Sichuan University

About: Sichuan University is a education organization based out in Chengdu, China. It is known for research contribution in the topics: Population & Catalysis. The organization has 107623 authors who have published 102844 publications receiving 1612131 citations. The organization is also known as: Sìchuān Dàxué.

Well-redispersed ceria nanoparticles: Promising peroxidase mimetics for H2O2 and glucose detection

Abstract: Well-redispersed ceria nanoparticles (CeO2 NPs) were synthesized by a simple hydrothermal method. The prepared CeO2 NPs exhibited excellent catalytic activity towards classical peroxidase substrate 3,3,5,5-tetramethylbiphenyl dihydrochloride (TMB·2HCl) in the presence of H2O2, based on which a colorimetric method that is highly sensitive and selective was developed for glucose detection. The composition, structure, morphology and peroxidase-like catalytic activity of CeO2 NPs are investigated in detail by using X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FT-IR), thermal analysis (TG) and UV-vis absorption spectroscopy. According to this method, the detection of H2O2 and glucose are in linear range from 6.0 × 10−7 to 1.5 × 10−6 mol L−1 and 6.6 × 10−6 to 1.3 × 10−4 mol L−1, with the detection limit down to 5.0 × 10−7 mol L−1 H2O2 and 3.0 × 10−6 mol L−1 glucose, respectively. Further, this simple, cheap, highly sensitive and selective colorimetric method for glucose detection was successfully applied for the determination of glucose in human serum samples.

Efficient Electrochemical N2 Reduction to NH3 on MoN Nanosheets Array under Ambient Conditions

Abstract: Electrochemical N2 reduction reaction (NRR) under ambient conditions offers us an environmentally friendly route for artificial synthesis of NH3. However, up to now, few noble-metal-free electrocatalysts with satisfactory catalytic activities have been explored. In this Letter, we demonstrate that MoN nanosheets array on carbon cloth (MoN NA/CC) acts as a high-performance NRR electrocatalyst toward NH3 electrosynthesis in 0.1 M HCl under ambient conditions. This catalyst achieves a large NH3 yield of 3.01 × 10–10 mo1 s–1 cm–2 and a Faradaic efficiency of 1.15% at −0.3 V vs reversible hydrogen electrode with strong electrochemical durability and selectivity. Density functional theory calculations reveal that MoN NA/CC catalyzes NRR via the Mars–van Krevelen mechanism.

Polyethylenimine-grafted cellulose nanofibril aerogels as versatile vehicles for drug delivery.

Abstract: Aerogels from polyethylenimine-grafted cellulose nanofibrils (CNFs-PEI) were developed for the first time as a novel drug delivery system. The morphology and structure of the CNFs before and after chemical modification were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Water-soluble sodium salicylate (NaSA) was used as a model drug for the investigation of drug loading and release performance. The CNFs-PEI aerogels exhibited a high drug loading capability (287.39 mg/g), and the drug adsorption process could be well described by Langmuir isotherm and pseudo-second-order kinetics models. Drug release experiments demonstrated a sustained and controlled release behavior of the aerogels highly dependent on pH and temperature. This process followed quite well the pseudo-second-order release kinetics. Owing to the unique pH- and temperature-responsiveness together with their excellent biodegradability and biocompatibility, the CNFs-PEI aerogels were very promising as a new generation of controlled drug delivery carriers, offering simple and safe alternatives to the conventional systems from synthetic polymers.

Unusual Tuning of Mechanical Properties of Isotactic Polypropylene Using Counteraction of Shear Flow and β-Nucleating Agent on β-form Nucleation

Abstract: Isotactic polypropylene (iPP) has good comprehensive properties, viz. easy processing, high heat resistance, and good stiffness, etc., and in turn is widely used as a commodity plastic. However, under conventional processing conditions, iPP crystallizes into sizable spherulites with few tie molecules between spherulites. With such a crystalline texture, iPP exhibits very low impact toughness, especially at lower temperature, which restricts its more extensive application. Therefore, toughening of iPP has always been an open research. Up to now, four routes have been taken to improve impact strength of iPP, including copolymerizing with other olefin monomers, blending with rubber or thermoplastic elastomer, compounding with organic or inorganic fillers (e.g., nanoparticles), and adding β-nucleating agent. Without doubt, the modified iPP, more or less, increases its toughness. The enhancement of toughness is, unfortunately, at sacrifice of other properties, e.g., strength, heat resistance, etc. There are extremely few successful examples for simultaneously efficiently reinforcing and toughening iPP. It has been well established that for iPP oriented crystals (i.e., shish-kebabs) can bring out notable reinforcement on iPP, while β-form crystals of iPP can greatly increase its toughness. Flow (shear, elongational, or mixed) would induce formation of shish-kebabs whose content is governed to shear rate, shear duration, and molecular species and weight, etc. On the other hand, β-form crystals can be high production generated by addition of β-nucleating agent under quiescent conditions. This type of iPP crystals causes high toughness due to the β-R polymorphous transition and the loose structure of β-form crystals compared with R-crystals in favor of absorbing impact energy. Naturally, an idea arises that combination of flow-induced molecular orientation crystallization and β-nucleant-induced β-form crystals produces efficient reinforcement and toughening on iPP. However, as a matter of fact, there is not any example of it in the open literature. Themajor reason is that the coexistence of a β-nucleating agent and a shear flow at above a certain but low level of shear rate depresses β-form nucleation. Huo et al. performed a delicate study on iPP crystallization with β-nucleating agent and observed that as the shear rate rises, the content of β crystals constantly reduces, more greatly for higher nucleating agent content, showing counteraction between shear and β-nucleating agent for β-form formation. Apparently, it is a great practical challenge to prepare iPP parts withhighmolecular orientation and highβ-crystal proportion for the purpose of both strength and toughness enhancement. In the present work, we attempt to fabricate iPP with considerably increased strength and toughness, for the first time, utilizing the counteraction of shear-induced orientation crystallization and β-nucleating agent on β-form nucleation. The crystallization process of iPP is manipulated by two stages: one is flow-induced crystallization for high molecular orientation, and the other is β-nucleating-agent-induced nucleation for highβ-crystal content. More specifically, the oscillation shear supplied by an oscillation shear injectionmolding (OSIM) (its detailed definition is included in the Experimental Section) is imposed on β-nucleated iPP melt in the mold during injection molding. Initially, due to occurrence of shear flow and β-nucleating agent, β-form formation is restrained; thereby, the oriented R-crystals first form in the skin and intermediate layers of the sample.When the gate of the mold freezes, the shear ceases, and hereby, β-nucleating agent revives. The remainder of iPP melt in the core layer undergoes β-nucleation-induced crystallization. The results demonstrate that a large amount of shish-kebab structure appears in the surface and intermediate layers of the sample; at the same time, numerous β-form crystals form in the core layer, thus leading to prominent reinforcement and toughening for iPP.

Composition and poling condition-induced electrical behavior of (Ba0.85Ca0.15)(Ti1−xZrx)O3 lead-free piezoelectric ceramics

Abstract: Lead-free (Ba 0.85 Ca 0.15 )(Ti 1− x Zr x )O 3 (BCTZ) piezoelectric ceramics were fabricated by normal sintering in air atmosphere. BCTZ ceramics with x = 0.10 possess a coexistence of tetragonal and rhombohedral phases at ∼40 °C. The Curie temperature of BCTZ ceramics decreases with increasing the Zr content. Piezoelectric properties of BCTZ ceramics are dependent on the poling conditions (i.e., the poling temperature and the poling electric field), and the underlying physical mechanism is illuminated by the phase angle. The BCTZ ( x = 0.10) ceramic, which locates at the existence of two phases and is poled at E ∼ 4.0 kV/mm and T p ∼ 40 °C, exhibits an optimum electrical behavior at a room temperature of ∼20 °C: d 33 ∼ 423 pC/N, k p ∼ 51.2%, 2 P r ∼ 18.86 μC/cm 2 , 2 E c ∼ 0.47 kV/mm, ɛ r ∼ 2892, and tan δ ∼ 1.53%.