Changqing Ruan

Nonenzymatic biosensor based on CuxO nanoparticles deposited on polypyrrole nanowires for improving detectionrange

Cu(x)O (CuO and Cu₂O composite) nanoparticles modified polypyrrole (PPy) nanowires were fabricated and used as a biosensor for detecting glucose (GLC). PPy nanowires were prepared through electrodeposition, while Cu(x)O nanoparticles were deposited on PPy nanowires by electrodeposition and electrochemical oxidation in situ. The scanning electron microscopy images showed the Cu(x)O nanoparticles aligned along the PPy nanowires uniformly and the average size of Cu(x)O nanoparticles is about 90 nm. The electrocatalytic activity of Cu(x)O/PPy/Au towards GLC was investigated under alkaline conditions using cyclic voltammetry and chronoamperometry. The sensor exhibited a linear range up to 8 mM of GLC, which is more than two times of most of the existing non-enzymatic GLC sensors based on CuO or Cu₂O. The sensitivity of the sensor is 232.22 μAmM⁻¹ cm⁻² and detection limit is 6.2 μM (at signal/noise=3). Moreover, the sensor showed excellent selectivity, reproducibility and stability properties. These excellent performances make Cu(x)O/PPy/Au a good nonenzymatic GLC sensor.

Preparation of Porous Cellulose Beads via Introduction of Diamine Spacers.

The current work presents a synthesis route based on the reductive amination of 2,3-dialdehyde cellulose beads with diamines to render micrometer-sized beads with increased specific surface area (SSA) and porosity in the mesoporous range. Specifically, the influence of the reductive amination of 2,3-dialdehyde cellulose (DAC) using aliphatic and aromatic tethered mono- and diamines on bead microstructure was investigated. Aliphatic and aromatic tethered monoamines were found to have limited utility for producing porous beads whereas the introduction of diamines provided beads with a porous texture and an SSA increasing from <1 to >30 m(2)/g. Both aliphatic and aromatic diamines were found to be useful in producing porous beads having a pore size distribution range of 10 to 100 nm, as verified by N2 gas adsorption and mercury intrusion porosimetry analyses. The true density of the functionalized DAC beads decreased to an average of about 1.36 g/cm(3) as compared to 1.48 g/cm(3) for the unfunctionalized, fully oxidized DAC beads. The total porosity of the beads was, according to mercury porosimetry, in the range of 54-64%. Reductive amination with 1,7-diaminoheptane provided beads that were stable under alkaline conditions (1 M NaOH). It was concluded that the introduction of tethered diamines into DAC beads is a facile method for producing mesoporous beads.

Preparation of porous 2,3-dialdehyde cellulose beads crosslinked with chitosan and their application in adsorption of Congo red dye

Micrometer sized 2,3-dialdehyde cellulose (DAC) beads were produced via a recently developed method relying on periodate oxidation of Cladophora nanocellulose. The produced dialdehyde groups and pristine hydroxyl groups provided the DAC beads with a vast potential for further functionalization. The sensitivity of the DAC beads to alkaline conditions, however, limits their possible functionalization and applications. Hence, alkaline-stable and porous cellulose beads were prepared via a reductive amination crosslinking reaction between 2,3-dialdehyde cellulose beads and chitosan. The produced materials were thoroughly characterized with different methods. The reaction conditions, including the amount of chitosan used, conditions for reductive amination, reaction temperature and time, were investigated and the maintained morphology of the beads after exposure to 1M NaOH (aq.) was verified with SEM. Different washing and drying procedures were used and the results were studied by SEM and BET analysis. Furthermore, FTIR, TGA, EDX, XPS, DLS and elemental analysis were performed to characterize the properties of the prepared beads. Finally, the alkaline-stable porous chitosan cross-linked 2,3-dialdehyde cellulose beads were applied as adsorbent for the dye Congo red. The crosslinked beads displayed fast and high adsorption capacity at pH 2 and good desorption properties at pH 12, providing a promising sorption material.

Al2O3 Underlayer Prepared by Atomic Layer Deposition for Efficient Perovskite Solar Cells

Perovskite solar cells, as an emergent technology for solar energy conversion, have attracted much attention in the solar cell community by demonstrating impressive enhancement in power conversion efficiencies. However, the high temperature and manually processed TiO2 underlayer prepared by spray pyrolysis significantly limit the large-scale application and device reproducibility of perovskite solar cells. In this study, lowtemperature atomic layer deposition (ALD) is used to prepare a compact Al2 O3 underlayer for perovskite solar cells. The thickness of the Al2 O3 layer can be controlled well by adjusting the deposition cycles during the ALD process. An optimal Al2 O3 layer effectively blocks electron recombination at the perovskite/fluorine-doped tin oxide interface and sufficiently transports electrons through tunneling. Perovskite solar cells fabricated with an Al2 O3 layer demonstrated a highest efficiency of 16.2 % for the sample with 50 ALD cycles (ca. 5 nm), which is a significant improvement over underlayer-free PSCs, which have a maximum efficiency of 11.0 %. Detailed characterization confirms that the thickness of the Al2 O3 underlayer significantly influences the charge transfer resistance and electron recombination processes in the devices. Furthermore, this work shows the feasibility of using a high band-gap semiconductor such as Al2 O3 as the underlayer in perovskite solar cells and opens up pathways to use ALD Al2 O3 underlayers for flexible solar cells.

Favored surface-limited oxidation of cellulose with Oxone® in water

A novel method for favored primary alcohol oxidation of cellulose was developed. Cellulose pulp andCladophora nanocellulose were oxidized in a one-pot procedure by Oxone® (2KHSO5

Cellulose Nanofibers Prepared via Pretreatment Based on Oxone® Oxidation

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One-pot preparation of glucose biosensor based on polydopamine-graphene composite film modified enzyme electrode

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Tailor-Making Low-Cost Spiro[fluorene-9,9′-xanthene]-Based 3D Oligomers for Perovskite Solar Cells

Softwood sulfite bleached cellulose pulp was oxidized with Oxone® and cellulose nanofibers (CNF) were produced after mechanical treatment with a high-shear homogenizer. UV-vis transmittance of dispersions of oxidized cellulose with different degrees of mechanical treatment was recorded. Scanning electron microscopy (SEM) micrographs and atomic force microscopy (AFM) images of samples prepared from the translucent dispersions showed individualized cellulose nanofibers with a width of about 10 nm and lengths of a few hundred nm. All results demonstrated that more translucent CNF dispersions could be obtained after the pretreatment of cellulose pulp by Oxone® oxidation compared with the samples produced without pretreatment. The intrinsic viscosity of the cellulose decreased after oxidation and was further reduced after mechanical treatment. Almost translucent cellulose films were prepared from the dispersions of individualized cellulose nanofibers. The procedure described herein constitutes a green, novel, and efficient route to access CNF.