A low-cost paper-based aptasensor for simultaneous trace-level monitoring of mercury (II) and silver (I) ions.

Mercury (Hg2+) and silver (Ag+) ions possess the harmful effects on public health and environment that makes it essential to develop the sensing techniques with great sensitivity for the ions. Metal ions commonly coexist in the different biological and environmental systems. Hence, it is an urgent demand to design a simple method for the simultaneous detection of metal ions, peculiarly in the case of coexisting Hg2+ and Ag+. This study introduces a low-cost paper-based aptasensor to monitor Hg2+ and Ag+, simultaneously. The strategy of the sensing array is according to the conformational changes of Hg2+- and Ag+-specific aptamers and their release from the GO surface after the injection of the target sample on the sensing platform. Through monitoring the fluorescence recovery changes against the concentrations of the ions, Hg2+ and Ag+ can be determined as low as 1.33 and 1.01 pM. The paper-based aptasensor can simultaneously detect the ions within about 10 min. The aptasensor is applied prosperously to monitor Hg2+ and Ag+ in human serum, water, and milk. The designed aptasensor with the main advantages of simplicity and feasibility holds the supreme potential to develop a cost-effective sensing method for environmental monitoring, food control, and human diagnostics.

[Criterium pencil mines as an alternative to platinum rods (Inoclic) in achievement of the antibiogram in agar medium for countries with limited resources?] / Les mines de crayon pour critérium comme alternative aux tiges de platine (Inoclic) dans la réalisation de l'antibiogramme en milieu gélosé pour les pays à ressources limitées ?

The realization of the antibiotic susceptibility test in agar is the routine bacteriological examination for the determination and monitoring of bacterial susceptibility to antibiotics. In this study, we report the comparative results between pencil leads for criterium, as an alternative to platinum rods in the realization of the antibiotic susceptibility test. METHODOLOGY: Experimental study evaluating the comparability of the results between Criterium and Inoclic mines (by counting bacterial cells on agar after 5 successive dilutions of reason 10 from a bacterial suspension obtained after piercing through a colony; by measuring the inhibition diameters of 4 ATCC reference bacterial strains on an antibiogram in an agar medium) and evaluating the sterility of the criterium mines by culturing them on enriched broth (heart - brain type). RESULTS: 42 bacterial strains were used for bacterial cell counting. The results were of the same order of magnitude (107 CFU/mL) between Inoclic and criterium mines, for all strains and at all dilutions. The antibiotic susceptibility tests performed for the 4 reference strains by the Inoclics and criterium mines all complied (100%) with the expected limits for determining their sensitivity profile to the antibiotics tested. Compared to the bacterial growth inhibition diameters on antibiotic susceptibility tests, no intra-operator variability was observed, while significant inter-operator variability (both with Inoclic and 0.5 mm criterium mines) was observed with some strains and for inhibition diameters greater than 10 mm. The enriched broth cultures (BCC) and their subculture carried out on 10 criterium mines from 5 different batches were negative. CONCLUSION: Criterium mines seem to be a serious and less expensive alternative to Inoclic for the realization of antibiotic susceptibility testing in our resource-limited countries.

Nano-Fe3C@PGC as a novel low-cost anode electrocatalyst for superior performance microbial fuel cells.

We report a novel anode electrocatalyst, iron carbide nanoparticles dispersed in porous graphitized carbon (Nano-Fe3C@PGC), which is synthesized by facile approach involving a direct pyrolysis of ferrous gluconate and a following removal of free iron, but provides microbial fuel cells with superior performances. The physical characterizations confirm the unique configuration of iron carbide nanoparticles with porous graphitized carbon. Electrochemical measurements demonstrate that the as-synthesized Nano-Fe3C@PGC exhibits an outstanding electrocatalytic activity toward the charge transfer between bacteria and anode. Equipped with Nano-Fe3C@PGC, the microbial fuel cells based on a mixed bacterium culture yields a power density of 1856 mW m-2. The resulting excellent performance is attributed to the large electrochemical active area and the high electronic conductivity that porous graphitized carbon provides and the enriched electrochemically active microorganisms and enhanced activity towards the redox reactions in microorganisms by Fe3C nanoparticles.

Green and low-cost synthesis of nitrogen-doped graphene-like mesoporous nanosheets from the biomass waste of okara for the amperometric detection of vitamin C in real samples.

In this work, the low-cost nitrogen-doped graphene-like mesoporous nanosheets (N-GMNs) was synthesized from the biomass waste of okara for the first time for the construction of a nonenzymatic amperometric vitamin C biosensor. The N-GMNs modified glassy carbon electrode (N-GMNs/GCE) shows much lower overpotential for the electrooxidation of vitamin C comparing to the traditional GCE as well as the GCE modified by carbon nanotubes (CNTs/GCE), indicating the promising of N-GMNs/GCE for the sensitive and selective nonenzymatic amperometric vitamin C biosensing. As a nonenzymatic amperometric biosensor for vitamin C, the N-GMNs/GCE shows a higher sensitivity (144.65 µA mM-1 cm-2), a wider linear range (10-5640 µmol L-1) and a lower detection limit (0.51 µmol L-1) than GCE, CNTs/GCE or some of recently reported nanomaterials-based electrochemical vitamin C biosensors. Especially, the vitamin C concentration in real samples of commercial beverage, vitamin C injection and commercial juice can be determined by the proposed N-GMNs/GCE with satisfied results. Therefore, the utilization of okara as the raw material for the synthesis of nanostructured carbon of N-GMNs is a green method to fabricate an advanced and low-cost electrode material for developing the nonenzymatic electrochemical biosensor for vitamin C detection.

Cost-Efficient Graphitic Carbon Nitride as an Effective Photocatalyst for Antibiotic Degradation: An Insight into the Effects of Different Precursors and Coexisting Ions, and Photocatalytic Mechanism.

In this study, the photocatalytic activity of graphitic carbon nitride (g-C3 N4 ) synthesized via different precursors (urea, thiourea, and dicyandiamide) is investigated in the degradation process of tetracycline. Owing to the efficient charge separation and transfer, prolonged radiative lifetime of charge, large surface area, and nanosheet morphology, the urea-derived g-C3 N4 exhibits superior photocatalytic activity for tetracycline degradation under visible-light irradiation. This performance can compare with that of most reported g-C3 N4 -based composite photocatalysts. Through the time-circle degradation experiment, the urea-derived g-C3 N4 is found to have an excellent photocatalytic stability. The presence of NO3 - , CH3 COO- , Cl- and SO4 2- ions with the concentration of 10 mm inhibits the photocatalytic activity of urea-derived g-C3 N4 , where this inhibitory effect is more obvious for Cl- and SO4 2- ions. For the coexisting Cu2+ , Ca2+ , and Zn2+ ions, the Cu2+ ion exhibits a significantly higher inhibitory effect than Ca2+ and Zn2+ ions for tetracycline degradation. However, both the inhibitory and facilitating effects are observed in the presence of Fe3+ ion with different concentration. The h+ , . OH and . O2 - radicals are confirmed as major oxidation species and a possible photocatalytic mechanism is proposed in a urea-derived g-C3 N4 reaction system. This study is of important significance to promote the large-scale application of g-C3 N4 photocatalysts in antibiotic wastewater purification.

Preliminary investigation on the thermal conversion of automotive shredder residue into value-added products: Graphitic carbon and nano-ceramics.

Large increasing production volumes of automotive shredder residue (ASR) and its hazardous content have raised concerns worldwide. ASR has a desirable calorific value, making its pyrolysis a possible, environmentally friendly and economically viable solution. The present work focuses on the pyrolysis of ASR at temperatures between 950 and 1550°C. Despite the high temperatures, the energy consumption can be minimized as the decomposition of ASR can be completed within a short time. In this study, the composition of ASR was investigated. ASR was found to contain about 3% Ti and plastics of high calorific value such as polypropylene, polyethylene, polycarbonate and polyurethane. Based on thermogravimetric analysis (TGA) of ASR, the non-isothermal degradation kinetic parameters were determined using Coats-Redfern's and Freeman and Carroll methods. The evolved gas analysis indicated that the CH4 was consumed by the reduction of some oxides in ASR. The reduction reactions and the presence of Ti, silicates, C and N in ASR at 1550°C favor the formation of specific ceramics such as TiN and SiC. The presence of nano-ceramics along with a highly-crystalline graphitic carbon in the pyrolysis residues obtained at 1550°C was confirmed by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Raman imaging microscope (RIM) analyses.

Development of a Novel, Low-Cost, Disposable Wooden Pencil Graphite Electrode for Use in the Determination of Antioxidants and Other Biological Compounds.

The development of portable sensors that can be used outside the lab is an active area of research in the electroanalytical field. A major focus of such research is the development of low-cost electrodes for use in these sensors. Current electrodes, such as glassy-carbon electrodes (GCEs), are costly and require time-consuming preparation. Alternatives have been proposed, including mechanical pencil-lead electrodes (MPEs). However, MPEs themselves possess numerous drawbacks, particularly structural fragility. In this paper, we present a novel pencil-graphite electrode (PGE) fabricated from a regular HB#2 pencil. This PGE is a simple, disposable, extremely low-cost alternative to GCEs ($0.30 per PGE, vs. $190 + per GCE), and possesses the structural stability that MPEs lack. PGEs were characterized by square-wave voltammetry of ferricyanide, gallic acid, uric acid, dopamine, and several foodstuffs. In all cases, PGEs demonstrated sensitivities comparable or superior to those of the GCE and MPE (LOD = 5.62 × 10(-4) M PGE, 4.80 × 10(-4) M GCE, 2.93 × 10(-4) M MPE). Signal areas and peak heights were typically four to ten times larger for the PGE relative to the GCE.

Novel materials enable a low-cost temperature-light gradient incubator for microbial studies.

We describe the construction of temperature-light gradient incubator with a novel material: a thermally-conductive graphite foam that is lightweight, chemically resistant, economically competitive with metal, and much cheaper to fabricate. We combined this material with a variable-intensity LED light array to construct a low-cost light-temperature gradient incubator, and demonstrate its use for studies of microbial growth, enrichment, and isolation.

Advances in graphene-related technologies: synthesis, devices and outlook.

Graphene has been the subject of many scientific investigations since exfoliation methods facilitated isolation of the two-dimensional material. During this time, new synthesis methods have been developed which have opened technological opportunities previously hindered by synthetic constraints. An update on the recent advances in graphene-based technologies, including synthesis and applications into electrical, mechanical and thermal uses will be covered. A special focus on the patent space and commercial landscape will be given in an effort to identify current trends and future commercialization of graphene-related technologies.

Escrever nas coisas: a utopia contemporânea na linguagem dos adolescentes / To write on things: the contemporary utopia on adolescents language / Escribir en las cosas: la utopía contemporánea en el lenguaje de los adolescentes

The article deals with the practice of graffiti on streets, to examine the rules of these writings and refer them to the subversion of the ordinary language they operate. It is based on Walter Benjamin´s analysis of the language transformations that are on the base of modern social order. It argues that if science on the one hand reduces language to the point of turning it algorithmic, emptying its expressive potency, on the other hand, the youngsters these days rejoin the creative power of language. They exhibit on the city walls the incommensurability between what is shown on words and what can be read.(AU)

El artículo aborda la práctica de grafito de los adolescentes en las calles. Se basa en los análisis de W. Benjamin sobre las transformaciones del discurso que ordenan nuestro funcionamiento social para discutir los efectos subjetivos de estas transformaciones. Sitúa una discursividad propia de estos escritos, referida a la subversión del funcionamiento ordinario del lenguaje que promueven, y argumenta que si la ciencia depura el lenguaje hasta el punto del algoritmo, vaciando su potencia expresiva, los jóvenes de hoy retoman a la fuerza el poder creador del lenguaje, ostentando en los muros de la ciudad la inconmesurabilidad entre lo que se muestra como palabra y lo que se puede leer.(AU)

O artigo aborda a praticados adolescentes nas pichacoes de rua. Baseia-se nas analises de W. Benjamin sobre as transformacoes do discurso que ordenam nosso funcionamento social para discutir os efeitos subjetivos destas transformacoes. Situa uma discursividade propria destes escritos, referida a subversao do funcionamento ordinario da linguagem que promovem. Alem disso, argumenta que, se a ciencia depura a linguagem ate o ponto do algoritmo, esvaziando sua potencia expressiva, os jovens de hoje retomam a forca o poder criador da linguagem, ostentando nos muros da cidade a incomensurabilidade entre o que se mostra como palavra e o que se pode ler.(AU)

Escrever nas coisas: a utopia contemporânea na linguagem dos adolescentes / To write on things: the contemporary utopia on adolescents language / Escribir en las cosas: la utopía contemporánea en el lenguaje de los adolescentes

The article deals with the practice of graffiti on streets, to examine the rules of these writings and refer them to the subversion of the ordinary language they operate. It is based on Walter Benjamin´s analysis of the language transformations that are on the base of modern social order. It argues that if science on the one hand reduces language to the point of turning it algorithmic, emptying its expressive potency, on the other hand, the youngsters these days rejoin the creative power of language. They exhibit on the city walls the incommensurability between what is shown on words and what can be read.

El artículo aborda la práctica de grafito de los adolescentes en las calles. Se basa en los análisis de W. Benjamin sobre las transformaciones del discurso que ordenan nuestro funcionamiento social para discutir los efectos subjetivos de estas transformaciones. Sitúa una discursividad propia de estos escritos, referida a la subversión del funcionamiento ordinario del lenguaje que promueven, y argumenta que si la ciencia depura el lenguaje hasta el punto del algoritmo, vaciando su potencia expresiva, los jóvenes de hoy retoman a la fuerza el poder creador del lenguaje, ostentando en los muros de la ciudad la inconmesurabilidad entre lo que se muestra como palabra y lo que se puede leer.

O artigo aborda a praticados adolescentes nas pichacoes de rua. Baseia-se nas analises de W. Benjamin sobre as transformacoes do discurso que ordenam nosso funcionamento social para discutir os efeitos subjetivos destas transformacoes. Situa uma discursividade propria destes escritos, referida a subversao do funcionamento ordinario da linguagem que promovem. Alem disso, argumenta que, se a ciencia depura a linguagem ate o ponto do algoritmo, esvaziando sua potencia expressiva, os jovens de hoje retomam a forca o poder criador da linguagem, ostentando nos muros da cidade a incomensurabilidade entre o que se mostra como palavra e o que se pode ler.