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Xiaoyan Z.,Jiangnan University | Zhangyi L.,Jiangnan University | Zaijun L.,Jiangnan University | Zaijun L.,The Key Laboratory of Food Colloids and Biotechnology
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2017

The functionalization of graphene quantum dots has become a powerful method to modulate its chemical, electronic and optical properties for various applications. In the study, we reported a facile synthesis of valine-functionalized graphene quantum dots (Val-GQDs) and its use as a novel fluorescent probe for optical detection of Hg2 +. Herein, Val-GQDs was synthesized by the thermal pyrolysis of citric acid and valine. The resulting Val-GQDs has an average size of 3 nm and the edge of graphene sheets contains the rich of hydrophilic groups, leading to a high water-solubility. Compared to the GQDs prepared by thermal pyrolysis of citric acid, Val-GQDs exhibits a stronger fluorescence (> 10-fold) and better photostability (> 4-fold). Interestingly, the existence of valine moieties in the Val-GQDs results in a more sensitive fluorescent response to Hg2 +. The fluorescent signal will linearly decrease with the increase of Hg2 + concentration in the range from 0.8 nM to 1 μM with the correlation coefficient of 0.992. The detection limit is 0.4 nM (S/N = 3), which the sensitivity is > 14-fold that of GQDs. The analytical method provides the prominent advantage of sensitivity, selectivity and stability. It has been successfully applied in the optical detection of Hg2 + in real water samples. The study also provides a promising approach for the design and synthesis of functionalized GQDs to meet the needs of further applications in sensing and catalysis. © 2016 Elsevier B.V.


Xu X.,Jiangnan University | Ni X.,Jiangnan University | Cao Y.,Jiangnan University | Cao Y.,The Key Laboratory of Food Colloids and Biotechnology | And 4 more authors.
Electrophoresis | Year: 2014

Amphiphilic polymeric micelle, as a novel pseudostationary phase in EKC was used to determine eight kinds of corticosteroids namely hydrocortisone, prednisolone, hydrocortisone acetate, prednisone, cortisone acetate, prednisolone acetate, dexamethasone, and triamcinolone acetonide in cosmetics. Amphiphilic random copolymer poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) was micellizated via neutralization in alkaline aqueous solution. The influences of the molar ratio of monomer MMA to MAA, the concentration of polymer and pH on the polymeric micelle microstructure and EKC performances were investigated. As molar ratio of MMA to MAA in P(MMA-co-MAA) increased, both CMC and environmental polarity of the inner core in polymeric micelle decreased dramatically. With increasing monomer ratio, the size of polymeric micelles increased firstly, and then decreased, finally increased again. ζ potential of the micelle had a slight decline trend. As increment of polymer concentration, the size of the polymeric micelle increased steadily. By optimizing the monomer ratio, the polymer concentration, and pH of the running buffer, as well as operation conditions such as separation voltage and temperature, the eight analytes could be separated within 16.5 min using 7.5 mg/mL polymer with the monomer ratio of 7:3 dissolved in pH 9.2 borax buffer as the running buffer. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for eight analytes were between 85.9 and 106%. This method was of accuracy, repeatability, pretreatment simplicity, and could be applied to the quality control of cosmetics. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ni X.,Jiangnan University | Zhuo X.,Jiangnan University | Xu X.,Jiangnan University | Cao Y.,Jiangnan University | And 2 more authors.
Journal of Chromatography A | Year: 2014

The random amphiphilic polymeric aggregation, self-assembled from poly (methyl methacrylate-. co-methacrylic acid) (P(MMA-. co-MAA)), was explored as a novel pseudostationary phase (PSP) in electrokinetic chromatography (EKC) in our previous report. This work focused on physicochemical characteristics and PSP performances of the polymeric aggregations. The physicochemical characteristics of polymeric aggregations, including critical aggregation concentration (CAC), zeta potential, hydrodynamic diameter, and micropolarity were determined. Experimental results showed that polymeric aggregations had much lower CAC, which decreased the usage of copolymer in EKC, weakened ionic strength and shortened analysis time. The monomer molar ratio of the copolymer was a key factor for physicochemical characteristics and PSP performances of the polymeric aggregations. With the increase of the hydrophobic monomer molar ratio, CAC, micropolarity and dimension of polymeric aggregation decreased significantly while zeta potentials were similar. Correspondingly, separation window enlarged and methylene selectivity evaluated with six kinds of n-alkylphenone homologous series enhanced. Linear solvation energy relationships (LSER) analysis found that hydrophobic interaction is the most important interaction between analytes and polymeric PSPs. Compared with SDS micelle, polymeric aggregations owned more types of interactions, such as stronger hydrogen bonding and relative larger dipole interaction, which provided a bigger adjustment room to improve PSP selectivity. © 2014 Elsevier B.V.


Ni X.,Jiangnan University | Yu M.,Jiangnan University | Cao Y.,Jiangnan University | Cao Y.,The Key Laboratory of Food Colloids and Biotechnology | Cao G.,Jiangnan University
Electrophoresis | Year: 2013

In this work, the influences of ionic liquid (IL) as a modifier on microemulsion microstructure and separation performance in MEEKC were investigated. Experimental results showed that synergetic effect between IL 1-butyl-3-methylimidazolium tetrafluoro-borate (BmimBF4) and surfactant SDS gave a decreased CMC. With increment of IL in microemulsion, negative ζ potential of the microdroplets reduced gradually. The influence of IL on the dimensions of microdroplet was complicated. At BmimBF4 less than 8 mM, IL made microemulsion droplet smaller in size. While at BmimBF4 more than 10 mM, the size increased and reached to a maximum value at 12 mM, where the microdroplets were larger than that without IL. After that, the micreodroplet size decreased again. Relative fluorescence intensity of the first vibration band of pyrene to the third one (I1/I3) enhanced as IL was added to microemulsion, which indicated that this addition increased environmental polarity in the inner core of microdroplets. Prednisone, hydrocortisone, prednisolone, hydrocortisone acetate, cortisone acetate, prednisolone acetate, and triamcinolone acetonide were analyzed with MEEKC modified with IL to evaluate the separation performance. Cortisone acetate and prednisolone acetate could not be separated at all in typical microemulsion. The seven analytes could be separated by the addition of 10 mM BmimBF4 into the microemulsion system. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for seven analytes were between 86 and 114%. This method provides accuracy, reproducibility, pretreatment simplicity, and could be applied to the quality control of cosmetics. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Chen T.-Y.,Jiangnan University | Zhang C.-J.,Jiangnan University | Li Z.-J.,Jiangnan University | Li Z.-J.,The Key Laboratory of Food Colloids and Biotechnology | Gu Z.-G.,Jiangnan University
Chinese Journal of Inorganic Chemistry | Year: 2014

Tetrabutyl titanate and graphite oxide were dispersed in tertbutanol by ullrasonicalion and then added the lithium acetate solution into the above mixed solution under the microwave radiation to produce spinel Li4Ti5O12 (LTO) precursor/graphene oxide. On the one hand, the microwave radiation will promote the hydrolysis of tetrabutyl titanate, thus the reaction for forming the precursor can be completed in 15 min. On the other hand, “soft template” confinement effect of tertbutanol leads to form the LTO precursor with very small particle size and uniform morphology. Meanwhile, small LTO precursor particles will fully embed the graphene oxide nanosheets through their second agglomeration. Finally, the LTO precursor/graphene oxide was calcined at 800 °С for 8 h to obtain spinel LTO@graphene (LTO@G). The study shows that LTO crystal in the LTO@G has a diameter of 0.2~1.5 μm and the tap density of LTO@G reached 1.7 g·cm-3. The graphene is located inside the crystal and significantly improve the electronic conductivity. The conductivity of LTO@G was found to be 1.84× 10-3 S·m-1, which is remarkably higher than pure phase LTO (1.1 ×10-7 S·m-1). In 1C and 4C, the first discharge specific capacitances of LTO@G was found to be 170.1 mAh·g-1 and 97.5 mAh·g-1, respectively. These results demonstrated that the LTO@G has good high-rate capability and tap density, it can be widely used in various commercial lithium ion battery. © 2014, Chinese Chemical Society, All rights reserved.


Huang Y.-J.,Jiangnan University | Zhou X.-Y.,Jiangnan University | Li Z.-J.,Jiangnan University | Li Z.-J.,The Key Laboratory of Food Colloids and Biotechnology | And 2 more authors.
Chinese Journal of Inorganic Chemistry | Year: 2013

Different anionic surfactant was empolyed as additive for the seed-mediated synthesis of gold nanorods and effect of the kind of anionic surfactant on the morphology and optical property of gold nanorods were also investigated. In the presence of sodium dodecyl benzene sulfonate (SDBS), the yield of gold nanorods is obviously higher that of the reaction system using sodium dodecyl sulfate. The reaction conditions of the seed-mediated synthesis of gold nanorods added SDBS were optimized, and the optimal concentrations of hexadecyltrimethylammonium bromide, SDBS, ascorbic acid and silver nitrate were found to be 0.04 mol·L-1, 2.4 mmol·L-1, 1.2 mmol·L-1 and 0.08 mmol·L-1, respectively. Under the condition, the growth of gold nanorods can complete within 30 minutes, the as-prepared gold nanorods offer a surface plasmon resonance absorption with a maximum absorption peak at 823 nm and aspect ratio of (5±0.03). When changing silver nitrate concentration in the growth solution, the size of gold nanorods also changed. In addition, we also discussed the action mechanism of SDBS. In comparsion with classical seed-mediated synthesis method, proposed method for synthesis of gold nanorods shows an obvious improvement of size adjustable, monodispersity and biological toxicity, and it can be widely applied to a variety of optical and biological analysis.


Lu J.,Jiangnan University | Ni X.,Jiangnan University | Cao Y.,Jiangnan University | Cao Y.,The Key Laboratory of Food Colloids and Biotechnology | And 2 more authors.
Electrophoresis | Year: 2015

A novel catanionic surfactants vesicle system composed of octyltriethylammonium bromide/ sodium dodecyl benzene sulfonate (C8NE3Br/SDBS) has been developed as pseudostationary phase (PSP) in EKC. The C8NE3Br/SDBS system possesses a large vesicle phase region and none of agglomeration phenomena appeared while mixing cationic and anionic surfactants at any molar ratio. Electrophoretic and chromatographic parameters including elution window, hydrophobic selectivity, polar group selectivity, and shape selectivity were characterized using the vesicle at molar ratio of C8NE3Br to SDBS of 3:7 as PSP. Compared with SDS micelles, the vesicle PSP possessed a wider elution window and a better selectivity. The retention behavior and selectivity differences between the novel vesicle and SDS micelles were evaluated through linear solvation energy relationship (LSER) analysis. Though the cohesiveness and the hydrogen bond acidity have greatest influences on the solutes retention and selectivity in both the vesicle and SDS micelle, the vesicle PSP demonstrated a higher hydrophobicity and a lower hydrogen bonding donating capability owing to compact bilayer structure of vesicle. Additionally, the vesicle system had a stronger hydrogen bond accepting capability than SDS micelle. Consequently, according to LSER analysis, the bigger coefficients for v, b, and a revealed the vesicle PSP had a better separation selectivity than conventional SDS micelle. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ruiyi L.,National University of Ireland, Maynooth | Qianfang X.,The Key Laboratory of Food Colloids and Biotechnology | Zaijun L.,The Key Laboratory of Food Colloids and Biotechnology | Zaijun L.,Jiangnan University | And 3 more authors.
Biosensors and Bioelectronics | Year: 2013

The study developed an electrochemical immunosensor for ultrasensitive detection of microcystin-LR in water. Graphene oxide and chloroauric acid were alternately electrodeposited on the surface of glassy carbon electrode for 20 cycles to fabricate graphene-gold nanocomposite. The composite was characterized and its apparent heterogeneous electron transfer rate constant (37.28±0.16cms-1) was estimated by Laviron's model. To immobilize microcystin-LR antibody and improve the electrical conductivity, 2,5-di-(2-thienyl)-1-pyrrole-1-(p-benzoic acid) and chloroauric acid were electrodeposited on the modified electrode in sequence. The ionic liquid was then dropped on the electrode surface and finally microcystin-LR antibody was covalently connected to the conducting polymer film. Experiment showed the electrochemical technique offers control over reaction parameters and excellent repeatability. The graphene-gold nanocomposite and gold nanoparticles enhance electron transfer of Fe(CN)6 3-/4- to the electrode. The ionic liquid, 1-isobutyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide, improves stability of the antibody. The sensor displays good repeatability (RSD=1.2%), sensitive electrochemical response to microcystin-LR in the range of 1.0×10-16-8.0×10-15M and detection limit of 3.7×10-17M (S/N=3). The peak current change of the sensor after and before incubation with 2.0×10-15M of microcystin-LR can retain 95% over a 20-weeks storage period. Proposed method presents remarkable improvement of sensitivity, repeatability and stability when compared to present microcystin-LR sensors. It has been successfully applied to the microcystin-LR determination in water samples with a spiked recovery in the range of 96.3-105.8%. © 2013 Elsevier B.V.


Fan Y.,The Key Laboratory of Food Colloids and Biotechnology | Fang Y.,The Key Laboratory of Food Colloids and Biotechnology | Ma L.,The Key Laboratory of Food Colloids and Biotechnology
Colloids and Surfaces B: Biointerfaces | Year: 2014

Unsaturated fatty acid liposomes (Ufasomes) have attracted interests because of the ready availability of unsaturated fatty acids and the simple assembly strategy. However, the colloidal instability of the ufasomes hinders them from applying in the fields of drug delivery and food additives. In the present work, conjugated linoleic acid (CLA) with triple activities of bioactive, assembling and crosslinking was employed as a new molecular building block to construct ufasome and afterwards crosslinked ufasome. First, CLA ufasome was self-assembled from CLA molecules in response to pH variation, and the suitable CLA concentrations and pH ranges were determined by surface tension measurement and acid-base titration. Subsequently, the self-crosslinked CLA ufasome was prepared by intra-ufasomal crosslinking of conjugated double bonds in the CLA molecules. The morphologies of the self-crosslinked CLA ufasomes were imaged using transmission electron microscopy (TEM), from which the size of 20-50. nm and the bilayer thickness of 2.7. ±. 0.5. nm were detected. Most importantly, based on the comparison of the bilayer thicknesses of the different fatty acids, the molecular arrangement in the bilayer membrane of the self-crosslinked CLA ufasome is named "side-by-side" model contrary to the ordinary "tail-to-tail" model. The pH stability of the self-crosslinked CLA ufasome was examined in virtue of dynamic light scattering tests. Finally, in vitro release results of 5-fluorouracil from the self-crosslinked CLA ufasome showed that the process was slow and sustainable. © 2014 Elsevier B.V.


He Z.-Q.,The Key Laboratory of Food Colloids and Biotechnology | Zhang M.-J.,The Key Laboratory of Food Colloids and Biotechnology | Fang Y.,The Key Laboratory of Food Colloids and Biotechnology | Jin G.-Y.,The Key Laboratory of Food Colloids and Biotechnology | Chen J.,The Key Laboratory of Food Colloids and Biotechnology
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

Four novel alkylaryl sulfate extended surfactants were synthesized by introducing a phenyl group, together with a polypropylene oxide (PPO) chain, as the intermediate polarity spacer in the extended surfactant molecules. Some characteristic properties of the novel extended surfactants were investigated in view of the effect of spacer structure on the performance of the surfactants. It is found that not only the PPO chain but also the phenyl group exerts a strong influence on the performance since these extended surfactants exhibit low cmc, great effectiveness and efficiency of surface tension reduction, high electrolyte resistance and ultralow interfacial tension comparing with the phenyl-free counterpart. It is notable that using a polarizable phenyl group as a junction unit in the intermediate polarity spacer may produce two potential effects: one is obviously resulting in a more gradual polarity transition intramolecularly than that of the PPO chain itself as a spacer; and the other is possibly forming a denser molecular packing and a thicker interfacial layer when the novel extended surfactants occupy at air/water (brine) surface or decane/water (brine) interface, which is attributed to a well-designed molecular structure in favor of forming a more gradual polarity transition zone in the interfacial layer. © 2014 Elsevier B.V.

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