Publications by authors named "Zhang Pudun"

Acetylation of Cellulose nanocrystal (CNC) can reduce its surface polarity and therefore extends its application in biomedical and chemical fields. A method combining uniform design (UD) and response surface methodology (RSM) was developed to produce the acetylated CNC with arbitrary degree of substitution (DS) and crystallinity index (CrI). The effects of three factors (i.

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The fluorescence of carbon quantum dots (CQDs) has been paid a lot of attention, but its photothermal performance attracts less attention since preparing CQDs with high photothermal conversion efficiency (PCE) is a big challenge. In this work, CQDs with an average size of 2.3 nm and a PCE of up to 59.

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A highly luminescent nitrogen-doped carbon quantum dots (N-CQDs) with a quantum yield of 44% was prepared by a facile hydrothermal synthesis method using citric acid (CA) and ethylenediamine (EDA) with a molar ratio of 1:1 at 200 °C for 5 h. The hypochlorite (ClO) ions significantly quench the fluorescence of the N-CQDs according to a pseudo-second-order kinetic model. A sensitive and selective quantification method with an excellent linearity in the range of 1.

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Effects of montmorillonite (MMT) on the crystallization behavior of poly(L-lactic acid) (PLLA) were investigated by variable-temperature FTIR spectroscopy. The variations of carbonyl band (1800-1720 cm) of different PLLA/MMT nanocomposites were focused due to its strong intensity and the involved abundant structure information. Difference spectrometry was used to evaluate the structural variations of PLLA after introducing MMT, and perturbation correlation moving window two-dimensional analysis (PCMW2D) split the temperature range into two sub-regions, i.

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Monitoring the evolution of polymer aging, especially early-stage aging, over both time and dimensionality can provide in-depth insight into aging-induced material invalidation and even disastrous accidents. However, it remains a great challenge because currently available methods for polymer aging only provide statistic results at a macroscopic scale. Herein, we report the first three-dimensional early-stage visualization (ESV) technique of polymer aging by using the fluorophore-bonded boronic acid to specifically target aging-induced hydroxyl groups through the B-O click reaction.

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The evolutions of the crystalline polymorphs of poly(l-lactic acid) (PLLA) at 85 °C and 145 °C were respectively studied by Fourier transform infrared (FTIR) spectroscopy coupled with two-dimensional correlation spectroscopy (2DCOS) and perturbation-correlation moving-window two-dimensional (PCMW2D) analysis in the carbonyl stretching band region (1820-1720 cm). The perturbation region was divided into a few sub-regions by PCMW2D based on the spectral variations. Further 2DCOS analyses were implemented on these sub-regions.

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It is a trend to substitute bioplastics for petroleum-based plastics in food packaging. Glycerol-plasticized soy protein isolate (SPI) is promising as a replacement for traditional petroleum-based plastics. Hydrogen bonding (H-bonding) plays a key role in plasticization of SPI film.

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Although multivariate curve resolution (MCR) has been applied to the analysis of Fourier transform infrared (FTIR) imaging, it is still problematic to determine the number of components. The reported methods at present tend to cause the components of low concentration missed. In this paper a new idea was proposed to resolve this problem.

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A series of chlorobutyl rubber/polyamide-12 (CIIR/PA-12) blends compatibilized by different amounts of maleic anhydride (MAH) grafted polypropylene (PP-g-MAH) were investigated by attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) mapping. Multivariate curve resolution (MCR) was used to process the FT-IR images. Both the spectra of pure components in the blends and their concentration distributions in a micro-region were acquired.

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Fourier transform infrared (FT-IR) imaging coupled with principal component analysis (PCA) is used to characterize the photooxidation of polypropylene (PP) and identify the photooxidative products at different oxidation times. PP slices were exposed to ultraviolet (UV) irradiation for times up to 60 hours and spatially resolved spectra were acquired with a transmission FT-IR imaging system in order to view the steric inhomogeneity of the photooxidation process of PP. The evolution of the oxidized products with irradiation time is shown through the application of PCA.

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The rule of current change was studied during capillary electrophoresis (CE) separation process while the conductivity of the sample solution was different from that of the buffer. Using a quadratic spline wavelet of compact support, the wavelet transforms (WTs) of capillary electrophoretic currents were performed. The time corresponding to the maximum of WT coefficients was chosen as the time of current inflection to calculate electroosmotic mobility.

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FTIR microscopic imaging was used to investigate the miscibility behavior of ethylene/vinyl acetate copolymer (EVA) and C5 petroleum resin. Images with an area of 500 x 500 microm(2) were collected in the reflection mode. The miscibility was characterized by probing the spatial distribution of the carbonyl group (C=O) of EVA in the whole images.

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In this paper, fluorescence correlation spectroscopy (FCS) was applied to measure the hybridization fraction of the ssDNA probe with its perfectly matched 146 mer ssDNA and a base mismatched 146 mer ssDNA from human methylenetetrahydrofolate reductase (MTHFR) gene. The ssDNA fragments in this study were obtained by asymmetric PCR techniques. The measurements were performed on a laboratory-built FCS system based on the two components fitting procedure.

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In this paper, fluorescence correlation spectroscopy (FCS) was applied to measure the size of water-soluble quantum dots (QDs). The measurements were performed on a home-built FCS system based on the Stokes-Einstein equation. The obtained results showed that for bare CdTe QDs the sizes from FCS were larger than the ones from transmission electron microscopy (TEM).

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Modified nucleosides excreted in urine have been studied as possible bio-markers for malignant tumors. Reversed-phase high performance liquid chromatography (RP-HPLC) is one of the most popular analytical tools. However, its analysis time is longer than desired.

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A capillary electrophoretic method for determining the inorganic anions in the ash of black powder has been developed. The components and pH of the buffer solution, the concentration of osmotic flow modifier and the separation voltage were investigated. The optimized parameters were 5.

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Thirteen normal and modified nucleosides, primarily degradation products of transfer ribonucleic acid (tRNA), were evaluated as potential tumor markers for cancer patients. Their urinary concentrations were determined by means of micellar electrokinetic capillary chromatography (MEKC) in the urine from 54 healthy adults and 70 cancer patients, then quantitatively expressed as a function of creatinine excretion. It was found that urinary nucleosides for cancer patients were on the average significantly higher than those for healthy controls, however, no significant differences were found between male and female or between different ages.

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