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This work proposes a highly specific method of Cr6+ determination based on the double reactions of two metals, Co2+ with dithizone to form a (DTZ)-Co2+ complex, and the replacement of Co2+ in the formed complex with Cr6+.

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.

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

Porous carbon nanoparticles (PCNPs) of four different sizes (~180 nm, ~51 nm, ~41 and ~25 nm) were dispersed into a nematic liquid crystal (NLC) in 0.25 wt% concentration. PCNPs were derived from b...

In this work, a detailed investigation on the temperature-dependant surface features of biomass derived porous carbon nanoparticles was conducted. The carbon nanoparticles were prepared by carbonization of Caesalpinia Sappan waste pods in single step pyrolysis, using a range of temperature from 400 to 1000 °C. The systematic analysis of materials obtained at different temperatures assisted to correlate the effect of pyrolysis temperature on the surface properties. Different methods were employed which were beneficial to demonstrate the overall surface area and porous features constituted by pores of different size (micropores, mesopores) and shapes such as cylindrical or narrow slit shape. This study confirmed the optimization of material properties with rise in pyrolysis temperature; as a result, Caesalpinia Sappan derived carbon nanoparticles pyrolyzed at 1000 °C (CSCNP1000) exhibited the largest surface area (794 m2 g−1 by BET) and pore volume (0.37 cm3 g−1) in the series. The resulted carbon products were microporous/mesoporous in nature, the condition which is considered suitable for the energy storage applications. The energy storage device, supercapacitor, was fabricated which exhibited a specific capacitance of 170.5 F g−1 at 0.25 A g−1. This work demonstrated the suitability of temperature dependent surface of a carbon nanoparticle to be actively used as a cost-effective energy storage device.

Mercury (Hg) contamination of the major environmental matrices, arising from human indiscriminate pursuit of industrialization without recourse to environment beneficiation is rife and worrisome. Amongst all the different forms of Hg, huge interest has been devoted to the inorganic Hg2+ determination, especially in water. Herein, a creatinine (CRN) conjugated on 3,3′-dithiodipropionic acid di(N-hydroxysuccinimide ester) (DTSP) functionalized gold nanoparticles (Au@DTSP/CRN)-based colorimetric assay was developed for Hg2+ detection in water samples. The DTSP was used to functionalize gold nanoparticles through the Au–S interaction, so as to impart a significantly high stability on the fabricated Au@DTSP, while also conferring coordination capacity on the nanoparticles. The Au@DTSP can bind to the amino group of CRN through its N-hydroxysuccinimide ester moiety, with the formation of an amide bond. The generated optical probe Au@DTSP/CRN aggregated in the presence of Hg2+, with a distinct change of solution colors from ruby red, through purple and to blue-grey within 10 min. The detection limit of 28.5 nM was achieved with linear calibration curves within 0.10–0.35 and 0.35–4.00 μM, while using the absorbance ratio (A680/A521) as the analytical response. Recoveries of 99.0–103.2% were obtained and the relative standard deviations were less than 5.5%. The Au@DTSP/CRN nanoprobe was applied for quantitative determination of Hg2+ in real water samples without significant interference from other metal ions, which is a positive indication of its utilitarian potentiality for Hg2+ profiling in aqueous environment.

A highly stable and dispersed aqueous nanocomposite of silver nanoparticles/poly(vinyl alcohol-co-ethylene glycol)/poly(3-aminophenyl boronic acid) (Ag/(PVA-PEG)/PABA) was synthesized. PVA and PEG was blended at the optimum volume ratio of 16:4 to obtain poly(vinyl alcohol-co-ethylene glycol) (PVA-PEG) blend. 3-Aminophenyl boronic acid served as the reductant of silver nitrate and was in situ oxidatively polymerized to obtain poly(3-aminophenyl boronic acid) (PABA). Subsequently, (PVA-PEG) blend served as matrix for PABA polymerization. The polymer blend helped to improve PABA solubility by providing platform for PABA anchoring, through covalent bonding with the free hydroxyl groups of the blend. Additionally, PABA is a highly conducting polymer, hence the synthesized nanocomposite demonstrated improved conductivity. The maximum absorption peak of Ag/(PVA-PEG)/PABA was at 422 nm, with particle sizes between 10 and 15 nm and zeta potential value of 25.8 mV. FESEM showed spherical AgNPs sprinkled on the surface of the nanocomposite while 40% Ag was presented in EDX result. The Ag/(PVA-PEG)/PABA exhibited good antibacterial potency against Bacillus cereus and Escherichia coli where the ruptured bacterial cell was observed on FESEM. Importantly, it showed reliable biocompatibility without imparting deleterious red blood cell hemolysis and non-cytotoxic to normal human cell line. Overall, these results emphasized the exciting biomedical potentials of Ag/(PVA-PEG)/PABA nanocomposite.

Surface properties always play a dominant role in the energy storage devices. Understanding the surface phenomena is the key to tune the energy storage device using biowaste based porous nano carbons. Here, Callerya atropurpurea pod derived peculiar porous nano carbons are synthesized by pyrolysis at different temperatures without any synthetic templates approach. Elaborate analysis of surface textures on the effect of pore size, volume and specific surface area on specific capacitance and frequency response behavior of nano carbons were studied in detail. Electrochemical characterizations establish the mutuality of porosity and micro textural properties of nano carbons with specific capacitance. The electrochemical characterization of the novel materials as super capacitor electrode shows a high specific capacitance of 326.54 F g−1at 0.25 A g−1in 1.0 MKOH. A practical symmetric super capacitor device is fabricated with a specific capacitance of 86.38 F g−1at 0.1 A g−1, and high energy density of 27.0 Wh kg−1.This symmetric super capacitor also possesses outstanding capacitance retention of 92.16% for 5000 charge discharge cycles and also stability of 97.17%, after volt-age holding at the maximum voltage for 100 hours. Present manuscript gives the strong evidence for structure-property relationships so that one can tune the energy storage devices effectively

A binder-free electrode has been fabricated by directly growing MoSe2 nanosheets on the macroporous Ti mesh skeleton (MoSe2 NS-Ti) via a facile hydrothermal deposition method. The as-prepared MoSe2 NS-Ti electrode is characteristic of robust porous hierarchical nanostructures with large surface area, enriched exposed active edges and improved electroconductivity. As a result, in comparison to the bare MoSe2 electrode, the MoSe2 NS-Ti electrode shows dramatically enhanced electrocatalytic activity and pseudocapacitive performance due to its desirable structural features.

In this study, a sensitive and selective colorimetric probe for fluoride detection was established. The detection strategy is based on the interaction between dithiobis(succinimidylpropionate) modified gold nanoparticles (DSP@AuNP) and 3-aminophenylboronic acid (APBA), which was used as the recognition molecule for fluoride. AuNPs were modified with DSP, a notable amine coupling ligand, so that they can bind with the amino group of APBA to furnish a colorimetric probe denoted as APBA–DSP@AuNP. The boronic acid moiety of the probe is appropriately positioned to bind with fluoride in a slightly acidic environment provided by phosphate buffer (pH = 5.2) through the Lewis acid–base interaction, resulting in the probe's aggregation. The color of APBA–DSP@AuNP undergoes different color transitions from ruby red to purple and blue-gray within 15 minutes, depending on the concentration of fluoride. The absorbance ratio (A650/A520) was used as the analytical signal, which was linear with fluoride concentration over two ranges of 75–1000 μM and 1000–3000 μM. The limit of detection was estimated as 56.5 μM, which was much lower than the maximum acceptable limit of fluoride (210 μM) in drinking water given by the US EPA. The practical applicability of APBA–DSP@AuNP was demonstrated by applying it to fluoride detection in tap water, with acceptable accuracy (97 to 102%).

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 (

A sensitive colorimetric assay is reported for carbamate pesticide detection. The detection strategy was based on carbamate hydrolyzed product induced aggregation of l-cysteine-modified gol...

A facile molecular wedging method is used to exfoliate graphite flakes into graphene sheets, with concurrent functionalization to form pyrene-1-boronic acid functionalized graphene (PBA/G). Different techniques are used to characterize the prepared materials such as field emission scanning electron microscope, energy dispersive X-ray analyzer, Raman, Fourier transformed infrared spectroscopy and fluorescence spectroscopy to evaluate their structural and morphological characteristics. The intercalation of PBA into graphite sheets, followed by exfoliation can be observed under the electron microscope. Elemental analyses show that the PBA acts more than intercalant, it is functionalized onto the graphene sheets upon exfoliation to form PBA/G. Raman analysis indicates PBA/G has a lower number of graphene layers as a result of successful exfoliation by PBA. Electrochemical impedance studies show that the PBA/G possesses high affinity for dopamine through the diol groups interaction, which renders it to have enhanced detection for dopamine.

Sialic acid (SA) is a notable tumor marker in human. Its increased level beyond the normal concentration in human biological samples is related to different kinds of cancers development. In this contribution, a novel colorimetric assay is reported for SA detection in form of N-acetylneuraminic acid. The sensitive detection strategy is proposed via the specific SA induced aggregation of 3‑aminophenyl boronic acid (3APBA) assembled on dithiobis(succinimidylpropionate) functionalized gold nanoparticles (AuNPs-DSP). DSP was functionalized on AuNPs through a strong Au S interaction and 3APBA was assembled on AuNPs-DSP by the amine coupling reaction between the carboxyl group of DSP on gold nanoparticles surface and the amino group of 3APBA to generate a covalent amide bond. The addition of 3APBA to buffered AuNPs-DSP generated a ruby red colloidal nanosensor. With increasing concentration of SA, a probe color turned rapidly from red to blue-gray via aggregation of AuNPs-DSP-3APBA. At optimal conditions, the absorbance ratio (A700/A520) was linear with SA concentrations ranging from 0.08 to 0.25 mM and 0.30–0.70 mM. A limit of detection of 35.0 μM was achieved which is the lowest amongst reported colorimetric methods for SA determination. The practical efficacy of the assay was demonstrated on human serum, along with no interfering effects and satisfactory accuracy and precision.

Herein, magnetic mesoporous carbon was synthesized via a facile and green soft template method and used for the magnetic solid-phase extraction (MSPE) of antioxidants, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). After the MSPE, the antioxidants were determined by high-performance liquid chromatography with diode array detection (HPLC-DAD). The adsorption of BHT and BHA was attributed to π–π stacking interaction and hydrogen bonds. Moreover, some important parameters affecting the extraction efficiency were optimized. Under optimum conditions, wide linear curves of BHT and BHA in the range of 0.5–6.0 μg mL−1 with satisfactory precisions (RSDs < 2.9%) were achieved. The limit of detection for BHT and BHA was found to be 0.14 and 0.22 μg mL−1, respectively. The recoveries were between 72 and 99%. Finally, the MSPE with the HPLC-DAD method was successfully applied to determine BHT and BHA in real water samples without any interference peaks.

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 Cu2+ 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 Cu2+ (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 Cu2+-mediated reaction in terms of the reaction time and sensitivity. This system has been demonstrated to allow quantitative measurement of Cu2+ with a detection limit as low as 26.8 nM and also has high specificity that can distinguish Cu2+ from other metal ions. Further, the method was tested with a real mineral water sample for Cu2+ concentration determination. Satisfactory recoveries of 90.8% and 99.8% were achieved.

Tuning of porosity and surface properties of nanoparticles especially on carbon-based nanomaterials, adopting a ‘greener’ or self-activation synthesis technique for electrical charge storage, is progressing. Herein, we report the self-activation of Teak wood sawdust in a nitrogen atmosphere at different activation temperatures to synthesize carbon nanoparticles. The activated carbon nanoparticles synthesized at 900 °C exhibits a maximum ~ 360 m2 g−1 surface area with ~ 2 nm average pore size diameter. Five electrolytes viz. KOH, KCl, Na2SO4, NaCl, and H3PO4 are used for studying the supercapacitance nature of the activated carbon nanoparticles in a 3-electrode configuration. A maximum specific capacitance of ~ 208 F g−1 @ 0.25 A g−1 is obtained in 1 M KOH as the electrolyte. Two symmetric supercapacitors, aqueous (1 M KOH) and solid-state (PVA/KOH), are fabricated, and their performance difference is compiled. The solid-state symmetric supercapacitor performs in a wider voltage window (1.7 V) with a superior energy density of 27.1 Wh kg−1 at a power density of 178 W kg−1.

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.

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.

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.

In this work, we present the novel robust material, modified natural rubber (NR) composites filled with gold nanoparticles (AuNPs). To investigate its outstanding properties, dielectric, electrical and mechanical properties of NR and modified NR composites filled with gold nanoparticles (AuNPs) were studied. The NR and all composite films were prepared by using solution casting method. The size of the synthetic AuNPs was analyzed by Transmission Electron Microscope (TEM) technique. The dispersion of AuNPs fillers within the NR matrix was investigated by scanning electron microscopy (SEM). Dielectric and electrical properties of NR composites were analyzed as function of filler concentration and frequency in a range of 100-105 Hz, observed with the LCR analyzer. Elastic modulus of all samples was evaluated by a strain gauge set up. It was found that the dielectric constant is inversely related to the frequency. Moreover, the dielectric constant and the electrical conductivity strongly increase in proportional to the AuNPs filler content. In comparison at AuNPs concentration of 0.0010% by weight, it was observed that the dielectric constant of NR composites is eight times larger than the pure NR, while the mechanical properties of the NR composites slightly increase in proportional to the AuNPs. As consequence, the interfacial surface area significantly affects the electrical and mechanical properties of those NR composites.

A sensitive and selective colorimetric assay for silver ion (Ag+) detection is demonstrated, based on creatinine (CRN) assembled on dithiobis(succinimidylpropionate) modified gold nanoparticles (DSP-AuNPs) as an optical probe. DSP was firstly modified on AuNPs to generate DSP-AuNPs through the highly efficient Au-S covalent interaction. Under pH 8.4 phosphate buffer, CRN can be assembled on DSP-AuNPs surface through the amine coupling reaction between the carboxyl group of DSP and the amino group of CRN, with the formation of an amide bond. Thus, CRN assembled on DSP-AuNPs denoted as DSP-AuNPs@CRN was used for Ag+ detection. The morphology of DSP-AuNPs@CRN was found to be highly dispersed and spherical particles with Dh of 41.5 ± 2.8 nm. When adding Ag+, progressive particle clustering of the nanoparticles was observed, Dh increased up to 324.7 ± 2.7 nm and naked eye color changed from red to blue-grey within 30 min, arising from particle aggregation. The absorption peak of dispersed and aggregated DSP-AuNPs@CRN was at 522 and 680 nm, respectively. The calibration curve plotted between the absorbance ratio (A680/A522) and Ag+ concentration was linear with two concentration ranges (0.50–3.00 µM and 3.00–35.00 µM Ag+). The assay detection limit of 0.13 µM is far below the USEPA maximum acceptable limit of Ag+ in drinking water at 0.93 μM. Finally, the assay has been successfully applied to Ag+ detection in water sample with good accuracy and precision.

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.

Arsenic (As) in soils and hair collected from schools in Ron Phibun district, Nakhon Si Thammarat province, Thailand, where former tin mining operation were located, was determined by hydride generation atomic absorption spectrophotometry. The relationship between As content in soils and hair with distance from secured landfill was also investigated. Soil and hair samples were collected from 6 schools in summer (February) and rainy season (July). For soils, silt+clay (

Hierarchical molybdenum disulfide microspheres have been successfully prepared through a zinc ion-assisted hydrothermal route followed by an acid corrosion strategy. It is found that the MoS2 microspheres comprised of numerous nanosheets with few-layered feature exhibit a 3D flower-like morphology. It is believed that the MoS2/ZnS composites can act as a precursor for the formation of hierarchical MoS2 microspheres. Additionally, the electrochemical properties of the as-prepared MoS2 microspheres as an electrode material for supercapacitors have also been investigated. Compared with the MoS2 nanosheet, the resultant MoS2 microsphere demonstrates superior pseudcapacitive properties including high specific capacitance, good cycling and rate capability, which could be credited to its novel hierarchical architecture feature.

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

In this paper, we developed a facile approach to synthesize well-dispersed 3D hierarchical porous MoS

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 highly efficacious green reductant, Chromolaena odorata phenolic extract (COPE), was used for the biosynthesis of silver nanoparticles (AgNPs) and iron was further in situ deposited to form silver@zero valent iron nanoparticles (Ag@ZVI NPs). Phenolic compounds were extracted from Chromolaena odorata leaves using our carefully formulated method and was further validated by ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. COPE was then used as a green bio-resource for room temperature synthesis of AgNPs. After successful synthesis of AgNPs, ferric (III) chloride was then added to realize Ag@ZVI NPs. X-ray diffraction validated the growth of Fe0 on the (111) crystalline facet of AgNPs during the formation of Ag@ZVI NPs. The synthesized AgNPs and Ag@ZVI NPs are highly stable, spherical and dispersed, with demonstrable antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Vibrio parahaemolyticus, Staphylococcus aureus and Listeria monocytogenes. The minimum inhibitory concentration and minimum bactericidal concentration ranged from 1 to 4 μg/mL and 2–8 μg/mL, respectively. Additionally, the antioxidant studies were probed by the DPPH-RSA, ABTS-RSA and MCA, which all confirmed the ability of the biosynthesized nanomaterials to scavenge radicals. The colorimetric sensing ability of COPE AgNPs was tested against hydrogen peroxide (H2O2) by visual observation and UV–vis spectrophotometry. A wide linear range from 5 to 200 µM as well as a low detection limit of 1.46 µM H2O2 was achieved. The practicality of the AgNPs sensor towards H2O2 was successfully performed on water sample with reliable accuracy.

Tin sulfide (SnS) becomes a competitive alternative anode material for lithium ion batteries (LIBs) due to its cost-effects and high theoretical capacity. Herein, a simple freeze-drying and annealing synthetic strategy was exploited to in-situ couple SnS with nitrogen-doped porous carbon nanosheets to fabricate SnS@NPC nanocomposites. In this nanostructure, SnS nanoparticles were well embedded into citric acid-derived nitrogen-doped carbon hierarchical frameworks with enlarged surface areas and abundant porosity. Besides, the reversible Li-ion storage property of this novel nanostructured anode in LIBs was also investigated and compared with the bare SnS counterpart. It was indicated that the SnS@NPC hybrid electrode exhibited a tremendously boosted electrochemical performance. After cycling 200 times at 100 mA g−1 and 300 times at 1000 mA g−1, a high specific capacity of 851.5 mA h g−1 and 607.6 mA h g−1 was remained respectively. Furthermore, with SnS@NPC as anode and the activated carbon (AC) as cathode, a new-type of lithium ion capacitor (LIC) was also fabricated, which exhibited a specific capacitance of 70.1 F g−1 at 0.1 A g−1 and a maximum energy density of 155.5 Wh kg−1 at 213.6 W kg−1. The well-engineered nanostructures as well as the aroused synergistic effect between SnS and nitrogen-doped carbon materials are considered to be responsible for the enhanced electrochemical property.

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.

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 AgNO3 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 H2O2 detection. Wide linearity from 5 to 1000 μM H2O2, 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.

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.

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.

In this paper, we developed a facile approach to synthesize well-dispersed 3D hierarchical porous MoS2 architectures with assistance of polyacrylate and demonstrated their applications in lithium ion batteries (LIBs). It was confirmed that the uniform flower-like MoS2 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 MoS2 nanosheets into hierarchical structures and could well stabilize and disperse MoS2 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 MoS2 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.

DNA–RNA hybrid (DRH) plays important roles in many biological processes. Here, we use a thermodynamic theory to analyze the free energy and unpeeling properties of the overstretching transition for the DRH molecule and compare the results with double-helix DNA. We report that the RNA strand of DRH is easier to get unpeeled than the DNA strand while the difficulty in unpeeling the double helix DNA lies in between. We also investigate the sequence effect, such as GC content and purine content, on the properties of unpeeling the DRH. Further, to study the temperature effect, the force-temperature phase diagram of DRH and DNA are calculated and compared. Finally, using a kinetic model, we calculate the force–extension curves in the DRH stretching and relaxation process under different pulling rates and temperatures. Our results show that both pulling rate and temperature have important influences on the stretching and relaxation kinetics of unpeeling the DRH. Putting all these results together, our work provides a comprehensive view of both the thermodynamics and kinetics in DRH overstretching.

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.

A method for extracting coenzyme Q10 (CoQ10) from Artemia was developed. 1 g of fresh Artemia was incubated with 75 % acetic acid at (30 ± 2)°C for 24 h, followed by three consecutive extractions with a mixture of 5 mL of hexane and 5 mL of ethanol, then analysis by a validated high-performance liquid chromatography with a diode-array detector. The calibration curve for CoQ10 was linear in a range of 1–50 μg mL−1. The limits of detection and quantification were 0.3 μg mL−1 and 1.1 μg mL−1, respectively. Mean recoveries were 94–100 % with a high precision of below 10 %. The method developed was found to be simple, efficient and the time required for releasing CoQ10 from Artemia was short. The method provides not only low energy consumption but is also practical for industrial applications.

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.