Nano

The pollution of water due to the release of heavy metals are particularly problematic and supplies of clean water have become a major problem worldwide. The heavy metal ions can cause toxicities and serious side effects toward human health; therefore, these metal ions should be removed from water and wastewater. A variety of strategies have been developed for efficient heavy metal removal from waters. Adsorption/ion exchange strategy play a great important role in removing heavy metal ions due to their advantages. Nanomaterials are excellent adsorbents and extensive studies have been performed to remove heavy metals from wastewater by developing and using various nanomaterials. Recent developments for the heavy metals removal by various nanomaterials, mainly including carbon-based nanomaterials, iron-based nanomaterials and photocatalytic nanomaterials in batch and flow systems are described in this review.

The CrCuFeMnNi high entropy alloy (HEA) powder was synthesized by mechanical alloying. The effects of milling time and subsequent annealing on the structure evolution, thermostability and magnetic property were investigated. After 50h of milling, the CrCuFeMnNi HEA powder consisted of a major FCC phase and a small amount of BCC phase. The crystallite size and strain lattice of 50h-ball-milled CrCuFeMnNi HEA powder were 12nm and 1.02%, respectively. The powder exhibited refined morphology and excellent chemical homogeneity. The supersaturated solid solution structure of the as-milled HEA powder transformed into FCC1, FCC2, a small amount of BCC and $\rho$ phase in annealed state. Most of the BCC phase decomposed into FCC (mainly FCC2 phase) and $\rho$ phases, and the dynamic phase transition was almost in equilibrium at 900${}^{\circ }$C. The saturated magnetization and coercivity force of the 50h-ball-milled CrCuFeMnNi HEA powder were respectively 16.1emu/g and 56.2Oe.

An efficient and stable catalyst was prepared utilizing reduced graphene oxide, Ag nanoparticles and melamine sponge for the restoration of large volume effluent containing 4-nitrophenol at room temperature. And the as-prepared sample is suitable for continuous flow system. Almost 99% 4-nitrophenol ($1.0\times 10^{-4}$molL${}^{-1}$, 100mL) can be removed within 4min in the presence of the aforementioned sample. Moreover, it also exhibits remarkable stability in continuous flow system. This may offer a new route to the fabrication of efficient flowing catalytic system.

By adopting N, N-Dimethylformamide (DMF) atmosphere annealing at room temperature, planar perovskite solar cells with a p-i-n structure of ITO/PEDOT:PSS/Perovskite/PCBM/C${}_{60}$/Al are fabricated by a simple one-step solution process in ambient air with humidity around 50%, and the influence of DMF atmosphere on perovskite solar cells (PSCs) is systematically investigated. Compared to the reference device without DMF reaction, the perovskite films treated by modest DMF annealing show a better distribution and a higher densification, and thus the power conversion efficiency (PCE), short circuit current density ($J_{\mathrm{\text{sc}}})$ and fill factor (FF) are increased by about 17%, 8% and 6%, respectively. This work displays the importance of solvent annealing for perovskite film prepared by the one-step spin-coating method, and possibly provides a simple and cost-effective way to efficiently fabricate PSCs in ambient air.

Novelty Cu₂O multi-branched nanowires and nanoparticles with size ranging from $\sim$15nm to $\sim$60nm have been synthesized by one-step hydrothermal process. These Cu₂O nanostructures when used as anode materials for lithium-ion batteries exhibit the excellent electrochemical cycling stability and reduced polarization during the repeated charge/discharge process. The specific capacity of the Cu₂O nanoparticles, multi-branched nanowires and microscale are maintained at 201.2mAh/g, 259.6mAh/g and 127.4mAh/g, respectively, under the current density of 0.1A/g after 50 cycles. The enhanced electrochemical performance of the Cu₂O nanostructures compared with microscale counterpart can be attributed to the larger contact area between active Cu₂O nanostructures/electrolyte interface, shorter diffusion length of Li${}^{+}$ within nanostructures and the improved stress release upon lithiation/delithiation.

Poly(3-methylthiophene)/reduced graphene oxide (P3MT/RGO) modified glassy carbon electrode (GCE) was fabricated via a facile procedure. P3MT was directly electrodeposited on the RGO coated electrode and employed for the electrochemical detection of paracetamol (PCT). The morphology of composite was characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the electrochemical behaviors of PCT on P3MT/RGO/GCE. Experimental parameters, such as the scan rates, polymerization laps and the pH of buffer solution were optimized. Under the optimal conditions, the anodic peak current in DPVs varies linearly with the concentration of PCT, and the limit of detection was 0.025$\mu$M. Moreover, the proposed P3MT/RGO/GCE also exhibited superior stability and reproducibility.

Polyaniline (PANI)/Zn ferrite composites were fabricated by simple two-step method. The crystal phase, particle size, morphology, thermal stability and conductivity were characterized. Electromagnetic parameters of PANI/Zn ferrite composites were measured at room temperature in the frequency of 2–18GHz. The prepared composite had an amorphous fluffy structure, Zn ferrite nanoparticles with diameters ranging from 20nm to 30nm are encapsulated in PANI or on PANI surface, and the thermal stability of the composite is poor. But Zn ferrite content plays a key role in influencing this structure and regulating microwave attenuation capability. The PANI/Zn ferrite composites showed an enhanced microwave absorption performance in Ku band at thin coating thickness which corresponds to RL value below $-10$dB and the minimum reflection loss (RL) is $-54.4$dB at 17.6GHz with the coating thickness of 1.4mm.

Herein, a simple-green road for preparing carbon dots (CDs) from the mixture of PEG6000 and papain with approving fluorescence has been successfully developed for the first time. Meanwhile, the current CDs were characterized by analytical means such as fluorescence, UV visible spectrophotometer, HR-TEM, XPS and FTIR and so on. Afterwards, this kind of CDs were employed for analyzing doxycycline (DC) relying on the mechanism that the functional group of DC had interactions with CDs, hence, leading to the fluorescence quenching. Also, this DC analytical method mentioned here permitted in a linear range of $5.0\times 10^{-8}$mol/L-$5.0\times 10^{-4}$mol/L as well as a detection limit of 18nM at a signal-to-noise ratio (S/N) of 3. More importantly, the CDs prepared here were still explored for milk real samples, indicating their potential for broadening avenues towards other various applications.

The H₂ uptake performance at room temperature of porous tungsten oxide nanomaterials with and without a catalytic Pd coating was studied by the quartz crystal microbalance technique. Tungsten oxide composed mainly of WO₃ was synthesized by inert gas condensation method using He. The samples consisted of semi-amorphous nanomaterials of low crystallinity and high porosity, as revealed by SAED, TEM, XRD, Raman spectroscopy and N₂ adsorption–desorption isotherms. The H₂ uptake capacity of the porous oxide was studied under increasing H₂ exposure pressures (1000–7000Pa), with and without Pd coating. After reaching a maximum value of 1.2 H₂wt.%, at 1160Pa, the H₂ uptake capacity of the Pd-coated oxide consistently decreased. Successive hydrogenation cycles were carried out on the Pd-coated oxide at 3300 Pa and 6000 Pa to evaluate the H₂ uptake performance of the sample under this H₂ loading and unloading process. It was found that the H₂ uptake capacity decreased from around 1 to values below 0.53H₂wt.%, which is the reference H₂ storage capacity achieved by a 15nm-thick Pd film. We argued that water molecule formation in the Pd/oxide interface and sublayers negatively affects the H₂ uptake capacity of the oxide under successive hydrogenation cycles at room temperature.

In this study, the controllable fabrication of a variety of vertically aligned, single-crystalline [110]-oriented Si nanowire arrays with sharp tips on (110)Si substrates is achieved using a combined self-assembled nanosphere lithography and multiple electroless Ag-catalyzed Si etching processes. All of the experiments were performed at room temperature. The morphological evolution and formation mechanism of long tapered [110]Si nanowire arrays during the multiple tip-sharpening cycle processes have been investigated by scanning electron microscopy, transmission electron microscopy and water contact angle measurements. Field emission measurements demonstrate that the field-emission behaviors of all nanowire samples produced in this study agree well with the Fowler–Nordheim theory, and the produced long tapered [110]Si nanowire array possesses superior electron emission characteristics, with a very low turn-on field of 1.4V/$\mu$m and a high field enhancement factor of 3816. The simple and room temperature fabrication of the well-ordered long tapered [110]Si nanowire array and its excellent electron field emission performance suggest that it can serve as a good candidate for applications in high-performance Si-based vacuum electronic nanodevices.

Developing anisotropic particles of different shapes has been a hot topic of research since decades as they possess special features not possible to achieve through other means. It is considered challenging to control atoms for developing their particles of certain size and shape. In this study, different shapes of gold particles were developed while employing a pulse-based electron–photon–solution interface process. Gold atoms, when they are in certain transition state, develop their monolayer assembly around the light glow known in argon plasma generating at the bottom of copper capillary known in cathode. The rate of uplifted gold atoms to develop monolayer assembly at solution surface is controlled by electron streams and traveling photons of high-density entering the solution. Gold atoms dissociated from the precursor on transforming photons (propagating through immersed graphite rod known in anode) to heat energy. Double-packets of nanoshape energy are generated under tuned pulse protocol when they are placed over the compact monolayer assembly resulting in tiny-sized particles of own shape. On the separation of joined tiny particles into two equilateral triangular-shaped tiny particles, each atom of their one-dimensional array elongated on both sides from the centre while exerting opposite poles forces of surface format. This results in convertion of each array of atoms into a structure of smooth elements. Due to immersing force of solution surface and their termination at the centre of light glow, tiny-shaped particles pack from different zones where their structures of smooth elements assemble to develop monolayers of developing particle in a certain shape. Developing particles of one-dimension undertake assembling of structures of smooth elements where packing of their tiny-shaped particles is from the near regions belonging to rearward sides of north–south poles at the solution surface, whereas, developing particles of multi-dimension undertake assembling of structures of smooth elements where packing of their tiny-shaped particles is from the regions of east–west poles and near regions of east–west poles on the solution surface. Depending on the number and orientation of assembled structures of smooth elements nucleating monolayers for different particles, their different anisotropic shapes develop. At fixed precursor concentration, increasing the process time results in developing particles of low aspect ratio. Under tuned parameters, particles of unprecedented features developed.

Here, the lamellar-shaped Bi₂S₃ grown on a porous TiO₂ monolith was obtained by a two-step method including a sol–gel route and hydrothermal treatment. The photocatalytic activity of the as-synthesized Bi₂S₃/TiO₂ composites was evaluated for photodegradation of methylene blue (MB) dye in aqueous solution under the visible-light irradiation. Based on our experimental results, 5% (molar ratio of Bi₂S₃ to TiO${}_2)$ Bi₂S₃/TiO₂ photocatalysts exhibited a maximum photodegradation rate of MB up to 96.9% under visible-light irradiation for 120 min. Our findings indicated that the lamellar-shaped Bi₂S₃ can extend the light absorption up to visible areas, and porous TiO₂ can provide enhanced specific surface area and more mass transfer pathway to enhance the photodegradation efficiency. Furthermore, porous TiO₂ can accept the electrons from the Bi₂S₃ conduction band due to the relatively positive electrode potential to impede the photoproduced electron and hole combination to result in advanced photocatalytic performance.

We have fabricated BiFeO₃ thin film deposited on Pt/Ti/SiO2/Si substrates by the chemical solution deposition method. The effects of annealing temperature on the thin film structure, resistance switching (RS) properties, conduction mechanisms are investigated. It exhibits improved RS window with high ON/OFF ratio ($\sim$10⁴) for the sample annealed at 650${}^{\circ }$C. XPS characterization indicates that cation ratio of Fe${}^{2+}$/Fe${}^{3+}$ is increased with increasing annealing temperature. Crystal lattice distortion generated by Fe${}^{2+}$ cations, along with oxygen vacancies, commonly contribute to opening the RS window and the increment of conductive filaments. The film’s conduction mechanisms under different annealing temperatures are fully discussed. The RS properties of this system can be effectively improved by increasing the annealing temperature, which is crucial prerequisite for future applications of BFO-based thin film device in resistance random access memory.