Hybrid Acid/Base Electrolytic Cell for Hydrogen Generation and Methanol Conversion Implemented by Bifunctional Ni/MoN Nanorod Electrocatalyst.

Combining the methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER) within an integrated electrolytic system may offer the advantages of enhanced kinetics of the anode, reduced energy consumption, and the production of high-purity hydrogen. Herein, it is reported the construction of Ni─MoN nanorod arrays supported on a nickel foam substrate (Ni─MoN/NF) as a bifunctional electrocatalyst for electrocatalytic hydrogen production and selective methanol oxidation to formate. Remarkably, The optimal Ni─MoN/NF catalyst displays exceptional HER performance with an overpotential of only 49 mV to attain 10 mA cm-2 in acid, and exhibits a high activity for MOR to achieve 100 mA cm-2 at 1.48 V in alkali. A hybrid acid/base electrolytic cell with Ni─MoN/NF electrode as anode and cathode is further developed for an integrated HER-MOR cell, which only requires a voltage of 0.56 V at 10 mA cm-2 , significantly lower than that of the HER-OER system (0.70 V). The density functional theory studies reveal that the incorporation of Ni effectively modulates the electronic structure of MoN, thereby resulting in enhanced catalytic activity. The unique combination of high electrocatalytic activity and excellent stability make the Ni─MoN/NF catalyst a promising candidate for practical applications in electrocatalytic hydrogen production and methanol oxidation.

TiO2nanorod arrays/Ti3C2TxMXene nanosheet composites with efficient photocatalytic activity.

Semiconductor photocatalysis holds significant promise in addressing both environmental and energy challenges. However, a major hurdle in photocatalytic processes remains the efficient separation of photoinduced charge carriers. In this study, TiO2nanorod arrays were employed by glancing angle deposition technique, onto which Ti3C2TxMXene was deposited through a spin-coating process. This hybrid approach aims to amplify the photocatalytic efficacy of TiO2nanorod arrays. Through photocurrent efficiency characterization testing, an optimal loading of TiO2/Ti3C2Txcomposites is identified. Remarkably, this composite exhibits a 40% increase in photocurrent density in comparison to pristine TiO2. This enhancement is attributed to the exceptional electrical conductivity and expansive specific surface area inherent to Ti3C2TxMXene. These attributes facilitate swift transport of photoinduced electrons, consequently refining the separation and migration of electron-hole pairs. The synergistic TiO2/Ti3C2Txcomposite showcases its potential across various domains including photoelectrochemical water splitting and diverse photocatalytic devices. As such, this composite material stands as a novel and promising entity for advancing photocatalytic applications. This study can offer an innovative approach for designing simple and efficient photocatalytic materials composed of MXene co-catalysts and TiO2for efficient water electrolysis on semiconductors.

Self-Supported Pd Nanorod Arrays for High-Efficient Nitrate Electroreduction to Ammonia.

Electrochemical nitrate (NO3 - ) reduction to ammonia (NH3 ) offers a promising pathway to recover NO3 - pollutants from industrial wastewater that can balance the nitrogen cycle and sustainable green NH3 production. However, the efficiency of electrocatalytic NO3 - reduction to NH3 synthesis remains low for most of electrocatalysts due to complex reaction processes and severe hydrogen precipitation reaction. Herein, high performance of nitrate reduction reaction (NO3 - RR) is demonstrated on self-supported Pd nanorod arrays in porous nickel framework foam (Pd/NF). It provides a lot of active sites for H* adsorption and NO3 - activation leading to a remarkable NH3 yield rate of 1.52 mmol cm-2  h-1 and a Faradaic efficiency of 78% at -1.4 V versus RHE. Notably, it maintains a high NH3 yield rate over 50 cycles in 25 h showing good stability. Remarkably, large-area Pd/NF electrode (25 cm2 ) shows a NH3 yield of 174.25 mg h-1 , be promising candidate for large-area device for industrial application. In situ FTIR spectroscopy and density functional theory calculations analysis confirm that the enrichment effect of Pd nanorods encourages the adsorption of H species for ammonia synthesis following a hydrogenation mechanism. This work brings a useful strategy for designing NO3 - RR catalysts of nanorod arrays with customizable compositions.

Nanopatterned rGO/ZnO:Al seed layer for vertical growth of single ZnO nanorods.

In this work, we demonstrate a novel low-cost template-assisted route to synthesize vertical ZnO nanorod arrays on Si (100). The nanorods were grown on a patterned double seed layer comprised of reduced graphene oxide (rGO) and Al-doped ZnO nanoparticles. The seed layer was fabricated by spray-coating the substrate with graphene and then dip-coating it into a Al-doped ZnO sol-gel solution. The growth template was fabricated from a double-layer resist, spin-coated on top of the rGO/ZnO:Al seed layer, and patterned by colloidal lithography. The results show a successful chemical bath deposition of vertically aligned ZnO nanorods with controllable diameter and density in the nanoholes in the patterned resist mask. Our novel method can presumably be used to fabricate electronic devices on virtually any smooth substrate with a thermal budget of 1 min at 300 °C with the seed layer acting as a conductive strain-relieving back contact. The top contact can simply be made by depositing a suitable transparent conductive oxide or metal, depending on the specific application.

Novel Au Nanoparticle-Modified ZnO Nanorod Arrays for Enhanced Photoluminescence-Based Optical Sensing of Oxygen.

Novel optical gas-sensing materials for Au nanoparticle (NP)-modified ZnO nanorod (NR) arrays were fabricated using hydrothermal synthesis and magnetron sputtering on Si substrates. The optical performance of ZnO NR can be strongly modulated by the annealing temperature and Au sputtering time. With exposure to trace quantities of oxygen, the ultraviolet (UV) emission of the photoluminescence (PL) spectra of Au/ZnO samples at ~390 nm showed a large variation in intensity. Based on this mechanism, ZnO NR based oxygen gas sensing via PL spectra variation demonstrated a wide linear detection range of 10-100%, a high response value, and a 1% oxygen content sensitivity detection limit at 225 °C. This outstanding optical oxygen-sensing performance can be attributed to the large surface area to volume ratio, high crystal quality, and high UV emission efficiency of the Au NP-modified ZnO NR arrays. Density functional theory (DFT) simulation results confirmed that after the Au NPs modified the surface of the ZnO NR, the charge at the interface changed, and the structure of Au/ZnO had the lowest adsorption energy for oxygen molecules. These results suggest that Au NP-modified ZnO NR are promising for high-performance optical gas-sensing applications.

Endowing Polyetheretherketone Implants with Osseointegration Properties: In Situ Construction of Patterned Nanorod Arrays.

Polyetheretherketone (PEEK) is widely used in orthopedic and craniomaxillofacial surgeries as it exhibits excellent biocompatibility, mechanical property, and chemical stability. However, its clinical application is limited by the biological inertness of PEEK. Numerous efforts have been made to improve the bioactivity of this polymer over the years. However, modification methods that can not only promote osteogenesis but also maintain excellent properties are still limited. Hence, a facile hot die formation technique is developed for establishing patterned nanorod arrays on the PEEK surface in situ. This method can maintain the excellent properties of PEEK and can be used in implantation as it can facilitate osteogenic activity in the absence of any organic/inorganic differentiation-inducing factors. PEEK with 200-nm patterned nanorod arrays on the surface exhibits excellent osteogenic properties. This result is obtained by assessing the osteogenic differentiation properties of rat adipose-derived stem cells at the gene and protein levels in vitro. In vivo experimental results reveal that the surface-modified cylindrical PEEK 200 implants present with excellent osseointegration properties. Moreover, they can tightly bind with the surrounding bone tissue. A practical method for manufacturing single-component PEEK implants with excellent osseointegration properties is reported, and the materials can be possibly used as orthopedic implants.

Cerium-Doped Iron Oxide Nanorod Arrays for Photoelectrochemical Water Splitting.

In this work, a simple one-step hydrothermal method was employed to prepare the Ce-doped Fe2O3 ordered nanorod arrays (CFT). The Ce doping successfully narrowed the band gap of Fe2O3, which improved the visible light absorption performance. In addition, with the help of Ce doping, the recombination of electron/hole pairs was significantly inhibited. The external voltage will make the performance of the Ce-doped sample better. Therefore, the Ce-doped Fe2O3 has reached superior photoelectrochemical (PEC) performance with a high photocurrent density of 1.47 mA/cm2 at 1.6 V vs. RHE (Reversible Hydrogen Electrode), which is 7.3 times higher than that of pristine Fe2O3 nanorod arrays (FT). The Hydrogen (H2) production from PEC water splitting of Fe2O3 was highly improved by Ce doping to achieve an evolution rate of 21 µmol/cm2/h.

Cr-Doped CoP Nanorod Arrays as High-Performance Hydrogen Evolution Reaction Catalysts at High Current Density.

Developing highly efficient, low-cost electrocatalysts with long-time stability at high current density working conditions for hydrogen evolution reaction (HER) remains a great challenge for the large-scale commercialization of hydrogen production from water electrolysis. Herein, the Cr-doped CoP nanorod arrays on carbon cloth (Cr-CoP-NR/CC) is reported as high performance HER catalysts with overpotentials of 38 and 209 mV at the HER current densities of 10 and 500 mA cm-2 , respectively, outperforming the performance of the commercial Pt/C at high current density. And its HER performance shows almost no loss after 20 h working at 500 mA cm-2 . The high performance is attributed to the Cr doping, which optimizes the hydrogen binding energy of CoP and prevents its oxidation. The nanorod array structure helps the escaping of the generated hydrogen gas, which is suitable for working at high current density. The obtained Cr-CoP-NR/CC catalyst shows the potential to replace the costly Pt-based HER catalysts in the water electrolyzer.

Hierarchical Ni3S2nanorod@nanosheet arrays on Ni foam for high-performance supercapacitor.

We successfully designed and prepared hierarchical Ni3S2nanorod@nanosheet arrays on three-dimensional Ni foam via facile hydrothermal sulfuration. We conducted a series of time- and temperature-dependent experiments to determine the Ostwald ripening process of hierarchical Ni3S2nanorod@nanosheet arrays. The rationally hierarchical architecture creates an excellent supercapacitor electrode for Ni3S2nanorod@nanosheet arrays. The areal capacitance of this array reaches 5.5 F cm-2at 2 mA cm-2, which is much higher than that of Ni3S2nanosheet arrays (1.5 F cm-2). The corresponding asymmetric supercapacitor exhibits a wide potential window of 1.6 V and energy density up to 1.0 Wh cm-2when the proposed array is utilized as the positive electrode with activated carbon as the negative electrode. This electrochemical performance enhancement is attributable to the hierarchical structure and synergistic cooperation of macroporous Ni foam and well-aligned Ni3S2nanorod@nanosheet arrays. Our results represent a promising approach to the preparation of hierarchical nanorod@nanosheet arrays as high-performing electrochemical capacitors.

Core-shell coaxially structured NiCo2S4@TiO2nanorod arrays as advanced electrode for solid-state asymmetric supercapacitors.

An integrated electrode of core-shell coaxially structured NiCo2S4@TiO2nanorod arrays/carbon cloth (NiCo2S4@TiO2@CC) have been fabricated, via a two-step hydrothermal method. Comprehensive structural and compositional analyzes are performed to understand the effects of the NiCo2S4shell on the TiO2core. Such core-shell arrays structure can significantly provide abundant electroactive sites for redox reactions, convenient ion transport paths, and favorable structure stability. The NiCo2S4@TiO2@CC electrode represents a splendid specific capacitance (650 F g-1at 1 A g-1) and enhanced cycling stability (capacitance retention of 97% over 10 000 cycles at 5 A g-1). Additionally, the assembled NiCo2S4@TiO2@CC//CNT@CC solid-state asymmetric supercapacitors exhibit a maximal energy density of 0.6 mWh cm-3at 32.4 W cm-3, and topping cycling stability (85% capacitance retention after 5000 cycles at 5 mA cm-2). The results demonstrate that the well-designed NiCo2S4@TiO2@CC presented in this work are applicable for the development of electrode materials in energy storage devices.

Metallic and porous Ti nanorod arrays for visible-IR light absorption and dendrite-free stable lithium-metal batteries.

It is still a challenging task to prepare highly porous nanorod arrays of metals formed on substrates for optical and energy storage applications. Herein, we demonstrate the design and synthesis of black color, metallic and highly porous Ti nanorod arrays as novel current collectors for dendrite-free and highly stable Li-metal anodes. The high porosity of metallic nanorod arrays provides numerous heterogeneous nucleation sites and huge contact area and large space for the accommodation of Li metal. The conductive metallic Ti nanorod arrays enhance electrode integration. Effectively, it eliminates formation Li dendrites and demonstrates superior cycling stability over 300 cycles. Additionally, the unique porous structures of the nanorod arrays can decrease the amplitude of forced vibration in narrow space leading to light absorption. Interestingly, the metal is black instead of metallic color. The black metallic nanorod arrays can absorb more than 96% of both visible and infra-red lights. This black color metallic porous nanorod arrays may find additional applications in aerospace, energy, biomedical, defence, and chemical industries.

Enhanced Piezo-Photoelectric Catalysis with Oriented Carrier Migration in Asymmetric Au-ZnO Nanorod Array.

Current photocatalytic semiconductors often have low catalytic performance due to limited light utilization and fast charge carrier recombination. Formation of Schottky junction between semiconductors and plasmonic metals can broaden the light absorption and facilitate the photon-generated carriers separation. To further amplify the catalytic performance, herein, an asymmetric gold-zinc oxide (Asy-Au-ZnO) nanorod array is rationally designed, which realizes the synergy of piezocatalysis and photocatalysis, as well as spatially oriented electron-hole pairs separation, generating a significantly enhanced catalytic performance. In addition to conventional properties from noble metal/semiconductor Schottky junction, the rationally designed heterostructure has several additional advantages: 1) The piezoelectric ZnO under light and mechanical stress can directly generate charge carriers; 2) the Schottky barrier can be reduced by ZnO piezopotential to enhance the injection efficiency of hot electrons from Au nanoparticles to ZnO; 3) the unique asymmetric nanorod array structure can achieve a spatially directed separation and migration of the photon-generated carriers. When ultrasound and all-spectrum light irradiation are exerted simultaneously, the Asy-Au-ZnO reaches the highest catalytic efficiency of 95% in 75 min for dye degradation. It paves a new pathway for designing unique asymmetric nanostructures with the synergy of photocatalysis and piezocatalysis.

A photoelectrochemical aptasensor based on p-n heterojunction CdS-Cu2O nanorod arrays with enhanced photocurrent for the detection of prostate-specific antigen.

A sensitive photoelectrochemical (PEC) aptasensor was constructed for prostate-specific antigen (PSA) detection using an enhanced photocurrent response strategy. The p-n heterostructure CdS-Cu2O nanorod arrays were prepared on Ti mesh (CdS-Cu2O NAs/TM) by a simple hydrothermal method and successive ionic-layer adsorption reactions. Compared with the original CdS/TM, the synergistic effect of p-n type CdS-Cu2O NAs/TM and the internal electric field realizes the effective separation of photoinduced electron-hole pairs and improves the PEC performance. In order to construct the aptasensor, an amino-modified aptamer was immobilized on CdS-Cu2O NAs/TM to serve as a recognition unit for PSA. After the introduction of PSA, PSA was specifically captured by the aptamer on the PEC aptasensor, which can be oxidized by photogenerated holes to prevent electron-hole recombination and increase photocurrent. Under optimal conditions, the constructed PEC aptasensor has a linear range of 0.1-100 ng·mL-1 and a detection limit as low as 0.026 ng·mL-1. The results of aptasensor detection of human serum indicate that it has broad application prospects in biosensors and photoelectrochemical analysis.

Surface enhanced Raman spectroscopy as a novel tool for rapid quantification of heroin and metabolites in saliva

Background: Heroin can be detected and quantified by certain analytical methods, however, forensic professionals and criminal laboratories study for cheaper and faster detection tools. Surface-enhanced Raman spectroscopy (SERS) rises as a possible alternative tool with its widening application spectra. There are few studies regarding Raman and SERS spectra of heroin and its metabolites, which are unfortunately controversial. In this study, we compared five different surfaces in order to find out more efficient Raman-active substrate for opiate detection and rapid quantification of heroin and its metabolites in saliva. Materials and methods: Morphine standard material was used to identify proper surface for SERS analysis of opiates. Heroin and its metabolites (morphine, morphine-3-ß-glucuronide and 6-monoacetyl morphine) were calibrated between 50 ppb and 500 ppm and quantified on AuNRs with signal enhancement of silver colloids in saliva. Raman microscope with a 785-nm laser source was used. Results and Conclusion: Obtained results showed that heroin and its metabolites can be detected and quantified in saliva samples using a SERS-based system. Additionally, the present study revealed that synergetic effect of a specific gold nano-surface with ability controlling liquid motion and silver nanoparticles increase band numbers and intensities. Therefore, we suggest a fast, accurate and cost-effective method to detect and quantify heroin in biological fluids

Cellular Stemness Maintenance of Human Adipose-Derived Stem Cells on ZnO Nanorod Arrays.

Ever-growing tissue regeneration and other stem cell therapies cause pressing need for large population of self-renewable stem cells. However, stem cells gradually lose their stemness after long-term in vitro cultivation. In this study, a ZnO nanorod (ZnO NR) array is used to maintain the stemness of human adipose-derived stem cells (hADSCs). The results prove that after culturing hADSCs on ZnO NRs for 3 weeks, the stemness genes and protein expression level are higher than that on culture plates and ZnO film. ZnO NRs can maintain stemness of hADSCs without inhibiting the cell proliferation and oriented differentiation capabilities. KLF4 (Kruppel-like factor 4) is a Zn2+ -binding gene that plays a vital role in cell proliferation and differentiation. Sustained Zn2+ release and the increased expression of KLF4 can be detected, suggesting that ZnO NRs have efficiently released Zn2+ for stemness maintenance. Taken together, the nanotopography of ZnO NRs and the Zn2+ release synergistically facilitate stemness maintenance. This study has provided a powerful tool for directing cell fate, maintaining stemness, and realizing the expansion of stem cells in vitro, which will open a new route for the manufacture of large populations of stem cells and fulfilling the growing demand for the cell therapy market.

Label-Free Detection of E. coli O157:H7 DNA Using Light-Addressable Potentiometric Sensors with Highly Oriented ZnO Nanorod Arrays.

The detection of bacterial deoxyribonucleic acid (DNA) is of great significance in the quality control of food and water. In this study, a light-addressable potentiometric sensor (LAPS) deposited with highly oriented ZnO nanorod arrays (NRAs) was used for the label-free detection of single-stranded bacterial DNA (ssDNA). A functional, sensitive surface for the detection of Escherichia coli (E. coli) O157:H7 DNA was prepared by the covalent immobilization of the specific probe single-stranded DNA (ssDNA) on the LAPS surface. The functional surface was exposed to solutions containing the target E. coli ssDNA molecules, which allowed for the hybridization of the target ssDNA with the probe ssDNA. The surface charge changes induced by the hybridization of the probe ssDNA with the target E. coli ssDNA were monitored using LAPS measurements in a label-free manner. The results indicate that distinct signal changes can be registered and recorded to detect the target E. coli ssDNA. The lower detection limit of the target ssDNA corresponded to 1.0 × 102 colony forming units (CFUs)/mL of E. coli O157:H7 cells. All the results demonstrate that this DNA biosensor, based on the electrostatic detection of ssDNA, provides a novel approach for the sensitive and effective detection of bacterial DNA, which has promising prospects and potential applications in the quality control of food and water.

Obliquely Deposited Titanium Nitride Nanorod Arrays as Surface-Enhanced Raman Scattering Substrates.

In this work, titanium nitride (TiN) nanorod arrays were prepared as surface-enhanced Raman scattering (SERS) substrates using glancing angle deposition (GLAD) in a magnetron sputtering system. The nitrogen flow rate was varied from RN2 = 1 to 3 sccm, yielding five TiN uniform thin films and five TiN nanorod arrays. The figure of merit (FOM) of each TiN uniform film was measured and compared with the SERS signal of each TiN nanorod array. Rhodamine 6G (R6G) was used as the analyte in SERS measurement. For an R6G concentration of 10-6 M, the analytical enhancement factor (AEF) of the TiN nanorod array that was prepared at RN2 = 1.5 sccm was 104. The time-durable SERS performance of TiN nanorod arrays was also investigated.

Simple Fabrication of SnO2 Quantum-dot-modified TiO2 Nanorod Arrays with High Photoelectrocatalytic Activity for Overall Water Splitting.

Photoelectrochemical (PEC) water splitting has been demonstrated as a promising way to acquire clean hydrogen energy. However, the efficiency has been limited by the high recombination rate of photogenerated electron-hole pairs. Herein, we provided a simple approach to construct a novel SnO2 quantum dots (QDs) modified TiO2 nanorod arrays (NAs) by the calcination of SnCl2 -adsorbed TiO2 NAs. The photocurrent density of SnO2 QDs/TiO2 NAs exhibits about 5 times higher than that of parent TiO2 NAs at a bias of 0.4 V vs. Ag/AgCl. SnO2 QDs/TiO2 NAs also show a high photoelectrocatalytic activity for overall water splitting with an actual yield of H2 and O2 to be 27.85 and 11.87 µmol cm-2 h-1 , respectively. The excellent performance of photoanode for PEC water splitting could be attributed to its Z-scheme heterostructure for good separation efficiency and transport rate of photogenerated charge carries.

A Simple Route to Reduced Graphene Oxide-Draped Nanocomposites with Markedly Enhanced Visible-Light Photocatalytic Performance.

Nanocomposites (denoted RGO/ZnONRA) comprising reduced graphene oxide (RGO) draped over the surface of zinc oxide nanorod array (ZnONRA) were produced via a simple low-temperature route, dispensing with the need for hydrothermal growth, electrochemical deposition or other complex treatments. The amount of deposited RGO can be readily tuned by controlling the concentration of graphene oxide (GO). Interestingly, the addition of Sn(2+) not only enables the reduction of GO, but also functions as a bridge that connects the resulting RGO and ZnONRA. Remarkably, the incorporation of RGO improves the visible-light absorption and reduces the bandgap of ZnO, thereby leading to the markedly improved visible-light photocatalytic performance. Moreover, RGO/ZnONRA nanocomposites exhibit a superior stability as a result of the surface protection of ZnONRA by RGO. The mechanism on the improved photocatalytic performance based on the cophotosensitizations under the visible-light irradiation has been proposed. This simple yet effective route to the RGO-decorated semiconductor nanocomposites renders the better visible-light utilization, which may offer great potential for use in photocatalytic degradation of organic pollutants, solar cells, and optoelectronic materials and devices.

CdS@SiO2 Core-Shell Electroluminescent Nanorod Arrays Based on a Metal-Insulator-Semiconductor Structure.

Enormous advancement has been achieved in the field of one-dimensional (1D) semiconductor light-emitting devices (LEDs), however, LEDs based on 1D CdS nanostructures have been rarely reported. The fabrication of CdS@SiO2 core-shell nanorod array LEDs based on a Au-SiO2 -CdS metal-insulator-semiconductor (MIS) structure is presented. The MIS LEDs exhibit strong yellow emission with a low threshold voltage of 2.7 V. Electroluminescence with a broad emission ranging from 450 nm to 800 nm and a shoulder peak at 700 nm is observed, which is related to the defects and surface states of the CdS nanorods. The influence of the SiO2 shell thickness on the electroluminescence intensity is systematically investigated. The devices have a high light-emitting spatial resolution of 1.5 µm and maintain an excellent emission property even after shelving at room temperature for at least three months. Moreover, the fabrication process is simple and cost effective and the MIS device could be fabricated on a flexible substrate, which holds great potential for application as a flexible light source. This prototype is expected to open up a new route towards the development of large-scale light-emitting devices with excellent attributes, such as high resolution, low cost, and good stability.