Hierarchical core-shelled CoMo layered double hydroxide@CuCo2S4 nanowire arrays/nickel foam for advanced hybrid supercapacitors.

The development of core-shelled heterostructures with the unique morphology can improve the electrochemical properties of hybrid supercapacitors (HSC). Here, CuCo2S4 nanowire arrays (NWAs) are vertically grown on nickel foam (NF) utilizing hydrothermal synthesis. Then, CoMo-LDH nanosheets are uniformly deposited on the CuCo2S4 NWAs by electrodeposition to obtain the CoMo-LDH@CuCo2S4 NWAs/NF electrode. Due to the superior conductivity of CuCo2S4 (core) and good redox activity of CoMo-LDH (shell), the electrode shows excellent electrochemical properties. The electrode's specific capacity is 1271.4 C g-1 at 1 A g-1, and after 10, 000 cycles, its capacity retention ratio is 92.2 % at 10 A g-1. At a power density of 983.9 W kg-1, the CoMo-LDH@CuCo2S4 NWAs/NF//AC/NF device has an energy density of 52.2 Wh kg-1. This indicates that CoMo-LDH@CuCo2S4/NF has a great potential for supercapacitors.

Engineering Fano Resonances in Plasmonic Metasurfaces for Colorimetric Sensing and Structural Colors.

In this paper, we present the design and fabrication of a plasmonic metasurface based on titanium dioxide (TiO2) nanowire arrays integrated with plasmonic layers. The structure is engineered to produce Fano resonances within the visible spectrum, resulting from the coupling of localized surface plasmon resonances (LSPR), lattice modes, and nanowire's optical modes. Experimentally, we show that by tuning the geometrical features of the metasurface, such as the length, diameter, and lattice spacing of the nanowires, a high-quality factor single peak can be achieved in the reflection spectra, resulting in vivid structural colors in bright field. To our knowledge, this is the first demonstration of such vivid colors with nanowire arrays in bright field reflections. When characterized by refractive index fluids around the refractive index of water, the plasmonic metasurface also showed great potential for biochemical colorimetric sensing. The best design demonstrated a bulk sensitivity of 183 nm/RIU with high Q resonance features and linear changes in color values using image processing. .

On-Wire Design of Axial Periodic Halide Perovskite Superlattices for High-Performance Photodetection.

Precise synthesis of all-inorganic lead halide perovskite nanowire heterostructures and superlattices with designable modulation of chemical compositions is essential for tailoring their optoelectronic properties. Nevertheless, controllable synthesis of perovskite nanostructure heterostructures remains challenging and underexplored to date. Here, we report a rational strategy for wafer-scale synthesis of one-dimensional periodic CsPbCl3/CsPbI3 superlattices. We show that the highly parallel array of halide perovskite nanowires can be prepared roughly as horizontally guided growth on an M-plane sapphire. A periodic patterning of the sapphire substrate enables position-selective ion exchange to obtain highly periodic CsPbCl3/CsPbI3 nanowire superlattices. This patterning is further confirmed by micro-photoluminescence investigations, which show that two separate band-edge emission peaks appear at the interface of a CsPbCl3/CsPbI3 heterojunction. Additionally, compared with the pure CsPbCl3 nanowires, photodetectors fabricated using these periodic heterostructure nanowires exhibit superior photoelectric performance, namely, high ION/IOFF ratio (104), higher responsivity (49 A/W), and higher detectivity (1.51 × 1013 Jones). Moreover, a spatially resolved visible image sensor based on periodic nanowire superlattices is demonstrated with good imaging capability, suggesting promising application prospects in future photoelectronic imaging systems. All these results based on the periodic CsPbCl3/CsPbI3 nanowire superlattices provides an attractive material platform for integrated perovskite devices and circuits.

Template-Confined Oriented Perovskite Nanowire Arrays Enable Polarization Detection and Imaging.

Polarized light detection can effectively identify the difference between the polarization information on the target and the background, which is of great significance for detection in complex natural environments and/or extreme weather. Generally, polarized light detection inevitably relies on anisotropic structures of photodetector devices, while organic-inorganic hybrid perovskites are ideal for anisotropic patterning due to their simple and efficient preparation by solution method. Compared to patterned thin films, patterned arrays of aligned one-dimensional (1D) perovskite nanowires (PNWAs) have fewer grain boundaries and lower defect densities, making them well suited for high-performance polarization-sensitive photodetectors. Here, we fabricated PNWAs crystallographically aligned with variable line widths and alignment densities employing CD-ROM and DVD-ROM grating pattern template-confined growth (TCG) methods. The photodetectors constructed from MAPbI3 PNWAs achieved responsivity of 35.01 A/W, detectivity of 6.85 × 1013 Jones, and fast response with a rise time of 172 µs and fall time of 114 µs. They were successfully applied to high-performance polarization detection with a polarization ratio of 1.81, potentially applicable in polarized light detection systems.

Boosting Efficiency in Piezo-Photocatalysis Process Using Poled Ba0.7Sr0.3TiO3 Nanorod Arrays for Pollutant Degradation and Hydrogen Production.

Recently, the combination of the piezoelectric effect in the photocatalytic process, referred to as piezo-photocatalysis, has gained considerable attention as a promising approach for enhancing the degradation of organic pollutants. In this investigation, we studied the piezo-photocatalysis by fabricating arrays of barium strontium titanate (Ba0.7Sr0.3TiO3) nanorods (BST NRs) on a glass substrate as recoverable catalysts. We found that the degradation rate constant k of the rhodamine B solution achieved 0.0447 min-1 using poled BST NRs in the piezo-photocatalytic process, indicating a 2-fold increase in efficiency compared to the photocatalytic process (0.00183 min-1) utilizing the same material. This is mainly ascribed to the generation of the piezopotential in the poled BST NRs under ultrasonic vibration. Moreover, the BST NR array demonstrated a hydrogen (H2) production rate of 411.5 µmol g-1 h-1. In the photoelectrochemical process, the photocurrent density of poled BST NRs achieved 1.97 mA cm-2 at an applied potential of 1.23 V (ERHE (reversible hydrogen electrode)) under ultrasonic vibrations, representing a 1.7-fold increase compared with the poled BST NRs without ultrasonic vibrations. The measurement results from the liquid chromatograph mass spectrometer (LC-MS) demonstrated the formulation of a degradation pathway for rhodamine B molecules. Moreover, ab initio molecular dynamics (AIMD) simulation results demonstrate the dominance of hydroxyl radicals (•OH) rather than superoxide radicals (•O2-) in the degradation process. This study not only benefits the understanding of the principle of the piezo-photocatalytic process but also provides a new perspective for improving the catalytic efficiency for organic pollutants degradation.

Area-Selective Growth of Zinc Oxide Nanowire Arrays for Piezoelectric Energy Harvesting.

In this work, we present the area-selective growth of zinc oxide nanowire (NW) arrays on patterned surfaces of a silicon (Si) substrate for a piezoelectric nanogenerator (PENG). ZnO NW arrays were selectively grown on patterned surfaces of a Si substrate using a devised microelectromechanical system (MEMS)-compatible chemical bath deposition (CBD) method. The fabricated devices measured a maximum peak output voltage of ~7.9 mV when a mass of 91.5 g was repeatedly manually placed on them. Finite element modeling (FEM) of a single NW using COMSOL Multiphysics at an applied axial force of 0.9 nN, which corresponded to the experimental condition, resulted in a voltage potential of -6.5 mV. The process repeated with the same pattern design using a layer of SU-8 polymer on the NWs yielded a much higher maximum peak output voltage of ~21.6 mV and a corresponding peak power density of 0.22 µW/cm3, independent of the size of the NW array. The mean values of the measured output voltage and FEM showed good agreement and a nearly linear dependence on the applied force on a 3 × 3 µm2 NW array area in the range of 20 to 90 nN.

Modulating the density of silicon nanowire arrays for high-performance hydrovoltaic devices.

Hydrovoltaic devices (HDs) based on silicon nanowire (SiNW) arrays have received intensive attention due to their simple preparation, mature processing technology, and high output power. Investigating the impact of structure parameters of SiNWs on the performance of HDs can guide the optimization of the devices, but related research is still not sufficient. This work studies the effect of the SiNW density on the performance of HDs. SiNW arrays with different densities were prepared by controlling the react time of Si wafers in the seed solution (tseed) in metal-assisted chemical etching. Density of SiNW array gradually decreases with the increase oftseed. HDs were fabricated based on SiNW arrays with different densities. The research results indicate that the open-circuit voltage gradually decreases with increasingtseed, while the short-circuit current first increases and then decreases with increasingtseed. Overall, SiNW devices withtseedof 20 s and 60 s have the best output performance. The difference in output performance of HDs based on SiNWs with different densities is attributed to the difference in the gap sizes between SiNWs, specific surface area of SiNWs, and the number of SiNWs in parallel. This work gives the corresponding relationship between the preparation conditions of SiNWs, array density, and output performance of hydrovoltaic devices. Density parameters of SiNW arrays with optimized output performance and corresponding preparation conditions are revealed. The relevant results have important reference value for understanding the mechanism of HDs and designing structural parameters of SiNWs for high-performance hydrovoltaic devices.

Application of p and n-Type Silicon Nanowires as Human Respiratory Sensing Device.

Accurate and fast breath monitoring is of great importance for various healthcare applications, for example, medical diagnoses, studying sleep apnea, and early detection of physiological disorders. Devices meant for such applications tend to be uncomfortable for the subject (patient) and pricey. Therefore, there is a need for a cost-effective, lightweight, small-dimensional, and non-invasive device whose presence does not interfere with the observed signals. This paper reports on the fabrication of a highly sensitive human respiratory sensor based on silicon nanowires (SiNWs) fabricated by a top-down method of metal-assisted chemical-etching (MACE). Besides other important factors, reducing the final cost of the sensor is of paramount importance. One of the factors that increases the final price of the sensors is using gold (Au) electrodes. Herein, we investigate the sensor's response using aluminum (Al) electrodes as a cost-effective alternative, considering the fact that the electrode's work function is crucial in electronic device design, impacting device electronic properties and electron transport efficiency at the electrode-semiconductor interface. Therefore a comparison is made between SiNWs breath sensors made from both p-type and n-type silicon to investigate the effect of the dopant and electrode type on the SiNWs respiratory sensing functionality. A distinct directional variation was observed in the sample's response with Au and Al electrodes. Finally, performing a qualitative study revealed that the electrical resistance across the SiNWs renders greater sensitivity to breath than to dry air pressure. No definitive research demonstrating the mechanism behind these effects exists, thus prompting our study to investigate the underlying process.

A Highly Active and Durable Hierarchical Electrocatalyst for Large-Current-Density Water Splitting.

Designing bifunctional catalysts with high current densities under industrial circumstances is crucial to propelling hydrogen energy with a boost from fundamental to practical application. In this work, heterojunction nanowire arrays consisting of manganese oxide and cobalt phosphide (denoted as MnO-CoP/NF) are designed to meet the industrial demand by regulating the synergic mass transport and electronic structure coupling with numerous nano-heterogeneous interfaces. The optimal MnO-CoP/NF electrode exhibits remarkable bifunctional electrocatalytic performance with overpotentials of 259.5 mV for hydrogen evolution at a large current density of 1000 mA cm-2 and 392.2 mV for oxygen evolution at 1500 mA cm-2. Moreover, the MnO-CoP/NF electrode demonstrates superior durability and an ultralow voltage of 1.76 V at 500 mA cm-2, outperforming that of a commercial RuO2||Pt/C electrode. This work sheds light on the design of metallic heterostructures with optimized interfacial electronic structures and a high abundance of active sites for practical industrial water splitting applications.

Array density effect on the optical and photoelectric properties of silicon nanowire arrays via Ag-assisted chemical etching.

Ag-assisted chemical etching (AgACE) is a low-cost method to produce silicon nanowires (SiNWs) for photoelectric applications. Structure parameters of SiNWs have great impact on their optical and photoelectric properties, which are worth studying for fabricating high-performance devices. However, array density of SiNWs via AgACE, as an important structural parameter, has not been sufficiently investigated. Here, array density effect on the optical and photoelectric properties of SiNWs is experimentally investigated. SiNW arrays with different densities (silicon occupation ratio of 7%-34.5%) were prepared through controlling the reaction time of silicon wafers in the seed solution (tseed). The SiNW array with atseedof 90 s shows optimum light absorption over 98% in the wavelength range of 300-1000 nm, though all the samples have light absorption over 95% due to the light trapping effect of nanowire array structure. In addition, the SiNW array with atseedof 90 s exhibits the best photoelectric property. SiNW arrays with shortertseedand higher density suffer more surface recombination, harming the photoelectric property. In SiNW arrays with longertseedthan 90 s and lower density, some SiNWs topple down and break, which has an adverse effect on transport and collection of carriers. These results indicate that the array density of SiNWs via AgACE has obvious effect on their photoelectric property. SiNW arrays via AgACE with atseedof 90 s are ideal for photoelectric devices. This work is potential to guide SiNW fabrication for photoelectric applications.

A Facile Hydrothermal Synthesis and Resistive Switching Behavior of α-Fe2O3 Nanowire Arrays.

A facile hydrothermal process has been developed to synthesize the α-Fe2O3 nanowire arrays with a preferential growth orientation along the [110] direction. The W/α-Fe2O3/FTO memory device with the nonvolatile resistive switching behavior has been achieved. The resistance ratio (RHRS/RLRS) of the W/α-Fe2O3/FTO memory device exceeds two orders of magnitude, which can be preserved for more than 103s without obvious decline. Furthermore, the carrier transport properties of the W/α-Fe2O3/FTO memory device are dominated by the Ohmic conduction mechanism in the low resistance state and trap-controlled space-charge-limited current conduction mechanism in the high resistance state, respectively. The partial formation and rupture of conducting nanofilaments modified by the intrinsic oxygen vacancies have been suggested to be responsible for the nonvolatile resistive switching behavior of the W/α-Fe2O3/FTO memory device. This work suggests that the as-prepared α-Fe2O3 nanowire-based W/α-Fe2O3/FTO memory device may be a potential candidate for applications in the next-generation nonvolatile memory devices.

S-Scheme Porphyrin Covalent Organic Framework Heterojunction for Boosted Photoelectrochemical Immunoassays in Myocardial Infarction Diagnosis.

Cardiac troponin I (cTnI) is an extremely sensitive biomarker for early indication of acute myocardial infarction (AMI). However, it still remains a tough challenge for many newly developed cTnI biosensors to achieve superior sensing performance including high sensitivity, rapid detection, and resistance to interference in clinical serum samples. Herein, a novel photocathodic immunosensor toward cTnI sensing has been successfully developed by designing a unique S-scheme heterojunction based on the porphyrin-based covalent organic frameworks (p-COFs) and p-type silicon nanowire arrays (p-SiNWs). In the novel heterojunction, the p-SiNWs are employed as the photocathode platform to acquire a strong photocurrent response. The in situ-grown p-COFs can accelerate the spatial migration rate of charge carriers by forming proper band alignment with the p-SiNWs. The crystalline π-conjugated network of p-COFs with abundant amino groups also promotes the electron transfer and anti-cTnI immobilizing process. The developed photocathodic immunosensor demonstrates a broad detection range of 5 pg/mL-10 ng/mL and a low limit of detection (LOD) of 1.36 pg/mL in clinical serum samples. Besides, the PEC sensor owns several advantages including good stability and superior anti-interference ability. By comparing our results with that of the commercial ELISA method, the relative deviations range from 0.06 to 0.18% (n = 3), and the recovery rates range from 95.4 to 109.5%. This work displays a novel strategy to design efficient and stable PEC sensing platforms for cTnI detection in real-life serums and provides guidance in future clinical diagnosis.

Synergistic Tuning of CoO/CoP Heterojunction Nanowire Arrays as Efficient Bifunctional Catalysts for Alkaline Overall Water Splitting.

Bifunctional electrocatalysts with superior activity and durability are of great importance for electrocatalytic water splitting. Herein, hierarchical structured CoO/CoP heterojunctions are successfully designed as highly efficient and freestanding bifunctional electrocatalysts toward overall water splitting. The unique microstructure combining two-dimensional nanosheets with one-dimensional nanowires enables numerous exposed active sites, shortened ion-diffusion pathways, and enhanced conductivity, significantly improving performance. Such freestanding electrodes achieve high current density over 400 mA cm-2 at low overpotentials and have exceptional electrocatalytic activity as well as long-term durability for both hydrogen and oxygen evolution reactions under alkaline conditions. Remarkably, a high current density of 20 mA cm-2 is generated at a low cell voltage of 1.56 V in an alkaline water electrolyzer, originating from synergistic interactions between CoO and CoP exposing active sites and facilitating charge transfer and enhancing kinetics. This work provides new insight into designing low-cost but high-performance bifunctional electrocatalysts for practical water splitting.

Rational Design of Molybdenum-Doped Cobalt Nitride Nanowire Arrays for Robust Overall Water Splitting.

Rational design of efficient electrocatalysts is highly imperative but still a challenge for overall water splitting. Herein, we construct self-supported Co3 N nanowire arrays with different Mo doping contents by hydrothermal and nitridation processes that serve as robust electrocatalysts for overall water splitting. The optimal Co3 N-Mo0.2 /Ni foam (NF) electrode delivers a low overpotential of 97 mV at a current density of 50 mA cm-2 as well as a highly stable hydrogen evolution reaction (HER). Density functional theory (DFT) calculations prove that Mo doping can effectively modulate the electronic structure and surface adsorption energies of H2 O and hydrogen intermediates on Co3 N, leading to improved reaction kinetics with high catalytic activity. Further modification with FeOOH species on the surface of Co3 N-Mo0.2 /NF improves the oxygen evolution reaction (OER) performance benefiting from the synergistic effect of dual Co-Fe catalytic centers. As a result, the Co3 N-Mo0.2 @FeOOH/NF catalysts display outstanding OER catalytic performance with a low overpotential of 250 mV at 50 1 mA cm-2 . The constructed Co3 N-Mo0.2 /NF||Co3 N-Mo0.2 @FeOOH/NF water electrolyzer exhibits a small voltage of 1.48 V to achieve a high current density of 50 mA cm-2 at 80 °C, which is superior to most of the reported electrocatalysts. This work provides a new approach to developing robust electrode materials for electrocatalytic water splitting.

Alleviating Zn Dendrites by Growth of Ultrafine ZnO Nanowire Arrays through Horizontal Anodizing for High-Capacity, Long-Life Zn Ion Capacitors.

Zn ion capacitors (ZICs) composed of a carbon-based cathode and a Zn anode are one of the most promising energy storage devices due to their inherent safety and high-power output. However, their poor cycling stability originating from the Zn dendrites' formation and low energy density limited by insufficient activated carbon properties remain major challenges for development of high-performance ZICs. Hence, we constructed a facile and effective strategy to alleviate "edge effects" and suppress Zn dendrites by growing ZnO nanowire arrays on Zn foil (ZnO@Zn) using a horizontally potentiostatic anodizing technique. The electrochemical characterizations and in situ optical microscopy observation revealed that the introduction of ZnO nanowire arrays can significantly suppress the growth of Zn dendrites and enhance the cycling stability of the Zn anode. The superfine and interlaced ZnO nanowire arrays provide uniform nucleation sites and high electrical conductivity for the Zn metal anode, reducing the local current density and promoting the rapid diffusion and migration of Zn ions on the Zn anode surface. As a result, the ZnO@Zn electrode has a very low nucleation overpotential and excellent cycle stability, far superior to the bare Zn anode. Furthermore, a ZnO@Zn//NPHC ZIC assembled with an N, P-codoped hard carbon (NPHC) cathode delivers a high specific capacity of 110.3 mAh g-1 at 0.1 A g-1 and achieves outstanding cycling stability with 90% capacity retention together with ∼100% Coulombic efficiency after 20000 cycles.

Integrated one-dimensional CuO-nanowire arrays/Cu-foam nanoarchitecture for ultrahigh sensitive and non-enzymatic electrochemical determination of histamine levels in different-bacteria fermented mandarin fish.

Integrated one-dimensional CuO-nanowire arrays/Cu-foam (CuO-NWAs/Cu-foam) nanostructure, which was fabricated by oxidation and calcination, has been newly utilized as non-enzymatic electrocatalytic electrode for exploring histamine level. Under optimal condition of pH at 13 and potential at 0.55 V (vs Ag/Ag/Cl), the sensitivity of CuO-NWAs/Cu-foam electrode towards non-enzymatic electrochemical histamine determination presented as high as 12.94 mA mM-1 cm-2, linear range spanned between 0.5 and 1046 µM, a detection limit (S/N = 3) was about 44 nM. The unprecedented causes of ultrahigh sensitivity were physically contributed to enhancing active surface area and declining charge transfer resistance. More crucially, the outstanding selectivity, stability and reproducibility facilitated its practical capacity on evaluating histamine levels in different-bacteria fermented mandarin fish, which triggered the potential feasibility for commercializing non-enzymatic electrochemical determination of histamine with high sensitivity, reliable precision and low expenditure.

In-situ construction of Au/Cu2O nanowire arrays for sensitive glucose sensing.

Architecture design is widely regarded as a rational strategy to enhance the sensing performance of electrocatalysts. Herein, the novel three-dimensional hybrids based on Au and Cu2O were successfully synthesized via steps of in-situ growth, including anodic oxidation, annealing and galvanic displacement. Cu2O appeared in the morphology of nanowire array on conductive substrate, and was decorated by Au nanoparticles. Benefiting from the unique architecture and binder-free fabrication process, the Au/Cu2O nanowire arrays possessed high conductivity and abundant exposed active sites, as well as facilitated the direct electron transfer among detection object, electrocatalyst and current collector. Moreover, Au/Cu2O particles as contrast were fabricated to clarify the effect of structure on sensing ability. The Au/Cu2O nanowire arrays drove the glucose electro-oxidation reaction with great catalytic activity, in which a potential as low as 0.4 V was needed to reach a high sensitivity of 2.098 mA mM-1 cm-2. The excellent selectivity, stability and reproducibility were also obtained by the sensor. Furthermore, the quantitative detection of glucose level in diluted human serum were performed and the satisfactory result make the obtained sensor have the potential for practical applications.

Current density-induced emergence of soft and hard magnetic phases in Fe nanowire arrays.

The capability of generating magnetically soft and hard phases in a material is important in many aspects, ranging from basic science to applications. Here, the emergence of soft and hard magnetic phases is reported in Fe nanowire (NW) arrays with a diameter of 35 nm fabricated by using a pulsed electrochemical deposition method in porous aluminum oxide templates under different current density (Cd) values in the range of 25-100 mA cm-2. The variation ofCdinfluences the grain size, crystallinity, electrodeposition efficiency and length of the Fe NWs, as characterized by x-ray diffraction, high-resolution transmission electron microscopy, vibrating sample magnetometry and field-emission scanning electron microscopy. IncreasingCdfrom 25 to 80 mA cm-2results in a significant decrease in coercivity and squareness from 1590 to 900 Oe and 0.9 to 0.5, respectively, inducing the soft and hard phases along the length of Fe NWs. Further increasing theCdleads to the separation of the phases, as evidenced by first-order reversal curve analysis. From a theoretical aspect, the emergence of the soft phase may lead to the occurrence of the fanning reversal mode in the NWs, for which there is no precedent in previous experimental investigations.

Highly Bright Gold Nanowires Arrays for Sensitive Detection of Urea and Urease.

In this work, highly fluorescent gold nanowire arrays (Au NWs) are successfully synthesized by assembling Zn2+ ions and non-emissive oligomeric gold-thiolate clusters using mercaptopropionic acid both as a reducing agent and a growth ligand. The synthesized Au NWs exhibited strong bluish green fluorescence with an absolute quantum yield up to 32% and possessed ultrasensitive pH stimuli-responsive performance in the range of 7.0-7.8. Based on the excellent properties of the as-prepared nanowire arrays, we developed a facile, sensitive, and selective fluorescent method for quantitative detection of urea and urease. The fabricated nanoprobe showed superior biosensing response characteristics with good linearities in the range of 0-100 µM for urea concentration and 0-12 U/L for urease activity. In addition, this fluorescent probe afforded relatively high sensitivity with the detection limit as low as 2.1 µM and 0.13 U/L for urea and urease, respectively. Urea in human urine and urease in human serum were detected with satisfied results, exhibiting a promising potential for biomedical application.

Single-Crystalline Perovskite p-n Junction Nanowire Arrays for Ultrasensitive Photodetection.

Highly sensitive photodetectors play significant roles in modern optoelectronic integrated circuits. Constructing p-n junctions has been proven to be a particularly powerful approach to realizing sensitive photodetection due to their efficient carrier separation. Recently, p-n-junction photodetectors based on organic-inorganic hybrid perovskites, which combine favorable optoelectronic performance with facile processability, hold great potential in practical applications. So far, these devices have generally been made of polycrystalline films, which exhibit poor carrier-transport efficiency, impeding the further improvement of their photoresponsivities. Here, a type of ultrasensitive photodetector based on single-crystalline perovskite p-n-junction nanowire arrays is demonstrated. The single-crystalline perovskite p-n-junction nanowire arrays not only possess high crystallinity that enables efficient carrier transport but also form a built-in electric field facilitating effective carrier separation. As a result, the devices show excellent photosensitivity over a wide spectral range from 405 to 635 nm with an outstanding responsivity of 2.65 × 102  A W-1 at 532 nm. These results will provide new insights into the design and construction of high-performance photodetectors for practical optoelectronic applications.