Nano

Mesoporous silica (MS) spheres of different sizes with pH-responsive characteristics were synthesized based on Stöber’s theory. Organic functionalization with aminopropyl and carboxyl groups resulted in different materials, namely, MS@NH₂@COOH. MS@NH₂@COOH were observed to have a large number of carboxyl groups and multiamine chains, and were grafted into pore channels and pore outlets through systematic characterization analyses. All modified samples demonstrated the controlling of the delivery rate of DOX from the siliceous matrix. We also compared the drug release behavior of the DOX-loaded materials at high pH (7.4) and low pH (5.5) and studied the cytotoxicity on A549 cells. The experimental results indicated that the drug delivery system can better control drug release and have potential applications in the drug delivery field.

Ag nanoparticles decorated N-doped carbon black with different Ag content was synthesized via a straightforward method. The catalysts have been conducted in the catalytic hydrogenation of nitrophenols in the presence of sodium borohydride. The results show that Ag₄/NCB possesses the highest catalytic activity for the catalytic hydrogenation of $p$-nitrophenol ($p$-NP) to $p$-aminophenol ($p$-AP). The significant enhancement in catalytic activity can be attributed to the high dispersity and smaller size of Ag nanoparticles, and remarkable synergistic effect of the combination of Ag nanoparticles and N-doped carbon black.

In this study, LaFeO₃/ZnIn₂S₄ composites were synthesized via in situ synthesis. The composition, structure and optical absorption properties of LaFeO₃/ZnIn₂S₄ were characterized by X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy, fluorescence spectroscopy (PL), Fourier Transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The photocatalytic activity of the LaFeO₃/ZnIn₂S₄ photocatalyst was determined based on the degradation of methyl orange (MO). LaFeO₃/ZnIn₂S₄ composites showed much better photocatalytic performance compared with pure LaFeO₃ and ZnIn₂S₄. The enhanced photocatalytic performance was attributed to intimately contacted interfaces and charge transfer channels which can effectively transfer and separate the photogenerated charge carriers.

Based on the liquid-phase reduction mechanism, a controllable synthesis method, which uses piezoelectric-actuated high-frequency vibration self-circulating microfluidic reactor, to prepare silver nanoparticles is proposed. Firstly, the synthesis mechanism of silver nanoparticles and the working principle of the microfluidic reactor were analyzed. Then, in order to study and explore the influence of self-circulating and high frequency vibration on the synthesis of silver nanoparticles, a series of related synthesis experiments were carried out. The synthesized silver nanoparticles were characterized by UV-Visible spectroscopy and transmission electron microscopy. The effects of micropump driving voltage and high-frequency vibration on the synthesis of silver nanoparticles were analyzed. The experiment results show that when the silver nanoparticles were synthesized using piezoelectric-actuated high-frequency vibration self-circulating microfluidic reactor, the higher the driving voltage of the circulating reflux micropump, the faster the vortex rotation speed in the mixing pool and the more uniform the reagent reaction. Besides, high-frequency vibration can suppress the aggregation of silver nanoparticles, and balance the growth environment of particles, which is beneficial to the formation of silver nanoparticles with good monodispersity, high sphericity and small size deviation.

Crystal structure control is so important to the fluorescence properties that each element should be considered carefully. In conventional synthesis of Zn_xCd${}_{1-x}$S alloyed nanocrystals (NCs), most of studies focus on ligand–surface interaction on the formation of either zinc blende or wurtzite Zn_xCd${}_{1-x}$S nanocrystals, instead of the reactant source. In this work, mixed crystal phase was found easily in Zn_xCd${}_{1-x}$S alloyed NCs when reaction proceeded at high Zn/Cd source ratio condition. Therefore, we regulate the Zn/Cd ratio to obtain relative pure zinc-blende structure, and study the influence of structure change on the fluorescence properties. Further, we have proposed a two-step ZnS coating method to acquire Zn_xCd${}_{1-x}$S/ZnS NCs with separated crystal-phase between core and shell. Compared with maximum QY of 81% for Zn_xCd${}_{1-x}$S/ZnS NCs synthesized by conventional one-step coating method, the performance of the optimized NCs has significantly improved with maximum QY of 93%.

A graphene-based composite with high electrochemical performance for supercapacitor applications is fabricated by introducing nanoscale carbide-derived carbon (NCDC) into the fluorine-doped graphene (FG). The incorporation of fluorine can increase the specific capacitance of graphene by providing more pseudocapacitance, whereas the introduction of NCDC into the FG/NCDC composite offers high specific surface area (SSA) (up to 1317m²g${}^{-1}$) and hierarchical pore structure, resulting in an enhanced electric double layer capacitance. Due to the synergistic effect of pseudocapacitance and electric double layer capacitance, the specific capacitance of FG/NCDC composite can reach 321 F g${}^{-1}$ at a scan rate of 5mVs${}^{-1}$ in aqueous electrolyte. Notably, the specific capacitance of the FG/NCDC composite is very stable during long-term cyclic tests, with no significant degradation after 10,000 cycles. Due to its excellent supercapacitive performance, the FG/NCDC composite can be considered as a promising electrode material for high-performance supercapacitors.

MIL-101(Cr)/AC was synthesized by in situ incorporation of activated carbon powder via hydrothermal method. The water stability, n-hexane adsorption and regeneration of the MIL-101(Cr)/AC were experimentally measured. The results showed that the MIL-101(Cr)/AC exhibited the larger surface area (3319.3m²/g) than that of MIL-101(Cr) and AC, respectively. The addition of activated carbon was beneficial to improve the yield of MIL-101(Cr)/AC. The pore structure parameter and XRD of the MIL-101(Cr)/AC changed little after in water for 24h. Furthermore, the adsorption capacity of MIL-101(Cr)/AC for n-hexane was 786mg/g, which increased to 23.0% and 27.7% compared with MIL-101(Cr) and AC, respectively. Kinetic fitting of data indicated that the pseudo-first order model can more accurately describe the adsorption process of n-hexane on MIL-101(Cr)/AC and the intraparticle diffusion was not the sole rate-controlling step. Besides, the regeneration efficiency of MIL-101(Cr)/AC was over 92% after 10 consecutive n-hexane adsorption/desorption cycles.

Development of low-cost, highly active catalyst for efficient oxygen evolution reaction based on earth-abundant metals is still a great challenge. Here, we report that a rod-like bimetallic NiFe metal-organic framework (NiFe-MOF) can directly act as a highly efficient oxygen evolution reaction (OER) catalyst synthesized by a convenient-to-operate hydrothermal method. The rod-like NiFe-MOF can derive 10mAcm${}^{-2}$ with a low overpotential of only 26mV, and its Tafel slope is 40.82mVdec${}^{-1}$, which is superior to that of monometallic Ni-MOF or Fe-MOF, and even can be comparable to that of RuO₂. To identify the origin of enhancing OER activity, we resorted to X-ray diffraction, scanning electron microscope, transmission electron microscope, high resolution transmission electron microscopy image and nitrogen adsorption–desorption techniques and various electrochemical techniques to probe it gingerly. The results indicate that its high electrochemically active area and the synergistic effect of bimetallic node could be responsible for the surprisingly high catalytic performance of the NiFe-MOF. These results suggest that this kind of bimetallic MOF (NiFe-MOF) could be a promising electrocatalyst for oxygen evolution reaction.

In this study, a kind of novel rare-earth nanocrystals/hydroxypropylcellulose–poly (acrylic acid) (HPC–PAA) complex fluorescent nanogel, its responsive behavior to environmental temperature and pH value were reported. For preparation, with HPC being used as template, HPC–PAA nanogel was first synthesized by polymerization and crosslinking reaction of acrylic acid (AA) in water solution. In the process, a redox initiator, which composed of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED), was used to initiate the reaction. Then, the as-prepared nanogel reacted with Ce(NO${}_3{)}_3$ and NH₄F solution successively, and a novel CeF₃ nanocrystals/HPC–PAA complex nanogel was fabricated. The microstructure of the nanogel was characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), Thermogravimetric (TG) and Transmission electron microscopy (TEM). The environmental sensitivity of the nanogel was investigated by photoluminescence (PL) and UV–Visible spectrophotometer (UV–Vis). The thermo- and pH-sensitive fluorescence were studied by PL at various temperatures and pH values; besides, the behavior of drug loading and release was researched by PL with a famous antibiotic of Ibuprofen as model drug. The results show that the PL intensity of the nanogel was largely affected by environmental temperature, or content of Ibuprofen loaded in the nanogel. The as-prepared nanogel can be used as useful sensitive material to detect temperature and pH value change, and drug loading or release property of Ibuprofen can be detected by PL emission of the nanogels conveniently.

Ni-rich Li(Ni${}_{0.8}$Co${}_{0.1}$Mn${}_{0.1})$O₂ cathode material is widely recognized as one of the most cathode materials for lithium-ion batteries due to its high specific capacity, high energy density and low cost. In this paper, the NCM cathode material precursor Ni${}_{0.8}$Co${}_{0.1}$Mn${}_{0.1}$(OH)₂ was prepared by coprecipitation method and the optimum experimental conditions were investigated. The effects of water bath temperature on the electrochemical performances of the prepared materials were investigated by controlling the morphology. The results showed that 60^∘C was the best bath temperature for the precursor which has a regular spheroidal morphology and uniform particles with the diameter of 10$\mu$m. After coprecipitation, the samples calcined under oxygen atmosphere displayed good electrochemical properties. The discharge specific capacity is up to 194mA$\cdot$h$\cdot$g${}^{-1}$ and 134mA$\cdot$h$\cdot$g${}^{-1}$ at 0.2^∘C and 5^∘C, respectively. The initial coulombic efficiency is 87.57% at 0.2^∘C.

Heteroatom-doped ordered mesoporous carbons (OMCs) have currently been considered as promising electrode materials for electrochemical sensors due to the combined advantages of ordered mesoporous materials and heteroatom-doped carbon materials. Herein, a novel nitrogen and sulfur co-doped OMCs (N,S-OMC) has been prepared via a nanocasting strategy with an inexpensive methylene blue as single precursor. The obtained mesoporous carbon has platelet morphology, short mesoporous channel together with a large surface area (549m²/g) as well as rich N- and S-containing functional groups (6.8at.% N and 2.3at.% S). Compared with the graphene (GR) and carbon nanotube (CNT) electrode material, the N,S-OMC exhibited a higher electrochemical activity towards the oxidation of herbicide amitrole, ascribable to N,S-OMC’s open mesoporous structures and abundant electroactive defect sites on the carbon skeleton. And, an amitrole electrochemical sensor with N,S-OMC modified electrode as working electrode was fabricated, exhibiting a good selectivity, stability, reproducibility and wide linear range of 3–750$\mu$M. Moreover, the N,S-OMC-based electrochemical sensor was proved feasible in river water sample analyses, showing a satisfied recovery ranging from 97.03% to 105.42%. The results not only demonstrate cheap methylene blue can be used as single precursor for the N,S-OMC preparation, but also confirm the N,S-OMC is promising in amitrole sensor fabrication.

The electric field on a hemisphere-on-post nanowire is numerically calculated using the finite element method (FEM). The FEM calculation results show that the field is sufficiently strong for extracting a significant field emission current only in a small area at the top of the hemisphere, while the contribution to the field emission from the other part of the hemisphere and the flank side of the cylinder is negligible owing to the rapid drop of the electric field. Both the local current density at the top of the hemisphere ($J_c$) and the average current density across the nanowire cross-section ($J_a$) are calculated and the $J_a$-to-$J_c$ ratio ($\alpha$) is introduced to reflect the nonuniformity of the field emission. An empirical formula with proper parameters that can best fit the simulation results is derived for describing the dependence of $\alpha$ on the macroscopic electric field ($F_m$). As a result, the $J_a$–$F_m$ relationship is attained and the revision to the traditional Fowler–Nordheim (FN) formula caused by the nonuniformity of field distribution is found in both the pre-exponent part and the exponent part, so that the deviation of the FN plots from linearity often observed in experiments is partly accounted for. Moreover, the resistance at the emitter-substrate interface is shown to cause saturation in the field emission current and a downward bending of the FN plot in the high-field region.

Supported Co catalysts were prepared by impregnating the support (MgO, SiO₂ and Al₂O${}_3)$ with Co(acac)₂ solution, and diameter-selective growth of single-walled carbon nanotubes (SWCNTs) by ethanol chemical vapor deposition has been assessed on these Co catalysts. In contrast to Co/SiO₂ and Co/Al₂O₃ catalysts with relatively high surface areas, Co/MgO catalyst with a low surface area demonstrates the best performances in the diameter-selective growth of SWCNTs under an optimal growth condition. Multiple characterizations on catalysts and SWCNTs revealed that Co(acac)₂ was absorbed on MgO by ligand exchange and anhydrous solvent CH₂Cl₂ strengthened the anchoring of Co(acac)₂ on the MgO surface, which resulted in well-dispersed Co species upon calcination in air. Under a modest reduction temperature, the reduction of Co oxides provided Co clusters, which were anchored by the unreacted Co ions in the interior of MgO support, leading to the synthesis of SWCNTs with a narrow diameter distribution.

Two-dimensional hexagonal boron nitride is a fascinating nanomaterial with a broad range of potential applications. However, further development of this nanomaterial is hampered because of its poor functionality and low processability. One of the efficient strategies for improving the processability of two-dimensional hexagonal boron nitride is the covalent functionalization of this nanomaterial. In this study, we report on a straightforward approach for functionalization of two-dimensional hexagonal boron nitride by lithium cyclopentadienyl and its application for water treatment. Cyclopentadienyl-functionalized boron nitride was characterized by different spectroscopy and microscopy methods as well as thermal and BET analysis. The synthesized nanomaterial was able to efficiently remove methylene blue from water in a short time. Adsorption capacity of this nanomaterial was as high as 476.3mg/g, which was superior to the nonfunctionalized boron nitride. Our results showed that cyclopentadienyl-functionalized boron nitride is a promising candidate for the removal of cationic pollutants from water.