One-dimensional Nanowire Structures Research Articles

Ultrahigh Bipolar Photoresponse in a Self-Powered Ultraviolet Photodetector Based on GaN and In/Sn-Doped Ga2O3 Nanowires pn junction.

Self-powered ultraviolet photodetectors with bipolar photoresponse have great potential in the fields of ultraviolet optical communication, all-optical controlled artificial synapses, high-resolution ultraviolet imaging equipment, and multiband photoelectric detection. However, the current low optoelectronic performance limits the development of such polar switching devices. Here, we construct a self-powered ultraviolet photodetector based on GaN and In/Sn-doped Ga2O3 (IGTO) nanowires (NWs) pn junction structure. This unique nanowire/thin film structure allows GaN and IGTO to dominate the absorption of light at different wavelengths, resulting in a highly bipolar photoresponse. The device has a responsivity of 2.04 A/W and a normalized detectivity of 7.18 × 1013 Jones at 254 nm and a responsivity of -2.09 A/W and a normalized detectivity of -7 × 1013 Jones at 365 nm, both at zero bias. In addition, it has an extremely high Ilight/Idark ratio of 1.05 × 105 and ultrafast response times of 2.4/1.9 ms (at 254 nm) and 5.7/5.2 ms (at 365 nm). These excellent properties are attributed to the high specific surface area of the one-dimensional nanowire structure and the abundant voids generated by the nanowire network to enhance the absorption of light, and the p-n junction structure enables the rapid separation and transfer of photogenerated electron-hole pairs. Our findings provide a feasible strategy for high-performance wavelength-controlled polarity switching devices.

Towards high photoresponse of perovskite nanowire/copper phthalocyanine heterostructured photodetector

One-dimensional nanowire structures composed of perovskite are widely recognized for their exceptional optoelectronic performance and mechanical properties, making them a popular area of investigation in photodetection research. In this work, a perovskite nanowire/copper phthalocyanine heterojunction-based photodetector was fabricated, which exhibits high photoresponse in the visible-near-infrared region. The incorporation of a heterojunction significantly enhanced the photoelectric performance. Specifically, the photoresponsivity and external quantum efficiency of the nanowire-based device were elevated from 58.5 A W−1 and 1.35 × 104% to 84.5 A W−1 and 1.97 × 104% at 532 nm, respectively. The enhanced photoresponse of the heterojunction device can be attributed to the unique microstructure of nanowire arrays. The wrapping of the nanowires by copper phthalocyanine forms heterojunctions with a larger dissociation area, which facilitated exciton dissociation and enhanced device performance. This work provides a promising example for optimizing the performance of nanowire devices.

Lead-less perovskite alloy nanowire photodetector with high performance

Halide perovskites with one-dimensional nanowire structure have attracted more attention in the photodetectors (PDs) due to their single crystal nature and large aspect ratio. Although the network structure of perovskite nanowires (PNs) has become an important research object due to its simple solution process and good repeatability, it presents the cross-connection of nanowires, which hinders the transport of carriers, resulting in poor device performance. Herein, we introduced a hot-pressure welding strategy to reduce the micro-interfaces of the all-inorganic lead-less perovskite alloy nanowire network, greatly enhance the quality of the PNs and improve the device performance. To optimize the device performance, the hot-pressure strategy with different pressures was carried out. Finally, we demonstrated the all-inorganic CsPb0.01Sn0.99I3 PNPD with a responsivity, a detectivity and a linear dynamic range of 9.9 × 10−3 A W−1, 7.2 × 108 Jones and 73 dB at 473 nm, respectively. These results lay the foundation for improving the device performance of the Pb-free perovskite nanowire devices.

Multifunctional Textiles Based on Three-Dimensional Hierarchically Structured TiO2 Nanowires.

The development of three-dimensional (3D) micro-/nanostructures with multiscale hierarchy offers new potential for the improvement of the pristine textile properties. In this work, a polyester fabric coated with 3D hierarchically structured rutile TiO2 nanowires (THNWP) was fabricated by a facile hydrothermal strategy. The THNWP samples exhibit markedly improved photocatalytic activities and antibacterial properties owing to their 3D hierarchical architecture constructed by one-dimensional nanowire structures, good crystallinity, excellent light-harvesting capability, and fast electron-transfer rate. Furthermore, the unique 3D hierarchical nanostructures also combine with the monofilament to produce ternary-scale hierarchy, which endows the fabric surface with outstanding superamphiphobicity after further facile fluorination treatment. The supportive air-pockets trapped within the unique ternary-scale architectures are proved to be the crucial factor in the achievement of high liquid repellency, and the highest performing superamphiphobic surface is capable of repelling liquids down to a minimal surface tension of 23.4 mN m-1. We envision that our findings may possess great potential in the bottom-up design of high-performance textiles.

Wire spherical-shaped Co-MOF electrode materials for high-performance all-solid-state flexible asymmetric supercapacitor device

The exploration of an inexpensive, low-energy consumption and environmentally friendly preparation process to synthesize high capacitance performance MOF-based electrode materials is an important prerequisite for their commercialization. We propose a non-calcined strategy to synthesize nanowire microsphere shaped Co-BTC (CBNWM). Making MOF into one-dimensional nanowire structure can effectively increase its active sites and the ion transfer rate. After the MOF nanowires are entangle and reunite into microspheres, their mechanical property and chemical stability are improved. Therefore, compared with Co-BTC crystal (CBC), the electrochemical properties of CBNWM have been significantly improved. The specific capacity of CBNWM reaches 1020 F g−1 at 5 mV s−1 or 657 F g−1 at 0.5 A g−1 with the capacity remains 81.4% after 3000 cycles. Subsequently, a flexible asymmetric device of CBNWM//AC was fabricated, whose maximum energy density can achieve 34.4 W h kg−1 with the related power density of 375.3 W kg−1.

Interface Nanoengineering of PdNi-S/C Nanowires by Sulfite-Induced for Enhancing Electrocatalytic Hydrogen Evolution.

The interfacial structural design of materials in nanoscale is a promising approach to regulate the physicochemical properties of materials and further optimize material properties for a variety of potential applications. Herein, PdNi-S/C nanowires with inductive sulfite has been successfully crafted through hydrothermal synthesis and applied as a superior hydrogen evolution reaction (HER) catalyst. Based on the autocatalytic mechanism, PdNi alloy nanoparticles were synthesized by controlling reduction kinetics with the presence of formic acid. Meanwhile, the sulfite is selected as an effective inductive agent to form PdNi-S/C nanowires with amorphous interfaces. The morphology, composition, and electronic structure of the synthesized PdNi-S/C were studied in detail. The PdNi-S/C manifests excellent HER performance in alkaline solution with an overpotentials of 67 mV at current density of 10 mA cm-2, a Tafel slope of 69.4 mV dec-1, and significantly long-term durability. The improvement of HER performance of the PdNi-S/C is attributed to the one-dimensional nanowire structure, abundant sulfur vacancies and defects, and the synergistic effect between PdNi-S nanowires with the graphite carbon. Furthermore, this present work offers a novel method for structure adjustment of materials to effectively control their property and catalytic performance.

Superior liquid fuel oxidation electrocatalysis enabled by novel one-dimensional AuM (M = Pt, Pd) nanowires

Active and enduring catalysts for the electrooxidation reaction of liquid fuel play a crucial role in affecting the commercial application of direct fuel cells technology. Unfortunately, the electrocatalysts used in direct fuel cells fall far from the expectations and suffer from the issues of both extremely high cost and serious activity degradation. In this work, we herein demonstrate a template free method to successfully synthesize the unique one-dimensional AuM (M = Pt, Pd) nanowires. The alloy and electronic effect between Au and Pt (or Pd), as well as the unique one-dimensional nanowire structure are of vital significance for the electrocatalytic activity enhancements of Pt1Au1 and Pd1Au1 nanowires towards ethylene glycol and glycerol oxidation with the mass activity of 7.81 and 5.72 A mgPt−1, 6.55 and 4.52 A mgPd−1, respectively. Our efforts highlight a split-new channel to maximize catalytic efficiency with noble metal utilization for efficient liquid fuel electrocatalysis and beyond.

High efficiency solar-to-hydrogen conversion on a monolithically integrated InGaN/GaN/Si adaptive tunnel junction photocathode.

H2 generation under sunlight offers great potential for a sustainable fuel production system. To achieve high efficiency solar-to-hydrogen conversion, multijunction photoelectrodes have been commonly employed to absorb a large portion of the solar spectrum and to provide energetic charge carriers for water splitting. However, the design and performance of such tandem devices has been fundamentally limited by the current matching between various absorbing layers. Here, by exploiting the lateral carrier extraction scheme of one-dimensional nanowire structures, we have demonstrated that a dual absorber photocathode, consisting of p-InGaN/tunnel junction/n-GaN nanowire arrays and a Si solar cell wafer, can operate efficiently without the strict current matching requirement. The monolithically integrated photocathode exhibits an applied bias photon-to-current efficiency of 8.7% at a potential of 0.33 V versus normal hydrogen electrode and nearly unity Faradaic efficiency for H2 generation. Such an adaptive multijunction architecture can surpass the design and performance restrictions of conventional tandem photoelectrodes.

Grain Boundary Controlled Electron Mobility in Polycrystalline Titanium Dioxide

Grain Boundary Controlled Electron Mobility in Polycrystalline Titanium Dioxide

All-Nanowire Based Li-Ion Full Cells Using Homologous Mn2O3 and LiMn2O4

We report an all-nanowire based flexible Li-ion battery full cell, using homologous Mn2O3 and LiMn2O4 nanowires for anodes and cathodes, respectively. The same precursors, MnOOH nanowires, are transformed from hydrothermally grown MnO2 nanoflakes and directly attached on Ti foils via reaction with poly(vinyl pyrrolidone). The Mn2O3 anode and LiMn2O4 cathode are subsequently formed by thermal annealing and reaction with lithium salt, respectively. The one-dimensional nanowire structures provide short lithium-ion diffusion path, good charge transport, and volume flexibility for Li(+) intercalation/deintercalation, thus leading to good rate capability and cycling performance. As proof-of-concept, the Mn2O3 nanowire anode delivers an initial discharge capacity of 815.9 mA h g(-1) at 100 mA g(-1) and maintains a capacity of 502.3 mA h g(-1) after 100 cycles. The LiMn2O4 nanowire cathodes show a reversible capacity of 94.7 mA h g(-1) at 100 mA g(-1) and high capacity retention of ∼ 96% after 100 cycles. Furthermore, a flexible Mn2O3//LiMn2O4 lithium ion full cell is fabricated, with an output voltage of >3 V, low thickness of 0.3 mm, high flexibility, and a specific capacity of 99 mA h g(-1) based on the total weight of the cathode material. It also exhibits good cycling stability with a capacity of ∼ 80 mA h g(-1) after 40 charge/discharge cycles.

An approach toward TiO2 nanostructure growth with tunable properties: Influence of reaction time in a hydrothermal process

An approach has been developed to prepare TiO2 thin films with tunable morphology and physical properties by changing reaction time (6, 12 and 24h) in a hydrothermal process. As the reaction time increases, anatase TiO2 (101) preferred orientation is weaken, corresponding to surface morphology changes from one-dimensional nanowire structure to two-dimensional sheet structure then to three-dimensional nuts structure. Evolution of these structural are accompanied by significant variations of optical properties, photoluminescence and Raman properties including a widening of the band gap from 3.21 to 3.24eV, strong luminescence in the visible area, increase of Raman characteristic peak intensity and frequency shift phenomenon of Raman characteristic peaks. Compositional analysis indicates that TiO2 surface layer contains Ti and O elements, the ratio of Ti:O is 1:2.206 which is close to the atom ratio of TiO2. These findings help to grow specific TiO2 thin films with desired structure and properties for device applications.

Sn-doped bismuth telluride nanowires with high conductivity

Bismuth telluride (Bi(2)Te(3)) nanowires with sub-100 nm diameters were synthesized by Au-Sn co-catalyzed chemical vapor deposition. These Bi(2)Te(3) nanowires were single crystals with a hexagonal lattice. The Sn catalyst played a key role in achieving the one-dimensional nanowire structures, while the absence of Sn resulted in other morphologies such as nanoplates, nanooctahedrons and nanospheres. Raman spectra revealed that compared to the Bi(2)Te(3) bulk materials, the Bi(2)Te(3) nanowires displayed an A(1u) spectral peak, implying the breaking of symmetry. The temperature-dependent electrical measurement indicated that these Sn-doped Bi(2)Te(3) nanowires were metallic, with a high conductivity of 1.6 × 10(5) S m(-1) at 300 K.

Fabrication of one-dimensional nanowire structures utilizing crystallographic orientation in silicon and their conductance characteristics

We propose a process for fabricating one-dimensional Si nanowires with a point contact. The nanowire structure can be easily obtained through two steps: KOH etching of a {110} Si layer of a silicon on insulator substrate and sufficient oxidation of the Si patterns formed by etching. In the etching process, vertical sidewalls comprised of {111} planes are formed into a wire. In addition, other {111} planes, projecting obliquely along the vertical sidewalls, spontaneously appear in the etched substrate. This is due to the fact that the etching proceeds as {111} planes appear because the etch rate of the {111} plane is the lowest of all planes. The bottom-corner region of two inclined {111} planes becomes a point-contact structure by making the distance between two inclined planes appropriate. The oxidation process converts the two-dimensional wire into one-dimensional nanowire by the stress-dependent oxidation phenomena of the Si wire. Consequently, a Si nanowire with a point contact can be formed in the bottom region. The Si nanowires fabricated through this process show clear conductance steps with little fluctuation on plateaus at 45 K. In addition, we discuss the conductance step characteristics in connection with a calculated energy level for a nanowire in (110) Si.