermoelectric figure of merit (ZT). Recent studies have demonstrated that introducing periodic twin planes in III–V semiconductor nanowires can achieve a tenfold reduction in thermal conductivity while maintaining excellent electrical performance. Similarly, Pb_1−xGe_xTe alloys, through controlled spinodal decomposition, form stable nanostructures that maintain low thermal conductivity even after thermal cycling, crucial for high-temperature applications. Enhancing electrical properties is another key advantage of nanostructuring. PbTe-based materials, when heavily doped and engineered with nanoscale inclusions, have achieved a ZT of approximately 1.9 and a thermoelectric efficiency of around 12% over a 590 K temperature difference. Single-walled carbon nanotubes (SWCNTs) also show strong correlations between their electronic structure and thermoelectric conductivity, highlighting their potential for next-generation devices. Two-dimensional silicon–germanium (Si_xGe_γ) compounds offer ultra-low lattice thermal conductivity and high Seebeck coefficients, providing a promising pathway for future TE applications. Despite these advancements, challenges remain, particularly regarding scalability and integration into existing energy recovery systems. Techniques such as focused ion beam milling and solution-based synthesis of porous nanostructures are being developed to fabricate high-performance materials on a commercial scale. Moreover, integrating nanostructured semiconductors into real-world systems, such as automotive exhaust heat recovery units, requires improvements in material durability, fabrication efficiency, and device compatibility. In conclusion, nanostructured semiconductors offer a powerful route for enhancing waste heat-to-electricity conversion. Their ability to decouple electrical and thermal transport at the nanoscale opens new opportunities for high-efficiency, sustainable energy harvesting technologies. Continued research into scalable manufacturing techniques, material stability, and system integration is essential to fully unlock their potential for commercial thermoelectric applications. Full article

One-dimensional ZnO nanowires offer significant potential for optoelectronic applications, though their controlled synthesis remains challenging. This study optimized ZnO nanowire growth via carbothermal reduction vapor transport based on the vapor–liquid–solid mechanism. Key parameters investigated were gold catalyst thickness and annealing, source temperature, system pressure, and oxygen concentration. Results show that thinner Au films promote high-density, small-diameter nanowires. An optimal source temperature window (950–1000 °C) was identified, while pressure and oxygen content critically influenced growth mode by modulating vapor supersaturation. Under optimized conditions, aligned single-crystalline ZnO nanowires with hexagonal wurtzite structure were achieved. Structural and optical characterization confirmed high crystallinity and strong near-band-edge emission, demonstrating the efficacy of the developed approach for tailored nanowire synthesis. Full article

Transparent conductive materials (TCMs) are essential for optoelectrical devices ranging from smart windows and defogging films to soft sensors, display technologies, and flexible electronics. Materials, such as indium tin oxide (ITO) and silver nanowires (AgNWs), are commonly used and offer high optical transmittance and electrical conductivity, but suffer from brittleness, oxidation susceptibility, and require high-cost materials, greatly limiting their use. Carbon nanotube (CNT) networks provide a promising alternative, featuring mechanical compliance, chemical robustness, and scalable processing. This study reports an aqueous ink formulation composed of ultra-long mix-walled carbon nanotubes (UL-CNTs), compatible with the flow coating process, yielding uniform transparent conductive films (TCFs) on polyethylene terephthalate (PET), glass, and polycarbonate (PC). The resulting films exhibit tunable transmittance (85%–88% for single layers; ~57% for three layers at 550 nm) and sheet resistance of 7.5 kΩ/□ to 1.5 kΩ/□ accordingly. These TCFs maintain stable sheet resistance for over 5000 bending cycles and show excellent mechanical durability with negligible effects on heating performance. Post-deposition treatments, including nitric acid vapor doping or flash photonic heating (FPH), further reduce sheet resistance by up to 80% (7.5 kΩ/□ to 1.2 kΩ/□). X-ray photoelectron spectroscopy (XPS) results in reduced surface oxygen content after FPH. The photonic-treated heaters attain ~100 °C within 20 s at 100 V. This scalable, water-based process provides a pathway toward low-cost, flexible, and stretchable devices in a variety of fields, including printed electronics, optoelectronics, and thermal actuators. Full article

A photovoltaic-integrated broadband photodetector based on vertically-stacked lateral-aligned III–V nanowire arrays is proposed and investigated. The staggered arrangement configuration drastically reduces the competition between solar cell and photodetector that is difficult to avoid in vertically-stacked planar structures, which enables broadband strong absorption. The lower GaAs nanowires (NWs) act as Mie scattering centers, which scatter the incident light passing through the gaps back to the upper layer, enhancing the absorption of InAs NWs over a wide wavelength range from the ultraviolet to the infrared. Meanwhile, the light trapping effect of the upper InAs nanowires improves the absorption of lower GaAs NWs. At a near-infrared wavelength of 1400 nm, the photovoltaic-integrated InAs nanowire photodetector exhibits a photocurrent density of 168.83 mA/cm² and responsivity of 0.168 A/W, 90% and 93% higher than the single layer InAs nanowires. The conversion efficiency of the GaAs nanowire solar cell is also improved after integration. This work may pave the way for the development of self-powered miniaturized broadband photodetectors. Full article

The development of quantum-enhanced technologies requires single-photon sources, as well as methods for their characterization and verification. Here, we describe a methodology for measuring the correlation function of a single-photon source using an experimental setup that comprises a laser-excited fluorescence microscope equipped with a Hanbury Brown–Twiss intensity interferometer as one of the detection systems. Measurements of the response function of the device and the reference samples are performed. The second-order autocorrelation function of the exciton state of GaAs quantum dots in AlGaAs nanowires is obtained and reveals a single-photon emission. Full article

This study presents a high-performance silicon nanowire (SiNW) array biosensor for the combined detection of two key colorectal cancer (CRC) biomarkers: circulating tumor DNA (ctDNA) and carcinoembryonic antigen (CEA). The device was fabricated using conventional micromachining techniques, enabling the integration of dual SiNW arrays on a single chip with precise control over structure and surface functionalization. Specific probe DNA and anti-CEA antibodies were immobilized on distinct array regions to facilitate targeted binding. The biosensor demonstrated exceptional performance, achieving an ultralow detection limit of 10 aM for ctDNA with a linear range from 0.1 fM to 10 pM, and a sensitivity of 1 fg/mL for CEA. It exhibited high selectivity against interfering substances, including single-base mismatched DNA and non-specific proteins, and maintained robust performance in human serum samples. The platform offers a scalable, label-free, and real-time detection solution with significant potential for application in early CRC screening and personalized medicine. Full article

CdS nanowires have garnered considerable attention lately for their promising potential in next-generation nanolaser devices, attributed to their relatively high stability and exceptional emission efficiency within the Ⅱ–Ⅵ semiconductor family. In this study, tin-doped CdS nanowires with varying dimensions were synthesized, and the underlying mechanisms responsible for the formation of micro-cavities within these nanowires were systematically explored through scanning electron microscopy (SEM) analysis and photoluminescence mapping. The results show that a very distinct hexagonal-shaped micro-cavity is observed on the cross-section of CdS nanowires, and the size of the micro-cavity is determined by the radius of the nanowire. Additionally, through the use of angle-resolved micro-fluorescence Fourier imaging technology, it is found that under high excitation density conditions, the micro-cavity mode is more prominent at higher collection angles, which is consistent with the mode of the wall-pass cavity micro-cavity. Finally, the formation of the full reflection spectrum of the micro-cavity mode is confirmed through the wavelength shift and intensity shift phenomena related to the excitation power. These results further deepen our understanding of the micro-cavity modes in tin-doped cadmium sulfide nanowires, which may be of great significance for the application of these nanowires in new optical devices. Full article

Laser ranging technology holds a key position in the military, aerospace, and industrial fields due to its high precision and non-contact measurement characteristics. As a core component, the performance of the photon detector directly determines the ranging accuracy and range. This paper systematically reviews the technological development of photonic detectors for laser ranging, with a focus on analyzing the working principles and performance differences of traditional photodiodes [PN (P-N junction photodiode), PIN (P-intrinsic-N photodiode), and APD (avalanche photodiode)] (such as the high-frequency response characteristics of PIN and the internal gain mechanism of APD), as well as their applications in short- and medium-range scenarios. Additionally, this paper discusses the unique advantages of special structures such as transmitting junction-type and Schottky-type detectors in applications like ultraviolet light detection. This article focuses on photon counting technology, reviewing the technological evolution of photomultiplier tubes (PMTs), single-photon avalanche diodes (SPADs), and superconducting nanowire single-photon detectors (SNSPDs). PMT achieves single-photon detection based on the external photoelectric effect but is limited by volume and anti-interference capability. SPAD achieves sub-decimeter accuracy in 100 km lidars through Geiger mode avalanche doubling, but it faces challenges in dark counting and temperature control. SNSPD, relying on the characteristics of superconducting materials, achieves a detection efficiency of 95% and a dark count rate of less than 1 cps in the 1550 nm band. It has been successfully applied in cutting-edge fields such as 3000 km satellite ranging (with an accuracy of 8 mm) and has broken through the near-infrared bottleneck. This study compares the differences among various detectors in core indicators such as ranging error and spectral response, and looks forward to the future technical paths aimed at improving the resolution of photon numbers and expanding the full-spectrum detection capabilities. It points out that the new generation of detectors represented by SNSPD, through material and process innovations, is promoting laser ranging to leap towards longer distances, higher precision, and wider spectral bands. It has significant application potential in fields such as space debris monitoring. Full article

Methylene blue (MB), a widely used industrial dye, is a persistent pollutant with documented toxicity to aquatic organisms and potential health risks to humans, even at ultra-trace levels. Conventional monitoring techniques such as UV–Vis spectroscopy and fluorescence emission suffer from limited sensitivity, typically failing to detect MB below ~10⁻⁷ M. In this study, we introduce a surface-enhanced Raman spectroscopy (SERS) platform based on silver nanowire (AgNW) substrates that enables MB detection over an unprecedented dynamic range—from 1.5 × 10⁻⁴ M down to 1.5 × 10⁻¹⁶ M. Raman mapping confirmed the presence of individual signal hot spots at the lowest concentration, consistent with the theoretical number of analyte molecules in the probed area, thereby demonstrating near-single-molecule detection capability. The calculated enhancement factors reached up to 1.90 × 10¹², among the highest reported for SERS-based detection platforms. A semi-quantitative calibration curve was established spanning twelve orders of magnitude, and this platform was successfully applied to monitor MB degradation during two advanced oxidation processes (AOPs): TiO₂ nanotube-mediated photocatalysis under UV irradiation and atmospheric-pressure dielectric barrier discharge (DBD) plasma treatment. While UV–Vis and fluorescence techniques rapidly lost sensitivity during the degradation process, the SERS platform continued to detect the characteristic MB Raman peak at ~1626 cm⁻¹ throughout the entire treatment duration. These persistent SERS signals revealed the presence of residual MB or partially degraded aromatic intermediates that remained undetectable by conventional optical methods. The results underscore the ability of AgNW-based SERS to provide ultra-sensitive, molecular-level insights into pollutant transformation pathways, enabling time-resolved tracking of degradation kinetics and validating treatment efficiency. This work highlights the importance of integrating SERS with AOPs as a powerful complementary strategy for advanced environmental monitoring and water purification technologies. By delivering an ultra-sensitive, low-cost sensor (<USD 0.16 per test) and promoting reagent-free treatment methods, this study directly advances SDG 6 (Clean Water and Sanitation) and SDG 12 (Responsible Consumption and Production). Full article

Using the Bridgman technique, GaSe single crystals were obtained which were mechanically split into plane-parallel plates with a wide range of thicknesses. By heat treatment in air at 820 °C and 900 °C, for 30 min and 6 h, micro- and nanocomposite layers of Ga₂Se₃–Ga₂O₃ and β–Ga₂O₃ (native oxide) with surfaces made of nanowires/nanoribbons were obtained. The obtained composite Ga₂Se₃–Ga₂O₃ and nanostructured β–Ga₂O₃ are semiconductor materials with band gaps of 2.21 eV and 4.60 eV (gallium oxide) and photosensitivity bands in the green–red and ultraviolet-C regions that peaked at 590 nm and 262 nm. For an applied voltage of 50 V, the dark current in the photodetector based on the nanostructured β–Ga₂O₃ layer was of 8.0 × 10⁻¹³ A and increased to 9.5 × 10⁻⁸ A upon 200 s excitation with 254 nm-wavelength radiation with a power density of 15 mW/cm². The increase and decrease in the photocurrent are described by an exponential function with time constants of τ_1r = 0.92 s, τ_2r = 14.0 s, τ_1d = 2.18 s, τ_2d = 24 s, τ_1r = 0.88 s, τ_2r = 12.2 s, τ_1d = 1.69 s, and τ_2d = 16.3 s, respectively, for the photodetector based on the Ga₂Se₃–Ga₂S₃–GaSe composite. Photoresistors based on the obtained Ga₂Se₃–Ga₂O₃ composite and nanostructured β–Ga₂O₃ layers show photosensitivity bands in the spectral range of electronic absorption bands of ozone in the same green–red and ultraviolet-C regions, and can serve as ozone sensors (detectors). Full article

Semiconductor photonic nanowires are critical components for nanoscale light manipulation in integrated photonic and electronic devices. Optimizing their optical performance requires enhanced photon conversion efficiency, for which a promising solution is to combine semiconductors with noble metals, using the surface plasmon resonance of noble metals to enhance the photon absorption efficiency. Here, we report plasmon-enhanced light emission in a hybrid nanowire device composed of perovskite semiconductor nanowires and silver nanoparticles formed using superfluid helium droplets. A cesium lead halide perovskite-based four-layer structure (CsPbBr₃/PMMA/Ag/Si) effectively reduces the metal’s plasmonic losses while ensuring efficient surface plasmon–photon coupling at moderate power. Microphotoluminescence and time-resolved spectroscopy techniques are used to investigate the optical properties and emission dynamics of carriers and excitons within the hybrid device. Our results demonstrate an intensity enhancement factor of 29 compared with pure semiconductor structures at 4 K, along with enhanced carrier recombination dynamics due to plasmonic interactions between silver nanoparticles and perovskite nanowires. This work advances existing approaches for exciting photonic nanowires at low photon densities, with potential applications in optimizing single-photon excitations and emissions for quantum information processing. Full article

Hydroxyapatite nanowires (HAW) can effectively improve the bone repair ability in bone engineered tissue. However, due to their single function, the application of HAWs in biological tissue engineering materials is limited. In this study, strontium-doped hydroxyapatite nanowires (SrHAW) were synthesized by a hydrothermal method and coated with polydopamine (PDA) to improve the function of HAWs. The material structure, biocompatibility evaluation, and differentiation capability testing of PDA-coated strontium-doped hydroxyapatite (SrHAW@PDA) nanowires were conducted. Then, the nanowires were co-cultured with rat bone marrow mesenchymal stem cells (BMSCs) and rat umbilical vein endothelial cells (UVECs) to prepare cell spheroids. Compared with the undoped and uncoated HAW, the SrHAW@PDA nanowires enhanced the cell activity and their angiogenesis and osteogenesis abilities. In addition, their performance in the three-dimensional spheroid also played a positive role in the cells in the spheroid. Due to the presence of PDA, the adhesion between the cells in the three-dimensional spheroid and the nanowires were enhanced. In summary, these results show that SrHAW@PDA has the potential to be used as an alternative material to regulate cell biological activity in three-dimensional cell spheroids. Full article

A simple method is developed to produce free-standing films of polypyrrole (PPy) in one step. It consists of the interfacial polymerization (without surfactants) of pyrrole (dissolved in chloroform) with an oxidant (ammonium persulfate, dissolved in water). It is observed that the area of the formed film only depends on the size of the interface, achieving the manufacture of PPy films of up to 300 cm², with a thickness of 200 microns. Transmission electron microscopy (TEM) images show the presence of superimposed nanoplatelets of ca. 100 nm main axis. These nanoparticles seem to aggregate in two dimensions to form the free-standing film. Scanning electron microscopy (SEM) shows a compact surface with nanowires decorating the surface. PPy films show an electrical conductivity of 63 (±3) S cm⁻¹. PPy conductive films are then applied in the construction of an antenna that shows a response in two bands: at 1.52 GHz (−13.85 dB) and at 3.50 GHz (−33.55 dB). The values are comparable to those of other antennas built with different PPy films. The simple synthesis of large-area PPy films in a single step would allow the fabrication of large quantities of electronic elements (e.g., sensors) with uniform properties in a short time. Full article

With an ultrahigh aspect ratio and a similar chemical composition to the biomineral in bone and tooth, ultralong hydroxyapatite nanowires (UHAPNWs) exhibit a meritorious combination of high flexibility, excellent mechanical performance, high biocompatibility, and bioactivity. Despite these exciting merits, the rapid and green synthesis of UHAPNWs remains challenging. In this work, we have developed an environment-friendly, rapid, and highly efficient synthesis of ultrathin UHAPNWs by the microwave-assisted calcium oleate precursor hydrothermal method using biogenic creatine phosphate as the bio-phosphorus source. Owing to the controllable hydrolysis of bio-phosphorus-containing creatine phosphate and the highly efficient heating of microwave irradiation, ultrathin UHAPNWs with a homogeneous morphology of several nanometers in diameter (single nanowire), several hundred micrometers in length, and ultrahigh aspect ratios (>10,000) can be rapidly synthesized within 60 min. This effectively shortens the synthesis time by about two orders of magnitude compared with the traditional hydrothermal method. Furthermore, ultrathin UHAPNWs are decorated in situ with bioactive creatine and self-assembled into nanowire bundles along their longitudinal direction at the nanoscale. In addition, ultrathin UHAPNWs exhibit a relatively high specific surface area of 84.30 m² g^–1 and high ibuprofen drug loading capacity. The flexible bio-paper constructed from interwoven ibuprofen-loaded ultrathin UHAPNWs can sustainably deliver ibuprofen in phosphate-buffered saline, which is promising for various biomedical applications such as tissue regeneration with anti-inflammatory and analgesic functions. Full article