Huixiang Wu

Synthesis of maltodextrin-grafted-cinnamic acid and evaluation on its ability to stabilize anthocyanins via microencapsulation

Abstract In this work, maltodextrin-grafted-cinnamic acid (MD-g-CA) was synthesised and used as wall material to improve the stability of purple sweet potato anthocyanins (PSPa) via microencapsualtion. MD-g-CA was prepared through esterification in a two-step convenient synthesis procedure and characterised using infra-red (IR) spectroscopy. The IR data indicated the typical ester carbonyl stretching at around 1721 cm−1. Moreover, MD-g-CA could give about 40% inhibition of DPPH radical and present excellent UV-absorption, which were notably better than that of native MD. Maltodextrin (MD) and MD-g-CA were used to prepare PSPa microcapsules by spray drying. The stability of PSPa was evaluated by UV-Vis analysis. The microcapsules produced by MD-g-CA showed a spheres-like appearance with some cracks. Storage tests revealed that the degradation rate of PSPa embedded by MD-g-CA was much lower than that of free PSPa under the same condition. Thus, MD-g-CA could be used as an effective wall material to improve stability of anthocyanins.

Highly Sensitive Fluorescent Sensor for Cartap Based on Fluorescence Resonance Energy Transfer Between Gold Nanoparticles and Rhodamine B

Cartap residue poses a great threat to human health and its derivatives would remain in soils, natural waters and other environmental domains for a long time. Herein, a simple, rapid and ultrasensitive analytical method for the determination of cartap based on fluorescence resonance energy transfer (FRET) between Au nanoparticles (AuNPs) and rhodamine B (RB) is first described. With the presence of citrate-stabilized AuNPs, the fluorescence of RB was remarkably quenched by AuNPs via FRET. The fluorescence of the AuNPs-RB system was recovered upon addition of cartap, cartap can be adsorbed on the surface of AuNPs due to its amino group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the FRET between AuNPs and RB was weakened and the PL intensity of RB was recovered accordingly. A good linear correlation for detection of RB was exhibited from 1 nM to 180 nM, and the detection limit reached 0.88 nM, which was much lower than the safety limit required by USA, UK and China. To the best of our knowledge, it has been the lowest detection ever without the aid of costly instrumentation. This method was successfully carried out for the assessment of cartap in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost and non-time-consuming compared with traditional methods.

A Highly Sensitive Fluorescent Sensor for Amitrole Determination in Aqueous Samples

A simple yet sensitive fluorescent sensor was reported for amitrole analysis based on integration of gold nanoparticles (AuNPs) and CdTe quantum dots (CdTe QDs) via inner filter effect (IFE). The fluorescence of GSH-coated CdTe QDs can be significantly quenched by AuNPs, and gradually restored in the presence of amitrole. Addition of amitrole induced AuNPs aggregation and decreased their characteristic surface plasmon absorption, which diminished the IFE between them. The sensor platform realized high sensitivity and good reproducibility in low concentration amitrole ranging from 9.5nM to 1000nM with a detection limit down to 4.75nM under the optimized conditions. It also resisted a wide range of interfering counterparts and showed analytical performance comparable to the majority of analytical methods reported in prior studies. We envisioned the first fluorescent amitrole sensor would be potentially useful for low cost on-site amitrole monitoring in real application.

A Ratiometric Fluorescent Assay for Fluazinam Based on FRET Between CdTe Quantum Dots and Porphyrin

A fluorescent detection system for fluazinam was reported using fluorescence resonance energy transfer (FRET) method based on CdTe quantum dots (CdTe QDs) and 5, 10, 15, 20-tetrakis(4-methacryloyloxy) phenyl porphyrin (TMaPP). TMaPP and water-soluble CdTe QDs were synthesized successfully and characterized using FT-IR, 1H NMR, XPS and TEM, respectively. FRET mechanism between CdTe QDs and TMaPP was confirmed by detailed studies on their fluorescent spectra. After a co-culture of TMaPP and CdTe QDs, fluorescent intensity of CdTe QDs decreased significantly while that of TMaPP increased concomitantly due to altered FRET. Addition of fluazinam led to impaired energy transfer from CdTe QDs to TMaPP and therefore fluorescence recovery of CdTe QDs with fluorescence quenching of TMaPP. The correlation of fluazinam concentration with the fluorescence intensity ratio FQDs∕FTMaPP provided the basis for quantitative analysis, and a broad linear range varying from 0.01μM to 5μM with a low detection limit of 2.3nM was...

Development of Simple and Effective Dual-Readout Sensor Based on Gold Nanoparticles and Cadmium Telluride Quantum Dots for Cartap Analysis

Cartap is among the most popular pesticides that are widely used to boost food production, however, its residues pose a great threat to human health and the environment. We presented simple and effective colorimetric sensor based on aggregation of gold nanoparticles (AuNPs) with appropriate diameter and fluorescent sensor via inner filter effect (IFE) of AuNPs on cadmium telluride quantum dots (CdTe QDs), respectively. Firstly, effect of diameter of AuNPs was investigated and the results indicated that AuNPs with diameter of 13nm (AuNPs13nm) showed better sensitivity toward cartap. Thus, AuNPs13nm was chosen for colorimetric and fluorescent cartap assay. On one hand, mercaptoacetic acid (MA) was functionalized on AuNPs13nm for the improvement of anti-disturbance ability for discrimination study. A decent linear relationship for cartap was obtained in the range from 1μM to 50μM with detection limit of 1.32μM for colorimetric readout; on the other hand, fluorescent sensor based on AuNPs13nm displayed excell...