Carbon-Based Ternary Nanocomposite: Bullet Type ZnO-SWCNT-CuO for Substantial Solar-Driven Photocatalytic Decomposition of Aqueous Organic Contaminants.

A facile two-step synthesis of ternary hetero-composites of ZnO, CuO, and single-walled carbon nanotubes (SWCNTs) was developed through a recrystallization process followed by annealing. A series of nanocomposites were prepared by varying the weight ratio of copper(II) acetate hydrate and zinc(II) acetate dihydrate and keeping the weight ratio of SWCNTs constant. The results revealed the formation of heterojunctions (ZnO-SWCNT-CuO, ZSC) of three crystal structures adjacent to each other, forming a ternary wurtzite-structured nanoparticles along with defects. Enhanced charge separation (electron-hole pairs), reduced band gap, defect-enhanced specific surface area, and promoted oxidation potential were key factors for the enhanced photocatalytic activity of the ternary nanocomposites. OH• radicals were the main active species during dye degradation, and O2-• and h+ were also involved to a lesser extent. A type II heterojunction mechanism approach is proposed based on the charge carrier migration pattern. Among the synthesized nanocomposites, the sample prepared using copper(II) acetate hydrate and zinc(II) acetate dihydrate in a 1: 9 ratio (designated a ZSC3) showed the highest photocatalytic activity. ZSC3 achieved 99.2% photodecomposition of methylene blue in 20 min, 94.1% photodecomposition of Congo red in 60 min, and 99.6% photodecomposition of Rhodamine B in 40 min under simulated sunlight. Additionally, ZSC3 showed excellent reusability and stability, maintaining 96.7% of its activity even after five successive uses. Based on overall results, the ZSC sample was proposed as an excellent candidate for water purification applications.

Facile Preparation of a Bispherical Silver-Carbon Photocatalyst and Its Enhanced Degradation Efficiency of Methylene Blue, Rhodamine B, and Methyl Orange under UV Light.

The combination of organic and inorganic materials is attracting attention as a photocatalyst that promotes the decomposition of organic dyes. A facile thermal procedure has been proposed to produce spherical silver nanoparticles (AgNPs), carbon nanospheres (CNSs), and a bispherical AgNP-CNS nanocomposite. The AgNPs and CNSs were each synthesized from silver acetate and glucose via single- and two-step annealing processes under sealed conditions, respectively. The AgNP-CNS nanocomposite was synthesized by the thermolysis of a mixture of silver acetate and a mesophase, where the mesophase was formed by annealing glucose in a sealed vessel at 190 °C. The physicochemical features of the as-prepared nanoparticles and composite were evaluated using several analytical techniques, revealing (i) increased light absorption, (ii) a reduced bandgap, (iii) the presence of chemical interfacial heterojunctions, (iv) an increased specific surface area, and (v) favorable band-edge positions of the AgNP-CNS nanocomposite compared with those of the individual AgNP and CNS components. These characteristics led to the excellent photocatalytic efficacy of the AgNP-CNS nanocomposite for the decomposition of three pollutant dyes under ultraviolet (UV) radiation. In the AgNP-CNS nanocomposite, the light absorption and UV utilization capacity increased at more active sites. In addition, effective electron-hole separation at the heterojunction between the AgNPs and CNSs was possible under favorable band-edge conditions, resulting in the creation of reactive oxygen species. The decomposition rates of methylene blue were 95.2, 80.2, and 73.2% after 60 min in the presence of the AgNP-CNS nanocomposite, AgNPs, and CNSs, respectively. We also evaluated the photocatalytic degradation efficiency at various pH values and loadings (catalysts and dyes) with the AgNP-CNS nanocomposite. The AgNP-CNS nanocomposite was structurally rigid, resulting in 93.2% degradation of MB after five cycles of photocatalytic degradation.

Selective growth of Ti3+/TiO2/CNT and Ti3+/TiO2/C nanocomposite for enhanced visible-light utilization to degrade organic pollutants by lowering TiO2-bandgap.

A convenient route was developed for the selective preparation of two stable nanocomposites, Ti3+/TiO2/CNT (labeled as TTOC-1 and TTOC-3) and Ti3+/TiO2/carbon layer (labeled as TTOC-2), from the same precursor by varying the amount of single-walled carbon nanotubes used in the synthesis. TiO2 is an effective photocatalyst; however, its wide bandgap limits its usefulness to the UV region. As a solution to this problem, our prepared nanocomposites exhibit a small bandgap and wide visible-light (VL) absorption because of the introduction of carbonaceous species and Ti3+ vacancies. The photocatalytic efficiency of the nanocomposites was examined via the degradation of methylene blue dye under VL. Excellent photocatalytic activity of 83%, 98%, and 93% was observed for TTOC-1, TTOC-2, and TTOC-3 nanocomposites within 25 min. In addition, the photocatalytic degradation efficiency of TTOC-2 toward methyl orange, phenol, rhodamine B, and congo red was 28%, 69%, 71%, and 91%, respectively, under similar experimental conditions after 25 min. Higher reusability and structural integrity of the as-synthesized photocatalyst were confirmed within five consecutive runs by photocatalytic test and X-ray diffraction analysis, respectively. The resulting nanocomposites provide new insights into the development of VL-active and stable photocatalysts with high efficiencies.

Hierarchical Nanocauliflower Chemical Assembly Composed of Copper Oxide and Single-Walled Carbon Nanotubes for Enhanced Photocatalytic Dye Degradation.

We present the fabrication and proficient photocatalytic performance of a series of heterojunction nanocomposites with cauliflower-like architecture synthesized from copper(II) oxide (CuO) nanocrystals and carbon nanotubes with single walls (SWCNTs). These unique photocatalysts were constructed via simplistic recrystallization succeeded by calcination and were labeled as CuOSC-1, CuOSC-2, and CuOSC-3 (representing the components; CuO and SC for SWCNTs, and the calcination time in hours). The photocatalytic potency of the fabricated nanocomposites was investigated on the basis of their capability to decompose methylene blue (MB) dye under visible-light irradiation. Every as-synthesized nanocomposite was effective photocatalyst for the photodecomposition of an MB solution. Moreover, CuOSC-3 exhibited the best photocatalytic activity, with 96% degradation of the visible-light irradiated MB solution in 2 h. Pure CuO nanocrystals generated through the same route and pure SWCNTs were used as controls, where the photocatalytic actions of the nanocomposite samples were found to be remarkably better than that of either the pure CuO or the pure SWCNTs. The recycling proficiency of the photocatalysts was also explored; the results disclosed that the samples could be applied for five cycles without exhibiting a notable change in photocatalytic performance or morphology.

Heterojunction formation between copper(II) oxide nanoparticles and single-walled carbon nanotubes to enhance antibacterial performance.

We delineate the excellent bactericidal efficacy of stable heterojunction nanocomposites composed of single-walled carbon nanotubes (SWCNTs) and copper(II) oxide (CuO) synthesized via facile recrystallization and calcination. The bactericidal effectiveness of the fabricated nanocomposites was examined using the standard broth-dilution method and the growth-inhibition-zone analysis method, in which bacteria cultured in an incubator in tryptic soy broth medium were subjected to the prepared samples. The bactericidal activity of all of the as-synthesized samples is evident in both methods, displaying a substantial decrease in bacterial colonies and resulting in clear inhibition zones, respectively. Among the CuO-SWCNT nanocomposites, the sample subjected to calcination at 500 °C for 5 h was found to exhibit the best performance against Staphylococcus aureus and Escherichia coli, forming inhibition zones 182% and 162% larger than those formed by pure CuO, respectively.

Effect of Polymeric In Situ Stabilizers on Dispersion Homogeneity of Nanofillers and Thermal Conductivity Enhancement of Composites.

Boron nitride (BN) nanofiller-based polymer composites have been considered promising candidates for efficient heat-dissipating packaging materials because of their superior thermal conductivity, mechanical strength, and chemical resistance. However, strong aggregation of the BN nanofillers in the composite matrix as well as the difficulty in the modification of the chemically inert surface prevents their effective use in polymer composites. Herein, we report an effective method by using in situ stabilizers to achieve homogeneous dispersion of boron nitride (BN) nanofillers in an epoxy-based polymeric matrix and demonstrate their use as efficient heat-dissipating materials. Poly(4-vinylpyridine) (P4VP) is designed and added into the epoxy resin to produce in situ stabilizers during preparation of hexagonal BNs (h-BNs) and BN nanotubes (BNNTs) dispersion. In-depth experimental and theoretical studies indicated that the homogeneous distribution of BN nanofillers in epoxy composites achieved by using the in situ stabilizer enhanced the thermal conductivity of the composite by ∼27% at the same concentration of the BN nanofillers. In addition, the thermal conductivity of the h-BN/epoxy composite (∼3.3 W/mK) was dramatically improved by ∼48% (4.9 W/mK) when the homogeneously dispersed BNNTs (∼1.8 vol %) were added. The concept of the proposed in situ stabilizer can be further utilized to prepare the epoxy composites with the homogeneous distribution of BN nanofillers, which is critical for reproducible and position-independent composite properties.

Recrystallization techniques for the synthesis of ZnO nanorods: an in situ process for carbon doping and enhancing the dispersion concentration of ZnO nanorods.

Zinc acetate is recrystallized as lumber-shaped tetragonal rods by a novel recrystallization technique. Subsequently, the recrystallized zinc acetate is converted into ZnO nanorods in a glass vial by the simplest and cheapest method without utilizing any expensive instrumentation. Carbon is doped in ZnO nanorods during the preparation ZnO nanorods without any extra steps, chemicals, or effort. The carbon-doped ZnO nanorods can be dispersed in a solvent at very high concentrations and are also stable for a very long time, which are comparatively higher than those of the other existing ZnO nanoparticles. The higher dispersion concentration and higher stability of ZnO nanoparticles are explained by a scheme that demonstrates the suspending mechanism of the ZnO nanoparticles at higher concentrations with higher stabilities in a solvent through the anchoring groups of carbon. No materials are used for surface modification; no surface coatings, ionic materials, or pH controlling materials are used to increase the dispersion concentration and stability. This is the first observation of the doped carbon playing a significant role in the dispersion of ZnO nanoparticles at higher concentrations by withholding them in the solvent. Therefore, doped carbon at the surface of ZnO nanoparticles prevents the self-aggregation of ZnO nanoparticles in the solution phase by interfacial barrier layers among ZnO nanorods and interfacial interactive layer between ZnO nanorod and solvent.

Alignment of Carbon Nanotubes in Carbon Nanotube Fibers Through Nanoparticles: A Route for Controlling Mechanical and Electrical Properties.

This is the first study that describes how semiconducting ZnO can act as an alignment agent in carbon nanotubes (CNTs) fibers. Because of the alignment of CNTs through the ZnO nanoparticles linking groups, the CNTs inside the fibers were equally distributed by the attraction of bonding forces into sheetlike bunches, such that any applied mechanical breaking load was equally distributed to each CNT inside the fiber, making them mechanically robust against breaking loads. Although semiconductive ZnO nanoparticles were used here, the electrical conductivity of the aligned CNT fiber was comparable to bare CNT fibers, suggesting that the total electron movement through the CNTs inside the aligned CNT fiber is not disrupted by the insulating behavior of ZnO nanoparticles. A high degree of control over the electrical conductivity was also demonstrated by the ZnO nanoparticles, working as electron movement bridges between CNTs in the longitudinal and crosswise directions. Well-organized surface interface chemistry was also observed, which supports the notion of CNT alignment inside the fibers. This research represents a new area of surface interface chemistry for interfacially linked CNTs and ZnO nanomaterials with improved mechanical properties and electrical conductivity within aligned CNT fibers.