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A sensitive and selective method for the detection of arsenic(iii) (As 3+ ) based on chitosan-stabilized gold nanoparticles (CS/AuNPs) decorated with a 2,2'-thiodiacetic acid (TDA) nanoprobe was developed and used to detect and indicate the contamination of rice, drinking water and environmental water samples. AuNPs were reduced and stabilized with CS and subsequently functionalized with TDA. As 3+ interacted with the carboxylate group of TDA to form an As-TDA complex, inducing the aggregation of CS/AuNPs@TDA. The aggregation of CS/AuNPs@TDA was accompanied with a change in color from red to bluish purple and a shift in surface plasmon resonance wavelength from 525 nm to 645 nm. The response for the detection of As 3+ was linear at concentrations from 10 to 1000 μg L -1 with a limit of detection of 6.1 μg L -1 . The method exhibited selectivity toward As 3+ among various cations (As 5+ , Cu 2+ , Fe 3+ , Fe 2+ , Hg 2+ , Al 3+ , Cr 3+ , Cd 2+ , Co 2+ , Ni 2+ , Pb 2+ and Zn 2+ ) and anions (Br - , Cl - , F - , SO 4 2- , NO 3 - and PO 4 2- ). The CS/AuNPs@TDA nanoprobe was applied to detect As 3+ in rice, drinking water and environmental water samples. The results were consistent with those obtained via inductively coupled plasma-optical emission spectrometry (ICP-OES). Satisfactory recoveries ranging from 88.22% to 105.74% (RSDs of 0.25-2.99%) were obtained from spiked samples., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A polyvinyl alcohol/gum tragacanth molecularly imprinted nanofiber fabricated by electrospinning (PVA/GT-MIN) was used as an efficient adsorbent for the solid phase extraction (SPE) of bisphenol A (BPA) in water samples. PVA and GT were functional polymers and BPA was the template for molecular imprinting. BPA was bound to the polymer matrix through hydrogen bonding. The SEM image of PVA/GT-MIN demonstrated a rough morphology with pores and a diameter of 501 nm. The data for the adsorption of BPA on PVA/GT-MIN fitted the Freundlich isotherm and pseudo-second-order kinetics models. The proposed SPE using PVA/GT-MIN coupled with high performance liquid chromatography-diode array detection presented good linearity from 50 μg/L-5 mg/L (R 2  = 0.9999) and yielded a limit of detection of 21 μg/L. The PVA/GT-MIN was applied to extract bottled water for BPA analysis and recoveries were 93.1-97.7 % (RSDs ≤ 3.6 %). This study presents a novel, easily prepared PVA/GT-MIN adsorbent for the extraction of BPA in water., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A new, simple, and selective colorimetric method of determining formaldehyde in Hevea brasiliensis latex was developed by using a casein/ferric chloride/polyvinyl alcohol hydrogel composite (casein/FeCl 3 /PVA) in a modified Leach test. Under heating, formaldehyde reacted with 8% casein in the presence of 0.1% FeCl 3 and 4.3% HCl (v/v) entrapped in a 30% PVA hydrogel packed in a syringe. A purple-colored product was formed with a maximum absorbance of 525 nm. The color change was evaluated at the color detection zone indicated on the the syringe. The %magenta values were easily evaluated by using a mobile phone application and employed to determine formaldehyde content. The casein/FeCl 3 /PVA composite gave a readable response in a formaldehyde detection range from 0.04 to 0.80% with a linear response between %magenta and formaldehyde concentration (R 2  = 0.9955). The detection limit was 0.032%, and precisions were in the range 0.67-4.94%. The casein/FeCl 3 /PVA composite was applied to the analysis of ammonia-preserved latex samples, and recoveries of formaldehyde from samples spiked at 0.1, 0.3, and 0.5% ranged from 81.55 to 99.51% (RSDs ≤ 5.41%). The recoveries and precision of the proposed method were comparable with those of high-performance liquid chromatography (HPLC). The developed method was also selective, showing no interference from other latex preservatives, i.e., phenol, ammonia, or tetramethylthiuram disulfide., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A novel magnetic composite bead was synthesized using carbon 18, paracetamol and alginate (mC18/Pa/Alg). The bead was applied to simultaneously adsorb butylated hydroxytoluene, butylated hydroxyanisole, and bisphenol A from water samples by magnetic solid-phase extraction (MSPE). The adsorbed analytes were determined by gas chromatography-flame ionization detection. The morphology and composition of the bead were examined by field emission scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction analysis, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller surface analysis. The best condition of MSPE included an adsorbent bead made with 0.8% sodium alginate, a 0.3 g adsorbent dose, a sample solution pH of 7, and a desorption time of 20 min in methanol. The proposed method exhibited linearity at concentrations between 0.015 and 1.00 μg mL -1 of analytes. Limits of detection ranged from 6.86 to 9.66 ng mL -1 . Recoveries from 80.3 to 100.1% were achieved with interday and intraday precisions (RSDs) of 0.4-4.3%., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A novel ligand-free heterogeneous catalyst was synthesized via pyrolysis of Samanea saman pods to produce carbon nanospheres (SS-CNSs), which served as a carbon support for immobilizing palladium nanoparticles through an in situ reduction technique (Pd/SS-CNS). The SS-CNSs effectively integrated 3% of Pd on their surfaces with no additional activation procedures needed. The nanomaterials obtained underwent thorough characterization employing various techniques such as FT-IR, XRD, FE-SEM, TEM, EDS, ICP-AES, and BET. Subsequently, the efficiency of this Pd/SS-CNS catalyst was assessed for the synthesis of biaryl derivatives via Suzuki coupling, wherein different boronic acids were coupled with various aryl halides using an environmentally benign solvent mixture of EtOH/H 2 O and employing only 0.1 mol% of Pd/SS-CNS. The catalytic system was conveniently recovered through centrifugation and demonstrated reusability without any noticeable decline in catalytic activity. This approach offers economic viability, ecological compatibility, scalability, and has the potential to serve as an alternative to homogeneous catalysis., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A fast, simple, and selective colorimetric assay for quantifying cypermethrin in water samples is proposed using l-cysteine functionalized gold nanoparticles (AuNPs@Cyst). Cypermethrin is hydrolyzed by potassium hydroxide to obtain hydrolyzed cypermethrin in the form of 3-phenoxybenzaldehyde by-product (HCy). The detection strategy is based on the aggregation of AuNPs@Cyst caused by hydrogen-bonding recognition between the aldehyde group of HCy and the amine group of l-cysteine on the surface of AuNPs@Cyst. As a result, in the presence of HCy under optimal pH 7, AuNPs@Cyst aggregates within 7 min, exhibiting a distinct color change from red to blue-gray, which can be evaluated with the naked eye and UV-visible spectrophotometry. From FE-TEM image, the stable and spherical AuNPs@Cyst had an average size of 13.8 ± 1.6 nm, and from zeta potential analysis, the charge of AuNPs@Cyst was -25.04 ± 1.66 mV. The surface plasmon resonance band of dispersed AuNPs@Cyst was red shifted from 525 nm to 634 nm when AuNPs@Cyst was aggregated. The absorbance ratio ( A 634 / A 525 ) was linearly related to cypermethrin concentrations from 0.5 to 13.0 mg L -1 . The limit of detection was 0.2 mg L -1 and precision, expressed as relative standard deviations (RSDs), ranged from 1.9 to 7.3%. In the presence of interfering pesticides (carbaryl, ethion, profenofos and abamectin), only cypermethrin produced a significantly different response, confirming the selectivity of AuNPs@Cyst. Finally, AuNPs@Cyst was applied to determine cypermethrin in water samples, achieving very satisfied recoveries (>98.6%) and RSDs lower than 6.1%., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

This work proposes a highly specific method of Cr 6+ determination based on the double reactions of two metals, Co 2+ with dithizone to form a (DTZ)-Co 2+ complex, and the replacement of Co 2+ in the formed complex with Cr 6+ . The fast degradation of DTZ in solution in wet analysis was overcome by preparing dithizone functionalized polyurethane nanofibers that were electrospun into a membrane (DTZ/PU-NF) and a microwell plate film (DTZ/PU-MPF). For comparison, the performance of diphenylcarbazide (DPC), a currently used complexing agent for Cr 6+ , was also investigated. Colour changes were detected as red-green-blue values. The DTZ/PU-NF was smooth, with an average diameter of 384.09 nm and no bead appeared. A dense network structure was formed. The best formulation of DTZ, PU and Co 2+ was also applied as a microwell plate film. In the presence of Cr 6+ , the colour of DTZ-Co 2+ changed from red to magenta. Among the three studied methods, the colorimetric DTZ-Co 2+ /PU-NF presented the best results. Its linearity range was 0.001-1.0 mg L -1 , with a regression equation of Cr 6+ = -0.189 + (0.0056 × red) + (0.0086 × green) - (0.0129 × blue), R 2 of 0.990. The limit of detection was 0.001 mg L -1 and the precision was 1.7%. The applicability of DTZ/PU-NF was validated for Cr 6+ in vegetable oils with recoveries of 89.5-116.8%. The sensitivity of DTZ/PU-NF was ten times higher than that of DTZ/PU-MPF. The methods based on DTZ-Co 2+ /PU-NF and DTZ-Co 2+ /PU-MPF proved to be highly selective, rapid, user-friendly, simple and reliable., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Dimer optical antennas (OAs) enable great fluorescence enhancement and excitation volume reduction and hence potentially can be a very useful tool for single-molecule detection. The realization of broadband fluorescence enhancement with a dimer OA remains an essential step for its usage in multi-color single-molecule fluorescence (SMF) detection. Although silver dimer OAs have been shown to be able to yield broadband fluorescence enhancement over the visible spectrum, they are amenable to oxidization, hard to functionalize, and could cause cytotoxicity. To overcome these limitations, in this work, we took advantage of nano-sized silver due to its optical properties and gold due to its chemical properties and developed an ameliorated Ag@Au dimer OA in terms of its overall performance. The Ag@Au nanoparticle in the dimer OA contains a 70 nm silver core and an ultra-thin (∼1-5 nm) gold shell which play a key role in its optical responses. Furthermore, we employed three typical dyes, i.e. , FAM, TAMRA and Cy5, representing the blue, yellow and red ranges, respectively, and characterized their single-molecule fluorescence enhancements in the presence of Au or Ag@Au OAs. Our results indicate that, in contrast to its Au counterpart, the Ag@Au dimer OA prepared here can greatly improve its optical response in the blue range and eventually achieve broadband fluorescence enhancement throughout almost the whole visible spectral range. Meanwhile, it also maintains good chemical stability and accessibility to functionalization. Such Ag@Au dimer OAs are thus expected to have many important applications in the future, including single-molecule sequencing and multi-color biosensing.

The current method used in latex industries to determine the volatile fatty acids contents of Hevea brasiliensis latex is steam distillation. However, the accuracy of the method has been debated for some time. We assessed the accuracy of the method and developed a new, more reliable high-performance liquid chromatographic method of determining acids in latex. The volatile fatty acids (formic, acetic, propionic, butyric, and valeric acids) and nonvolatile organic acids (oxalic, malic, lactic, citric, and succinic acids) in latex are directly determined simultaneously for the first time with high sensitivity and without losses during sample preparation. To avoid errors from derivatization, an acid-resistant Prevail HPLC column and a gradient mobile phase of 25 mM potassium dihydrogen phosphate (pH 2.5) and acetonitrile were employed. Under optimum conditions, the calibrations of both types of acids demonstrated satisfactory correlation coefficients of  ≥0.990, with limits of detection ranging from 0.02 to 395 mM. The developed method demonstrated the profiles of acids in field and concentrated latex of the same batch. Moreover, the evolution of the profiles of all studied acids in both types of latex during a 3-month period was also revealed., (© 2022 Wiley-VCH GmbH.)

The flow-cell based single-molecule manipulation technique has found many applications in the study of DNA mechanics and protein-DNA interactions. However, the force in these experiments has not been fully characterized and is usually limited to a moderate force regime (<25 pN). In this work, using the "tethered-bead" assay, the hydrodynamic drag of DNA has been quantitatively evaluated based on a "bead-spring chain" model. The force derived from the Brownian motion of the bead thus contains both contributions from this equivalent hydrodynamic drag of DNA and the pulling force from the tethered bead. Next, using flow-cell based DNA pulling experiments, the linear relationship between the flow rate and total hydrodynamic force on the bead-DNA system has been demonstrated to be valid over a wide force range (0-110 pN). Consequently, the force can be directly converted from the flow rate by a linear factor that can be calibrated either by the bead's Brownian motion at low flow rates or using DNA overstretching transition. Furthermore, the hydrodynamic force and torque due to the shear flow on the bead as well as the equivalent stretching force on DNA are calculated based on theoretical models with the hydrodynamic drag on DNA also considered. The calculated force-extension curves show a good agreement with the measured ones. These results offer important insights into the force in flow-cell based single-molecule stretching experiments and provide a foundation for establishing flow-cells as a simple, low-cost, yet flexible and precise tool for single-molecule force measurements over a wide force range.

Ethnopharmacological Relevance: Lavandula angustifolia Mill. Essential oil (Lavender EO) has a long history of medicinal use and is particularly claimed to possess anxiolytic and sedative properties. Lavender EO aromatherapy has been used to reduce distress and improve insomnia naturally. Increasing evidence appeared to show similarities between the effects of lavender EO and the anxiolytic drugs, benzodiazepines. However, its effects on sleep-wake and electrical brain patterns in comparison to that of the standard anxiolytic, diazepam, remained to be explored., Aim of the Study: The aim of this work was to investigate electroencephalography (EEG) profiles and sleep-pattern elicited by lavender EO inhalation compared to that of diazepam, a standard anxiolytic drug in in vivo rat model., Materials and Methods: Adult male Wistar rats were anesthetized for electrode implantation on the frontal and parietal skulls. EEG signals were recorded for 180 min following intraperitoneal injection of diazepam (10 mg/kg) or during continuous inhalation of lavender EO (200 μL) or distilled water (control). Fast Fourier transform was used for the analyses of EEG power spectra and sleep-wake parameters., Results: During a 30-60 min period, diazepam and lavender EO significantly increased frontal powers of 0.78-45.31 and 7.03-18.36 Hz, respectively. Both treatments also increased parietal powers with lower magnitudes of significant change. Significant increases in some frequency ranges remained until a 60-90 min period. Sleep-wake analyses also revealed that diazepam significantly reduced time spent in wake, increased time spent in non-rapid eye movement (NREM), increased episode duration of NREM, decreased numbers of wake episode and decreased rapid eye movement (REM) sleep latency. On the other hand, lavender EO only significantly decreased wake episodes and latency to REM sleep. Lavender EO inhalation reduced numbers of wake episode but maintain normal time spent in wake, NREM and REM sleeps., Conclusions: These findings might suggest beneficial and distinct anxiolytic-like effects of lavender EO for sleep enhancing purposes., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A click chemistry assay based on a newly discovered DNAzyme, CLICK-17, with azide modified gold nanoparticles (azide-AuNPs) and alkyne capped dsDNA (alkyne-linker DNA) was employed for novel and selective detection of Cu 2+ visually. The strategy involved using CLICK-17 to mediate a catalytic reaction for triazole formation between azide-AuNPs and alkyne-linker DNA under the help of Cu 2+ (without sodium ascorbate) or Cu + , which eventually led to the aggregation of AuNPs. The obvious color change from ruby red to bluish purple was then observed by the naked eye and the absorbance peak shifted from 525 to 570 nm. Interestingly, CLICK-17 and Cu + -catalyzed click reaction had the best performance compared to either Cu + alone or CLICK-17 and Cu 2+ -mediated reaction in terms of the reaction time and sensitivity. This system has been demonstrated to allow quantitative measurement of Cu 2+ with a detection limit as low as 26.8 nM and also has high specificity that can distinguish Cu 2+ from other metal ions. Further, the method was tested with a real mineral water sample for Cu 2+ concentration determination. Satisfactory recoveries of 90.8% and 99.8% were achieved., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Gold nanoparticles/polyaniline boronic acid/sodium alginate aqueous nanocomposite ((PABA-SAL)@AuNPs) was fabricated. Aniline boronic acid (ABA) served as reductant of gold salt, all within the SAL solution. While ABA reduced gold salt to its nanoparticles, the ABA monomer was also oxidized to its conducting polymeric form (PABA). The presence of PABA in the reaction mixture exerted solubility and stability challenge, thus SAL was used as stabilizer and solubilizer for PABA. The numerous cis-diol groups of SAL could bind to boronic acid groups of PABA to furnish PABA-SAL repeating polymer structure for AuNPs anchoring. Sparkling ruby red (PABA-SAL)@AuNPs have absorption peaks at 529 and 718 nm. Average particle sizes of nanocomposite were within 15-20 nm, with hydrodynamic diameter of 48.6 ± 0.9 nm, zeta potential of -32.5 ± 1.6 mV and conductivity value of 2015.3 ± 3.2 μS/cm. (PABA-SAL)@AuNPs possessed antibacterial activities against seafood associated bacterial isolates, with MIC and MBC ranging from 4 to 8 μg/mL. The moderate antioxidant capacity of (PABA-SAL)@AuNPs was observed, without any deleterious damages on human red blood cells. It also has good biocompatibility on Caco-2 and RAW 264.7, with cell viability not less than 70%. These results confirm the high prospect of (PABA-SAL)@AuNPs for possible biomedical applications., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A sensitive detection strategy for ascorbic acid (AA), using sodium alginate reduced/stabilized gold nanoparticles (SA-AuNPs) as the optical probe, is reported. The SA-AuNPs were prepared by mixing gold salt and SA under stirring for 2 h at room temperature, without any further steps. The mixture was aged at 4 °C overnight, after which a faint-purple colloidal solution of SA-AuNPs was obtained. Characterization shows that the synthesis is incapable of reducing all Au 3+ to Au°, but rather to mixture of Au°/Au + . The addition of AA to the SA-AuNPs probe reduced completely all Au + to new AuNPs which were deposited on the pre-formed SA-AuNPs seed, leading to size increment and absorption spectra enhancement. The assay exhibited a good linearity between 12.5 and 150.0 μM AA and low limit of quantification of 11.2 μM. It was further used for AA quantitation in vitamin C injection and fruit juice with satisfactory accuracy and precision., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The silver/poly(3-aminophenyl boronic acid)/sodium alginate nanogel (Ag@PABA-SA) was fabricated through green, in situ chemical oxidative polymerization method. 3-Aminophenyl boronic acid (APBA) served as the room temperature reductant of AgNO 3 which acted as an oxidant towards the polymerization of APBA to its conducting polymeric form (PABA). Importantly with SA present, PABA will bind to hydroxyl groups of SA through covalent bonding to generate PABA-SA semi-interpenetrating network, on which AgNPs were concomitantly deposited. This results highly stable, dispersed polymer based AgNPs. The morphology, size, surface charge, composition and thermal stability of nanogel was characterized by UV-vis, Raman and FTIR spectroscopy, TEM, FESEM, EDX, XRD, DLS and zeta potential analysis, TGA and DTG. The Ag@PABA-SA nanogel was investigated as colorimetric probe towards H 2 O 2 detection. Wide linearity from 5 to 1000 μM H 2 O 2 , with low limit of detection of 1.0 μM in addition to satisfactory precision (< 3.5 %) and recovery (95-105 %) and high selectivity was achieved., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this work, the synthesis method and applications of nanocomposite polymer stabilized silver nanoparticles (AgNPs) are reported. 3-Aminophenyl boronic acid (3APBA) was used as a reductant of silver nitrate which acted as an oxidant for the polymerization of 3APBA through in situ chemical oxidative polymerization to poly(3-aminophenyl boronic acid) or PABA. The formation of PABA in the reaction mixture led to particle agglomeration owing to PABA poor solubility. However, in the presence of hydrophilic poly(vinyl alcohol) (PVA), PABA binds to the free hydroxyl group of PVA to form a composite polymer (PABA-PVA), which perfectly stabilized the formed AgNPs. Succinctly, PVA acted as a solubilizer and stabilizer for (PABA-PVA)AgNPs synthesis. Synthesis was optimized and sharp absorption peaks at 290 nm and 426 nm were observed, attributing to the π-π* transition of the benzenoid ring of PABA and the characteristic absorption spectrum of AgNPs, respectively. (PABA-PVA)AgNPs was characterized using UV-vis, TEM, FESEM, EDX, XRD, FTIR, TGA/DTG, DLS and zeta potential analysis. In addition, the antibacterial, antioxidant and metal chelating capacities of (PABA-PVA)AgNPs were evaluated. The (PABA-PVA)AgNPs exhibited significant antibacterial activity against Escherichia coli and Listeria monocytogenes, and good antioxidant and metal chelating properties of (PABA-PVA)AgNPs, thus validating its attractive biological applications., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this paper, we developed a facile approach to synthesize well-dispersed 3D hierarchical porous MoS 2 architectures with assistance of polyacrylate and demonstrated their applications in lithium ion batteries (LIBs). It was confirmed that the uniform flower-like MoS 2 architectures were assembled by nanosheets comprising about ∼10 stacking layers. Polyacrylate was revealed to have a significant impact on controlling the formation of the uniform hierarchical flower-like architectures with desirable dispersity. It was believed that the polyacrylate could direct assembly of the MoS 2 nanosheets into hierarchical structures and could well stabilize and disperse MoS 2 architectures. Furthermore, a stable cycling capability (839 mAh g -1 at 0.1 A g -1 after 120 cycles) and superior rate ability of the MoS 2 architectures were achieved as anodes for LIBs. This remarkably enhanced electrochemical property could be ascribed to their beneficial structural features and surface-dominated capacitive contribution.

A colorimetric method was developed for the determination of the mold toxin fumonisin B1 (FB1). It is based on the aggregation of cysteamine-capped gold nanoparticles (Cys-AuNPs). The assay involves alkaline hydrolysis of FB1 to obtain hydrolyzed fumonisin B1 (HFB1). The latter induces the aggregation of Cys-AuNPs which results in a color change from wine-red to blue-gray, best at a pH value of 9.0. A plot of absorbance ratio at 645/520 nm versus FB1 concentration is linear in the 2-8 μg kg -1 FB1 concentration range, and the detection limit is 0.90 μg kg -1 . Inter-day and intra-day precisions are <6.2%, and recoveries from spiked samples ranged from 93 to 99%. The assay was successfully applied to the determination of FB1 in corn samples. It has a high selectivity over other competitive mycotoxins including aflatoxin, zearalenone, citrinin and patulin. The method is more selective than the detection of FB1 directly which may lead to false-positive errors. Graphical abstract Schematic representation of colorimetric assay of fumonisin B1 (FB1). FB1 was alkali-hydrolyzed and its product (hydrolyzed fumonisin B1) induces cysteamine-capped gold nanoparticles (Cys-AuNPs) via hydrogen bondings. The aggregation of Cys-AuNPs causes changes in color from wine-red to blue-gray.

The fluorescence enhancement in an over-etched gold zero-mode waveguide (ZMW) was investigated through both numerical simulation and experiments. Using Cy3 and Cy5 as the fluorescent probes, the simulation showed that the undercut not only enhances the fluorescence signals of both fluorophores, but also greatly improves the radial uniformity of the excitation fields in the ZMW. Furthermore, using a focused-ion-beam tool, we fabricated Au-ZMW arrays with different radius and undercut. The fluorescence enhancement per molecule and the effective excitation volume of the Au-ZMW were then measured as functions of its radial size and over-etching depth by using fluorescence correlation spectroscopy. It was found that the undercut can significantly enhance the fluorescence signal per molecule in the ZMW, but it also slightly increased the excitation volume. Decreasing the radial size of the ZMW can efficiently reduce the excitation volume and also further enhance the fluorescence per molecule. These results together indicate that combining the undercut and reduction of radius of the ZMW can serve as a simple and effective way to essentially improve the performance of an Au-ZMW for single molecule fluorescence detection.

A magnetic nanographene oxide sorbent as a selective sorbent for the magnetic solid-phase extraction combined with high-performance liquid chromatography and fluorescence detection was developed and proved to be a robust method for zearalenone determination in corn samples. Optimum extraction of zearalenone (20 mg magnetic nanographene oxide sorbent, extraction for 15 min, desorption time of 15 min using 1 mL of 0.5% formic acid in methanol) resulted in low limits of detection (05 mg/L) and quantitation (0.13 mg/L) and good linearity range of 0.13-1.25 mg/L with the correlation coefficient of 0.9957. Acceptable recoveries (79.3-80.6%) with relative standard deviations below 4% and satisfactory intra- and interday precisions (2-7.4%) were achieved. Additionally, the proposed method has been proved to be good in several aspects: easily prepared sorbent with high affinity to zearalenone, convenient and fast procedure, and high extraction efficiency., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The authors describe a rapid, sensitive and selective colorimetric assay for sialic acid (SA) based on the use of gold nanoparticles (AuNPs) modified with 3-aminophenylboronic acid (3-APBA) which acts as the recognition probe for SA. 3-APBA contains amino groups and boronic acid groups through which it can assemble on citrate stabilized AuNPs. It reacts with the cis-diol groups of SA by reversible formation of a cyclic boronate ester in slightly acidic buffer. Detection involves the sequential addition of AuNPs, phosphate buffer, 3-APBA and SA in a tube, vortex mixing, acquisition of photographic images or absorption spectra, and calculation of the result. The method is simple, rapid, and does not require cumbersome steps such as the preparation of stable boronic acid functionalized AuNPs as used in colorimetric sensing of saccharides. Under the optimum conditions, the ratio of absorbances at 700 and 520 nm increases linearly in the 0.15-1.00 mM SA concentrations range, and the detection limit is 60 µM. This is comparable to the detection limit obtained in other colorimetric assays reported. Acceptable intra- and inter-day precisions of three SA concentrations (0.50, 1.00 and 2.00 mM) ranged from 1.9-4.2% and 4.2-6.4%, respectively. The efficacy of the method was demonstrated by analyzing simulated human saliva which gave recoveries ranging from 98.7-106.0%. Graphical abstract Schematic of a colorimetric method for detection of sialic acid (SA) in simulated saliva. It is based on aggregation of gold nanoparticles with 3-aminophenyl boronic acid (3-APBA) which assembles on AuNPs while the boronic acid group binds to cis-diols of SA to form a boronate ester.

Inorganic bromide (Br - ) is an important contaminant ion as it can originate from the overuse of illegal methyl bromide as a fumigant in stored rice samples. Herein, we developed a simple and highly sensitive colorimetric sensor for bromide ion detection in rice samples. The sensor is based on the anti-aggregation of gold nanoparticles (AuNPs) by Br - in the presence of Cr 3+ , which made the method more selective than other typical aggregations of nanoparticles. The AuNPs underwent an aggregation process as a result of the coordination of Cr 3+ and the carboxylate group of a citrate ion stabilized the AuNPs, resulting in a red-to-blue color change. When Br - was pre-mixed with the AuNPs and Cr 3+ was added, the solution color changed from blue to red with an increase in the Br - concentration. The anti-aggregation process can be detected with the naked eye and monitored using UV-vis spectrophotometry. The linear calibration curve ranged between 0.31 and 3.75 μM Br - with a low LOD and LOQ of 0.04 and 0.13 μM. The recovery was excellent, ranging from 79.9-92.2% with an RSD of less than 4.0%. The good inter-day and intra-day precisions were 2.9-6.4% and 3.1-7.1%, respectively. The developed sensor has proved to provide a robust method for Br - detection in rice samples., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

The association of a plasmonic nano-antenna with single-molecule FRET technique presents new prospects to investigate the dynamics of biological molecules. However, the presence of a plasmonic nano-antenna significantly modifies the FRET rate and efficiency; this makes its applicability to the prevalent single-molecule FRET experiments unclear. Herein, using gold nanoparticle antennas of different sizes and DNA hairpins labelled with FRET pairs (Cy3 and Cy5) as the model system, we performed experiments to study the folding dynamics of single DNA hairpins at various salt concentrations. Our results indicate that gold nanoparticle antennas can enhance single-molecule fluorescence of Cy3 and Cy5 up to 3-5 folds, substantially reduce the FRET efficiency, and alter the obtained FRET efficiency histograms. However, the folding dynamics of DNA hairpins remains unaffected, and the correct kinetic and dynamic information can still be extracted from the seriously modified FRET efficiencies. Therefore, our experiments demonstrate the feasibility and compatibility for applying plasmonic nano-antennas to the mostly used single-molecule FRET assays, which provide a broad range of possibilities for the future applications of these nano-antennas in studying various essential biological processes.

Background: Essential oils (EOs) have been claimed to modulate mental functions though the most of data were obtained from subjective methods of assessment. Direct effects of EO on brain function remained largely to be confirmed with scientific proof. This study aimed to demonstrate quantifiable and reproducible effects of commercial vetiver (Vetiveria zizanioides) EO inhalation on sleep-waking and electroencephalogram (EEG) patterns in adult male Wistar rats. The experiments were conducted during November 2013 - February 2014., Materials and Methods: The following electrode implantation on the skull, control, and treated animals were subjected for EEG recording while inhaling water and vetiver EO (20 and 200 µl), respectively. Fast Fourier transform was used for analysis of EEG power spectrum., Results: One-way ANOVA analysis confirmed that vetiver EO inhalation significantly increased total waking and reduced slow-wave sleep time. Moreover, EO inhalation decreased alpha and beta1 activity in both frontal and parietal cortices and increased gamma activity in the frontal cortex. Changes in these frequencies began almost from the start of the inhalation., Conclusion: These data suggest refreshing properties of vetiver EO on electrical brain activity and alertness.

A passive sampler (the polar organic chemical integrative sampler; POCIS) was assessed for its ability to sample natural estrogens (17β-estradiol, E2; estrone, E1 and estriol, E3) and the synthetic estrogen (17α-ethynylestradiol, EE2) in the outlet of a sewage treatment works over several weeks. The performance of the POCIS was investigated and optimised in the laboratory before field deployment with high recoveries (66-99%) were achieved for all estrogens. Moreover, it was shown that POCIS does not exhibit any preferential selectivity towards any of the target compounds. The sampling rates of E1, E2 and E3 were 0.018 ± 0.009, 0.025 ± 0.014 and 0.033 ± 0.019 L d(-1), respectively. Following field deployments of 28 days in the discharge of a sewage works, POCIS was shown to enhance the sensitivity of estrogen detection, especially for E3, and provide time-weighted average (TWA) concentrations of E1, E2 and E3, ranging from undetectable to 12 ng L(-1) upstream of the outflow of a sewage treatment works, 13 to 91 ng L(-1) at the outflow and 8 to 39 ng L(-1) downstream of the outflow. This revealed that E1, E2 and E3 are not completely removed during sewage treatment, with concentrations most likely being maintained by contributions from conjugated estrogen analogues. Grab water samples showed considerable variation in the concentrations of estrogens over a longer period (6 months). The results confirm that POCIS is an effective and non-discriminatory method for the detection of low concentrations of estrogens in the aquatic environment.

A simple sequential injection analysis (SIA) with spectrophotometric detection for an assay of acidity in fruit juice was investigated. An alkaline reagent (sodium hydroxide), a sample and an indicator (phenolphthalein) were first aspirated and stacked as adjacent zones in a holding coil. With flow reversal through a reaction coil to the detector, zone penetration occurred, leading to a neutralization reaction that caused a decrease in the color intensity of the indicator being monitored for absorbance at 552 nm. The effects of various parameters were studied. Linear calibration graphs for acidities of 0.2 - 1.0 and 0.5 - 2.5% w/v citric acid as a standard, with a relative standard deviation of 1% (acidity of 0.3 - 0.6% w/v as citric acid, n=11) and a sample throughput of 30 samples h(-1), were achieved. The developed method was validated by a standard titrimetric method for assaying the acidity of fruit juice samples.