Nanograss Array Research Articles

In-situ synthesis of SnO2/CoFe2O4/Fe3O4 nanograss array composite: A redox-active electrode material for battery-type supercapacitors

Nanocomposites containing mixed transition metal oxides demonstrate significant promise as materials for supercapacitors, specifically due to their enhanced surface area, synergistic effect of multiple metal cations, excellent electrical conductivity, and improved electrochemical properties. In this study, we synthesized a nanocomposite with a nanograss array morphology consisting of SnO2/CoFe2O4/Fe3O4 using an in-situ sol-gel method. For comparison, we synthesized a composite (CoFe2O4/Fe3O4) without SnO2. Through a systematic characterization employing various analytical techniques, we examined the structural, morphological, and textural attributes of the resulting composites. The results reveal that the phase percentages of CoFe2O4, SnO2, and Fe3O4 were 38%, 33%, and 29% in the SnO2/CoFe2O4/Fe3O4 composite. Also, the nanograss array of SnO2/CoFe2O4/Fe3O4 is composed of nano-sized primary particles, while CoFe2O4/Fe3O4 showed spherical-like nanoparticle morphology. The BET surface area of the SnO2/CoFe2O4/Fe3O4 composite was found to be seven times higher than that of CoFe2O4/Fe3O4. We also evaluated the electrochemical performance of the SnO2/CoFe2O4/Fe3O4 composite as a cathode material for battery-type supercapacitors. The synergistic combination of SnO2 and CoFe2O4/Fe3O4 in the SnO2/CoFe2O4/Fe3O4 electrode resulted in a high specific capacity of 465C g−1 at 1 A g−1, which is 2.5 times higher than the CoFe2O4/Fe3O4 electrode. Additionally, the SnO2/CoFe2O4/Fe3O4 electrode exhibited a remarkable rate capability of 87% at 10 A g−1 and excellent cyclic performance with 96% capacity retention after 5000 cycles. A hybrid supercapacitor was fabricated, featuring a cathode composed of a composite electrode consisting of SnO2/CoFe2O4/Fe3O4 and an anode comprising activated carbon (AC). This fabricated SnO2/CoFe2O4/Fe3O4//AC HSC device configuration exhibited impressive performance characteristics, boasting a notable energy density of 38.4 Wh kg−1 at 1468.2 W kg−1. These findings underscore the significant impact of SnO2 on the physio/electrochemical properties of the CoFe2O4/Fe3O4 composite. The outstanding electrochemical performance of this electrode underscores its potential for application in next-generation hybrid supercapacitors.

Flexible TiO2 nanograss array film decorated with oxygen vacancies introduced by facile chemical reduction and their photocatalytic activity

Flexible TiO 2 nanograss array film was prepared by simple chemical oxidation of Ti wire mesh at a low temperature of 353 K. To improve its visible-light-driven photocatalytic activity, we further carried out a low-temperature chemical reduction to introduce oxygen vacancies in the solution of ethylene glycol (EG) and ammonium fluoride (NH4F). The results of XPS and EPR confirmed the formation of surface and bulk oxygen vacancies was confirmed, and their concentrations increased as the reduction time increased. Compared with the as-annealed TiO 2 film, the as-reduced specimens exhibited higher visible-light-driven photocatalytic activity. When reduction time was 48h, the photocatalytic activity was increased by 15.8 times compared to the as-annealed sample. The remarkable improvement in photocatalytic activity should be ascribed to the oxygen vacancies’ introduction. The most excellent photocatalytic performance was obtained when a suitable concentration ratio of surface oxygen vacancies to bulk oxygen vacancies was reached. Low-temperature chemical reduction in the solution of EG + NH4F is very efficient and convenient for introducing defects such as oxygen vacancies and Ti3+.

Flexible TiO2 nanograss array film decorated with BiOI nanoflakes and its greatly boosted photocatalytic activity

A flexible TiO2 nanograss array film on Ti wire mesh was prepared by a mild chemical reaction. To overcome its shortcoming of almost no absorption of visible light, successive ionic layer adsorption and reaction (SILAR) was executed to decorate the prepared TiO2 film with BiOI. The results of XRD and SEM measurements showed that BiOI nanoflakes formed on the surface of TiO2 film, and the loading amounts of BiOI nanoflakes increased with the increase in SILAR cycles. The XPS results confirmed the heterojunction formation of BiOI-TiO2. The photocurrent measurement suggests that a moderate loading amount of BiOI nanoflakes is beneficial to improve the charge separation efficiency, which is ascribed to the heterojunction formation of BiOI-TiO2. The BiOI-decorated TiO2 film with SILAR cycles of seven showed the most excellent visible-light photocatalytic activity among all the samples. Compared with the bareTiO2 nanograss array film, its visible-light photocatalytic activity increased by 11.7 times. The flexible BiOI-decorated TiO2 nanograss array film with high photocatalytic activity shows great applications in air pollution and the pollution caused by offshore oil spills.

Enhancement of the photocatalytic activity of N-doped TiO2 nanograss array films by low-temperature sulfur doping

Moderate in-situ chemical oxidation of Ti meshes was used to prepare nitrogen-doped (N-doped) anatase TiO2 nano-grass array films with urea as the nitrogen source. Further sulfur doping through immersion of the films in a thiourea solution at a relatively low temperature of 353 K was subsequently performed to enhance the visible-light-driven photocatalytic activity of the films. SEM images confirmed that the loose microstructure of the nanograss arrays became compact after N-doping or N, S co-doping. N-doping and N, S co-doping decreased the band gap values of the TiO2 films and increased the effective visible light utilization. XPS analysis revealed that nitrogen mainly existed in interstitial form. Subsequent sulfur ions appeared as S6+, S4+, and S2−, with S6+ and S4+ replacing Ti4+, and S2− replacing O2−, respectively. With an increase in the urea treatment time, the sulfur ions were oxidized, achieving higher valence states. S6+ substitution resulted in a charge imbalance, which could only be neutralized by hydroxide ions. The imbalance made it easier for water that had settled on the TiO2 films to chemically dissociate, and thereby generating hydroxyl radicals. OH• radicals as well as Ο2•−radicals played a significant role in the degradation of RhB dye. The RhB decolorization activity achieved by the N, S co-doped samples was 48 times that of the undoped samples.

Low-temperature S-doping on N-doped TiO2 films and remarkable enhancement on visible-light performance

Sulfur doping of nitrogen-doped TiO2 nanograss array films was realized through facile thiourea solution immersion at a low temperature of 353 K. Doped nitrogen and sulfur atoms were found mainly in the interstitial form. Nitrogen doping (N-doping) and sulfur doping (S-doping) enhanced visible light absorption and decreased the band gap of undoped TiO2 films from 3.10 to 3.01 and 2.81 eV, respectively. Furthermore, N-doped and N, S co-doping made the water absorbed on TiO2 was easier to chemically dissociate and generate hydroxide groups. N-doping favored to produce more O2•− radicals and S-doping benefit to generate more OH• radicals. Both OH• and O2•− active radicals played a significant role in the degradation of RhB. The photocatalytic activity of undoped TiO2 films was increased by 2.5 times by N-doping through urea treatment. By further S-doping, the photocatalytic performance of N-doped TiO2 films was enhanced by 4.0 times again.

Oriented CuCo2S4 nanograss arrays/Ni foam as an electrode for a high-performance all-solid-state supercapacitor

An oriented nanograss array consisting of CuCo2S4 nanocrystallines was directly prepared on Ni foam by a hydrothermal method. The uniform arrays with a single blade diameter of ∼100 nm and length of ∼4 μm can grow tightly on Ni foam without any binders. The ordered one-dimensional structure facilitates the electron transport to Ni substrates along the axial direction. The electrochemical properties were presented in three- and two-electrode configurations, demonstrating an enhanced specific capacitance and a long-term cycling stability. As a practical all-solid-state device, it achieved a high energy density of 31.88 W h kg−1 at a power density of 3.20 kW kg−1. Even at a higher power density of 15.23 W h kg−1, the device still had an energy density of 16.5 kW kg−1. After 5000 cycles, the retention ratio was higher than 99% at high current density of 11.36 A g−1.

Hierarchical porous NiCo2O4 nanograss arrays grown on Ni foam as electrode material for high-performance supercapacitors

A novel hierarchical porous NiCo2O4 nanograss array directly grown on Ni foam has been constructed via a simple one-step hydrothermal method combined with a calcination treatment, and possessed high electrochemical performance.

Electrochemical DNA biosensor based on the BDD nanograss array electrode

BackgroundThe development of DNA biosensor has attracted considerable attention due to their potential applications, including gene analysis, clinical diagnostics, forensic study and more medical applications. Using electroactive daunomycin as an indicator, the hybridization detection was measured by differential pulse voltammetry in this study.ResultsElectrochemical DNA biosensor was developed based on the BDD film electrode (fBDD) and BDD nanograss array electrode (nBDD). In comparison with fBDD and AuNPs/CA/fBDD electrode, the lower semicircle diameter of electrochemical impedance spectroscopy obtained on nBDD and AuNPs/CA/nBDD electrode indicated that the presence of nanograss array improved the reactive site, reduced the interfacial resistance, and made the electron transfer easier. Using electroactive daunomycin as an indicator, the hybridization detection was measured by differential pulse voltammetry.ConclusionsThe experimental results demonstrated that the prepared AuNPs/CA/nBDD electrode was suitable for DNA hybridization with favorable performance of faster response, higher sensitivity, lower detection limit and satisfactory selectivity, reproducibility and stability.

Detection of Heavy Metals Based on Boron-doped Diamond Nanograss Array, Boron-doped Diamond Film and Glassy Carbon Electrodes

Detection of Heavy Metals Based on Boron-doped Diamond Nanograss Array, Boron-doped Diamond Film and Glassy Carbon Electrodes

Nanograss array boron-doped diamond electrode for enhanced electron transfer from Shewanella loihica PV-4

The inhibited electron transfer from electricigens to the electrode is one of the main limitations for the performance of microbial fuel cells (MFCs). This study compares catalytic current generation and electrochemical behavior of Shewanella loihica PV-4 on boron-doped diamond (BDD) and nanograss array BDD electrode in an electrochemical cell. Experimental results show that the good biocompatibility and electron transportation ability of nanograss array BDD greatly improve the direct electron transfer and can make it suitable for the anode of high performance MFC.

Facile synthesis of SnO 2 nanograss array films by hydrothermal method

SnO 2 nanograss array films (SNAFs) were synthesized on indium tin oxide glass substrates by hydrothermal method. The effects of preparing conditions such as precursor concentration, reaction temperature and growth time on the formation of the SNAFs have been investigated in detail by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and photoluminescence spectrum. It is shown that the precursor concentration plays an important role in determining the morphology of the prepared SnO 2. The average diameter, length and growth rate of the SNAFs can be controlled to some extent by varying growth time. The reaction temperature has also influence on the growth rate of SNAFs. Moreover, the growth mechanism of the SNAFs was also discussed. Room-temperature photoluminescence spectra were further carried out to investigate their optical properties.

Electrochemical Detection of Catechol Based on As‐Grown and Nanograss Array Boron‐Doped Diamond Electrodes

AbstractThe electrochemical behavior of different redox systems and detection of catechol were performed on the as‐grown boron‐doped diamond (BDD) electrodes and the nanograss array BDD. Compared with as‐grown BDD, the electron transfer on the nanograss array BDD surface became slower toward the negatively charged Fe(CN)63−, whereas changed little toward the positively charged Ru(NH3)63+. The nanograss array BDD showed higher electrocatalytic activity toward the catechol detection than did the as‐grown BDD. Good linearity was observed for a concentration range from 5 to 100 μM with a sensitivity of 719.71 mA M−1 cm−2 and a detection limit of 1.3 μM on the nanograss array BDD.

Enhanced electrogenerated chemiluminescence of a ruthenium tris(2,2′)bipyridyl/tripropylamine system on a boron-doped diamond nanograss array

Significant enhancement of the ECL signals from the Ru(bpy)(3)(2+)/TPA system was achieved when using a BDD nanograss array, mainly because of the highly facile oxidation of TPA. The facile oxidation of TPA is due to the superior properties of the BDD nanograss array, such as improved electrocatalytic activity and accelerated electron transfer.

Preparation of superhydrophobic and oleophobic diamond nanograss array

The paper reports on the fabrication of superhydrophobic boron-doped diamond nanograss surfaces. The boron-doped diamond nanograss array (BDD NG) was prepared simply by reactive ion etching (RIE) with oxygen plasma of highly boron-doped (the boron doping level is 8 × 1019 B cm−3) polycrystalline diamond electrodes. Depending on the RIE conditions, substrates with different nanograss densities can be prepared. Chemical functionalization of the NG array surface with octadecyltrichlorosilane (OTS) or 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTS) led to the formation of superhydrophobic surfaces. Under optimized conditions, BDD NG surfaces with contact angles as high as 160° and quasi null hysteresis (< 2°) can be reached. A water droplet deposited on the surface tends to roll off when the NG surface was tilted by a few degrees. Furthermore, the BDD NG array chemically modified with PFTS displays oleophobic properties. A contact angle of 94° was measured for hexadecane. The resulting surfaces were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, and contact angle (CA) measurements.

Boron-doped diamond nanograss array for electrochemical sensors

A novel BDD nanograss array has been prepared simply on a heavily doped BDD film by reactive ion etching for use as an electrochemical sensor, which improved the reactive site, promoted the electrocatalytic activity, accelerated the electron transfer, and enhanced the selectivity.