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We have designed a single-particle detection assay for quantifying Hg2+ by DFM-correlated Raman spectroscopy. A tetrahedral DNA-directed core-satellite nanostructure is used as the SERS probe.

Accurate, sensitive and selective detection of metabolic biomarkers in biofluids are of vital significance for health self-monitoring and chronic disease prevention. Here, for the first time, a smart dual-responsive nanozyme sensor (DNS) was developed for simultaneous analysis of glucose and caffeine utilizing stimuli-responsive yolk-shell gold nanoparticles (GNPs)-embedded MIL-53 (Al) (GNPs@MIL-53) structures. After the introduction of glucose, GNPs@MIL-53 displays excellent glucose oxidase (GOx)-like activity to induce the conversion of glucose to gluconic acid and H

In this work, synthesized carbon quantum dots (CQDs) and zinc oxide nanoparticles (ZnO NPs) are used to form ZnO/CQDs nanocomposite. The characterization of this nanocomposite using X-ray diffraction (XRD) indicates that ZnO NPs and ZnO/CQDs nanocomposite have the same profile, suggesting that the presence of CQDs does not impinge the crystal structure of ZnO in ZnO/CQDs nanocomposite. Besides, an analysis performed with scanning electron microscopy (SEM) displays plate-like nanostructure with an average thickness of about 22 nm and 25 nm for ZnO NPs and ZnO/CQDs, respectively. Furthermore, the reflectance study in the visible range shows a reduction of sunlight reflection intensity of ZnO/CQDs compared with the reflection intensity of ZnO NPs. In addition, the photocatalytic studies indicate that the rate of photocatalytic degradation of methylene blue (MB) of ZnO/CQDs nanocomposites is higher than that of ZnO NPs. Indeed, in optimized conditions, the photocatalytic activity can reach 100% within 45 min of sunlight exposure for the degradation of 7.5 mg/L MB using ZnO/CQDs while it takes 90 min using ZnO NPs under the same conditions. These fascinating results is attributed to the reduction of the reflective properties of ZnO/CQDs. KEY WORDS: Fluorescent carbon quantum dots (CQDs), Photocatalytic degradation of methylene blue, Sunlight reflectance property, Synthesis of ZnO nanoparticles Bull. Chem. Soc. Ethiop. 2023, 37(2), 463-476. DOI: https://dx.doi.org/10.4314/bcse.v37i2.15 &nbsp

Hydrogen peroxide (H2O2) widely involves in intracellular and intercellular redox signaling pathways, playing a vital role in regulating various physiological events. Nevertheless, current analytical methods for the H2O2 assay are often hindered by relatively long response time, low sensitivity, or self-interference. Herein, a zeolitic imidazolate framework-8 (ZIF-8)-based surface-enhanced Raman scattering (SERS) sensor has been developed to detect H2O2 released from living cells by depositing ZIF-8 over SERS active gold nanoparticles (AuNPs) grafted with H2O2-responsive probe molecules, 2-mercaptohydroquinone. Combining the superior fingerprint identification of SERS and the highly efficient enrichment and selective response of H2O2 by ZIF, the ZIF-8-based SERS sensor exhibits a high anti-interference ability for H2O2 detection, with a limit of detection as low as 0.357 nM. Satisfyingly, owing to the enhanced catalytic activity derived from the successful integration of AuNPs and ZIF, the response time as short as 1 min can be obtained, demonstrating the effectiveness of the SERS sensor for rapid H2O2 detection. Furthermore, the developed SERS sensor enables real-time detection of H2O2 secreted from living cells under phorbol myristate acetate stimulation, as cells can be cultured on-chip. This study will pave the way toward the development of a metal-organic framework-based SERS platform for application in the fields of biosensing and early disease diagnosis associated with H2O2 secretion, thus exhibiting promising potential for future therapies.

1,4-Benzenedithiol (BDT)-bridged core-satellite assemblies, as surface-enhanced Raman spectroscopy (SERS) mechanical probes, can be employed for real-time monitoring of the dynamics of endocytic forces and the accompanying trajectory of nanoparticles during the endocytosis process. These mechanical probes exhibit good responses in terms of SERS intensity ratios while undergoing mechanical pressure. Force tracing and the accompanying trajectory of nanoparticles are resolved accurately to render the endocytosis process in live cells. Density functional theory simulation results further proved the sensing scheme due to the electrons transforming between BDT and gold nanoparticles. Furthermore, this SERS mechanical probe is a valid method to visualize endocytic forces at multiple locations and establish a direct criterion to discriminate between cancer cells and normal cells.

A sensitive and reliable method was developed to determine methylene blue (MB) and its metabolite residues, including azure A (AZA), azure B (AZB), and azure C (AZC) in aquatic products by HPLC–MS/MS. The samples were extracted by acetonitrile and cleaned up by alumina-neutral (ALN) cartridges. The analytes were separated on a Sunfire C18 column (150 mm × 2.1 mm, 5 µm). The method was validated according to the European criteria of Commission Decision 2002/657/CE. Good linearity between 1–500 µg/L was obtained with correlation coefficients (R2) greater than 0.99. The limit of quantification (LOQ) was 1.0 µg/kg. The average recoveries at three levels of each compound (1, 5, and 10 µg/kg) were demonstrated to be in the range of 71.8–97.5%, with relative standard deviations (RSDs) from 1.05% to 8.63%. This method was suitable for the detection of methylene blue and its metabolite residues in aquatic products.

A green and facile hydrothermal synthesis approach is proposed for the preparation of nitrogen-doped carbon quantum dots (N-CQDs) with wolfberry. These N-CQDs were developed as a highly sensitive fluorescent 'on-off-on' switch sensor for the sensing of Fe

Pesticide residues in foodstuffs can lead to several undesirable effects. A simple and high-throughput targeted screening method analyzing multi-residue pesticide in aquaculture water based on ultra-high-performance liquid chromatograph-Q/Orbitrap mass spectrometry (UHPLC-Q/Orbi MS) was developed and validated. In this technique, the peaks of the compound using precursor ions were recorded by the full scan, which was used for rough quantitative analysis with single point matrix matched calibration. The qualitative identification was performed following the stringent confirmation criteria with fragment ions, retention time, and an isotopic pattern. Additionally, solid-phase extraction with an HLB (Hydrophilic/Lipophilic Balanced) column was selected to enrich and separate target pesticides from water. The screening detection limit of 33 compounds are less than 2 ng&middot, L&minus, 1, while 26 compounds range from 2 ng&middot, 1 to 10 ng&middot, 1, 19 compounds are at the range of 10&ndash, 200 ng&middot, 1, and the other two compounds are 200 ng&middot, 1 and 1000 ng&middot, 1. Most of the recovery results were found to be between 60~130%. Finally, the method was successfully applied to the analysis of pesticide residues in 30 water samples from aquaculture environment in Shanghai, indicating its applicability in pesticide screening for environmental monitoring.

Lysosomes with a single-layered membrane structure are mainly involved in the scavenging of foreign substances and play an important role in maintaining normal physiological functions of living cells. In this work, near-neutrally charged fluorescent carbon dots (CDs) were prepared with lipophilicity through a facile one-pot hydrothermal carbonization of chloranil and triethylenetetramine at 160 °C for 3 h. The as-obtained CDs are proved to have good photostability, low cost, and excellent biocompatibility. Importantly, the as-prepared CDs with high quantum yield of 30.8% show excitation-dependent emission with great stability, and thus, they can be well used for the long-term target imaging of lysosomes in living cells without further modification. Meanwhile, the CDs can quickly enter into the lysosomes within 30 min, and the green fluorescence (FL) of CDs reaches the plateau when incubated for 60 min. By comparing the fluorescent intensity, the information about distribution and amount of lysosomes in different cells can be obtained. The proposed CD-based strategy demonstrates great promise for label-free target imaging of lysosomes in living cells. Graphical abstract The near-neutral carbon dots (CDs) with lipophilicity are used as label-free fluorescent nanoprobes for the long-term imaging of lysosomes in living cells.

A rapid colorimetric method using cysteine-modified silver nanoparticles (Cys-AgNPs) is applied for the detection of 3-monochloropropane-1,2-diol (3-MCPD). Indeed, in the presence of 3-MCPD, the color of Cys-AgNPs solution changes from yellow to pink within five minutes at 100 °C and pH 9.3. This change is mainly attributed to the ability of amino group of cysteine to react with 3-MCPD to form N-(2,3-dihydroxypropyl)-amino acid grafted on AgNPs (3-MCPD-Cys-AgNPs) in alkaline medium. This color change makes 3-MCPD to be clearly detectable by unassisted visual means even at 0.1 μg⋅mL−1. Besides, using UV–Vis spectroscopic technique, a linear range from 0.1 μg⋅mL−1 to 1.25 μg⋅mL−1 for 3-MCPD detection is obtained, with a calculated detection limit of 0.084 μg⋅mL−1. These results suggest that this sensing technique is sensitive to 3-MCPD and may have a substantial application in the rapid detection of food contaminants particularly, where quality and safety of food products are paramount concern.

Real-time analysis of DNA aptamer conformational changes is essential to understanding the function of DNA aptamers at the single-molecular level. Herein, we design core-satellite nanostructures as surface-enhanced Raman scattering (SERS) molecular-rulers to monitor the change process of single Hg2+ aptamer under dark-field microscopy (DFM-) correlated Raman spectroscopy. Applying the SERS molecular-ruler, the individual Hg2+ aptamer conformational change events triggered by Hg2+ that leads to the stepwise closing of the satellite to the core is continuously monitored by changes in SERS intensity. Moreover, individual Hg2+ aptamer conformational change events are confirmed by in-situ scanning electron microscopy (SEM) and finite difference time-domain (FDTD) calculation. Furthermore, the SERS molecular-ruler is a valid method for studying aptamer intermediate states, the binding sites in aptamer and the kinetics of Hg2+ aptamer configuration change at the single-molecule level. Such findings are promising for exploring the mechanism of DNA aptamer configuration change and providing the fundamental understanding for designing various DNA aptamer based biological applications. For future applications, SERS molecular-ruler has the potential to realize multi-level optical storage and presents a new practical and effective method for designing multi-level storage system.

Collision at a single molecule level was achieved based on the nanoimpact of an individual pyrroloquinoline quinone (PQQ) modified multiwalled carbon nanotube (MWCNT) at the carbon fiber ultramicroelectrode (C UME). Electrocatalytic amplification of the current responses was observed when the PQQ-modified MWCNT collided with C UME in the presence of hydrazine (N2H4) in a Tris-HCl buffer solution, which was also supported by the conventional cyclic voltammetry and chronoamperometry techniques. The enhanced catalytic oxidation of N2H4 was due to the “addition-elimination” redox cycling mechanism of PQQ/PQQH2, where the oxidation of N2H4 occurred together with the reduction of PQQ under an external bias, and the formed PQQH2 intermediate would be reoxidized back to PQQ simultaneously. The average collision current, duration, and charge for PQQ-modified MWCNT at 1.0 V vs Ag/AgCl were 105 pA, 0.45 ms, and 49 fC, respectively. As a result, the turnover frequency of electrocatalytic oxidation of N2H4 by PQQ was ...

In this study, Ricinodendron heudelotii (akpi) shells are used as precursor to prepare activated carbon via chemical activation using phosphoric acid. The characterization of the obtained activated carbon is performed using X-ray diffraction (XRD), Boehm titration method and adsorption of acetic acid. The results show that the prepared activated carbon has a microstructure and a higher specific surface area (1179 m 2 /g), suggesting that the acid treatment has a significant positive influence on its sorption properties. The maximum adsorption capacity and pollutant elimination efficiency are found to be 43.48 mg/g and 90%, respectively. These results suggest that this low cost agent is an efficient tool to remove organic pollutants especially imidacloprid from wastewater. KEY WORDS : Chemical activation, Adsorption, Activated carbon, Pesticide removal, Waste treatment Bull. Chem. Soc. Ethiop. 2017 , 31(3), 397-409. DOI: http://dx.doi.org/10.4314/bcse.v31i3.4

A nanostructured gold-silver soaked in polyethylene glycol 400 (Au-Ag@PEG) is designed using gold(I) chloride and silver nitrate (AgNO3) as precursors and, polyethylene glycol 400 (PEG) as capping agent. The result of the structure characterization using Selected Area Electron Diffraction (SAED) has showed that the synthesized nanomaterial has a good crystallinity while Transmission Electron Microscopy (TEM), energy dispersive X-ray spectrometry (EDX) and Dynamic Light Scattering (DLS) measurements suggest mixed Au-Ag nanoparticles with an average diameter size of around 7 nm and 30 nm for Au and Ag respectively.

Ideal SERS substrates and rapid sampling are crucial for on-site detection of pesticide residues. In this work, silver nanoparticles and graphene oxide were successfully prepared on cellulose paper (Ag NPs/GO paper) using a screen printing technique. The screen printing ink containing graphene oxide and silver nanoparticles was orderly printed onto cellulose paper substrates by controlling the printing cycles to fabricate controllable SERS substrates in large batches for the detection of pesticide residues. It was found that for up to four cycles, the SERS effect increased with the number of Ag NP printing cycles and no obvious change was observed. The prepared Ag NPs/GO paper may exhibit a high enrichment ability due to the π–π stacking and electrostatic interactions of GO toward pesticide molecules. The results suggest that the high density of Ag NPs/GO on the prepared paper is enough for ultrasensitive SERS detection of thiram, thiabendazole and methyl parathion in complex surfaces with a low limit of detection of 0.26 ng cm−2, 28 ng cm−2, and 7.4 ng cm−2, which are much lower than the maximal residue limits in fruit prescribed by the U.S. Environmental Protection Agency. Thus, the sensitive SERS detection of pesticide residues based on Ag NPs/GO paper offers great potential for its practical application in environmental analysis and food safety.

A functional surface-enhanced Raman scattering (SERS) nanosensor which can simultaneously detect nitric oxide (NO) and peroxynitrite (ONOO-) in living cells is explored. The SERS nanosensor is fabricated through modifying gold nanoparticles (AuNPs) with newly synthesized 3,4-diaminophenylboronic acid pinacol ester (DAPBAP), which has two reactive groups. The simultaneous detection achieved in this work is not only because of the SERS spectral changes of the nanosensor resulting from the dual reactivity of DAPBAP on AuNPs with NO and ONOO- but also by the narrow SERS bands suitable for multiplex detection. Owing to the combination of SERS fingerprinting information and chemical reaction specificity, the nanosensor has great selectivity for NO and ONOO-, respectively. In addition, the nanosensor has a wide linearity range from 0 to 1.0 × 10-4 M with a submicromolar sensitivity. More importantly, simultaneous monitoring of NO and ONOO- in the Raw264.7 cells has been fulfilled by this functional nanosensor, which shows that the SERS strategy will be promising in comprehension of the physiological issues related with NO and ONOO-.

γ-Glutamyl transpeptidase (GGT) has attracted considerable attention for its regulatory effect on glutathione metabolism in living organisms; further, its close relationship with physiological dysfunctions such as hepatitis and liver cancers has enhanced its applicability. Therefore, the accurate detection of GGT levels is particularly important for the early diagnosis of diseases. Thus, we herein report the development of a surface-enhanced Raman spectroscopic (SERS) probe, namely bis-s,s'-((s)-4,4'-thiolphenylamide-Glu) (b-(s)-TPA-Glu), that comprises of a γ-glutamyl moiety for detection of the GGT activity. In this system, detection was achieved by observing differences in the SERS spectral profiles of the b-(s)-TPA-Glu probe and its corresponding hydrolysis product that resulted from the catalytic action of GGT. This SERS probe system exhibited a high selectivity toward GGT due to a combination of its specific catalytic action and the distinctive spectroscopic fingerprint of the SERS technique. The developed SERS approach was also found to be approximately linear in the range of 0.2-200 U/L, and a limit of detection of 0.09 U/L was determined. Furthermore, the proposed SERS method was suitable for detection of the GGT activity of clinical serum samples and also for evaluation of the inhibitors of GGT. Consequently, this approach is considered to be a promising diagnostic and drug screening tool for GGT-associated diseases.

The accurate detection of hydrogen peroxide (H2O2)-involved metabolites plays a significant role in the early diagnosis of metabolism-associated diseases, whereas most of current metabolite-sensing systems are often hindered by low sensitivity, interference of coexisting species, or tedious preparation. Herein, an electrochemistry-regenerated surface-enhanced Raman scattering (SERS) sensor was developed to serve as a universal platform for detecting H2O2-involved metabolites. The SERS sensor was constructed by modifying newly synthesized 2-mercaptohydroquinone (2-MHQ) molecules on the surface of gold nanoparticles (AuNPs) that were electrochemically predeposited on an ITO electrode. Metabolites were detected through the changes in the SERS spectrum as a result of the reaction of 2-MHQ with H2O2 induced by the metabolites. Combining the superiority of SERS fingerprint identification and the specificity of the related enzymatic reactions producing H2O2, the designed SERS sensor was highly selective in detecting glucose and uric acid as models of H2O2-involved metabolite with limits of detection (LODs) of 0.159 μM and 0.0857 μM, respectively. Moreover, the sensor maintained a high SERS activity even after more than 10 electrochemical regenerations within 2 min, demonstrating its effectiveness for the rapid detection of various metabolites with electrochemistry-driven regulation. Importantly, the presented SERS sensor showed considerable practicability for the detection of metabolites in real serum samples. Accordingly, the SERS sensor is a new detection platform for H2O2-involved metabolites detection in biological fluids, which may aid the early diagnosis of metabolism-related diseases.

In this study, in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) are used to investigate the redox reaction and adsorption behavior of anthraquinone-2-carboxylic acid (AQ-2-COOH) on an Ag electrode at different pH values. The obtained results indicate that AQ-2-COOH is adsorbed tilted on the Ag electrode through O-atom of ring carbonyl in a potential range from −0.3 to −0.5 V vs. SCE, but the orientation turns to more tilted orientation with both O-atom of the ring carbonyl and carboxylate group in positive potential region for pH 6.0 and 7.4. However, at pH 10.0, the orientation adopts tilted conformation constantly on the Ag electrode with both O-atom of the anthraquinone ring and carboxylate group in the potential range from −0.3 to −0.5 V vs. SCE or at positive potentials. Moreover, the adsorption behavior of AQ-2-COOH has been further confirmed by AR-XPS on the Ag surface. Proposed reasons for the observed changes in orientation are presented.

A bio-inspired polydopamine (PDA) molecularly imprinted substrate is fabricated by one-step oxidative self-polymerization of dopamine and template molecules in weakly alkaline medium on screen-printed electrode (SPE). Through the catechol and amine groups on PDA surface, Au nanoparticles (AuNPs) can be easily anchored and growth on PDA-MIP coating, thereby forming a three-dimensional (3D) architecture. By adjusting the reaction conditions, the particle size and distribution of PDA and AuNPs can be well controlled. Benefiting from the “hot spots” generated by AuNPs and recognition sites produced by MIP, the AuNP/PDA-MIP nanocomposite can serve as excellent SERS substrate enabling selective enrichment and identification of phthalate plasticizers (PAEs). Using this substrate, an enhancement factor (EF) up to 1.70 × 107 for dimethyl phthalate (DMP) is achieved with a detection limit as low as 1.0 × 10−10 M. Furthermore, the rebinding kinetics study demonstrates that the portable MIP-based SERS substrate can promptly reach the adsorption equilibrium within 10 min. Thanks to its highly selectivity, the substrate exhibits low SERS interference for structural analogues benzyl butyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP). Besides, the straightforward SERS recognition of DMP in surface water, commercial bottled water and liquor samples are successfully realized using this substrate. This green and environmental-friendly fabrication method is promising for synthesis of highly performance sensing substrate, adsorbent or catalysts. Combining with portable Raman spectrometer, the fabricated MIP-based SERS substrate has exhibited a great potential as on-site device for environmental monitoring, food safety and homeland security.

Multi-modal detection of analytes using plasmonic nanoprobes has inspired intensive interests due to its remarkable structure features and optical functions. In this study, we have developed a robust and trimodal sensing strategy capable of visual colorimetric and fluorescence discrimination and accurate surface-enhanced Raman spectroscopy (SERS) detection of Cu2+ by stimuli-responsive binaphthalene (BAMH)-functionalized Au nanorods (GNRs@BAMH). The phenolic hydroxyl group and Schiff-base of BAMH act as scaffolds and reporters for Cu2+ due to their preferential affinity with Cu2+, which enables visualization of Cu2+ from complex matrices by the decreased fluorescent signals accompanied with a simultaneous increase in a colorimetric response of GNRs@BAMH. The detection limits of colorimetric and fluorescent assays are 3.0 nM and 0.42 nM, respectively. Importantly, the GNRs@BAMH is capable of highly sensitive SERS analysis of Cu2+ in environmental and biological specimens with detection limit of 0.38 pM due to the chelation-triggered GNRs self-aggregation. Considering merits of this multifunctional platform such as flexibility, simplicity of the detection procedures, without any additional pre-treatment, it is a promising technique for point-of-care screening or in-field monitoring.

Antarctic Krill, rich in many nutrients, is supposed to be one of the strategic food sources. However, it is not acceptable for direct consumption as traditional food, as its high content of fluoride is harmful to adults and children. Therefore, the safety of fluoride residue in Antarctic krill for food production should be investigated. In this research, the fluoride toxicity in Antarctic Krill was evaluated through mice feeding experiment. Their body weight was found not to be influenced by fluoride. However, dental fluorosis was observed in the krill group and the NaF group. Fluoride content in liver, kidney, urine, and bones are significantly different (P

Inspired by the addition-elimination catalytic mechanism of natural pyrroloquinoline quinone (PQQ) containing proteins, PQQ-modified hybrid nanomaterials have been increasingly developed recently as biomimetic heterogeneous electrocatalysts. However, up until now, no existing electrochemical approach was able to assess the intrinsic catalytic activity of PQQ sites, impeding the design of efficient PQQ-based electrocatalysts. Herein, in this work, we introduced a new method to calculate the turnover frequency (TOF) of any individual PQQ functional group for electrocatalytic oxidation of tris(2-carboxyethyl)phosphine (TCEP), through the study of single PQQ-decorated carbon nanotube (CNT) collisions at a carbon fiber ultramicroelectrode by chronoamperometry. The core advantage of this approach is being able to resolve the number of PQQ catalytic sites grafted on each individual CNT, so that the charge of any CNT collision event can be accurately translated into the intrinsic activity of the respective PQQ functional groups. The resulting collision-induced current responses clearly showed that the functionalization of CNTs with PQQ could indeed enhance its catalytic performance by 3 times, reaching a TOF value of 133 s

The published version of this article, unfortunately, contained error. Modifications have been made to the Abstract, Introduction, Results and discussion, and Acknowledgements section. The original article has been corrected.

Synthesis of high-quality metal nanoparticle (NP) decorated graphene (GN) with uniform and controllable nanostructures has attracted considerable attention due to its excellent electronic structure and optical properties. Herein, we develop a facile and robust process for tailoring hexanethiol (SH)-modified Ag NP-decorated graphene nanomaterials (Ag/GN-SH) by coupling in situ reduction and the covalent assembly technique. The as-prepared Ag/GN-SH combines adequate Raman “hot spots” among the high-density Ag NPs and the excellent adsorption performance of GN, making it an excellent surface-enhanced Raman scattering (SERS) substrate for highly selective and sensitive detection of PAHs. Moreover, the Ag/GN-SH can be used as a solid-phase extraction (SPE) adsorbent for qualitative and quantitative detection of PAHs in seawater from their discriminant SERS peaks. The Ag/GN-SH-based SPE-SERS is effective over a wide range of concentrations (0.1 nM to 0.5 mM) for PAHs, with tens of pM detection limits [signal to noise ratio (S/N) = 3], and the detection concentration deviation is less than 15% between the SPE-SERS and GC-MS. This study not only offers a new method for on-site removal of PAHs but also provides a strategy for simultaneous multiplexed detection of PAHs.

In this study, an environment-friendly hydrothermal synthesis of hydrophilic silica-functionalized CdTe quantum dots (SQDs) has been developed by treatment of tetraethyl orthosilicate (TEOS) in the presence of CdTe QDs. The proposed SQDs show favorable photoluminescence (PL) at the peak wavelength of 620 nm with a quantum yield of approximately 32%, and exhibit excellent selectivity and sensitivity toward sparfloxacin (SPFX) in the range from 0.05 × 10−6 to 200 × 10−6 mol L−1. The detection limit of SPFX is as low as 0.035 × 10−6 mol L−1. The results show that the remarkably enhanced PL intensity of SQDs can be attributed to the hydrogen-bond interactions between the SQDs and SPFX. Furthermore, the amount of SPFX in the human serum samples detected by the present method and HPLC are in good agreement, indicating that the proposed SQDs can serve as a powerful tool for biological analysis.

Loop-mediated isothermal amplification (LAMP) eradicates the need of thermocycler in DNA amplification. Signals are usually obtained via fluorometry or turbidimetry, but such methods need improvement in order to become more effortless and reliable. The authors describe a set of six specific primers targeting the species-specific tlh gene of Vibrio parahaemolyticus which were used in accelerated LAMP reaction. Gold nanoparticles (AuNPs) were functionalized with streptavidin (Avidin-AuNPs), and engineered to signal the LAMP reaction. Two of the loop primers for LAMP were biotinylated and then can produce a DNA that can cause clusterization of Avidin-AuNPs based on the formation of avidin-biotin complex. This leads to a color change of the solution from red to blue. Amplification is completed within 30 min and can be visually detected within 5 min. The detection limit of the method is found to be 8.6 cfu per reaction. This visual detection scheme does not require any fluorescent reagents and detection instruments. Conceivably, the method has a wide scope because such Avidin-AuNPs can be used as nanoprobes for a variety of other LAMP products. This rapid and universal strategy holds promise in point of care testing and food testing, particularly in resource-limited regions. Graphical abstract Six specific primers (two of them are biotinylated) were used to realize the accelerated Loop-Mediated Isothermal Amplification. Streptavidin modified gold nanoparticles (Avidin-AuNPs) cluster on the DNA products, leading to the apparent change of color from red to blue, which is readily identified even by unaided eye.

A sensitive screen-printed electrode modified with multi-walled carbon nanotubes (MWCNTs/SPE) was applied to determine simultaneously m-nitrophenol, o-nitrophenol and p-nitrophenol. The electrochemical response showed that o-nitrophenol, m-nitrophenol and p-nitrophenol were entirely separated at the MWCNTs/SPE interface. Under the optimized conditions, it was found that the detection limits were 8.1×10-8 , 5.5×10-7 and 2.0×10-7 M and the linear calibration ranges were 1.0×10-6 ~1.9×10-5 M, 2.5×10-6 ~2.1×10-5 M and 2.0×10-6 ~2.0×10-5 M for m-nitrophenol, o-nitrophenol and p-nitrophenol respectively, proving that the electrode presented here could be easily used to determine nitrophenol isomers simultaneously with high sensitivity within pH range from 4.8 to 8.0. The applications in water samples showed that no interferences appeared with deviations below 5% to the determination of nitrophenol isomers with 1000 fold excess, indicating a good response of this method for nitrophenol isomers detection. This disposable modified SPE combining with a portable electrochemical device were performed for wastewater samples on-field rapid determination.

In this work, we report the features of size-selective fragmentation of gold nanoparticles (AuNPs) by thioanisole. Large particles are observed as prone to easier fragmentation than the smaller ones, the key-role being played by the effect of surface charge and surface coverage.

In these recent years, magnetite (Fe3O4) has witnessed a growing interest in the scientific community as a potential material in various fields of application namely in catalysis, biosensing, hyperthermia treatments, magnetic resonance imaging (MRI) contrast agents and drug delivery. Their unique properties such as metal–insulator phase transitions, superconductivity, low Curie temperature, and magnetoresistance make magnetite special and need further investigation. On the other hand, nanoparticles especially gold nanoparticles (Au NPs) exhibit striking features that are not observed in the bulk counterparts. For instance, the mentioned ferromagnetism in Au NPs coated with protective agents such as dodecane thiol, in addition to their aptitude to be used in near-infrared (NIR) light sensitivity and their high adsorptive ability in tumor cell, make them useful in nanomedicine application. Besides, silver nanoparticles (Ag NPs) are known as an antimicrobial agent. Put together, the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{Fe}}_{ 3} {\text{O}}_{ 4} {\text{Au}}_{x} {\text{Ag}}_{y} \left( {\left\{ {x,y} \right\} = \{ 0 , 1\} } \right)$$\end{document}Fe3O4AuxAgyx,y={0,1} nanocomposites with tunable size can therefore display important demanding properties for diverse applications. In this review, we try to examine the new trend of magnetite-based nanomaterial synthesis and their application in catalysis and nanomedicine.

A freeze method for deproteinization coupling with the chitosan purification process was developed for the determination of 8 synthetic food colorants in protein-rich samples. The solvents for extraction and different methods for deproteinization were examined and selected. Chitosan was employed for the purification after deproteinization, and further compared with the traditional polyamine purification method. Determination of the purified extract was conducted through the separation using high performance liquid chromatography and detection by multi-wavelength mode. Under the optimum conditions, the method showed good linearity between 0.6 and 10mg/kg, for the 8 synthetic colorants, and the limit of detection was between 0.1 and 0.4 mg/kg as was defined when the ratio of signal to noise was three. The recoveries of the spiked samples were found to be between 83% and 91%. The intra-day precision and inter-day precision was estimated to be 3-10% and 6-12%, respectively. The developed method could be applied to deproteinization and clean-up for pretreatment of protein-rich samples.

A Surface Enhanced Raman Scattering (SERS) substrate based on Ag/β-AgVO3 nanobelts deposited on copper foil (Cu@Ag/β-AgVO3) was used for the detection of carbamate pesticides: carbofuran, carbaryl, isoprocarb and propoxur. Cu@Ag/β-AgVO3 has shown an excellent SERS activity for carbamate pesticides compared to silver nanoparticles (AgNPs). Under optimized conditions, detection limits of 2.5 pM, 10 pM, 50 pM and 75 pM were obtained for carbaryl, carbofuran, isoprocarb and propoxur respectively, suggesting that Cu@Ag/β-AgVO3 is a good candidate for use as a SERS substrate for the trace level detection of these pesticides.