Nanoneedle Arrays Research Articles

Electronic modulation of Co2P nanoneedle arrays by the doping of transition metal Cr atoms for a urea oxidation reaction.

Urea electrolysis is of great interest for energy-related applications, but it is limited by a complex six-electron transfer process with slow kinetics. Herein, the in situ growth of Cr-doped Co2P homogeneous nanoneedle arrays on nickel foam substrates (Cr-Co2P/NF) was reported for the first time by a typical hydrothermal and low-temperature phosphorization process. The appropriate amount of Cr doping was found to promote the electronic modulation of active centers and the expansion of the specific active surface area, resulting in the superior performance of the urea oxidation reaction (UOR). It is noteworthy that Cr0.4-Co2P/NF exhibited a superior performance of the UOR at an onset potential of 1.290 V and a cell voltage of 1.333 V at 50 mA cm-2 in 1 M KOH containing 0.5 M urea, which is one of the best catalytic activities reported so far. The experimental results demonstrate that the enhanced catalytic activity can be attributed to favorable electronic regulation, an improved charge transfer rate and increased exposure to active sites. Density functional theory (DFT) calculation indicates that the appropriate doping of Cr effectively regulates and controls the adsorption energy of urea and the conductivity of the Co2P material itself. This work provides new ideas for the development of robust catalysts for the electrolysis of urea through doping strategies.

Hexadecyl trimethyl ammonium bromide assisted growth of NiCo2O4@reduced graphene oxide/ nickel foam nanoneedle arrays with enhanced performance for supercapacitor electrodes.

NiCo2O4@reduced graphene oxide (rGO)/nickel foam (NF) composites were prepared via a hydrothermal method followed by annealing assisted by hexadecyl trimethyl ammonium bromide (CTAB). NiCo2O4@rGO/NF nanoneedle arrays grew directly on Ni foam (NF) without using a binder. The effect of graphene oxide (GO) concentration on the electrochemical properties of the composite was studied. When the GO concentration was 5 mg L−1, the as-prepared NiCo2O4@rGO/NF reaches the highest specific capacitance of 1644 F g−1 at a current density of 1 A g−1. Even at 15 A g−1, the specific capacitance is still 1167 F g−1 and the capacitance retention rate is 89% after 10 000 cycles at 10 A g−1. Furthermore, a NiCo2O4@rGO/NF//graphene hydrogel (GH) asymmetric supercapacitor cell (ASC) device was assembled and exhibits a high specific capacitance of 84.13 F g−1 at 1 A g−1 and excellent cycle stability (113% capacitance retention) after 10 000 charge/discharge cycles at 10 A g−1. This provides potential for application in the field of supercapacitors due to the outstanding specific capacitance, rate performance and cycle stability of NiCo2O4@rGO/NF.

Polymeric Nanoneedle Arrays Mediate Stiffness‐Independent Intracellular Delivery (Adv. Funct. Mater. 3/2022)

Polymeric Nanoneedle Arrays In article number 2104828, Yaping Chen, Nicolas H. Voelcker, Roey Elnathan, and co-workers demonstrate the fabrication of relatively low-cost and high throughput polymeric nanoneedles from cell culture polystyrene. The nanoneedles with precise geometry are imprinted directly on polystyrene from the cell culture petri dish via nanoimprint lithography. The nanoneedles arrays can precisely manipulate cellular processes and mediate intracellular delivery in mammalian cells. This presents opportunities for novel integration of nanostructures into traditional polymeric cell cultureware.

Polarization-insensitive broadband omni-directional anti-reflection in ZnO nanoneedle array for efficient solar energy harvesting.

Broadband omni-directional anti-reflection characteristics have been an important issue because they can maximize the optical absorption in photovoltaic devices. Here, we investigate the optical properties of ZnO nanoneedle arrays to demonstrate broadband anti-reflection, omni-directionality, and polarization insensitivity using optical simulations and experimental approaches. The results of this work clarify that the ZnO nanoneedle array plays an important role as a broadband anti-reflection layer due to its spatially graded refractive index, omni-directionality and polarization insensitivity. To take advantage of these structures, we prepared a ZnO nanoneedle array on the surface of conventional SiNx/planar Si solar cells to prove the broadband omni-directional anti-reflection for solar energy harvesting. Current density–voltage results show that SiNx/planar Si solar cells with ZnO nanoneedle arrays lead to a nearly 20% increase in power conversion efficiency compared to SiNx/planar Si solar cells, and a 9.3% enhancement in external quantum efficiency is obtained under identical conditions. Moreover, the photocurrent results of SiNx/planar Si solar cells with ZnO nanoneedle arrays clearly demonstrate the incident angle- and polarization-insensitive characteristics compared to those of typical SiNx/planar Si solar cells. Our results demonstrate the optical multi-functionality of ZnO nanoneedle arrays and pave the way for high-performance optoelectronic devices that require broadband omni-directional anti-reflection and polarization insensitivity.

Efficient nitric oxide electroreduction toward ambient ammonia synthesis catalyzed by a CoP nanoarray

A CoP nanoneedle array supported on Ti mesh acts as a high-active electrocatalyst with a low onset potential toward NO-to-NH3 conversion, achieving a faradaic efficiency of 88.3% and a yield of 47.22 μmol h−1 cm−2.

Nonenzymatic Glucose Sensor Based on Porous Co3O4 Nanoneedles.

Herein, porous Co3O4 nanoneedle arrays were synthesized on nickel (Ni) foam (Co3O4 NNs/NF) by one-step hydrothermal method. Some electrochemical methods were used to investigate its nonenzymatic glucose sensing performance in alkaline solution. The results show that the sensitivity of Co3O4 NNs/NF electrode to glucose is 4570 μA mM−1 cm−2. The linear range is 1 μM-0.337 mM, and the detection limit is 0.91 μM (S/N = 3). It also displays good selectivity and repeatability for glucose. The good electrochemical sensing performance of Co3O4 NNs/NF based sensor for glucose can be attributed to interconnected porous structure and large specific surface area of Co3O4.

Microfluidic mechanoporation for cellular delivery and analysis.

Highly efficient intracellular delivery strategies are essential for developing therapeutic, diagnostic, biological, and various biomedical applications. The recent advancement of micro/nanotechnology has focused numerous researches towards developing microfluidic device-based strategies due to the associated high throughput delivery, cost-effectiveness, robustness, and biocompatible nature. The delivery strategies can be carrier-mediated or membrane disruption-based, where membrane disruption methods find popularity due to reduced toxicity, enhanced delivery efficiency, and cell viability. Among all of the membrane disruption techniques, the mechanoporation strategies are advantageous because of no external energy source required for membrane deformation, thereby achieving high delivery efficiencies and increased cell viability into different cell types with negligible toxicity. The past two decades have consequently seen a tremendous boost in mechanoporation-based research for intracellular delivery and cellular analysis. This article provides a brief review of the most recent developments on microfluidic-based mechanoporation strategies such as microinjection, nanoneedle arrays, cell-squeezing, and hydroporation techniques with their working principle, device fabrication, cellular delivery, and analysis. Moreover, a brief discussion of the different mechanoporation strategies integrated with other delivery methods has also been provided. Finally, the advantages, limitations, and future prospects of this technique are discussed compared to other intracellular delivery techniques.

Stable and enhanced electrochemical performance based on hierarchical core–shell structure of CoMn2O4@Ni3S2 electrode for hybrid supercapacitor

Herein, accessible and low-cost CoMn2O4@Ni3S2 core–shell nanoneedle arrays have been prepared via a two-step approach comprised with hydrothermal-calcination and electrochemical deposition procedures, successfully. In the beginning, CoMn2O4 nanoneedle arrays took root on Ni foam to form the core skeleton and subsequently, hierarchical Ni3S2 nanosheets uniformly overlaid on the surface of CoMn2O4 nanoneedles shaping the shell structure. This CoMn2O4@Ni3S2 material was measured directly as supercapacitor electrode and presented high specific capacity of 192.2 mAh g−1 with current density of 1 A g−1. Besides, the electrode delivered outstanding cyclical stability as the capacity retention attained 90.2% after charge–discharge measurement at a large current density of 10 A g−1 for 10 000 cycles. Furthermore, a hybrid supercapacitor assembled by CoMn2O4@Ni3S2 cathode and activated carbon anode represented a high energy density of 51.2 Wh kg−1 with the power density of 1030.0 W kg−1. This work shows a facile and inexpensive procedure to design high-performance and strong-stability supercapacitor electrodes.

High performance flexible asymmetric supercapacitor constructed by cobalt aluminum layered double hydroxide @ nickel cobalt layered double hydroxide heterostructure grown in-situ on carbon cloth

HypothesisThree-dimensional layered layered double hydroxide (LDH) nanostructure materials grow in-situ on excellent conductive and flexible carbon cloth (CC) substrate not only reduce the ability of binders in resisting ions transfer, but also make them to be quasi-vertically arranged well on substrates without aggregation. This would result in enough electroactive sites, to obtain superior electrochemical performance. ExperimentsA hierarchical CoAl-LDH@NiCo-LDH composite was prepared on a surface-modified carbon cloth by a simple two-step hydrothermal process. In this process, CoAl-LDH nanosheets (NSs)/CC acting as the inner core were wrapped up in NiCo-LDH nanoneedle arrays (NNAs) evenly. Also, a flexible quasi-solid-state supercapacitor device was constructed using CoAl-LDH@NiCo-LDH/CC and activated carbon (AC) as a positive electrode and a negative electrode, respectively. FindingsThe CoAl-LDH@NiCo-LDH/CC developed had an excellent specific capacitance (2633.6F/g at 1 A/g) with remarkable cyclic performance (92.5% retention of its incipient over 5000 cycles at 4 A/g). The flexible quasi-solid-state supercapacitor device CoAl-LDH@NiCo-LDH/CC//AC/CC yielded a splendid energy density of 57.8 Wh/kg at a power density of 0.81 kW/kg and a brilliant power density of 16.09 kW/kg at 38.0 Wh/kg in a broad potential window of 1.55 V. Furthermore, the exceptional cyclic stability and excellent flexibility of the device show it can be applied in flexible energy storage systems.

Co3O4 Nanoneedle Array Grown on Carbon Fiber Paper for Air Cathodes towards Flexible and Rechargeable Zn-Air Batteries.

An economical and efficient method is developed for preparing flexible cathodes. In this work, a dense mesoporous Co3O4 layer was first hydrothermally grown in situ on the surface of chopped carbon fibers (CFs), and then carbon fiber paper (Co3O4/CP) was prepared by a wet papermaking process as a flexible zinc-air battery (ZAB). The high-performance air cathode utilizes the high specific surface area of a single chopped carbon fiber, which is conducive to the deposition and adhesion of the Co3O4 layer. Through the wet papermaking process, Co3O4/CP has ultra-thin, high mechanical stability and excellent electrical conductivity. In addition, the assembled ZAB exhibits relatively excellent electrochemical performance, with a continuous cycle of more than 180 times at a current density of 2 mA·cm−2. The zinc-air battery can maintain a close fit and work stably and efficiently even under high bending conditions. This process of combining single carbon fibers to prepare ultra-thin, high-density, high-conductivity carbon fiber paper through a papermaking process has huge application potential in the field of flexible wearables.

High-performance asymmetric supercapacitor based on urchin-like cobalt manganese oxide nanoneedles and biomass-derived carbon nanosheet electrode materials

A novel high-performance asymmetric supercapacitor (ASC) has been fabricated based on the cobalt manganese oxide (Co2Mn3O8) nanoneedles as a positive electrode and the hibiscus fruits-based carbon nanosheet (HBFC) as a negative electrode. The Co2Mn3O8 nanoneedles are synthesized by employing a one-step hydrothermal procedure using nickel foam as a support framework for the nanoneedle growth. The Co2Mn3O8 sample shows a distinct urchin-like morphology structure consisting of uniform nanoneedle arrays. The HBFC is prepared by chemical activation of the hibiscus fruits biomass carbon precursor using NH4Cl and KOH activation reagents. The as-prepared Co2Mn3O8 nanoneedles exhibited the highest specific capacity of 238 mAh g−1 at a current density of 1 A g−1. Moreover, the novel Co2Mn3O8//HBFC ASC device assembled based on those electrode materials at a maximum operating potential of 1.7 V shows an excellent energy density of 24.3 Wh kg−1 at a power density of 850 W kg−1. Besides, long-term cycling stability of 91.7% capacitance retention after 10,000 cycles in 2 M KOH electrolyte.

Anti-reflection effect of large-area ZnO nano-needle array on multi-crystalline silicon solar cells

The current diamond-wire-sawed multi-crystalline silicon wafer lacks an effective light trapping structure, which results in high reflectivity and hinders the improvement of efficiency. In this work, we proposed an enhanced light trapping structure outside the junction of multi-crystalline silicon solar cells, that is, constructing a ZnO nano-needle array on the surface of the textured multi-crystalline silicon to minimize the reflection in the visible-near infrared band to achieve light trapping effect. Solar cells with ZnO nano-needle structure exhibit excellent light trapping performance over a wide band (350–1100 nm). The low-cost and simple preparation method makes this enhanced light trapping structure has broad application prospects.

In-Situ derived Co1-xS@nitrogen-doped carbon nanoneedle array as a bifunctional electrocatalyst for flexible Zinc-air battery

• Co 1-x S@NC is prepared via a facile “CBD deposition-PDA coating-sulfurization” method. • The excellent OER and ORR electrocatalytic activities both mainly derive from Co 1-x S. • The 3D array structure of Co 1-x S@NC facilitates OER/ORR-related charge-and-mass transport. • There is wrapping-protection of NC on Co 1-x S and strong electron coupling between them. • Promising quasi-solid-state rechargeable Zn-air battery based on Co 1-x S@NC is achieved. It is of great significance to develop high-performance bifunctional electrocatalysts for catalyzing two vital reactions in rechargeable zinc-air battery (ZAB). Transitional metal sulfides and N-doped carbon materials are widely reported as effective electrocatalysts of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), respectively. Herein, an 3D-array-structured catalyst composed of Co 1-x S nanoneedles enwrapped by nitrogen-doped carbon (NC) is in-situ grown on carbon fibre paper substrate. It is revealed that the metastable hexagonal Co 1-x S itself possesses attractive electrocatalytic activities toward both OER and ORR. Additionally, owing to the wrapping-protection effect of polydopamine-derived NC on Co 1-x S, the strong electron coupling between Co 1-x S and NC, and the 3D array structure, Co 1-x S@NC presents excellent OER/ORR catalytic activities and long-term stabilities, superior to Co@NC, Co 1-x S, and NC, and comparable to noble metals and other reported state-of-the-art bifunctional oxygen electrocatalysts. A small energy gap (Δ E ) of 0.66 V between the ORR half-wave potential (0.86 V vs RHE) and OER potential (1.52 V vs RHE) at a current density of 10 mA cm −2 , and a diffusion-limit ORR current density of 11.37 mA cm −2 are achieved. Notably, the flexible ZAB using the catalyst exhibits a markedly higher peak power density of 242 mW cm 2 , and a small charge/discharge voltage gap of ∼ 0.68 V with a high round-trip efficiency of ∼ 64% when cycling at 5 mA/cm 2 .

ZIF-67 grown on a fibrous substrate via a sacrificial template method for efficient PM2.5 capture and enhanced antibacterial performance

In the design air filtration materials, surface modification and porosity control are appealing strategies to achieve a higher quality factor. In this study, a sacrificial template method was introduced to obtain hierarchically metal–organic framework (MOF)-loaded micro/nano-backbone fibrous filters. Cobalt carbonate hydroxide hydrate nanoneedle arrays were first grown on polyester fabric as a sacrificial template that provide Co2+ source for constructing a ZIF-67 on micro/nano fibrous backbone substrate, which resulted in a combination of enokitake-like and bead-on-string-like structure simultaneously. This unique structure effectively reduced the pore size of the fabric and provided a modified surface with a maximum exposure of MOFs. As a consequence, the composite fabric filter exhibited excellent PM2.5 removal efficiency of 97.5 ± 1.2%, while with only a small increase in pressure drop (∼14 Pa). Particularly, the PM2.5 filtration quality factor was up to 0.051, which is 200% higher than that of pristine PET. Furthermore, the composite fabric filter showed excellent antibacterial activity against both S. aureus and E. coli. This study facilitated the design of hierarchically MOF-loaded fibrous filter materials with excellent comprehensive filtration performance.

Template-assisted interfacial self-assembly of amphiphilic poly(ethylene oxide)–poly(propylene oxide)-based triblock copolymers for automatic control of molecular alignment

Hierarchical self-assembled nanoarchitectures based on peculiar self-assembly of block copolymers are advantageous for the nanofabrication of functionally versatile materials with a wide range of potential applications from bioelectronic devices to flexible displays. Herein, we developed a simple yet efficient, cost-effective, scalable strategy for the fabrication of an ultrafast responsive and highly reliable self-constructed polymer nanolayer for automatic control of molecular alignment by using the template-assisted interfacial self-assembly of amphiphilic poly(ethylene oxide)–poly(propylene oxide)-based triblock copolymers. A new type of ultrathin polymer nanolayer was facilely fabricated on polar electrode surface using simple doping in liquid crystal (LC) medium and in situ interfacial self-assembly of a small amount of amphiphilic triblock copolymers in the closed LC cell. A hydrophobic and ultrathin polymer nanolayer with dense nanoneedle arrays formed by interfacial hydrogen bonding between hydrophilic poly(ethylene oxide) block and hydrophilic indium tin oxide electrode induces a spontaneous homeotropic alignment of LCs during programmed self-assembly process. Moreover, this facile approach endows the polymer nanolayer with ultrafast electro-optical switching and high molecular alignment force characteristics, as well as an excellent alignment stability during long-term operation. Compared to commercial polyimide layer, our polymer nanolayer accomplishes the ultrafast falling response time with an improvement of 55.3% and fast rising response time with a reduction of 36.4%.

S doped Cu2O-CuO nanoneedles array: Free standing oxygen evolution electrode with high efficiency and corrosion resistance for seawater splitting

Electrochemical splitting of seawater is highly preferable over freshwater electrolysis to produce sustainable hydrogen terrifically due to its abundance in nature. Seawater electrolysis is encouraging to produce green hydrogen and safe drinking water. The accomplishment of seawater electrolysis needs robust and cost-effective anode material that should acquire an excellent catalytic activity, durability, and selectivity for OER and have high resistance against Cl- corrosion. Here we report a free-standing anode consisting of partially amorphous sulfur substituted copper oxide (S-Cu2O-CuO) nanoneedles directly grow on Cu foil. Benefiting from high electrical conductivity, plentiful active sites, high intrinsic activity per active site, and fast rate for ionic and electronic transfer, these disorders nanoneedles structured S-Cu2O-CuO demonstrate outstanding OER performance needing an overpotential of 450 mV to attain a high geometric activity (1000 mA cm−2) in 1 M KOH. Its disordered surface structure and amorphous features lead to improved corrosion resistance and durability, making it a prospective anode for direct seawater electrolysis. It requires an overpotential of 420 mV to achieve a geometric activity of 500 mA cm−2 in alkaline seawater and sustain water electrolysis for 100 h without making hypochlorite. Because of the facile, scalable, and economical approach, the catalyst is highly promising for large-scale realistic alkaline seawater electrolysis.

NiO-Coated CuCo2O4 Nanoneedle Arrays on Carbon Cloth for Non-enzymatic Glucose Sensing

Transition-metal oxide nanocomposites with a core–shell structure exhibit excellent catalytic performance because of their large surface area and the synergetic effect resulting from their special structures. In this work, a two-step hydrothermal method was used to synthesize hierarchical CuCo2O4/NiO core–shell nanoneedle arrays (NNAs) on conductive carbon cloth (CC) as a self-supported electrode. The morphology and structure of CuCo2O4/NiO NNAs/CC were studied in detail by various microscopes and spectroscopes. The synthesized CuCo2O4/NiO NNAs exhibited excellent electrocatalytic properties toward glucose oxidation due to the hierarchical core–shell structure and the resulting synergetic effect. Therefore, CuCo2O4/NiO NNAs/CC showed excellent characteristics for glucose determination with high sensitivity (4140 μA mM–1 cm–2), broad linear range (0.5–6000 μM), and outstanding selectivity and stability. Moreover, the proposed sensor was evaluated to determine glucose in human serum samples with satisfactory recovery, indicating its potential practical application in quantitative analysis of blood glucose levels.

Needle-like Co3O4 nanoarrays as a dual-responsive amperometric sensor for enzyme-free detection of glucose and phosphate anion

The high cost and easy denaturation of natural enzymes under environmental conditions largely hinder their practical usefulness in sensing devices. Currently, great efforts have been focused on exploring of novel functional nanomaterials to replace natural enzymatic systems. In this study, we developed a hydrothermal growth of free-standing cobalt oxide (Co3O4) nanoneedle arrays on a flexible carbon cloth (CC) substrate and used them as electrode materials with a high catalytic activity for nonenzymatic glucose sensing. Benefiting from the densely arrayed and free-standing Co3O4 nanoneedles with a large surface area, the resulting Co3O4/CC electrode exhibits an excellent sensing performance for glucose with a broad linear range and low detection limit (0.23 μM). More importantly, the Co3O4/CC electrode also exhibited a good performance for determining phosphate ions in a glucose containing alkaline solution. Under optimal condition, the resulted electrode exhibits a linear range of 0.1–1.0 mM and 1.0–30.0 mM with a detection limit of 10 μM for phosphate anion. The as-proposed electrode was further used for the determination of glucose and phosphate ions in human blood serum and urine samples with satisfactory recoveries, verifying the feasibility and great potential as a sensitive, selective, potable, and low-cost electrochemical electrode in sensing application.

Polymeric Nanoneedle Arrays Mediate Stiffness‐Independent Intracellular Delivery

AbstractTunable vertically aligned nanostructures, usually fabricated using inorganic materials, are powerful nanoscale tools for advanced cellular manipulation. However, nanoscale precision typically requires advanced nanofabrication machinery and involves high manufacturing costs. By contrast, polymeric nanoneedles (NNs) of precise geometry can be produced by replica molding or nanoimprint lithography—rapid, simple, and cost‐effective. Here, cytocompatible polymeric arrays of NNs are engineered with identical topographies but differing stiffness, using polystyrene (PS), SU8, and polydimethylsiloxane (PDMS). By interfacing the polymeric NN arrays with adherent and suspension mammalian cells, and comparing the cellular responses of each of the three polymeric substrates, the influence of substrate stiffness from topography on cell behavior is decoupled. Notably, the ability of PS, SU8, and PDMS NNs is demonstrated to facilitate mRNA delivery to GPE86 cells with 26.8% ± 3.5%, 33.2% ± 7.4%, and 30.1% ± 4.1% average transfection efficiencies, respectively. Electron microscopy reveals the intricacy of the cell–NN interactions; and immunofluorescence imaging demonstrates that enhanced endocytosis is one of the mechanisms of PS NN‐mediated intracellular delivery, involving the endocytic proteins caveolin‐1 and clathrin heavy chain. The results provide insights into the interfacial interactions between cells and polymeric NNs, and their related intracellular delivery mechanisms.

Fabrication of Diamond Nanoneedle Arrays Containing High‐Brightness Silicon‐Vacancy Centers

AbstractThe optically active silicon‐vacancy (SiV) center in diamonds is an excellent candidate for quantum photonics and sensing applications. To date, optimizing the photoluminescence (PL) collection efficiency of SiV centers has proven difficult. To address this issue, the current study presents a simple two‐step method for preparing single‐crystalline diamond nanoneedle arrays. In the first step, silicon‐doped (001) textured diamond films are deposited with a mixture of microcrystalline and nanocrystalline grains in a microwave plasma CVD (MPCVD) system, using tetramethylsilane (TMS) gas as the dopant source. Subsequently, air annealing is used to selectively etch nanocrystalline diamond and sp2 amorphous carbon phases, while retaining the [001]‐oriented diamond nanoneedles with a curved top surface. In comparison to the as‐deposited films, the PL emission of SiV centers in these diamond nanoneedles is enhanced by a factor of up to 12.1. The finite‐difference time‐domain simulations further demonstrate that removing the nanocrystalline diamond and sp2 carbon from the sidewall of the diamond nanoneedles results in a remarkable increase in photoluminescence collection. Therefore, the findings have established for the first time the constraint effect of sp2 carbon on the optical collection of color centers at the sidewall rather than the top surface.