Composite Nanorods Research Articles

Calcination induced PEG-Ni-ZnO nanorod composite and its biomedical applications

PEGylation of nickel-zinc oxide nanorods (PEG-Ni-ZnONRs) composites was synthesized by a modified co-precipitation method and calcined at different temperatures to optimize their properties suitable for biomedical applications. The upshot of calcination on the properties of PEG-Ni-ZnONRs formulated, were analyzed using different characterization techniques via UV–Visible diffuse reflectance spectroscopy (DRS), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and energy dispersive X-ray (EDX) coupled with SEM analysis. The XRD analysis showed the hexagonal wurtzite crystal structure of PEG-Ni-ZnONRs; while the SEM analysis revealed the formation of enhanced nanorod after calcination of PEG-Ni-ZnONRs up to 700 °C. The antibacterial and antifungal activities of the enhanced properties of the formulated PEG-Ni-ZnONRs, were examined using Ager Well Diffusion Method (AWDM) against four bacterial and five fungal pathogenic strains with enhanced antibacterial and antifungal activities. It is noteworthy that after calcination, the morphology, structural and bandgap properties of PEG-Ni-ZnONRs were influenced and enhanced for biomedical applications.

Enhanced Thermoelectric Performance of Novel Reaction Condition-Induced Bi2S3-Bi Nanocomposites.

This is the first report on the enhanced thermoelectric (TE) properties of novel reaction-temperature (TRe) and duration-induced Bi2S3-Bi nanocomposites synthesized using a facile one-step polyol method. They are well characterized as nanorod composites of orthorhombic Bi2S3 and rhombohedral Bi phases in which the latter coats the former forming Bi2S3-Bi core-shell-like structures along with independent Bi nanoparticles. A very significant observation is the systematic reduction in electrical resistivity ρ with a whopping 7 orders of magnitude (∼107) with just reaction temperature and duration increase, revealing a promising approach for the reduction of ρ of this highly resistive chalcogenide and hence resolving the earlier obstacles for its thermoelectric application potentials in the past few decades. Most astonishingly, a TE power factor at 300 K of the highest Bi content nanocomposite pellet, made at 27 °C using ∼900 MPa pressure, is 3 orders of magnitude greater than that of hot-pressed Bi2S3. Its highest ZT at 325 K of 0.006 is over twice of that of similarly prepared CuS or Ag2S-based nanocomposites. A significantly improved TE performance potential near 300 K is demonstrated for these toxic-free and rare-earth element-free TE nanocomposites, making the present synthesis method as a pioneering approach for developing enhanced thermoelectric properties of Bi2S3-based materials without extra sintering steps.

Electrospinning Ag-TiO2 Nanorod-Loaded Air Treatment Filters and Their Applications in Air Purification.

The efficient treatment of the problem of air pollution is a practical issue related to human health. The development of multi-functional air treatment filters, which can remove various kinds of pollutants, including particulate matter (PM) and organic gases, is a tireless pursuit aiming to address the actual needs of humans. Advanced materials and nano-manufacturing technology have brought about the opportunity to change conventional air filters for practical demands, with the aim of achieving the high-efficiency utilization of photons, a strong catalytic ability, and the synergetic degradation of multi-pollutants. In this work, visible-responding photocatalytic air treatment filters were prepared and combined with a fast and cost-effective electrospinning process. Firstly, we synthesized Ag-loaded TiO2 nanorod composites with a controlled size and number of loaded Ag nanoparticles. Then, multi-functional air treatment filters were designed by loading catalysts on electrospinning nanofibers combined with a programmable brush. We found that such Ag-TiO2 nanorod composite-loaded nanofibers displayed prominent PM filtration (~90%) and the degradation of organic pollutants (above 90%). The superior performance of purification could be demonstrated in two aspects. One was the improvement of the adsorption of pollutants derived from the increase of the specific surface area after the loading of catalysts, and the other was the plasmonic hot carriers, which induced a broadening of the optical absorption in the visible light range, meaning that many more photons were utilized effectively. The designed air treatment filters with synergistic effects for eliminating both PM and organic pollutants have promising potential for the future design and application of novel air treatment devices.

An Optical Fiber Immunosensor With a Low Detection Limit Based on Plasmon Coupling Enhancement

An optical fiber immunosensor with a low detection limit based on plasmon coupling enhancement is proposed for detecting human immunoglobulin G (IgG). Graphene oxide (GO)-gold nanorod composites are synthesized and modified onto a photonic crystal fiber (PCF) surface coated with a Au film. GO, as a biosensitive layer, is used to decorate the gold nanorods and concentrate target molecules. The experimental result indicates that the refractive index sensitivity is drastically enhanced to 22248 nm/RIU because of plasmon coupling. Correspondingly, the human IgG detection limit decreases to 6 ng/mL. Moreover, the PCF is insensitive to temperature fluctuation, which can further reduce the measurement error.

Construction of triblock copolymer-gold nanorod composites for fluorescence resonance energy transfer via pH-sensitive allosteric

To explore the effects of microenvironmental adjustments on fluorescence, a pH-sensitive nanocomposite system based on fluorescence resonance energy transfer (FRET) was constructed. The model system included a modified triblock copolymer (polyhistidine-b-polyethylene glycol-b-polycaprolactone) and gold nanoparticles. A near-infrared dye was used as the donor, and spectrally matched gold nanorods, attached after C-terminus modification with α-lipoic acid, were used as the receptor to realize control of the FRET effect over the fluorescence intensity for two polymer configurational changes (i.e., “folded” and “stretched” states) in response to pH. After synthesis and characterization, we investigated the self-assembly behavior of the system. Analysis by quartz crystal microbalance revealed the pH sensitivity of the polymer, which exhibited “folding” and “stretching” states with changes in pH, providing a structural basis for the FRET effect. Fluorescence spectrophotometry investigations also revealed the regulatory impact of the assembled system on fluorescence.

Construction of BiPO4/CdS heterojunction photocatalysts for enhanced degradation of organic pollutants under visible light

In this study, the composite of CdS nanorods loaded with BiPO4 nanoparticles was fabricated as a novel efficient photocatalyst and exhibited strong photocatalytic degradation activities for the degradation of organic pollutants. Among the composites with different mass ratios, 1.8BiPO4/CdS showed the best catalytic activity, and the removal rates of malachite green (MG), reactive red (X-3B) and ciprofloxacin (CIP) in 80 min were 98%, 99%, and 70%, respectively. The COD removal efficiencies of MG (55%), X-3B (50%) and CIP (44%) by 1.8BiPO4/CdS composites further proved the superiority of the performance of BiPO4/CdS heterojunctions under visible light. About 90% MG, 88% X-3B and 58% CIP could be degraded after four cycles indicating the good stability of the materials. The enhanced photocatalytic properties can be attributed to the efficient charge separation as well as interfacial charge transfer from CdS to BiPO4, which is evidenced by XPS analysis and species trapping. The well dispersion of BiPO4 on CdS can preserve it from photocorrosion, which effectively enhances the photostability of degradation properties. Moreover, several recommendations and ideas are proposed for improving the utilization of solar energy and environmental restoration in the future.

Effect of calcination temperature on structural, morphological and electrochemical properties of Sn doped Co3O4 nanorods

Tremendous attention has been devoted for the development of highly efficient and stable electrode materials for supercapacitor applications. In this study, Sn-doped Co3O4 nanorods were prepared via solvothermal process using PVP and oxalic acid as surfactants. The phase, morphology and composition of Sn-doped Co3O4 nanorods were examined by XRD and SEM/EDX techniques. The electrochemical properties were studied via cyclic voltammetry (CV), galvanostatic charging-discharging (GCD), electrochemical impedance spectroscopy (EIS) measurements. The CV results show that electrode based on 5 at. % Sn-doped Co3O4 (5Sn-doped Co3O4) nanorods delivered the highest specific capacitance (842.44 F/g) at 5 mV/s than that of the electrode based on pure Co3O4 (729.39 F/g). In order to further tune the performance of this electrode, the structure, morphology and electrochemical behavior of 5Sn-doped Co3O4 sample were optimized via variety of calcination temperatures ranging from 250 to 400 °C. Notably, the 5Sn-doped Co3O4 sample calcined at 350 °C exhibited higher electrochemical performance (specific capacitance ~913.10 F/g) than other samples calcined at low or high calcination temperatures. The CV curves of 5Sn-doped Co3O4/T-350 °C at scan rates of 5–35 mV/s also showed pseudocapacitor behavior and good electrochemical reversibility. Moreover, the prepared novel electrode material has also displayed good rate capability (71.77%) at current density of 1–10 A/g and long-term stability of 92.23% after 3000 cycles. These excellent electrochemical characteristics of 5Sn–Co3O4/T-350 °C nanorods verified that it will be highly suitable electrode material for supercapacitor applications.

Hierarchical composites of NiCo2S4 nanorods grown on carbon nanofibers as anodes for high-performance lithium ion batteries

The increasing requirement for clean energy storage has urged the advancement of lithium ion batteries (LIBs) with high specific capacity and cycling stability. In this work, we report a facile method to synthesize hybrid membranes of NiCo2S4 nanorod arrays uniformly grown onto each carbon nanofiber (NiCo2S4/CNF), which as anode materials can achieve high performance for LIBs. The conductive networks of CNFs can facilitate the electron transport at the interfaces and diffusion of ions to readily react with NiCo2S4, thus leading to increased lithium storage. The CNFs can mitigate the drastic expansion/contraction of NiCo2S4 nanorods, resulting in enhanced cycling stability. As a consequence, the LIBs with NiCo2S4/CNF hybrid membranes as anode materials exhibit high capacity (1060 mA h/g) at 0.2 A/g and good durability for 100 cycles.

Catalytic properties of the composite of La-doped ZnO nanorods and Ag2CrO4 nanoparticles

To study the application of ZnO in photocatalysis, a composite of La-doped ZnO nanorods and Ag2CrO4 nanoparticles was prepared by hydrothermal and precipitation methods. At a fixed concentration, the volume of Ag+ precursor has a significant effect on the composition and structure of the composite. With the increase in the Ag+ source volume, the amount of Ag2CrO4 nanoparticles generated in the composite increases. When the volume of the Ag+ source exceeds some critical value, although the amount of Ag2CrO4 nanoparticles in the composite continues to increase, the quality of the crystals is lower. Both the content and crystal quality of Ag2CrO4 nanoparticles affect the photocatalytic properties of the composite. The introduction of additional oxygen vacancy defects in nanorods leads to the formation of more, and larger, Ag2CrO4 nanoparticles in the composite without degradation of crystal quality. Then, two dyes (methyl orange and methylene blue) were selected to examine the photocatalytic properties of the samples. The improvement of photocatalytic performance of the composite samples is realized by the separation of electron–hole pairs in both ZnO and Ag2CrO4 crystals.

Adsorption Characteristics of Reactive Red 2BF onto MnFe2O4 Nanorods Fabricated by the Facile Alcohol-Solution Combustion–Calcination Technique

Magnetic MnFe2O4 nanorods were fabricated by the alcohol-solution combustion–calcination technique. The morphology, microstructure, and composition of as-prepared MnFe2O4 nanorods were characterized using the transmission electron microscopy (TEM), the X-ray diffraction (XRD), the energy dispersive spectroscopy (EDS), and the vibrating sample magnetometer (VSM). Moreover, the magnetic MnFe2O4 nanorods were employed to remove reactive red 2BF (RR-2BF), the experimental results showed the pseudo-second-order kinetics model could be applied to describe the adsorption process of RR-2BF onto MnFe2O4 nanorods in the initial RR-2BF concentrations of 100–400 mg/L, while, the isotherm data of RR-2BF onto MnFe2O4 nanorods could conform to Langmuir model owing to the value of the square deviations, which revealed that, the adsorption of RR-2BF onto MnFe2O4 nanorods was the monolayer adsorption mechanism.

Poly(3‐hexylthiophene)/Gold Nanorod Composites as Efficient Hole‐Transporting Materials for Perovskite Solar Cells

Hole-Transporting Materials In article number 2000109, Zong-Xiang Xu and co-workers determine that the highest power conversion efficiency of perovskite solar cells based on a poly(3-hexylthiophene)/gold nanorod (P3HT/AuNR) composite hole-transporting material reaches up to 16.88%, which is an increase of 26% from that of a pristine P3HT-based device (13.40%). The enhanced performance is attributed to the higher carrier mobility and increased light utilization efficiency induced by the addition of AuNRs with localized surface plasmon resonance effect in the polymer matrix.

A dynamically optical and highly stable pNIPAM @ Au NRs nanohybrid substrate for sensitive SERS detection of malachite green in fish fillet

A universal surface-enhanced Raman scattering (SERS) substrate with tuneable plasmonic behaviour and long-term stability was synthesized and characterized, and the substrate was applied in the sensitive detection of fungicide malachite green (MG) in fish fillets. Temperature-responsive poly (N-isopropyl acrylamide) (pNIPAM) template and anisotropic Au nanorods (NRs) were synthesized to prepare pNIPAM @ Au NRs nano-hybrids with dynamically optical and SERS properties and high stability. Results showed that excitation wavelength-dependent SERS efficiency could be tailored by temperature-induced swelling and collapse of the nano-hybrids, thus anticipated optical and SERS properties of the composites could be obtained. Furthermore, the SERS performance, uniformity, long-term stability analysis, and MG in fish evaluation showed that the detection of MG in fish tissues was realized with a limit of detection of 1.58 × 10−9 M (0.73 ng/g), and the pNIPAM @ Au NRs composites could serve as effective SERS substrates allowing trace level detection of contaminants for the food industry.

Effect of DC voltage on morphology and size distribution of silver nanorods synthesized through plasma-liquid interaction method

A plasma-liquid interaction method was used to produce silver nanorods from silver nitrate and sucrose solution at different DC voltages. Sucrose was used as stabilizing and reducing agent in this reduction reaction. A fixed molar ratio of silver nitrate was used to elaborate the effect of DC plasma voltage on shape size and elemental composition of nanorods. The formation of silver nanorods was confirmed from SEM images. Some copper nanoparticles were also formed due to degradation of anode during plasma reduction process, which were uniformly distributed over the surface of nanorods. The nanorods had well-defined shape and alignment at an applied voltage of 4 kV. The elemental analysis provided EDX peaks at 3 keV, 1.8 keV, 0.5 keV and 0.3 keV, which correspond to Ag, Si, O and Cu, respectively. The applied voltage only effected the shape and size of the nanorods. The size of nanorods varied from 662 nm to 964 nm, 483 nm to 703 nm and 572 nm to 841 nm for 2 kV, 4 kV and 6 kV, respectively. The size distribution histograms reveal narrowest size distribution of nanorods at 4 kV voltage followed 6 kV and 2 kV.

A facile combustion process for the preparation of magnetic MnFe2O4 nanorods and their adsorption mechanism of methyl blue

Magnetic MnFe2O4 nanorods were fabricated via the alcohol-solution combustion and calcination process. The morphology, microstructure, and composition of the as-prepared MnFe2O4 nanorods were characterized by x-ray diffraction, energy dispersive spectroscopy, and transmission electron microscopy and using a vibrating sample magnetometer. In addition, the magnetic MnFe2O4 nanorods were employed to remove methyl blue (MB) from aqueous solutions; the experimental results showed that the pseudo-second-order kinetic model was fitted well for the adsorption of MB onto MnFe2O4 nanorods in the initial MB concentration range of 100–400 mg l−1, while the isotherm data of MB onto MnFe2O4 nanorods could conform to the Langmuir model owing to the value of the square deviation (R2 > 0.99), and the maximum adsorption capacity of MB was 102.2 mg g−1, which suggested that the adsorption mechanism of MB onto MnFe2O4 nanorods at room temperature was the monolayer and multilayer adsorption. The effects of the solution pH and the recycle on the MB adsorption were evaluated. The adsorption capacity of MB onto MnFe2O4 nanorods could keep a high level at pH greater than 5. More than 78% of the removal efficiency of MB onto MnFe2O4 nanorods could be maintained after 10 cycles.

Fabrication of Hybrid Catalyst ZnO Nanorod/α-Fe2O3 Composites for Hydrogen Evolution Reaction

This report presents the synthesis of ZnO nanorod/α-Fe2O3 composites by the hydrothermal method with different weight percentages of α-Fe2O3 nanoparticles. The as-synthesized nanorod composites were characterized by different techniques, such as X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). From our results, it was found that the ZnO/α-Fe2O3 (3 wt%) nanorod composites exhibit a higher hydrogen evolution reaction (HER) activity when compared to other composites. The synergetic effect between ZnO and (3 wt%) of α-Fe2O3 nanocomposites resulted in a low onset potential of −125 mV, which can effectively produce more H2 than pure ZnO. The H2 production rate over the composite of ZnO/α-Fe2O3 (3 wt%) clearly shows a significant improvement in the photocatalytic activity in the heterojunction of the ZnO nanorods and α-Fe2O3 nanoparticles on nickel foam.

Poly(3‐hexylthiophene)/Gold Nanorod Composites as Efficient Hole‐Transporting Materials for Perovskite Solar Cells

Poly(3‐hexylthiophene)/gold nanorod (P3HT/AuNR) composites are developed and introduced as hole‐transporting materials (HTMs) to fabricate mixed‐ion perovskite solar cells (PSCs). The highest power conversion efficiency of the optimized devices based on the composite HTM reaches up to 16.88%, which is an increase of 26% from that of a pristine P3HT‐based device (13.40%). The enhanced performance can be attributed to the increased crystallinity of P3HT induced by the addition of AuNRs in the polymer matrix and the localized surface plasmon resonance effect of AuNRs, which lead to higher carrier mobility and increased light utilization efficiency. This work provides a comprehensive understanding of the effect of plasmonic AuNRs in PSCs application and a useful method to further improve the performance of PSCs.

Superior and Reversible Lithium Storage of SnO2/Graphene Composites by Silicon Doping and Carbon Sealing.

The poor cycle stability and reversibility seriously hinder the widespread application of SnO2 materials as anodes for lithium-ion batteries (LIBs). A novel sandwich-architecture composite of Si-doped SnO2 nanorods and reduced graphene oxide with carbon sealing (Si-SnO2@G@C) is engineered and fabricated by a facile two-step hydrothermal process and subsequent annealing treatment, which exhibit not only extraordinary rate performance and ultrahigh reversible capacity but also excellent cycle stability and high electrical conductivity as the anode of LIBs. The Si-doped SnO2 nanoparticles on the surface of graphene were firmly wrapped in the C-coating and formed a porous sandwich structure, which can efficiently prevent the Sn nanoparticles from aggregation and provide more extra space for accommodating the volume variations and more active sites for reactions. The carbon layer also blocks the direct contact of the SnO2 nanorods with electrolyte and prevents the graphene nanosheets from the restacking. More importantly, the reversibility of lithiation/delithiation reactions can be remarkably improved by the doping silicon. The doped Si not only accelerates the diffusion of Li+ but also brings a significant increase in the specific capacity. As a consequence, the Si-SnO2@G@C nanocomposite can maintain a high capacity of 654 mAh/g at 2 A/g even after 1200 cycles with negligible capacity loss and excellent reversibility with a Coulombic efficiency retention over 99%, which can be capable of the alternative to commercial graphite anodes. This work provides a new strategy for the reasonable design of advanced anode materials with superior and reversible lithium storage capacity.

Hierarchical Sr-ZnO/g-C3N4 heterojunction with enhanced photocatalytic activities

It is urgent to develop new photocatalytic materials that could optimize H2 generation and efficiently degrade environmentally persistent pollutants. Herein, Sr-ZnO/g-C3N4 spherical flowers composed of hierarchical nano-rods composites have been successfully synthesized via facile single step method and utilized in photocatalysis for efficient degradation of Methylene green (MG) and H2 production under UV–vis irradiation. The resultant Sr-ZnO/g-C3N4 showed enhanced activities for MG degradation (i.e. 96 % in 20 min), and H2 evolution (31.2 μmolh−1 g-1) which is much obvious compared to the bare g-C3N4, ZnO and Sr-ZnO. It is investigated that Sr ion doping has extended the light absorption toward visible light region. The g-C3N4 grafted Sr-ZnO provided an extra boost up absorption spectra in the visible light region compared to bare ZnO. The photoluminescence spectroscopy and photo-electrochemical measurement confirmed excellent photo-generated charge carrier’s separation in the hierarchical structure of spherical flowers. The improved activities are attributed to the combined impact of in-situ doping, hierarchical morphology, and heterojunction formation.

Microwave-Assisted Synthesis of ZnO-rGO Core-Shell Nanorod Hybrids with Photo- and Electro-Catalytic Activity.

The unique two-dimensional structure and surface chemistry of reduced graphene oxide (rGO) along with its high electrical conductivity can be exploited to modify the electrochemical properties of ZnO nanoparticles (NPs). ZnO-rGO nanohybrids can be engineered in a simple new two-step synthesis, which is both fast and energy-efficient. The resulting hybrid materials show excellent electrocatalytic and photocatalytic activity. The structure and composition of the as-prepared bare ZnO nanorods (NRs) and the ZnO-rGO hybrids have been extensively characterised and the optical properties subsequently studied by UV/Vis spectroscopy and photoluminescence (PL) spectroscopy (including decay lifetime measurements). The photocatalytic degradation of Rhodamine B (RhB) dye is enhanced using the ZnO-rGO hybrids as compared to bare ZnO NRs. Furthermore, potentiometry comparing ZnO and ZnO-rGO electrodes reveals a featureless capacitive background for an Ar-saturated solution whereas for an O2 -saturated solution a well-defined redox peak was observed using both electrodes. The change in reduction potential and significant increase in current density demonstrates that the hybrid core-shell NRs possess remarkable electrocatalytic activity for the oxygen reduction reaction (ORR) as compared to NRs of ZnO alone.

Organic-Inorganic Composite Nanorods as an Excellent Mimicking Peroxidases for Colorimetric Detection and Evaluation of Antioxidant.

N,N'-Dicarboxy methyl perylene diimide-coated CeO2 nanorods (PDI/CeO2 NR) were synthesized via an ultrasonic-assisted method. PDI/CeO2 exhibits the superb mimic peroxidase functions confirmed by the catalyzed oxidation of TMB by hydrogen peroxide in less than 60 s along with color transformation from colorless to blue. The catalytic mechanism was confirmed to be an electronic transfer mechanism by fluorescence experiment. Thus, a visual colorimetric sensor was constructed for hydrogen peroxide detection with a low detection limit (LOD = 2.23 μM). Comparing the inhibition effects of l-cysteine (Cys), ascorbic acid (AA) and glutathione (GSH) on the catalytic oxidation of TMB, it can be found that they possessed different types of inhibition on the oxidation of TMB by H2O2 using PDI/CeO2, and AA has better antioxidant effect, followed by Cys and GSH. On the basis of the excellent antioxidant effect of AA, a low-cost colorimetric sensor was also used to detect AA, and a lower LOD value (0.68 μM) was obtained in the linear range of 5.0-30 μM.