Nano

The treatment of phenol-containing wastewater is a hot topic in the field of environmental chemistry. In this work, the hydroxyl grafted graphite phase carbon nitride (g-C₃${\text{N}}_4)$ was prepared by alkaline hydrothermal (AH) treatment, and its degradation of phenol under visible light was investigated. XRD, UV-Vis, FT-IR, XPS, N₂ adsorption, PL, ESR, TPD and EIS were used to characterize the as-prepared catalysts. The results showed that the hydroxyl group grafting does not influence the crystal structure, optical property and specific surface area of catalyst. Compared with the hydroxyl group modified g-C₃N₄ prepared by H₂O₂ method, the alkali hydrothermal treatment can graft more hydroxyl groups onto the g-C₃N₄ surface, leading to the higher electron–hole separation efficiency. The as-prepared catalyst using this method had more surface negative charges and stronger adsorption capacity for the reaction substrate phenol. The g-C₃N₄ prepared by this alkali hydrothermal treatment displayed the phenol degradation rate constant of 0.22h${}^{-1}$, which is 3.72 and 2.06 times higher than that of neat and H₂O₂ treated g-C₃N₄, as well as excellent catalytic stability and structural stability. The possible reaction mechanism was proposed.

Recently, ferroelectric resistive switching (RS) effect in the ferroelectric/semiconductor heterostructures has been widely studied and the RS performance has been greatly improved. However, the relationships between ferroelectric and RS behaviors as well as interface structure of ferroelectric/semiconductor heterostructures need to be further studied. Herein, a ${\text{La}}_{0.67}$${\text{Sr}}_{0.33}$MnO₃ (LSMO) layer with the thickness of 7 nm is inserted into ${\text{PbZr}}_{0.52}$${\text{Ti}}_{0.48}$O₃/Nb:SrTiO₃ (PZT/NSTO) heterostructures, and its effects on the ferroelectric and RS behaviors are investigated. The PZT/NSTO heterostructures show significantly asymmetric ferroelectric loops, and the RS ratio in which can reach to three orders of magnitude. However, by inserting the LSMO layer, the ferroelectric loops became relatively symmetric, but the RS effect almost disappeared. It can be considered that the LSMO layer affects the interfacial energy band structure of the PZT/NSTO heterostructures, which makes ferroelectric polarization lose its effect on the modulation of the depletion layer width. Therefore, the existence of the adjustable depletion layer is very important for the RS effect of ferroelectric/semiconductor heterostructures.

Respiratory disease caused by the presence of bacteria in the atmosphere seriously threatens human health. Air pollution as harmful suspended particles, like haze, is conducive to bacterial spread and growth; it must be prevented to avoid harming the respiratory tract. Herein, filtration membranes possessing superior antibacterial activity are considered as an effective means to protect humans from atmospheres contaminated with bacteria. The aim of this study is to prepare an environmentally friendly and biodegradable multifunctional biopolymer composite nanofibrous membrane, which can be used as a candidate material for air filtration applications. Since traditional air filtration materials do not degrade in the natural environment, we synthesized a nanofibrous membrane composed of gelatin (GT) and silk fibroin (SF), in which antibacterial agent can anchor via electrostatic spinning. Also, both GT and SF can break down in the natural environment, which avoids secondary pollution of the atmosphere. Preliminary experiments show that GS nanofibrous membranes are excellent carriers of antibacterial agent for antibacterial applications. Several characterizations and testing measurements indicate that resultant nanofibrous membranes are effective against Gram-positive and Gram-negative bacteria. Moreover, a water vapor transmission rate test shows the excellent filtration performance of the materials.

Nanostructured nonlinear optical (NLO) materials are attracting increasing interest as optical limiters for various applications. In this study, one-dimensional nanostructured Na₂Ti₃O₇ was synthesized by a typical hydrothermal method and systematically characterized. The results showed that one-dimensional nanostructured Na₂Ti₃O₇ has good crystallinity and thermal stability. Its morphology can be easily controlled to form nanotubes, nanobelts and nanorods by altering the amounts of added NaOH. The robustness of the NLO properties of one-dimensional nanostructured Na₂Ti₃O₇ in broadband optical limiting (OL) applications was investigated by the open-aperture Z-scan method. At laser wavelengths of 532 nm and 1064 nm, the effective nonlinear extinction coefficients showed nonmonotonic dependence on the morphology; nanotubes gave the maximum value. The results confirmed that the NLO and OL responses of one-dimensional nanostructured Na₂Ti₃O₇ can be effectively optimized by tailoring the morphology. In addition, the nonlinear extinction coefficients of these three types of one-dimensional nanostructured Na₂Ti₃O₇ are better than those of multi-walled carbon nanotubes, a benchmark one-dimensional OL material, at 532 nm and 1064 nm; they therefore have potential applications in nonlinear optics. Nonlinear scattering and photothermal effect measurements showed that the OL shown by one-dimensional nanostructured Na₂Ti₃O₇ can be mainly attributed to nonlinear scattering and free-carrier absorption at both irradiation wavelengths. The fabrication of one-dimensional nanostructured Na₂Ti₃O₇ with different morphologies via this simple approach paves the way for the synthesis and tuning of new one-dimensional materials with desirable photonic properties for various applications.

Anatase TiO₂ photocatalysts with exposed (001) facets have attracted great attention for environmental protection technology due to their high reactivity for degradation of organic species. In this work, potassium hydrogen phthalate (denoted as KHP), as the most commonly used reference standard solution for calibrating photoelectrochemical chemical oxygen demand (denoted as PeCOD) instrument, was selected as the study sample. The intrinsic degradation kinetics of KHP on (001) surface was investigated by a photoelectrochemical (denoted as PEC) method with a purposely (001) faceted double-layered structure TiO₂ photoanode. The high kinetics constants of fast process of KHP and other acids indicate that the (001) surface possesses a higher reactivity of aromatic carboxylic acid as theoretically predicted. Meanwhile, the investigation of the KHP adsorption properties on A001 photoanode provides the possibility of using this photoanode as a sensor in a new type of PeCOD instrument for organic acid determination.

There is a broad interest in using graphene or graphene oxide (GO) sheets as a transducer for selective and label-free detection of biomolecules such as DNA, tumor marker, biological ions, etc. Here, a chemical vapor deposition (CVD) graphene-based Hall effect biosensor used for ultrasensitive label-free detection of DNA via DNA hybridization is reported. Hall effect measurements based on the Van der Pauw method are used to perform single-base sequence selective detection of DNA on graphene sheets, which are prepared by CVD. The mobility decreases and the sheet resistance increases with the adding of either complementary or one-base mismatched DNA to the graphene device. The hole carrier concentration of the graphene devices increases apparently with the addition of complementary DNA while it is hardly affected by the one-base mismatched DNA. The detection limit as low as 1pM was realized with a linear range from 1pM to 100nM. Moreover, the Hall effect biosensor was able to distinguish the complementary DNA from one-base mismatched DNA with a high specificity of $\approx$6.2 which is almost two orders of magnitude higher than that of the previously reported graphene biosensors based on DNA–DNA hybridization.

Novel ZnIn₂S₄/FeUiO-66 (ZFeU) photocatalyst with different proportion of FeUiO-66 has been successfully prepared by a facile one-pot solvothermal reaction. The as-synthesized nanocomposites have been thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), Brunauer–Emmett–Teller (BET) characterization, photoluminescence (PL) analysis and electrochemical impedance spectrum (EIS). The photocatalytic performance of ZFeU nanocomposites for the photodegradation of RhB under visible light irradiation was better than that of ZnIn₂S₄ and FeUiO-66 alone. The experiment results showed the 20% ZFeU nanocomposites had the best photocatalytic properties. At the same time, a probable mechanism was discussed and it was believed that introduction of FeUiO-66 on ZnIn₂S₄ would minimize the recombination of photogenerated electron-hole pairs, leading to the enhancement of the photocatalytic activity.

Highly blue fluorescence carbon dots (CDs-MCM) were successfully prepared via a simple hydrothermal method with citric acid and ethylene diamine tetraacetic acid doped mesoporous silica MCM-41. The CDs-MCM exhibited uniform particle size and possessed good excitation-dependent characteristic. It showed highly selectivity and sensitivity in detection of Cr(VI), folic acid and good linear ranges of 0–37.5$\mu$M ($R^2=0.9903$) and 0–50$\mu$M ($R^2=0.9949$). The low detection limits were 79.31nM and 118.73nM for Cr(VI) and folic acid, respectively. It revealed that inner filter effect dominated in Cr(VI) quenching of the CDs-MCM fluorescent, while that of folic acid belonged to static quenching. The CDs-MCM were successfully used to detect the Cr(Vl) and folic acid in water and vegetable samples with satisfactory results. It provided new insight into environmental Cr(VI) and folic acid detection.

Despite the resistance-type gas sensors attracting intensive research interest, the vulnerability to the interference of humidity is a great challenge for their large-scale productions and applications. Herein, a convenient “gas-sensitized sensing material + adhesive” approach for the fabrication of superhydrophobic interface has been proposed to settle the problem. The multiwalled carbon nanotubes (MWCNTs)/styrene-ethylene/butylene-styrene block copolymer (SEBS) layer formed by spraying the cyclohexane suspension of MWCNTs and SEBS with micro/nanostructure endows the sensor with outstanding superhydrophobic property, presenting that the apparent contact angles (CA) are up to 179.6^∘. The superhydrophobic paper sensor exhibited high sensing performance for acetone vapor and most importantly exceptional anti-humidity. The response of as-prepared sensor for other gaseous chemicals was consistent with that of MWCNTs, which indicated that the “gas-sensitized sensing $\mathrm{\text{material}}+\mathrm{\text{adhesive}}$” approach did not change the MWCNTs gas-sensitive characteristics. The approach builds an efficient bridge between gas-sensitive particles and flexible, superhydrophobic systems, inspiring a new simple way to the development of gas sensor with high immunity to humidity.

(1) Background: Though X-ray excited photodynamic therapy (X-PDT) breakthrough the bottom neck of PDT application in deep tumor by overcoming light penetration depth limitation, the quantum yield of the hydrophilic X-PDT nanoparticles (NPs) still hampered its further application in vivo. Thus, establishing a proper hydrophilic decoration method which can maximally maintain the quantum yield of X-ray excited luminescent NPs is of urgent demand. (2) Methods: We synthesized NaGdF₄: ${\text{15\%Tb}}^{3+}$ (NGF) as X-ray excited luminescent NPs and conducted hydrophilic decoration by two hydrophilic ligands, polyethylene glycol-NH₂ (PEG) and cysteamine (Cy) via place exchange reaction, and coupled with photosensitizer (MC540) to form a X-PDT nanosystem. We also conducted experiments in vitro and in vivo to evaluate the efficacy of the X-PDT system. (3) Results: Both PEG and Cy decoration NPs presented excellent emission intensity, which could well excite the coupled photosensitizer MC540 to generate significant X-PDT efficacy under low-dose X-ray radiation. Especially for the NGF-Cy-MC540 treatment group, the cell viability reduced to $\sim 15$% under 0.3Gy radiation and $\sim 40$% under only 0.1Gy radiation, which is the lowest radiation dosage in the literature reports so far. In vivo experiment showed about 36% of tumor inhibition rate under 0.3Gy X-ray. Besides, no biotoxicity was observed in NGF groups even in high concentrations, demonstrating good biocompatibility. (4) Conclusions: The hydrophilic decoration method by Cy or PEG via place exchange reaction may pave a brand new way and strategy for X-PDT further clinical application.

The conductive additives are often used to improve the conductivity of the electrode in lithium iron phosphate battery. In this work, a series of carbon-based conductive slurries of acetylene black, carbon nanotubes and graphene were obtained by the ball milling method and applied to the cathodes of lithium iron phosphate batteries. The conductivity of the ternary conductive slurry reaches 11.98Scm${}^{-1}$ and the result of Zeta potential indicates that the ternary conductive slurry has the best deposit stability. The average discharge capacity of lithium batteries with ternary conductive additive is 111.3mAhg${}^{-1}$ at the current density of 10C, which is 1.9 times higher than that of acetylene black conductive additive batteries widely used nowadays. The specific capacity of the battery is 129.2mAhg${}^{-1}$ after 200 cycles at the current density of 5C, and the capacity retention rate is 99.7%. The ternary conductive materials can form a continuous “point-line-surface” conductive network, increase the contact sites between lithium iron phosphate particles and conductive materials and provide a more efficient transmission path.

Development of microwave absorbing materials with tunable thickness and bandwidth is particularly important for practical applications, but its realization remains a great challenge. Here, we report carbon coated core-shell FeSiCr/Fe₃C embedded in two-dimensional carbon nanosheets network (FeSiCr/Fe₃C@C/C) nanocomposites fabricated by plasma arc-discharging method. FeSiCr/Fe₃C@C/C has the best microwave absorption properties in which the minimum calculated reflection loss (RL) can reach $-42.3$dB at 11.5GHz with a coating thickness of 2.4mm and the efficient absorption bandwidth (RL$<-10$dB) almost covers 4.5–18GHz range by adjusting the coating thicknesses from 1.3 to 5.0mm. The improved microwave absorption properties could be ascribed to the optimized impedance matching and enhanced polarization loss, conduction loss and internal reflections of the propagated microwave.

Ti₂${\text{Nb}}_{10}$${\text{O}}_{29}$ (TNO) is considered as a potential anode material due to its high capacity/power density and reliable safety. However, its poor electronic conductivity restricts its rate performance, which is important for its application in electric vehicles (EVs). In this study, we fabricated a hybrid of Ti₂${\text{Nb}}_{10}$${\text{O}}_{29-x}$/holey-reduced graphene oxide (TNO_x/HRGO) by a two-step method. In the structure of TNO_x/HRGO, TNO_x microspheres with oxygen vacancies are wrapped by gossamer-like HRGO. The oxygen vacancies of TNO_x and the high conductivity of HRGO can effectively enhance the electronic conductivity of the TNO_x/HRGO hybrid, and the HRGO holes are beneficial for the transmission of lithium-ion (${\text{Li}}^{+}$). The synergy effect of above features improves the rate performance of the TNO_x/HRGO hybrid. In addition, the existence of HRGO can buffer volume expansion during the insertion processes of ${\text{Li}}^{+}$, which can improve cyclic stability of the TNO_x/HRGO hybrid. Consequently, the TNO_x/HRGO electrode has excellent lithium-ion storage capacity, with high-rate performance (242mAh/g at 10^∘C, 225mAh/g at 20^∘C and 173mAh/g at 40^∘C) and excellent cyclic stability (98.0% capacity retention after 300 cycles at 10^∘C). This work reveals that TNO_x/HRGO can be a potential anode material for high-rate-performance lithium-ion storage.

Multi-element doped porous carbon materials are considered as one of the most promising electrode materials for supercapacitors due to their large specific surface area, abundant mesoporous structure, heteroatom doping and good conductivity. Herein, we propose a very simple and effective strategy to prepare nitrogen, sulfur co-doped hierarchical porous carbons (N-S-HPC) by one-step pyrolysis strategy. The effect of sole dopants as a precursor was a major factor in the transformation process. The optimized N-S-HPC-2 possesses a typical hierarchically porous framework (micropores, mesopores and macropores) with a large specific surface area (1284.87m² g${}^{-1})$ and N (4.63 atomic %), S (0.53 atomic %) doping. As a result, the N-S-HPC-2 exhibits excellent charge storage capacity with a high gravimetric capacitance of 360F g${}^{-1}$ (1 A g${}^{-1})$ in three-electrode systems and 178F g${}^{-1}$ in two-electrode system and long-term cycling life with 87% retention after 10,000 cycles in KOH electrolyte.