Dispersive liquid-liquid microextraction coupled with surface enhanced Raman scattering for the rapid detection of sodium benzoate.

Medicine safety has become a large concern and prompts an urgent need to develop a rapid, simple and sensitive analytical method, which can monitor excessive preservatives in medicine. In this work, dispersive liquid-liquid microextraction (DLLME) was combined with surface enhanced Raman scattering (SERS) for a quick analysis of a kind of preservatives, sodium benzoate, in ibuprofen oral solution. The experimental parameters affecting DLLME were systematically investigated. Under the optimal conditions, the whole procedure, including DLLME and the SERS analysis, could be carried out within 10 min. A good linearity between the concentration of sodium benzoate ranging from 10 to 500 mg L-1 and the SERS signal intensity could be obtained, and the correlation coefficient (R2) 0.9986. The method detection limit was 0.56 mg L-1. The relative standard deviation was less than 6.33% for ten replicates at the same sample concentrations. The analytical results prove that the method is suitable for rapid determination of sodium benzoate in ibuprofen oral samples

Dispersive liquid-liquid microextraction coupled with surface enhanced Raman scattering for the rapid detection of sodium benzoate

Abstract(#br)Medicine safety has become a large concern and prompts an urgent need to develop a rapid, simple and sensitive analytical method, which can monitor excessive preservatives in medicine. In this work, dispersive liquid-liquid microextraction (DLLME) was combined with surface enhanced Raman scattering (SERS) for a quick analysis of a kind of preservatives, sodium benzoate, in ibuprofen oral solution. The experimental parameters affecting DLLME were systematically investigated. Under the optimal conditions, the whole procedure, including DLLME and the SERS analysis, could be carried out within 10 min. A good linearity between the concentration of sodium benzoate ranging from 10 to 500 mg L −1 and the SERS signal intensity could be obtained, and the correlation coefficient (R 2 ) 0.9986. The method detection limit was 0.56 mg L −1 . The relative standard deviation was less than 6.33% for ten replicates at the same sample concentrations. The analytical results prove that the method is suitable for rapid determination of sodium benzoate in ibuprofen oral samples

Efficacy of adjunctive azithromycin versus single-dose cephalosporin prophylaxis for caesarean scar defect : Study protocol for a randomised controlled trial

Peer reviewedPublisher PD

Effects of size and surface on the auxetic behaviour of monolayer graphene kirigami

Graphene is an active element used in the design of nano-electro-mechanical systems (NEMS) owing to its excellent in-plane physical properties on mechanical, electric and thermal aspects. Considering a component requiring negative Poisson's ratio in NEMS, a graphene kirigami (GK) containing periodic re-entrant honeycombs is a natural option. This study demonstrates that a GK with specific auxetic property can be obtained by adjusting the sizes of its honeycombs. Using molecular dynamics experiments, the size effects on the auxetic behaviour of GK are investigated. In some cases, the auxetic difference between the hydrogenated GK and continuum kirigami (CK) is negligible, in which the results from macro CK can be used to predict auxetic behaviour of nano kirigami. Surface effect of GK is demonstrated from two aspects. One is to identify the difference of mechanical responses between the pure carbon GK and the hydrogenated GK at same geometry and loading condition. Another is from the difference of mechanical responses between the GK model and the CK model under same loading condition and geometric configuration. Generally, surface energy makes the GK possess higher variation of auxetic behaviour. It also results in higher modulus for the GK as comparing with that of the CK.The authors are grateful for the financial support from the National Natural-Science-Foundation of China (Grant Nos 11502217, 11372100) and the Australian Research Council (Grant No. DP140103137

Preparation and Performance Study of Carboxy-Functionalized Graphene Oxide Composite Polyaniline Modified Water-Based Epoxy Zinc-Rich Coatings

Graphene oxide is obtained by oxidation of graphite followed by ultrasonic exfoliation. It is a two-dimensional layered material with a large number of oxygen-containing functional groups on its surface. Polyaniline is a conductive polymer and has a unique corrosion protection mechanism. In this study, carboxy-functionalized graphene oxide/polyaniline (CGO/PANI) composites with a lamellar structure were prepared by in situ polymerization. The lamellar layer was used to form a labyrinthine structure in the coating to effectively retard the penetration of corrosive media. The electrical conductivity of polyaniline can promote the formation of conductive pathways between zinc particles and improve the utilization of zinc powder. Polyaniline is also able to passivate the substrate, further improving the coating’s ability to protect steel substrates against corrosion. In this paper, the in situ polymerization of aniline on carboxy-functionalized graphene oxide flakes was confirmed by scanning electron microscopy (SEM), Fourier infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), and the improvement of the corrosion resistance of the prepared composites on the epoxy zinc-rich coatings was evaluated by SEM, electrochemical impedance spectroscopy (EIS), and salt spray resistance tests. The results showed that aniline was successfully polymerized in situ on carboxy-functionalized graphene oxide, and the modified coating had significantly improved anticorrosive properties, where the best anticorrosive improvement was achieved when CGO: PANI = 0.03

MnII-Doped Cesium Lead Chloride Perovskite Nanocrystals: Demonstration of Oxygen Sensing Capability Based on Luminescent Dopants and Host-Dopant Energy Transfer

The design of photoluminescence-quenching probes for molecular oxygen (O-2) is always a large space to explore. Luminescent semiconductor nanocrystals (NCs) have been proposed as emerging oxygen-responsive probes, but the inherent O-2 sensing of phosphorescent semiconductor NCs has not been reported so far. Here, we demonstrate the O-2 sensing capability of Mn-II-doped CsPbCl3 nanocrystals (Mn:CsPbCl3 NCs) and reveal the role of O-2 on the optical de-excitation process of such perovskite nanocrystals (PNCs). By adjusting the amount and distribution of Mn-II dopants, as well as the host-dopant energy transfer process in PNCs, we highlight that O-2 can reversibly quench the Mn-II emission due to the temporary disturbance to the ligand field of near-surface Mn-II dopants in PNCs. In phosphorescence mode, the photoluminescence intensity of the Mn:CsPbCl3 NCs is quenched by 53% on increasing O-2 concentration from 0 to 100%. The Stern-Volmer plot shows a good linear in the 0-12% O-2 concentration range. High sensing reversibility and rapid signal response are also achieved. In our perception, the mechanism study makes our PNCs candidates for the optical probes of O-2, and it is enlightening to explore more possibilities of the inherent O-2 sensing based on the semiconductor-doped NCs (not restricted to Mn-II-doped PNCs) with phosphorescence emission

An electrochemical biosensor for the sensitive detection of specific DNA based on a dual-enzyme assisted amplification

In this work, a simple and ultrasensitive electrochemical DNA biosensor was developed based on the horseradish peroxidase (HRP)-catalyzed electrochemical process and exonuclease III (Exo III)-assisted target recycling amplification strategy. A biotin tag labeled molecular beacon (MB) with hairpin structure was ingeniously designed and assembled on an electrode as a recognition element. The 3' overhang end of the MB labeled with biotin would bind streptavidin (SA)-HRP to give a strong initial signal. Upon target DNA sensing, the MB probe would be stepwise removed by the Exo III accompanied by the release of the target DNA for the successive hybridization and cleavage process. Simultaneously, numerous biotin labeled mononucleotides were liberated, leading to a decrease in the binding of the biotin and SA-HRP polymer on the electrode. As a result, the amplified electrochemical current significantly decreased. Because of the autocatalytic target recycling amplification and the HRP-catalyzed electrochemical process, the dual enzyme-based strategy provided an ultrasensitive approach (down to the 10 fM level) for the electrochemical detection of DNA, and discriminated mismatched DNA from perfectly matched target DNA, which has great potential for early diagnosis in gene-related diseases