Nano

Optical manipulation on microscale and nanoscale structures opens up new possibilities for assembly and control of microelectromechanical systems and nanoelectromechanical systems. Static optical force induces constant displacement while changing optical force stimulates vibration of a microcantilever/nanocantilever. The vibratory behavior of a single carbon nanocoil cantilever under optical actuation is investigated. A fitting formula to describe the laser-induced vibration characteristics is deduced based on a classical continuum model, by which the resonance frequency of the carbon nanocoil can be determined directly and accurately. This optically actuated vibration method could be widely used in stimulating quasi-1D micro/nanorod-like materials, and has potential applications in micro-/nano-opto-electromechanical systems.

Environmental and energy issues have always been a hot topic of global research. Oil leakage has caused great damage to the environment, affecting a wide area and it is difficult to clean up. In most cases, carbon-based adsorbents are typically utilized to remove oil spills because of their economic benefits and high adsorbent efficiency. At the same time, its excellent material properties can also be used for the preparation of supercapacitors. In this paper, the carbon aerogels were prepared by the one-step method. The prepared materials endowed a 3D network structure with a huge number of micropores and mesoporous, and the material is light-weight, stable, hydrophobic and has affinity for oil (17.02g/g) to the KGM carbon aerogel. Through the physic-chemical characterization, the KGM carbon aerogel shows specific surface area is 689m²/g, high water contact angle (136.64${}^{\circ }$) and excellent reusability (more than 15 cycle times). In addition, we also discussed the electrochemical properties of the material and obtained the specific electrical capacity of 139F/g under the condition of 1A/g.

Here we report an optimized hot-injection method and a phase transfer strategy for the synthesis of water-soluble CuInS₂ QDs with desired properties. The structure and morphology studies demonstrate that the resulting QDs are CuInS₂ tetragonal phase with well-defined facets. It is also found that the crystal size gradually increases with the increase of reaction temperature, while the surface of QDs with pre- and post-phase transfer is functionalized with hydrophobic and hydrophilic ligands, respectively. Spectroscopy measurements reveal the size-dependent optical properties of CuInS₂ QDs, demonstrating the quantum confinement effect in this system.

A novel sensor material of Au nanoparticles (NPs) functionalized 1D $\alpha$-MoO₃ nanobelts (NBs) was fabricated by a facile lysine-assisted approach. The obtained Au/$\alpha$-MoO₃ product was characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive X-ray (EDX), and X-ray photoelectron spectra (XPS). Then, in order to investigate the gas sensing performances of our samples, a comparative gas sensing study was carried out on both the $\alpha$-MoO₃ NBs before and after Au NPs decoration by using ethanol vapor as the molecular probe. The results turned out that, after the functionalization of Au NPs, the sensor exhibited improved gas-sensing characteristics than the pure $\alpha$-MoO₃, such as response and recovery time, optimal operating temperature (OT) and excellent selectivity. Take for example 200ppm of ethanol, the response/recovery times were 34s/43s and 5.7s/10.5s, respectively, while the optimal operating temperature (OT) was lower to 200${}^{\circ }$C rather than 250${}^{\circ }$C. Besides, the functionalized sensor showed a higher response to ethanol at 200${}^{\circ }$C, and response was 1.6 times higher than the pure MoO₃. The mechanism of such improved sensing properties was interpreted, which might be attributed to the spillover effect of Au NPs and the electronic metal-support interaction.

In this study, we report the mercury ions (Hg${}^{2+}$) mediated phosphorus-containing carbon dots (PCDs) as a selective “off–on” fluorescence probe for glutathione (GSH), cysteine (Cys) and homocysteine (Hcys). PCDs obtained by hydrothermal reaction are sensitive to Hg${}^{2+}$ ions and its fluorescence can be significantly quenched owing to the electron transfer from the lowest unoccupied molecular orbital (LUMO) of PCDs to Hg${}^{2+}$. Interestingly, the weak fluorescence of Hg${}^{2+}$-mediated PCDs could be gradually recovered with the addition of GSH, Cys and Hcys. This can be attributed to the formation of Hg${}^{2+}$–S complex due to the super affinity of Hg${}^{2+}$–sulfydryl bond. The formation of Hg${}^{2+}$–S complex extremely reduces the oxidation ability of Hg${}^{2+}$ that inhibits the electron transfer from LUMO of PCDs to Hg${}^{2+}$ and re-opens the native electron transition from LUMO to the highest occupied molecular orbital (HOMO) of PCDs. Thus, the green fluorescence of PCDs is switched on. Furthermore, the present Hg${}^{2+}$-mediated PCDs assay exhibits a high selectivity for GSH, Cys and Hcy and has been successfully used to detect the total biothiols content in human urine samples.

Sulfated TiO₂ nanoparticles were successfully immobilized on zeolite through improving hydrolysis-deposition method. Microstructure, crystallization, surface state and surface area of composite catalysts were characterized by SEM, XRD, FTIR spectra, XPS and BET and the photocatalytic activity was evaluated by degradation of methyl orange under UV irradiation. We optimized these factors (SO${}_4^{2-}$ ions, calcination temperature and loading amount of sulfated TiO${}_2)$ on photocatalytic activity and crystallization of composite photocatalysts. The results indicated that the SO${}_4^{2-}$ ions are successfully immobilized on the surface of TiO₂, and sulfated TiO₂/zeolite show the highest photocatalytic activity for methyl orange at the [SO${}_4^{2-}$]/[Ti${}^{4+}$] molar rate of 1:1, calcination temperature of 600${}^{\circ }$C for 2h, and sulfated TiO₂ loading amount of 40%, respectively.

Nanoparticles of the semiconductor catalyst Cd_xZn${}_{1-x}$S were embedded into the metal organic framework MIL-101(Cr) to obtain Cd_xZn${}_{1-x}$S@MIL-101(Cr) nanocomposites. These materials not only possess high surface areas and mesopores but also show good utilization of light energy. The ultraviolet-visible diffuse reflectance patterns of Cd_xZn${}_{1-x}$S@MIL-101(Cr) nanocomposites showed that Cd${}_{0.8}$Zn${}_{0.2}$S@MIL-101(Cr) possessed good visible light response ability among the synthesized nanocomposites. The photocatalytic performance of the Cd_xZn${}_{1-x}$S@MIL-101(Cr) nanocomposites were tested via degradation and mineralization of methylene blue in neutral water solution under light irradiation using a 300W xenon lamp. As a result, using Cd${}_{0.8}$Zn${}_{0.2}$S@MIL-101(Cr) as a catalyst, 99.2% of methylene blue was mineralized within 30min. Due to the synergistic effect of adsorption by the MIL-101(Cr) component and photocatalytic degradation provided by the Cd${}_{0.8}$Zn${}_{0.2}$S component, the Cd${}_{0.8}$Zn${}_{0.2}$S@MIL-101(Cr) catalyst displayed superior photocatalytic performance relative to Cd${}_{0.8}$Zn${}_{0.2}$S and MIL-101(Cr). Furthermore, Cd${}_{0.8}$Zn${}_{0.2}$S@MIL-101(Cr) possessed excellent stability during photodegradation and exhibited good reusability. The remarkable photocatalytic performance of Cd${}_{0.8}$Zn${}_{0.2}$S@MIL-101(Cr) is likely due to the effective transfer of electrons and holes at the heterojunction interfaces.

Eu${}^{3+}$/Tb${}^{3+}$ co-doped nanocomposite containing CeO₂ nanocrystals was successfully prepared by an in situ sol–gel polymerization approach. High-resolution transmission electron microscopy demonstrated the homogeneous precipitation of CeO₂ nanocrystals among the polymethylmethacrylate (PMMA) matrix. The thermal stability and UV-shielding capability of the obtained nanocomposite were improved with increase of CeO₂ content. The tuning of the emissive color from green and yellow to red can be easily achieved by varying the dopant species and concentration. These results suggested that the obtained nanocomposite could be potentially applicable in transparent solid-state luminescent devices.

Two-dimensional poly(dimethylsiloxane) (PDMS) films with wavy patterns were studied in order to investigate reversible and irreversible wetting effects. Pre-strained, surface oxidized layers of PDMS were used to form relieved wavy geometries, on which hydrophobic functionalization was carried out in order to produce irreversible wetting effects. Wavy-patterned PDMS films showed time-dependent reversible wetting effects. The degree of surface wettability could be tuned by the choice of wavy groove geometries. And the groove geometries were controlled via O₂ plasma treatment and mechanical pre-straining. The pre-strained, buckled PDMS films were applied to the fabrication of hydrophobic polystyrene nano-patterns using colloidal self-assembly, where the colloids were arrayed in two-dimensional way. The wavy polystyrene films were found to be more hydrophobic relative to flat polystyrene films. The grooving methodology used in this study could be applied to enhancing the hydrophobicity of other types of polymeric thin films, eliminating the need for chemical treatment.

In this study, a series of LaMnO₃–diamond composites with varied LaMnO₃ mass contents supported on micro-diamond have been synthesized using a sol–gel method. The as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and the Fourier transform infrared spectra (FTIR). Meanwhile, the photocatalytic performances were also tested by photoluminescence (PL) spectroscopy, ultraviolet–visible diffuse reflection spectra (UV-Vis DRS) and the degradation of weak acid red C-3GN (RC-3GN). Results show that the peak position of LaMnO₃ is shifted to low angle after the introduction of diamond, and perovskite particles uniformly distributed on the surface of diamond, forming a network structure, which can increase the active sites and the absorption of dye molecules. When the mass ratio of LaMnO₃ and diamond is 1:2 (LMO–Dia-2), the composite shows the most excellent photocatalytic activity. This result offers a sample route to enlarge the range of the application of micro-diamond and provide a new carrier for perovskite photocatalysts.

Vertically aligned WO₃–CuO core–shell nanorod arrays for NH₃ sensing are prepared. The sensor is fabricated by preparing WO₃–CuO nanorod arrays directly on silicon wafer with interdigital Pt electrodes. The WO₃–CuO nanorod arrays are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The sensor based on the vertically aligned WO₃–CuO nanorod arrays exhibits ultrasensitive NH₃ detection, indicating $p$-type behavior. The optimum sensing temperature is found to be about 150${}^{\circ }$C. Both response and recovery time to NH₃ ranging from 50ppm to 500ppm are around 10–15s. A possible NH₃ sensing mechanism of the vertically aligned hybrid nanorod arrays is proposed.

The cetyltrimethyl ammonium bromide (CTAB)-modified montmorillonite (MMT) was synthesized via a novel “dissolution and reassembly” method. To determine the optimal formula, the adsorption of C.I. Reactive Red 2 (X3B) with CTAB/MMT was investigated. The optimal CTAB/MMT nanocomposite was used to remove 2,6-dichlorophenol and p-nitrophenol from aqueous solutions. The adsorption results can be described by Langmuir isotherm, and the adsorption capacities were 200mg/g and 125mg/g for 2,6-dichlorophenol and p-nitrophenol, respectively. To realize the quick separation and recycle, the magnetic CTAB/MMT was further strategized and synthesized. The adsorption equilibrium time was 15min for both contaminants; the ions’ strength showed a little bit of influence on the adsorption performance. In addition, compared with acidic condition, neutral condition was more beneficial to the adsorption reaction. Due to the addition of Fe₃O₄, the adsorption capacities of this magnetic nanocomposite for 2,6-dichlorophenol and p-nitrophenol were a little bit decreased, which were 170mg/g and 91mg/g, respectively. However, the magnetic nanocomposite can be separated within 30s under an external magnetic field, which would be useful in the practical application.

TiO₂ films were deposited from oxygen/titanium tetraisopropoxide (TTIP) plasmas at low temperature by Helicon-PECVD at floating potential ($V_f)$ or substrate self-bias of $-$50V. The influence of titanium precursor partial pressure on the morphology, nanostructure and optical properties was investigated. Low titanium partial pressure ([TTIP] $<$ 0.013Pa) was applied by controlling the TTIP flow rate which is introduced by its own vapor pressure, whereas higher titanium partial pressure was formed through increasing the flow rate by using a carrier gas (CG). Then the precursor partial pressures [TTIP$+$CG] $=0.027$Pa and 0.093Pa were obtained. At $V_f$, all the films exhibit a columnar structure, but the degree of inhomogeneity is decreased with the precursor partial pressure. Phase transformation from anatase ([TTIP] $<$ 0.013Pa) to amorphous ([TTIP$+$CG] $=0.093$Pa) has been evidenced since the O${}_2^{+}$ ion to neutral flux ratio in the plasma was decreased and more carbon contained in the film. However, in the case of $-$50V, the related growth rate for different precursor partial pressures is slightly ($\sim$ 15%) decreased. The columnar morphology at [TTIP] $<$ 0.013Pa has been changed into a granular structure, but still homogeneous columns are observed for [TTIP$+$CG] $=0.027$Pa and 0.093Pa. Rutile phase has been generated at [TTIP] $<0.013$Pa. Ellipsometry measurements were performed on the films deposited at $-$50V; results show that the precursor addition from low to high levels leads to a decrease in refractive index.