Core Shell Nanorod Arrays Research Articles

ZnS@Fe2O3 core–shell nanorod arrays for supercapattery applications; theoretical evaluation of faradic and non-faradic behavior using Dunn’s model

Supercapattery has emerged as an ideal energy storage device that has the features of both batteries and supercapacitors. In this work, ZnS@Fe2O3 core–shell nanorod arrays supported on Ti foil have been prepared by the cost-effective, efficient, and facile two-step hydrothermal method and investigated for high performance supercapattery applications. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirm the successful synthesis of the material, while the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images clearly show the successful deposition of the Fe2O3 shell over the ZnS core. Electrochemical characterizations including cyclic voltammetry, galvanostatic charge discharge and electrochemical impedence spectroscopy have been employed to investigate the electroactive nature of the materials. It is found that the ZnS@Fe2O3 exhibits excellent specific capacitance of 681 Fg−1 at 1 Ag−1 current density within the potential window of −0.2 to 0.75 V while demonstrating a significant capacitance retention of 85 % and 95 % coulombic efficiency over 2000 cycles. The contribution of faradic and non-faradic processes during electrochemical reactions is evaluated using Dunn’s model. The diffusion controlled mechanism is greater than the surface controlled mechanism in the synthesized material, which depicts the battery grade nature. Interestingly, the electrode was able to exhibit an excellent energy density of 86 Whkg−1 and a maximum power density of 4232 Wkg−1, which is significantly higher than the previously reported ZnS based and Fe2O3 based composites. A Supercapattery device has been assembled using ZnS@Fe2O3 as anode and reduced grapheme oxide (rGO) as cathode, which demonstrate a specific capacitance of 165 Fg−1 at 1 Ag−1 current density, exhibiting 66 Whkg−1 at power density of 3895 Wkg−1 with excellent retention in specific capacitance and coulombic efficiency at 15 Ag−1 after 3000 cycles.

Design and performance evaluation of hierarchical ZnCo2S4@PANI core-shell nanorod arrays for high-efficiency supercapacitor applications

Ternary transition metal sulfides (TMS) have gained significant attention due to their excellent energy and power density as Faradaic electrode materials to be utilized in supercapacitors (SCs). Among various conducting polymers, polyaniline (PANI) has rapidly evolved as a valuable pseudo-capacitor material. Though it deprived cycling stability due to instability in structural transformation, which is the major obstacle to its practical level utilization in energy related applications. Herein, the synthesis of an efficient and reliable ZnCo2S4@PANI nonorod arrays (NRAs) anode with structure-to-performance hierarchical morphology is designed to achieve excellent performance. Heterostructured, extremely porous ZnCo2S4 nanorods have acted as a conductive core, which has provided the strain-buffer-support, along with nanoscaled PANI layer to act as an electrochemical active counterpart, and has demonstrated outstanding specific capacitance while retaining the remarkable cyclic performance and rate capability. Implementing the perfectly uniform and compactly coated PANI, the synthesized anode has demonstrated a high specific capacitance of ∼815 F g−1 at a current density of 1 A g−1 and exceptional ∼91 % capacitance retention even after 4000 cycles at high 2 A g−1 current density. Such outcomes are much superior to the most reported electrochemical performances of PANI-related pseudo-capacitors in the literature. The enhanced electrochemical properties of the as synthesized ZnCo2S4@PANI NRAs anode demonstrate the ability of the stable componential structure as a hybrid electrode design to provide a new direction for researchers to utilize such porous framework as an operative support for proficient energy storage devices.

Novel hierarchical core-shell NiCo2S4@NiWO4 nanowire arrays for high performance pseudocapacitor

In this paper, a novel NiCo2S4@NiWO4 honeycomb core-shell nanorod array significantly improved the electrochemical storage properties of supercapacitors. The characteristic architecture of the NiCo2S4@NiWO4 electrode showed a remarkable specific capacity of 1273.5 C g−1 at a current density of 1 A g−1. The asymmetric supercapacitor (ACS) had a high specific capacitance of 1502.4 C g−1 at a current density of 1 A g−1 as well as excellent cycling stability at a current density of 10 A g−1 (101.25 % cycling retention rate after 10,000 cycles), and an energy density of 334 Wh kg−1 with a power density of 2.38 kW kg−1. The research emphasized that a strong electronic coupling effect was observed at the interface of NiCo2S4 and NiWO4 and electron transfer from Ni-W-O to Ni-Co-S occurred around the interface, which further improved the electron transfer properties of electrode materials and hit the mark extends the life of the electrode and significantly improves the performance of energy storage systems.

Oxygen vacancy-regulated nanorod array electrodes for boosting the electrocatalytic synthesis of ammonia from nitrate wastewater.

The adsorption of nitrate is the key to enhancing the electrocatalytic nitrate reduction reaction (NitRR). Herein, a typical hydrolysis-coupled redox (HCR) reaction has been designed to prepare unique 3D Cu/Fe2O3 core-shell nanorod array cathodes with controllable oxygen vacancy concentrations for NitRR. The optimal Cu/Fe2O3-13 achieves a high nitrate conversion of 99.10% and ammonia selectivity of 98.30%. The outstanding electrochemical performance is attributed to the enhancement mechanism of OVs and a unique nanorod array structure with a high density of surface-exposed OVs and high-throughput transport pathways for ion-aspects.

Work-function-induced interfacial built-in electric field optimized electronic structure of V-CoSx@NiTe as high capacity and robust electrode for supercapacitors

The pursuit of achieving high energy density and exceptional stability in supercapacitors presents both allure and challenge. Herein, we strategically engineered hierarchical V-CoSx@NiTe core-shell heterojunction nanorod arrays, with V-doped amorphous CoSx nanosheets as the shell and one-dimensional (1D) NiTe nanorods as the core on nickel foam (NF). Theoretical computations elucidated the disparate intrinsic work functions of V-CoSx and NiTe, culminating in a robust built-in electric field at the interface. This field orchestrated interfacial charge distribution, expediting electron transport and optimizing OH– adsorption. V doping enhanced electronic states density at the Fermi energy level of CoSx and introduced new reaction sites. Additionally, the good hydrophilic properties and unique hierarchical core-shell morphology of the amorphous V-CoSx@NiTe/NF electrodes were favorable for increasing the specific surface area, improving the structural stability and facilitating the diffusion of OH–. Consequently, V-CoSx@NiTe/NF attained an impressive areal capacitance of 10.52 F cm−2 at 2 mA cm−2, preserving energy storage performance, morphology, and composition across 15,000 cycles. An asymmetric supercapacitor (ASC) device constructed with V-CoSx@NiTe/NF as the positive electrode and commercial activated carbon (AC) as the negative electrode exhibited energy (power) density of 0.42 mWh cm−2 (1.63 mW cm−2), and maintained ∼100 % capacity after 10,000 cycles. Significantly, a single device powered both a fan and a light bulb, while two devices in series illuminated a blue light-emitting diode (LED) for up to 2 h. This investigation introduces an innovative strategy for designing high-performance supercapacitor anode materials.

Enhancing the performance of Self-Powered Deep-Ultraviolet photoelectrochemical photodetectors by constructing α-Ga2O3@a-Al2O3 Core-Shell nanorod arrays for Solar-Blind imaging

With the advancement of Ga2O3-based deep-ultraviolet (DUV) photodetectors (PDs), the integration of PDs into array image sensors has become a sought-after objective. However, while solar-blind imaging research primarily revolves around solid-state Ga2O3-based PDs, there remains a significant gap in the exploration of novel photoelectrochemical (PEC) PDs for solar-blind imaging applications. In this study, self-powered solar-blind PEC-PDs with enhanced performance are fabricated based on α-Ga2O3@a-Al2O3 core–shell nanorod arrays (NRAs). Under DUV irradiation and without external bias, the α-Ga2O3@a-Al2O3 devices demonstrate remarkable superiority over α-Ga2O3 devices. When the light intensity was at 0.50 mW cm−2, the photocurrent density notably rises from 4.60 to 11.24 μA cm−2, accompanied by a corresponding increase in responsivity from 9.60 to 22.70 mA W−1. The enhanced performance is attributed to the α-Ga2O3@a-Al2O3 heterostructure, which establishes a built-in electric field facilitating the separation and directed transport of photogenerated carriers at the interface. Moreover, for the first time, a 5 × 5 matrix of α-Ga2O3@a-Al2O3 core–shell NRAs-based PEC-type PDs is employed to demonstrate a proof-of-concept for self-powered solar-blind imaging, capable of effectively capturing the shapes of the letters “C” and “N”. This work underscores the immense potential of Ga2O3-based PEC-type PDs for future large-area solar-blind imaging applications.

Self-Powered Wavelength-Dependent Dual-Polarity Response Photodetector Based on CdS@PEDOT:PSS@Au Sandwich-Structured Core-Shell Nanorod Arrays.

Self-powered operation and multifunctionality have significantly oriented the development of photodetectors (PDs), which could be realized through nanoarchitecture construction and energy band structure design. Herein, a self-powered wavelength-dependent dual-polarity response PD based on (CdS@PEDOT:PSS@Au) sandwich-structured core-shell nanorod arrays (NRAs) is proposed. The synthesis approach of this three-layer heterostructure consists of a hydrothermal reaction, spin coating, and thermal evaporation. The n-CdS/p-PEDOT:PSS junction and the PEDOT:PSS/Au Schottky junction at the interfaces provide two photocurrent driving forces in opposite directions, and their contribution to the net photocurrent is controlled by the incident light wavelength due to the different light absorption ranges of the CdS core and the PEDOT:PSS shell. As a result, the polarity of the photocurrent switches from negative to positive as the wavelength increases. In addition, the response speed of negative photocurrents (∼10 ms) is faster than that of positive photocurrents (∼100 ms), which is consistent with the underlying mechanism of the dual-polarity response. Furthermore, color discrimination and imaging capabilities are demonstrated by deploying the PDs as sensing pixels and recognizing green and red patterns. The sandwich-structured core-shell NRA heterojunction system introduces a novel idea for dual-polarity response PDs.

Construction of CdS@ZnO core–shell nanorod arrays by atomic layer deposition for efficient photoelectrochemical H2 evolution

Photoelectrochemical (PEC) water splitting provides a promising strategy for the production of clean hydrogen fuel. Herein, a new CdS@ZnO core–shell nanorod arrays (NRAs) is successfully constructed by atomic layer deposition (ALD) for H2 evolution from PEC water splitting. The CdS@ZnO200 obtained after 200 ALD cycles presents a significantly enhanced PEC H2 evolution rate of 21.64 μmol·h−1·cm−2, which is about 9.4 times of pristine CdS NRAs (2.31 μmol·h−1·cm−2). The reasons for the improved PEC H2 evolution performance can be ascribed to several aspects: firstly, the Z-scheme charge transfer mechanism formed between CdS core and ZnO shell promotes the effective spatial separation of photo-induced electrons and holes; secondly, the close contact between the two semiconductors resulted from ALD process helps to reduce the transfer resistance of charge carriers. In addition, the CdS core is tightly wrapped by ZnO shell, which helps to prevent the photo-corrosion of CdS core. This work provides a new type of photoanode material suitable for PEC H2 evolution from water splitting, and provides an efficient anti-corrosion method for the use of photocorrosive semiconductor materials.

Robust and hydrophilic Mo-NiS@NiTe core-shell heterostructure nanorod arrays for efficient hydrogen evolution reaction in alkaline freshwater and seawater

Typically, the direct electrolysis of alkaline seawater for hydrogen production is very attractive, but it poses challenges due to the high energy barrier and slow reaction kinetics of the hydrogen evolution reaction (HER) in alkaline environments. The key to promising solutions lies in the design and development of non-precious metal catalysts with abundant reaction sites, robust stability, and resistance to Cl− corrosion. Hence, we demonstrated the fabrication of Mo-NiS@NiTe core–shell heterogeneous nanorods supported on nickel foam (Mo-NiS@NiTe/NF). These hydrophilic self-supporting nanorod arrays, functioning as binder-free HER electrocatalysts, provide numerous reactive sites and facilitate electron/mass transfer. The conductive core of NiTe promotes rapid electron transfer from NF substrate to NiS. The coupling interface with the heteroatom Mo synergistically modulates the electronic structure of the NiS shell, optimizing the adsorption/dissociation of H2O and improving the reaction kinetics. As a result, Mo-NiS@NiTe/NF exhibits excellent HER performance and outstanding long-term stability, requiring only 34 and 57 mV of overpotential to achieve a current density of 10 mA cm−2 in 1.0 M KOH and alkaline seawater, respectively. Additionally, it exhibits a Faraday efficiency of nearly 100% for hydrogen production and excellent long-cycle stability. Notably, the Mo-NiS@NiTe(−)||RuO2(+) couples outperform Pt/C(−)||RuO2(+) couples and exhibit excellent stability.

CdS@Ni3S2/Cu2S electrode for electrocatalysis and boosted photo-assisted electrocatalysis hydrogen production

Photo-assisted electrocatalysis (PA-EC) water splitting technology, which combines photocatalysis and electrocatalysis, has gradually become a research hotspot in the production of green hydrogen energy. Herein, for the first time, novel Cu/Ni alloy foam self-supporting CdS@Ni3S2/Cu2S core–shell nanorod arrays are prepared by a simple one-pot hydrothermal process. The CdS@Ni3S2/Cu2S exhibits both excellent electrocatalytic and photo-assisted electrocatalytic water splitting performance. During the long-time PA-EC water splitting test, the average H2 production rate reaches 568.1 μmol cm-2h−1, which is about 1.8 times higher than that of 284.1 μmol cm-2h−1 under dark condition. In addition, the electrical-to-hydrogen (ηETH) and solar-to-hydrogen (ηSTH) conversion efficiency reaches to be 97% and 8.9%, respectively. Mechanism investigation results show that during EC water splitting process, CdS nanorods mainly play as support material for the electroactive Ni3S2 and Cu2S. While, in the PA-EC process, CdS, Cu2S and Ni3S2 were photoexcited by light irradiation, and just as the presence of additional photogenerated electrons and holes, CdS@Ni3S2/Cu2S exhibits boosted photo-assisted water splitting properties. This work provides a new strategy for the construction of bifunctional photocatalysts combined with electrocatalysts in photo-assisted electrocatalysis overall water splitting.

Au-doped ZnO@ZIF-7 core-shell nanorod arrays for highly sensitive and selective NO2 detection

The exploration of novel NO2 sensors with high performance is of great importance for air quality monitoring and human health. In this work, Au-doped ZnO@ZIF-7 core-shell nanorod arrays were fabricated for high-performance NO2 detection. Due to the spill-over effects of Au nanoparticles, gas enriching and molecular sieving effects provided by ZIF-7 membranes, the ZnO-Au@ZIF-7 sensor affords highly sensitive and selective detection of NO2. The heterostructured ZnO-Au@ZIF-7 allows for ppb-level detection of NO2 (Response = 1.7–5 ppb) with excellent repeatability and provides improved selectivity, anti-humidity capacity, and long-term stability compared with bare ZnO, Au-doped ZnO or ZnO@ZIF-7 core-shell nanorod arrays. According to the calculation of density functional theory (DFT), the ZnO-Au@ZIF-7 sensor renders higher adsorption energy towards NO2 molecules compared with the aforementioned other materials, which also explains its outstanding sensing performances. We believe our approach that combines noble metals doped semiconductor metal oxides (SMOs) and MOF filtration membranes can be further extended to numerous new heterostructured SMO@MOF materials, which opens venues to the development of advanced chemiresistive gas sensors.

Regulated self-powered photoresponse properties and irradiance-adaptable behavior in ferroelectric SrTiO3/TiO2 heterojunction photodetectors

SrTiO3/TiO2 core–shell nanorod arrays were synthesized using a simple two-step hydrothermal method, and a self-powered irradiation-adaptive photodetector controlled by a ferroelectric depolarization field was designed.

Three-dimensional NiMoO4@CoWO4 core–shell nanorod arrays for electrochemical energy storage applications

We synthesized NiMoO4@CoWO4 with CoWO4 wrapped up NiMoO4 nanorods to form NiMoO4@CoWO4 core–shell nanorod arrays on Ni foam, which exhibited high specific capacitance and excellent electrochemical stability.

Surface Engineering of Ni wires and Rapid Growth Strategy of Ni-MOF Synergistically Contribute to High-Performance Fiber-Shaped Aqueous Battery.

The fiber-shaped aqueous battery (FSAB) has the advantages of flexibility, portability and safety making it promising for energy storage applications. In particular, FSABs based on metal wire current collectors with good electrical conductivity can provide excellent energy storage properties. However, the low adhesion caused by the smooth surface of the metal wire and the unavailability of many electrochemically active materials for use in FSAB is holding back their development. Herein, a substrate is effectively constructed for the strongly applicable growth of the active material via a Ni wire etching strategy. In addition, core-shell structured nanorod arrays consisting of NiCo2 O4 and Ni-metal-organic frameworks (MOFs) are constructed, where Ni-MOF can be obtained rapidly via β-Ni(OH)2 intermediates. The NCO/NM-15 electrode obtained by structural regulation exhibits high capacity and outstanding cycling stability. De calculations further demonstrate that the formation of NiCo2 O4 and Ni-MOF heterostructures results in a significant increase in the Fermi level leading to more active internal electrons, which facilitates electron transfer in electrochemical reactions. An assembled FSAB device can provide an energy density of 158.33µWhcm-2 and the devices can provide power for a calculator and an electronic watch screen, demonstrating a wide application prospect in the field of energy storage.

Enhanced performance of self-powered ultraviolet photodetectors coupled with the photovoltaic-pyroelectric effect based on ZnO/CuBO2 core-shell nanorod arrays

An innovative self-powered ultraviolet photodetector based on ZnO/CuBO 2 core-shell nanorod arrays was fabricated using cost-efficient and scalable preparation technologies, including a chemical hydrothermal method and an impregnation technique. The ZnO/CuBO 2 core-shell heterostructure exhibits significant diode behavior with a rectification ratio approaching 7016 at± 1 V because of the type-II band alignment formed at the heterojunction interface, acquiring a maximum responsivity of 165 mA /W1 with an external quantum efficiency of 55.3% (370 nm, 65 mW cm −2 ) and specific detectivity (4.13 ×10 12 cm Hz 1/2 W −1 ) under zero bias. Simultaneously, by applying an external bias to adjust the photovoltaic and pyroelectric effects and delving into the operating mechanisms, the photodetector based on the ZnO/CuBO 2 heterostructure achieves enhanced performance. The decay time has been shortened, and the responsivity has reached up to 38.82 A W −1 (apparent quantum efficiency ~ 13,010%) at − 2.5 V. Moreover, the effects of the power density on the photocurrent response and temperature induced by the photovoltaic-pyroelectric effect are discussed. This study reveals the potential of CuBO 2 (one of the Cu-delafossite families) as a hole transport layer in optoelectronic devices, broadens the application prospects of core-shell nanorod arrays based on the photovoltaic-pyroelectric effect, and provides a direction for modulating the performance of such devices. • CuBO 2 , as a p-type layer of copper delafossite, was firstly used to covered ZnO nanorods forming a core-shell structure. • The facile, convenient and low-cost processes were demonstrated to fabricate original self-powered ZnO NRs/CuBO 2 core-shell heterojunctions. • The performance of the photodetector has been enhanced by modulating photovoltaic and pyroelectric effects. • The curves of output current I pyr+pho , proportion of I pyr and temperature varying with the incident light power densities were fitted with the power-law I&T = AP α . • Significant excellent performance, e.g., R=165 mA W −1 @0 V, 38.82 A W −1 @-2.5 V (370 nm, 65 mW cm −2 ), D* λ =4.13×10 12 cm Hz 1/2 W −1 , RR=7016 at±1 V, was achieved for self-powered ultraviolet photodetectors with ZnO NRs/CuBO 2 core-shell sturcture.

Fabrication of a TiO2@Cu Core-Shell Nanorod Array as Coating for Titanium Substrate with Mechanical and Chemical Dual Antibacterial Property.

Titanium (Ti) is an excellent medical metal material, but the absence of good antibacterial property restricts its widespread application. To overcome this, we thus conducted a series of modifications for Ti. First, a titanium dioxide (TiO2) nanorod array was generated on the Ti surface by hydrothermal treatment (TiO2/Ti). With the polymer-mediated self-assembly method, a continuous copper (Cu) shell structure on the surface of the nanorod was then generated to form a TiO2@Cu core-shell nanorod array as coating for Ti (TiO2@Cu/Ti). Using pure Ti as the control group, the antibacterial properties of TiO2/Ti and TiO2@Cu/Ti were appraised. The results manifested that the mechanical and chemical dual function of the released Cu2+ and TiO2 nanorod array could effectively kill bacteria on the surface of Ti. Besides, the obtained coating exhibited no cytotoxicity and favorable biocompatibility. In this work, we found an antibacterial strategy based on multiple sterilization pathways, which made Ti have good antibacterial property and further improved its biocompatibility.

Construction of TiO2@C@Prussian Blue core-shell nanorod arrays for enhanced electrochromic switching speed and cycle stability

In this study, a novel TiO2@[email protected] Blue core-shell nanorod arrays film was constructed through two-step hydrothermal and electrodeposition methods. Such a designed structure could increase the specific surface area, reactive site, and conductivity of Prussian Blue (PB) and reduce the diffusion distance of ions due to the nano-architecture arrays of TiO2 and the high conductivity of the carbon layer, thus leading to the remarkably improved storage capacity and reaction speed of ions during the electrochromic (EC) process of PB. Moreover, porous morphology and strong adhesion on the FTO substrate of the TiO2 nanorod arrays could alleviate the lattice stress and volume expansion and enhance the binding force, thus improving the cycle stability of EC. Given these benefits, the TiO2@[email protected] films display a large optical modulation range (67%), fast switching speed (tc/tb = 1.25 s/2.71 s), and high coloration efficiency (129.4 cm2/C). In particular, the EC cycle stability is remarkably improved (96.3% after 5000 cycles), implying a promising application in high-performance EC devices (ECDs).

Nano-assembly hierarchical Fe–Ni–Se/Cu(OH)2 with induced interface engineering as highly efficient electrocatalyst for oxygen evolution reaction

Developing novel electrocatalysts with both high efficiency and low cost are highly imperative for the oxygen evolution reaction (OER). In this work, the hierarchical Fe-Ni-Se/Cu(OH)2/CF with core-shell structural nanorod arrays were fabricated via the facile electrodeposition treatment after the self-supported anodization of copper foam (CF). The as-prepared catalytic electrode presents prominent OER performance with the low overpotential of 272 mV at the current density of 100 mA cm−2 and behaves the impressive durability for almost 58 h, outperforming most of the previously reported electrocatalysts. The obtained excellent activity could be ascribed to the unique hierarchical structure composed of the Fe-Ni-Se shell with superb conductivity and the Cu(OH)2 nanorods core, which could establish the synergistic effect in the interface engineering and further increase electron transfer rate. Moreover, it is identified that the catalyst experienced the reconstruction of phases and microstructure during the OER operation. The produced oxygen vacancies and fluffy ultrathin nanosheets are beneficial to the reduction of reaction kinetics as well as the expose of active sites. Our study may pave the way to design noble-metal-free catalyst with rational structure and remarkable activity for water splitting in the future.

Effects of N Doping on Phase Transition and Visible-Light Photocatalytic Activity of ZnO/Zinc Titanate Core–Shell Nanorod Arrays

Effects of N Doping on Phase Transition and Visible-Light Photocatalytic Activity of ZnO/Zinc Titanate Core–Shell Nanorod Arrays

Morphology engineering of type-II heterojunction nanoarrays for improved sonophotocatalytic capability

Sonophotocatalysis is one of the most significant outcomes of the exploration of the interaction between piezoelectric field and charge carriers, which exhibits potential applications in dye degradation, water splitting, and sterilization. Although several heterojunction catalysts have been applied to improve the sonophotocatalytic capability, the importance of the morphology on the sonophotocatalytic capability has not been emphasized. In this study, brush-like ZnO nanorod arrays are synthesized on a stainless-steel mesh and subsequently vulcanized into ZnO/ZnS core–shell nanorod arrays to investigate the sonophotocatalytic capability of the heterojunction. The sonophotocatalytic capability increases from 25.1% to 45.4% through vulcanization. Afterward, the ZnO/ZnS nanorods are etched to ZnO/ZnS nanotubes without affecting the crystallography and distribution of the ZnS nanoparticle shell, further improving the capability to 63.3%. The improvement can be ascribed to the coupling effect of the enhanced piezoelectric field and the reduced migration distance, which suppresses the recombination of photoexcited electron–hole pairs while transforming the morphology from nanorod to nanotube, as proven by the electron spin resonance test and numerical simulations. This study explores a novel approach of morphology engineering for enhancing the sonophotocatalytic capability of heterojunction nanoarrays.