Quantitative determination of heavy metal contaminants in edible soft tissue of clams, mussels, and oysters.

Aquatic environments are important sources of healthy and nutritious foods; however, clams, mussels, and oysters (the bivalves most consumed by humans) can pose considerable health risks to consumers if contaminated by heavy metals in polluted areas. These organisms can accumulate dangerously high concentrations of heavy metals (e.g., Cd, Hg, Pb) in their soft tissues that can then be transferred to humans following ingestion. Monitoring contaminants in clams, mussels and oysters and their environments is critically important for global human health and food security, which requires reliable measurement of heavy-metal concentrations in the soft tissues. The aim of our present paper is to provide a review of how heavy metals are quantified in clams, mussels, and oysters. We do this by evaluating sample-preparation methods (i.e., tissue digestion / extraction and analyte preconcentration) and instrumental techniques (i.e., atomic, fluorescence and mass spectrometric methods, chromatography, neutron activation analysis and electrochemical sensors) that have been applied for this purpose to date. Application of these methods, their advantages, limitations, challenges and expected future directions are discussed.

High-Performance Magnesium Electrochemical Cycling with Hybrid Mg-Li Electrolytes.

Kinetics and coulombic efficiency of the electrochemical magnesium plating and stripping processes are to a significant extent defined by the composition of the electrolyte solution, optimization of which presents a pathway for improved performance. Adopting this strategy, we undertook a systematic investigation of the Mg0/2+ process in different combinations of the Mg2+-Li+-borohydride-bis(trifluoromethylsulfonyl)imide (TFSI-) electrolytes in 1,2-dimethoxyethane (DME) solvent. Results indicate that the presence of BH4- is essential for high coulombic efficiency, which coordination to Mg2+ was confirmed by Raman and NMR spectroscopic analysis. However, the high rates observed also require the presence of Li+ and a supplementary anion such as TFSI-. The Li+ + BH4- + TFSI- combination of ionic species prevents passivation of the magnesium surface and thereby enables efficient Mg0/2+ electrochemical cycling. The best Mg0/2+ performance with the stabilized coulombic efficiency of 88 ± 1% and one of the highest deposition/stripping rates at ambient temperature reported to date are demonstrated at an optimal [Mg(BH4)2]:[LiTFSI] mole ratio of 1:2.

Carbon Microsphere-Supported Metallic Nickel Nanoparticles as Novel Heterogeneous Catalysts and Their Application for the Reduction of Nitrophenol.

Nickel nanoparticles are gaining increasing attention in catalysis due to their versatile catalytic action. A novel, low-cost and facile method was developed in this work to synthesize carbon microsphere-supported metallic nickel nanoparticles (Ni-NP/C) for heterogeneous catalysis. The synthesis was based on carbonizing a polystyrene-based cation exchange resin loaded with nickel ions at temperatures between 500 and 1000 °C. The decomposition of the nickel-organic framework resulted in both Ni-NP and carbon microsphere formation. The phase composition, morphology and surface area of these Ni-NP/C microspheres were characterized by powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy and BET analysis. Elemental nickel was found to be the only metal containing phase; fcc-Ni coexisted with hcp-Ni at carbonization temperatures between 500 and 700 °C, and fcc-Ni was the only metallic phase at 800-1000 °C. Graphitization and carbon nanotube formation were observed at high temperatures. The catalytic activity of Ni-NP/C was tested in the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride, and Ni-NP/C was proved to be an efficient catalyst in this reaction. The relatively easy and scalable synthetic method, as well as the easy separation and catalytic activity of Ni-NP/C, provide a viable alternative to existing nickel nanocatalysts in future applications.

Multiple applications of bio-graphene foam for efficient chromate ion removal and oil-water separation.

This paper presents the synthesis of bio-graphene foams (bGFs) from renewable sources, and the application of bGFs as new adsorbents in removal of chromate ions and oil contaminants from waste water. A two-step synthetic method was developed to produce bGFs with unique porous architecture and high specific surface area (up to 805 m2 g-1) that is highly desirable for environmental applications. The adsorption performance of prepared bGFs for removal of chromate ions from water was studied in relation to CrO42- concentration, adsorbent load, pH, and contact time to confirm adsorption capacity, kinetics and pH dependence. The adsorption isotherms of chromate ions were consistent with the Langmuir model, revealing an outstanding adsorption capacity of 245 mg of Cr(VI)/g bGFs (pH∼7). bGFs were capable of reducing Cr(VI) in water below the maximum permissible level (0.050 mg dm-3) for human consumption (WHO). In a second application, our results convincingly showed excellent performance of bGFs in separating organic solvents and oils from water in a continuous oil-water separation process showing 99.1% and 98.8% separation efficiency for toluene and petroleum, respectively. Our findings confirm that the outstanding performance of bGFs, and suggest their use as efficient adsorbents for environmental remediation.

Synthesis and Application of Zero-Valent Iron Nanoparticles in Water Treatment, Environmental Remediation, Catalysis, and Their Biological Effects.

Present and past anthropogenic pollution of the hydrosphere and lithosphere is a growing concern around the world for sustainable development and human health. Current industrial activity, abandoned contaminated plants and mining sites, and even everyday life is a pollution source for our environment. There is therefore a crucial need to clean industrial and municipal effluents and remediate contaminated soil and groundwater. Nanosized zero-valent iron (nZVI) is an emerging material in these fields due to its high reactivity and expected low impact on the environment due to iron's high abundance in the earth crust. Currently, there is an intensive research to test the effectiveness of nZVI in contaminant removal processes from water and soil and to modify properties of this material in order to fulfill specific application requirements. The number of laboratory tests, field applications, and investigations for the environmental impact are strongly increasing. The aim of the present review is to provide an overview of the current knowledge about the catalytic activity, reactivity and efficiency of nZVI in removing toxic organic and inorganic materials from water, wastewater, and soil and groundwater, as well as its toxic effect for microorganisms and plants.

Advances in celiac disease testing.

Celiac disease (CD) is a T cell-mediated inflammatory autoimmune disorder of the upper small intestine caused by the ingestion of gluten. It is increasingly recognized as a global problem by experts and societies. The diagnosis of CD is of crucial importance because its delay strongly affects patient's health and quality of life. The diagnosis of CD is, however, complex and requires reliable, sensitive, specific, rapid, simple, and cost-effective, as well-as non-invasive analytical tools. There is also a high demand to develop simple point-of-care (POC) tests for non-specialists at home or in doctors' offices. Analytical techniques are now moving toward the development of fast, more simple, non-invasive, and POC analyses. The present review focuses on recent advances of CD biomarker detection in body fluids, concerning CD specific autoantibody detection in blood and saliva using electrochemical, optic-fiber, and piezoelectric biosensors and POC finger-prick tests, and identifying CD characteristic volatile organic compounds (VOCs) in urine and feces.

Biosensors for Non-Invasive Detection of Celiac Disease Biomarkers in Body Fluids.

Celiac disease is a chronic gluten-initiated autoimmune disorder that predominantly damages the mucosa of the small intestine in genetically-susceptible individuals. It affects a large and increasing number of the world’s population. The diagnosis of this disease and monitoring the response of patients to the therapy, which is currently a life-long gluten-free diet, require the application of reliable, rapid, sensitive, selective, simple, and cost-effective analytical tools. Celiac disease biomarker detection in full blood, serum, or plasma offers a non-invasive way to do this and is well-suited to being the first step of diagnosis. Biosensors provide a novel and alternative way to perform conventional techniques in biomarker sensing, in which electrode material and architecture play important roles in achieving sensitive, selective, and stable detection. There are many opportunities to build and modify biosensor platforms using various materials and detection methods, and the aim of the present review is to summarize developments in this field.

Understanding the role of hydrogen bonding in the aggregation of fumed silica particles in triglyceride solvents.

HYPOTHESIS: Fumed silica particles are thought to thicken organic solvents into gels by aggregating to form networks. Hydrogen bonding between silanol groups on different particle surfaces causes the aggregation. The gel structure and hence flow behaviour is altered by varying the proportion of silanol groups on the particle surfaces. However, characterising the gel using rheology measurements alone is not sufficient to optimise the aggregation. We have used confocal microscopy to characterise the changes in the network microstructure caused by altering the particle surface chemistry. EXPERIMENTS: Organogels were formed by dispersing fumed silica nanoparticles in a triglyceride solvent. The particle surface chemistry was systematically varied from oleophobic to oleophilic by functionalisation with hydrocarbons. We directly visualised the particle networks using confocal scanning laser microscopy and investigated the correlations between the network structure and the shear response of the organogels. FINDINGS: Our key finding is that the sizes of the pore spaces in the networks depend on the fraction of silanol groups available to form hydrogen bonds. The reduction in the network elasticity of gels formed by methylated particles can be accounted for by the increasing pore size and tenuous nature of the networks. This is the first report that characterises the changes in the microstructure of fumed silica particle networks in non-polar solvents caused by manipulating the particle surface chemistry.

Carbon Nanomaterial Based Biosensors for Non-Invasive Detection of Cancer and Disease Biomarkers for Clinical Diagnosis.

The early diagnosis of diseases, e.g., Parkinson's and Alzheimer's disease, diabetes, and various types of cancer, and monitoring the response of patients to the therapy plays a critical role in clinical treatment; therefore, there is an intensive research for the determination of many clinical analytes. In order to achieve point-of-care sensing in clinical practice, sensitive, selective, cost-effective, simple, reliable, and rapid analytical methods are required. Biosensors have become essential tools in biomarker sensing, in which electrode material and architecture play critical roles in achieving sensitive and stable detection. Carbon nanomaterials in the form of particle/dots, tube/wires, and sheets have recently become indispensable elements of biosensor platforms due to their excellent mechanical, electronic, and optical properties. This review summarizes developments in this lucrative field by presenting major biosensor types and variability of sensor platforms in biomedical applications.

Graphene Oxide-Assisted Liquid Phase Exfoliation of Graphite into Graphene for Highly Conductive Film and Electromechanical Sensors.

Here, we report a new method to prepare graphene from graphite by the liquid phase exfoliation process with sonication using graphene oxide (GO) as a dispersant. It was found that GO nanosheets act a as surfactant to the mediated exfoliation of graphite into a GO-adsorbed graphene complex in the aqueous solution, from which graphene was separated by an additional process. The preparation of isolated graphene from a single to a few layers is routinely achieved with an exfoliation yield of up to higher than 40% from the initial graphite material. The prepared graphene sheets showed a high quality (C/O ∼ 21.5), low defect (ID/IG ∼ 0.12), and high conductivity (6.2 × 10(4) S/m). Moreover, the large lateral size ranging from 5 to 10 µm of graphene, which is believed to be due to the shielding effect of GO avoiding damage under ultrasonic jets and cavitation formed by the sonication process. The thin graphene film prepared by the spray-coating technique showed a sheet resistance of 668 Ω/sq with a transmittance of 80% at 550 nm after annealing at 350 °C for 3 h. The transparent electrode was even greater with the resistance only 66.02 Ω when graphene is deposited on an interdigitated electrode (1 mm gap). Finally, a flexible sensor based on a graphene spray-coating polydimethylsiloxane (PDMS) is demonstrated showing excellent performance working under human touch pressure (<10 kPa). The graphene prepared by this method has some distinct properties showing it as a promising material for applications in electronics including thin film coatings, transparent electrodes, wearable electronics, human monitoring sensors, and RFID tags.

Cold condensation of dust in the ISM.

The condensation of complex silicates with pyroxene and olivine composition under conditions prevailing in molecular clouds has been experimentally studied. For this purpose, molecular species comprising refractory elements were forced to accrete on cold substrates representing the cold surfaces of surviving dust grains in the interstellar medium. The efficient formation of amorphous and homogeneous magnesium iron silicates at temperatures of about 12 K has been monitored by IR spectroscopy. The gaseous precursors of such condensation processes in the interstellar medium are formed by erosion of dust grains in supernova shock waves. In the laboratory, we have evaporated glassy silicate dust analogs and embedded the released species in neon ice matrices that have been studied spectroscopically to identify the molecular precursors of the condensing solid silicates. A sound coincidence between the 10 microm band of the interstellar silicates and the 10 microm band of the low-temperature siliceous condensates can be noted.

Coalescence in concentrated Pickering emulsions under shear.

We have investigated the rheology of concentrated oil-in-water emulsions stabilised by silanised silica nanoparticles. The emulsions behave like highly elastic solids in response to small, uniform strains. They become unstable and begin to break down, however, on yielding. We show that the emulsion elasticity is correlated with the salt concentration in the water and hence the particle aggregation in emulsions at a given drop volume fraction. A supporting observation is that destabilisation is favoured by minimising the attractive interactions between the particles. Microscopic observations revealed that coalesced drops have anisotropic shapes and wrinkled surfaces, direct evidence of the interfacial particle layer acting like a mechanical barrier to bulk emulsion destabilisation.

Generation and spectroscopic identification of ClCNS, ClNCS and NCCNS.

The photolysis of four chloro-substituted thiadiazoles (3,4-dichloro-, 3-chloro- and 3-chloro-4-fluoro-1,2,5-thiadiazole; 3,5-dichloro-1,2,4-thiadiazole) and 3,4-dicyano-1,2,5-thiadiazole was investigated in inert solid-argon matrices at cryogenic temperatures by means of UV irradiation at selected wavelengths of 254 and 280 nm. The photolysis products were identified by mid-IR and UV spectroscopy. Evidence for the existence of three novel pseudohalides, namely, chloronitrile sulfide (ClCNS), chlorine isothiocyanate (ClNCS) and cyanogen N-sulfide (NCCNS), was provided by direct spectroscopic methods supported by quantum chemical calculations. Ground-state geometries, vibrational frequencies, IR intensities, and UV excitation energies of ClCNS, ClNCS and NCCNS were obtained from calculations using the B3LYP, CCSD(T) and SAC-CI methods and the aug-cc-pV(T+d)Z basis set.

Photolysis of dimethylcarbamoyl azide in an argon matrix: spectroscopic identification of dimethylamino isocyanate and 1,1-dimethyldiazene.

The UV photolysis of dimethylcarbamoyl azide has been investigated in an argon matrix at cryogenic temperatures. The products of the photolysis were identified by infrared spectroscopy supported by quantum-chemical calculations. Sequential formation of dimethylamino isocyanate (Me2N-NCO), 1,1-dimethyldiazene (Me2N═N), and ethane was established. Therefore, the major decomposition channel is identified as Me2NC(O)N3 → Me2N-NCO → Me2N═N → Me-Me, via consecutive N2, CO, and N2 eliminations. Ground-state geometries, vibrational frequencies, IR intensities, and UV excitation energies of the transient dimethylamino isocyanate and 1,1-dimethyldiazene have been computed using the B3LYP and SAC-CI methods and the aug-cc-pVTZ basis set.

Generation and spectroscopic identification of selenofulminic acid and its methyl and cyano derivatives (XCNSe, X=H, CH3, NC).

Evidence for the existence of nitrile selenides, potential 1,3-dipolarophiles in cycloaddition reactions, has been provided by direct spectroscopic methods. The parent nitrile selenide, selenofulminic acid (HCNSe), and its methyl and cyano derivatives have been photolytically generated in an inert solid argon matrix from 1,2,5-selenadiazoles by 280, 254, and 313 nm UV irradiation, respectively, and studied by ultraviolet spectroscopy and mid-infrared spectroscopy. Ground-state geometries have been obtained from quantum-chemical calculations at the CCSD(T)/aug-cc-pVTZ level. Nitrile selenides are predicted to be linear with a relatively weak N-Se bond.

A matrix isolation and computational study of the [C, N, F, S] isomers.

The potential energy surface (PES) of the [C, N, F, S] system was investigated by quantum chemical and experimental methods. Seven minima were located on the ground state PES by density functional and ab initio electronic structure calculations. Four of these isomers, FSCN, FSNC, FCNS and FNCS, have an acyclic structure, while the other three, FC(NS), FS(CN) and FN(SC), form a three-membered fluorine-substituted ring. Out of these seven theoretically predicted isomers, FCNS and FC(NS) were successfully prepared in low-temperature Ar and Kr matrices by photochemical methods. The identification of these species was based on experimental considerations as well as on comparison of their IR spectra to computed anharmonic vibrational frequencies and infrared intensities. The present paper describes not only the first generation of both FCNS and FC(NS) species, but also reports the first time that a substituted CNS ring has been experimentally identified.