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1.
J Environ Manage ; 261: 110189, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32148265

RESUMO

The removal of styrene from wastewater by pervaporation was investigated by using composite PDMS membranes filled with reduced graphene oxide on PES support layers. Graphene oxide was synthesized through modified Hummers' method and then chemically reduced. The filler was characterized by TEM, SEM, XRD, and AFM. The top layers with different PDMS molecular weights were cast on the PES supports, which were prepared by phase inversion method. The characterizations of prepared membranes were investigated by SEM, AFM, contact angle measurement, TGA, and DSC. It was observed that presence of the filler in the polymeric matrix controls the swelling of the membrane and enhances its solubility parameter in favor of styrene. Moreover, it significantly improves the thermal stability of the membranes. The mechanism of separation in the process was found to be affected mainly by enhancing in the membrane's solubility rather than in its diffusivity. The pervaporative performance of prepared membranes showed their great affinity toward styrene so that the separation factor of the optimum membrane (M2/S) was increased about 250% (600.4 in comparison to 241.4 for the unfilled membrane) while its total flux was decreased from 772.5 g m-2.h-1for the unfilled membrane to 321.9 g m-2.h-1. Increasing the molecular weight of PDMS lowered the optimal rGO content due to the complexity of the diffusion path and occupation of free volume by longer polymer chains. Accordingly, a lower total flux (124.7 g m-2.h-1 for high MW compared to 718.0 g m-2.h-1 for low MW) and higher separation factor (822.5 for high MW compared to 230.8 for low MW) were yielded for the same filler content (0.1 wt% rGO).


Assuntos
Grafite , Águas Residuárias , Membranas Artificiais , Estireno
2.
Environ Monit Assess ; 192(4): 222, 2020 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-32146527

RESUMO

The determination of trace metal contents directly from a solid sample is a trend in modern atomic spectrometry. The aim of this study was to develop an analytical method for the routine determination of Cd in lichens using solid sampling graphite furnace atomic absorption spectrometry (SS-GF-AAS). For the determination of Cd, the temperature program of the graphite furnace was optimized using a mixed matrix modifier (Pd + Mg (NO3)2 + Triton X-100). The limit of detection and the limit of quantification were 0.9 µg/kg and 3 µg/kg, respectively. The analytical method for Cd determination in the plant matrix was verified by the analysis of certified reference materials of lichens, seaweed, and rye grass. The developed procedure was applied to the study of Cd distribution in thalli of Usnea antarctica lichen from James Ross Island, Antarctica. The SS-GF-AAS analytical method is particularly suited for use in environmental studies and plant physiology (the microanalysis of anatomical structures).


Assuntos
Cádmio , Poluentes Ambientais , Grafite , Líquens , Regiões Antárticas , Cádmio/análise , Monitoramento Ambiental , Poluentes Ambientais/análise , Ilhas , Líquens/química , Espectrofotometria Atômica
3.
J Photochem Photobiol B ; 204: 111587, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32062387

RESUMO

Although the photothermal therapy (PTT) has achieved tremendous progress in the recent times, still it has to improve an extensive way to achieve the efficient targeted photothermal removal of the tumor cells. Owing to this requirement, we demonstrated a novel class of reduced graphene oxide based photothermal therapeutic agent for the ablation of lung cancer cells (A549). A single step bio facile fabrication of graphene nanosheets using Memecylon edule leaf extract intermediated reduction of Graphene Oxide (GO). This process does not include the utilization of any toxic or harmful reducing agents. The relative results of different characterizations of graphene oxide and Memecylon edule leaf extract RGO delivers a potential representation by excluding the groups containing oxygen from GO and consecutive stabilization of the developed RGO. The reduced GO functionalization with the oxidized polyphenols results in their stability by avoiding the aggregation. The poly phenol anchored Reduced Graphene Oxide (RGO) exhibited exceptional near-infrared (NIR) irradiation of the lung cancer cells directed in vitro to deliver cytotoxicity. In an area of restricted success in the treatment of cancer, the results of our translation can provide a path for designing targeted PTT agents and also responds to stimulus environment for the safe ablation of the devastating disease.


Assuntos
Grafite/química , Raios Infravermelhos , Nanoestruturas/química , Polifenóis/química , Animais , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Cães , Química Verde , Humanos , Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/terapia , Células Madin Darby de Rim Canino , Magnoliopsida/química , Magnoliopsida/metabolismo , Nanoestruturas/uso terapêutico , Nanoestruturas/toxicidade , Fototerapia/métodos , Extratos Vegetais/química , Folhas de Planta/química , Folhas de Planta/metabolismo
4.
J Photochem Photobiol B ; 204: 111809, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32062390

RESUMO

The graphene oxide (GO)-based materials are appealing channels for water treatment, their separation from water for recycle remains a task. The Cu3(btc)2 (btc = benzene-1,3,5-tricarboxylic acid) metal organic framework (MOF) was covalently immobilized onto chitosan (CS)/graphene oxide (GO) to form a catalyst material, which was subjected to characterization by XRD, FTIR, SEM, TEM, BET, and UV-vis diffusive reflectance spectra. MOFs are permeable crystalline compounds consisting of metal ions and polyfunctional organic ligands. The structural characterization revealed that the Cu3(btc)2 and chitosan were incorporated into the graphene oxide structure. The adsorption of MB by GO-CS@Cu3(btc)2 catalyst was clearly defined by Langmuir isotherm and pseudosecond order kinetic model. GO-CS@Cu3(btc)2 was found to possess an adsorption capacity of ~357.15 mg/g. The findings displayed the probability of reusing the catalyst material for several photocatalytic processes. The GO-CS@Cu3(btc)2 catalyst material exhibited 98% degradation of MB within 60 min under UV irradiation. The obtained MB degradation results were fitted onto a Langmuir-Hinshelwood (L-H) plot. The GO-CS@Cu3(btc)2 catalyst material exhibited high degradation efficiencies at neutral pH conditions. The results have shown that the GO-CS@Cu3(btc)2 catalyst material can be used as a catalyst for adsorption and as a photocatalyst for the efficient degradation of methylene blue from aqueous solutions.


Assuntos
Quitosana/química , Complexos de Coordenação/química , Grafite/química , Azul de Metileno/química , Adsorção , Catálise , Cobre/química , Concentração de Íons de Hidrogênio , Cinética , Fotólise/efeitos da radiação , Raios Ultravioleta
5.
Bioresour Technol ; 304: 122992, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32086032

RESUMO

To meet the urgent demands for sustainable and efficient, environmental-friendly wastewater treatment, a Microbial fuel cell reactor system with MnO2/TiO2/g-C3N4 (manganese dioxide/ titanium dioxide/graphitic carbon nitride) @GAC (granular activated carbon) electrode was developed. It was both efficient and energy-saving in treating organic acid wastewater generated in Nylon production, with high-concentration COD and residual nitric acid. The MnO2/TiO2/g-C3N4 catalyst was deposited on GAC via in-situ growth and sol-gel method. The COD, NH4+-N and NO3--N was efficiently removed (respectively 98%, 99% and 99%). The COD removal capacity (17.77 kg COD m-3d-1) and the maximum power density (1176.47 mW m-3) was respectively 36.83% and 65.29% higher than the GAC cathode system. The anodic and cathodic microbial consortiums in MFC were analyzed and compared. The MnO2/TiO2/g-C3N4@GAC MFC system is technically feasible and cost-effective in treating industrial wastewater.


Assuntos
Fontes de Energia Bioelétrica , Carvão Vegetal , Eletricidade , Eletrodos , Grafite , Compostos de Manganês , Ácido Nítrico , Compostos de Nitrogênio , Óxidos , Titânio , Águas Residuárias
6.
Bioresour Technol ; 304: 122907, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32087548

RESUMO

The hydrophilic three-dimensional (3D) structure of graphene materials was produced with reducing agent-ethylene glycol through hydrothermal reduction. Numerous microorganisms with diverse community structure were established in anode surface, as the hydrophilicity of the graphene anode increased; more populations of Proteobacteria and Firmicutes families were identified in a higher hydrophilic anode. In addition, the start-up time of a microbial fuel cell (MFC) equipped with hydrophilic 3D graphene anode was only 43 h, which is much shorter than traditional 3D graphene-based anode systems. The most hydrophilic anode exhibited the maximal power density of 583.8 W m-3, 5 times larger than the least hydrophilic one. The content of oxygen in graphene materials improving hydrophilicity would play an important role in enhancing power density. This study proves that hydrophilic 3D graphene materials as the anode can improve MFC performance and start-up time.


Assuntos
Fontes de Energia Bioelétrica , Grafite , Eletrodos , Interações Hidrofóbicas e Hidrofílicas
7.
Top Curr Chem (Cham) ; 378(1): 18, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-32009187

RESUMO

DNA molecules with superior flexibility, affinity and programmability have garnered considerable attention for the controllable assembly of nanoparticles (NPs). By controlling the density, length and sequences of DNA on NPs, the configuration of NP assemblies can be rationally designed. The specific recognition of DNA enables changes to be made to the spatial structures of NP assemblies, resulting in differences in tailorable optical signals. Comprehensive information on the fabrication of DNA-driven NP assemblies would be beneficial for their application in biosensing and bioimaging. This review analyzes the progress of DNA-driven NP assemblies, and discusses the tunable configurations determined by the structural parameters of DNA skeletons. The collective optical properties, such as chirality, fluorescence and surface enhanced Raman resonance (SERS), etc., of DNA-driven NP assemblies are explored, and engineered tailorable optical properties of these spatial structures are achieved. We discuss the development of DNA-directed NP assemblies for the quantification of DNA, toxins, and heavy metal ions, and demonstrate their potential application in the biosensing and bioimaging of tumor markers, RNA, living metal ions and phototherapeutics. We hihghlight possible challenges in the development of DNA-driven NP assemblies, and further direct potential prospects in the practical applications of macroscopical materials and photonic devices.


Assuntos
Técnicas Biossensoriais/métodos , DNA/química , Nanopartículas/química , Imagem Óptica/métodos , Biomarcadores Tumorais/análise , Grafite/química , Humanos , Metais/química , Análise Espectral Raman
8.
J Environ Manage ; 255: 109936, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-32063312

RESUMO

Growing concerns of water pollution by dye pollutants from the textile industry has led to vast research interest to find green solutions to address this issue. In recent years, heterogeneous photocatalysis has harvested tremendous attention from researchers due to its powerful potential applications in tackling many important energy and environmental challenges at a global level. To fully utilise the broad spectrum of solar energy has been a common aim in the photocatalyst industry. This study focuses on the development of an efficient, highly thermal and chemical stable, environmentally friendly and metal-free graphitic carbon nitride (g-C3N4) to overcome the problem of fast charge recombination which hinders photocatalytic performances. Nitrogen-doped carbon quantum dots (NCQDs) known for its high electronic and optical functionality properties is believed to achieve photocatalytic enhancement by efficient charge separation through forming heterogeneous interfaces. Hence, the current work focuses on the hybridisation of NCQDs and g-C3N4 to produce a composite photocatalyst for methylene blue (MB) degradation under LED light irradiation. The optimal hybridisation method and the mass loading required for maximum attainable MB degradation were systematically investigated. The optimum photocatalyst, 1 wt% NCQD/g-C3N4 composite was shown to exhibit a 2.6-fold increase in photocatalytic activity over bare g-C3N4. Moreover, the optimum sample displayed excellent stability and durability after three consecutive degradation cycles, retaining 91.2% of its original efficiency. Scavenging tests were also performed where reactive species, photon-hole (h+) was identified as the primary active species initiating the pollutant degradation mechanism. The findings of this study successfully shed light on the hybridisation methods of NCQDs which improve existing g-C3N4 photocatalyst systems for environmental remediation by utilising solar energy.


Assuntos
Recuperação e Remediação Ambiental , Pontos Quânticos , Carbono , Catálise , Grafite , Nitrogênio , Compostos de Nitrogênio
9.
Bioresour Technol ; 300: 122642, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31911315

RESUMO

This study reports the use of multi-layered reduced graphene oxide (rGO) coating on porous nickel foam (NF) electrodes for enhancing biofilm growth of Rhodobacter Sphaeroides spp fed with methanol in microbial fuel cells (CH3OH-MFCs). Electrochemical methods were used to assess the methylotrophic activity on rGO/NF electrodes. The power density and current density offered by rGO/NF (1200 mW m-2 and 680 mA m-2) were 220-fold and 540-fold higher compared to bare NF (5.50 mW m-2 and 1.26 mA m-2), respectively. Electrochemical impedance spectroscopy results show that rGO/NF suppresses charge transfer resistance to CH3OH oxidation by 40-fold compared to the control. This improved performance is due to the ability of rGO coatings to decrease the wetting contact angle (improve the hydrophilicity) of NF from 1280 to 00. A preliminary cost analysis was carried out to assess the viability of rGO/NF electrodes via vitamin-C-enabled graphene oxide chemistry for CH3OH-MFCs applications.


Assuntos
Fontes de Energia Bioelétrica , Grafite , Ácido Ascórbico , Biofilmes , Eletrodos , Níquel , Fenótipo , Vitaminas
10.
Food Chem ; 312: 126089, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-31896452

RESUMO

A fluorometric and colorimetric dual-mode sensing platform based on graphitic carbon nitrite quantum dots (g-CNQDs) and Fe (II)-bathophenanthroline complex (BPS-Fe2+) was designed to the sensitive detection of nitrite (NO2-) in sausage and water. In this system, the fluorescence of g-CNQDs was quenched by BPS-Fe2+ complex due to the inner filter effect (IFE). When NO2- was present, Fe2+ was oxidized by nitrite to form BPS-Fe3+ complex with BPS, leading to the recovery of the fluorescence from g-CNQDs. Therefore, we constructed a "turn-off-on" fluorescence probe for detection of NO2-. Moreover, with the increase of NO2- concentration, the color of the solution changed from red to colorless, so the UV-vis measurements and on-site visual detection were realized. The method is capable of detecting NO2- in the concentration range of 2.32-34.8 µM with good selectivity and high sensitivity. In addition, the method has the potential to determine NO2- in water samples and sausage samples.


Assuntos
Carbono/química , Grafite/química , Produtos da Carne/análise , Nitritos/química , Fenantrolinas/química , Pontos Quânticos , Água/química , Colorimetria , Fluorescência , Corantes Fluorescentes , Fluorometria , Compostos de Ferro/química
11.
J Photochem Photobiol B ; 204: 111736, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31951858

RESUMO

The graphene-based nanomaterials have been measured as a most promising nanomaterials in the various fields. Graphene oxide having attractive and effective attention in the modified of medicine. Also, graphene oxide is one of the distinct bio-chemical properties with minimum cytotoxicity compared to the other nanomaterials. Up to till date, gastric treatments with reduced graphene oxide not studied so far. In this report, 7-ethyl- 10-hydroxycamptothecin (SN-38) coated graphene oxide synthesized (SN-rGO) effectively and are characterized using various analytical methods. The hydroxyl and carbonyl gatherings of oxidized SN38 will in general ingest onto GO by means of hydrogen bond arrangement with their leftover oxygen functionalities and offers steadiness to SN38. The morphological analyses showed the foldable fields of SN38-rGO NPs with acquire transparency, thin sheets and the crumpled structures. Further the photothermal efficiency and cytotoxicity of the SN-rGO were examined by MTT assay using two NCI-N87 and SGC-791 gastric carcinoma cells. In addition, the morphological changes were examined through the live and dead cells and nuclear staining biochemical techiniques and apoptosis were evaluated through flow cytometry analysis. Our result's suggested that the SN-38 coated reduced graphene oxide can be used for the photothermal treatment of gastric carcinoma for the future nanotechnology cancer therapies without using functionalized polymeric nanoparticles.


Assuntos
Antineoplásicos Fitogênicos/biossíntese , Camptotecina/análogos & derivados , Grafite/química , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/farmacologia , Camptotecina/biossíntese , Camptotecina/química , Camptotecina/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Humanos , Raios Infravermelhos , Microscopia de Fluorescência , Neoplasias Gástricas/metabolismo , Neoplasias Gástricas/patologia
12.
J Photochem Photobiol B ; 204: 111783, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31954265

RESUMO

Cadmium sulfide-graphitic carbon nitride nanocomposite was synthesized by pulsed laser ablation in liquid, and it was found from the results of optical and morphological characterizations that the proper anchoring of nanostructured cadmium sulfide on the nano-sheets of graphitic carbon nitride took place, which brought about the positive attributes such as enhanced visible light absorption and reduced photo-generated charge recombination, the key features required for an efficient photo-catalyst by solar light harvesting. The pulsed laser ablation in liquid method adopted for the synthesis of cadmium sulfide-graphitic carbon nitride has the following advantages: the shape and size of the synthesized particles can be controlled by altering the experimental parameters such as laser wavelength, pulse laser duration, the pH of the solution, the surfactants and the temperature of the solution, pulsed laser ablation in liquid method neither requires cumbersome equipment nor does it require intermediate chemicals and catalysts nor does it necessitate the post synthesis purification. The enhancement of photo-catalytic activity of cadmium sulfide-graphitic carbon nitride nanocomposite was tested for the photo-catalytic deactivation of Escherichia coli bacteria in water under visible light radiation. As anticipated, a significant improvement of photo-catalytic deactivation was observed, which is attributed to the enhanced and extended light absorption in the visible spectral region, and the formation of herterojunction between the semiconductors, which is instrumental in inhibiting the undesired recombination of photo-generated charge carriers. Quantitatively, the presence of cadmium sulfide on the graphitic carbon nitride surface contributed to a remarkable 129% increase of photo-catalytic degradation constant compared to pure graphitic carbon nitride, which resulted in the decrease of total depletion time of Escherichia coli from 156 min to 67 min with the cadmium sulfide-graphitic carbon nitride nanocomposite synthesized by pulsed laser ablation in liquid method. Our results on the efficient photo-catalytic deactivation of Escherichia coli under visible light assures that cadmium sulfide-graphitic carbon nitride nanocomposite can very well be used for photo-catalytic water purification by harvesting the abundant solar light.


Assuntos
Compostos de Cádmio/química , Grafite/química , Luz , Nanocompostos/química , Compostos de Nitrogênio/química , Sulfetos/química , Purificação da Água/métodos , Catálise , Escherichia coli/efeitos dos fármacos , Nanocompostos/toxicidade , Estudos Prospectivos
13.
J Environ Radioact ; 213: 106156, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31983456

RESUMO

Conventional beta counting technique based radiocarbon dating facility at Birbal Sahni Institute of Palaeosciences- Lucknow was established in 1974 (Rajagopalan,1978). In 2017-18, BSIP received an upgrade with installation of an Automated Graphitization Equipment (AGE) coupled with an Elemental Analyser, a Carbonate Handling System (CHS) along with an in-line stable isotope mass-spectrometer (IRMS). Using this combo, stable Carbon (C), Nitrogen (N) and Sulfur (S) isotopic measurements could be carried out in both organic and inorganic type samples followed by graphite preparation (~1 mg) for 14C measurement by Accelerator Mass Spectrometry (AMS). This communication addresses details of pre-processing, processing, and quality checks adopted for achieving acceptable and demonstrable accuracy and precision of measured Δ14C, δ13C, δ15N, and δ34S measurements. Information regarding chemical preparation of samples for aforesaid stable and radio isotopic analysis is provided in succinct manner. Overall, average coefficient of variation determining precision of our graphite powders for 14C measurements is ~2.4%. The mean age of blank (anthracite) processed using established EA-IRMS-AGE unit comes as 42,100 ± 300 years.


Assuntos
Espectrometria de Massas , Isótopos de Carbono , Grafite , Índia , Isótopos , Monitoramento de Radiação
14.
Chemosphere ; 243: 125456, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31995895

RESUMO

In this paper degradation of cytarabine drug has been studied through electrochemical oxidation process by using graphite electrode. The performance of graphite electrode on the degradation of cytarabine was evaluated by investigating the effects of key parameters: pH (3-9), current density (5-20 mA cm-2) and initial pollutant concentration (5-50 mg L-1) with 0.05 M NaCl as supporting electrolyte. Highest removal efficiency (98%) for 20 mg L-1 of initial cytarabine solution was attained within 60 min electrolysis at 10 mA cm-2. The increase in degradation rate of cytarabine was possibly because of the active chlorine species originated at anode during the electrolysis. Further, efficiency of the graphite electrodes was compared with a metal electrode (copper) and results showed that the cytarabine degradation was facilitated by the in-situ generated OH radicals. However, only 82% of cytarabine was removed after 60 min of reaction time at 15 mA cm-2. The scum of Cu2+ ions deposited on the anode surface inhibit the mass transfer among the cytarabine molecules and generated hydroxyl radicals. The kinetic study also suggests faster reaction rate at graphite (0.12 min-1) than copper (0.05 min-1) electrode. The increase in electrolyte concentration enhanced the degradation rate and decreased the energy consumption from 3.66 to 0.66 kWh m-3. Cytosine was identified as the major transformation product from the UV-Vis spectral analysis and LC-MS analysis. Further, total organic carbon analysis depicts that only 60% of the parent molecule was mineralized. Hence, graphite was found to be an efficient anode material as compared to copper for cytarabine degradation.


Assuntos
Citarabina/isolamento & purificação , Eletrólise/métodos , Grafite/química , Poluentes Químicos da Água/isolamento & purificação , Antineoplásicos/isolamento & purificação , Cloro , Eletrodos , Cinética , Oxirredução , Poluentes Químicos da Água/química
15.
Pharm Res ; 37(3): 40, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31970499

RESUMO

PURPOSES: Senescence is an inevitable and irreversible process, which may lead to loss in muscle and bone density, decline in brain volume and loss in renal clearance. Although aging is a well-known process, few studies on the consumption of nanodrugs by elderly people were performed. METHODS: We evaluated three different nanosystems: i) carbon based nanosystem (Graphene Quantum Dots, GQD), ii) polymeric nanoparticles and mesoporous silica (magnetic core mesoporous silica, MMSN). In previous studies, our group has already characterized GQD and MMSN nanoparticles by dynamic light scattering analysis, atomic force microscopy, transmission electron microscopy, X-ray diffraction, Raman analysis, fluorescence and absorbance. The polymeric nanoparticle has been characterized by AFM and DLS. All the nanosystems were radiolabeled with 99 m-Tc by. The in vivo biodistribution/tissue deposition analysis evaluation was done using elder (PN270) and young (PN90) mice injected with radioactive nanosystems. RESULTS: The nanosystems used in this study were well-formed as the radiolabeling processes were stable. Biodistribution analysis showed that there is a decrease in the uptake of the nanoparticles in elder mice when compared to young mice, showing that is necessary to increase the initial dose in elder people to achieve the same concentration when compared to young animals. CONCLUSION: The discrepancy on tissue distribution of nanosystems between young and elder individuals must be monitored, as the therapeutic effect will be different in the groups. Noteworthy, this data is an alarm that some specific conditions must be evaluated before commercialization of nano-drugs. Graphical Abstract Changes between younger and elderly individuals are undoubtedly, especially in drug tissue deposition, biodistribution and pharmacokinetics. The same thought should be applied to nanoparticles. A comprehensive analysis on how age discrepancy change the biological behavior of nanoparticles has been performed.


Assuntos
Grafite/química , Nanopartículas/química , Nanopartículas/metabolismo , Poliésteres/química , Dióxido de Silício/química , Fatores Etários , Animais , Marcação por Isótopo , Nanopartículas de Magnetita/química , Camundongos , Modelos Animais , Nanopartículas/administração & dosagem , Tamanho da Partícula , Porosidade , Propriedades de Superfície , Tecnécio/química , Distribuição Tecidual
16.
Anal Bioanal Chem ; 412(4): 915-922, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31900531

RESUMO

A tetrahedral DNA probe can effectively overcome the steric effects of a single-stranded probe to obtain well-controlled density and minimize nonspecific adsorption. Herein, a highly sensitive electrochemical biosensor is fabricated for determination of protein using a tetrahedral DNA probe and rolling circle amplification (RCA). N- and P-co-doped graphene (NP-rGO) is prepared, and AuNPs are then electrodeposited on it for DNA probe immobilization. Benefitting from the synergistic effects of the excellent electrical conductivity of NP-rGO, the stability of the tetrahedral DNA probe and the signal amplification of RCA, the biosensor achieves a low limit of 3.53 × 10-14 M for thrombin and a wide linear range from 1 × 10-13 to 1 × 10-7 M. This study provides a sensitive and effective method for the detection of protein in peripheral biofluids, and paves the way for future clinical diagnostics and treatment of disease. Graphical abstract.


Assuntos
Aptâmeros de Nucleotídeos/química , Técnicas Biossensoriais/métodos , Grafite/química , Trombina/análise , Sondas de DNA/química , Técnicas Eletroquímicas/métodos , Ouro/química , Humanos , Ácidos Nucleicos Imobilizados/química , Limite de Detecção , Nanopartículas Metálicas/química , Técnicas de Amplificação de Ácido Nucleico/métodos
17.
Nat Commun ; 11(1): 541, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31992713

RESUMO

The fast development of high-resolution electron microscopy (EM) demands a background-noise-free substrate to support the specimens, where atomically thin graphene membranes can serve as an ideal candidate. Yet the preparation of robust and ultraclean graphene EM grids remains challenging. Here we present a polymer- and transfer-free direct-etching method for batch fabrication of robust ultraclean graphene grids through membrane tension modulation. Loading samples on such graphene grids enables the detection of single metal atoms and atomic-resolution imaging of the iron core of ferritin molecules at both room- and cryo-temperature. The same kind of hydrophilic graphene grid allows the formation of ultrathin vitrified ice layer embedded most protein particles at the graphene-water interface, which facilitates cryo-EM 3D reconstruction of archaea 20S proteasomes at a record high resolution of ~2.36 Å. Our results demonstrate the significant improvements in image quality using the graphene grids and expand the scope of EM imaging.


Assuntos
Grafite/química , Microscopia Eletrônica/instrumentação , Microscopia Eletrônica/métodos , Fenômenos Químicos , Microscopia Crioeletrônica/métodos , Elétrons , Desenho de Equipamento , Processamento de Imagem Assistida por Computador , Membranas , Polímeros , Proteínas
18.
J Environ Manage ; 259: 110044, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31929029

RESUMO

Graphene oxide (GO) is a single-atom-thick sheet of carbon with oxygen-containing functional groups decorating its basal plane and edge sites. Most of its high surface area can be lost due to restacking of individual layers during the synthesis and drying of GO-based bulk sorbents. There is great interest to increase the specific surface area of graphene-based sorbents by introducing organic molecules as "pillaring agents" between GO sheets to hinder the stacking process and create sorbents with elevated surface area. This work synthesizes pillared GO by introducing chitosan (CS), a linear polysaccharide with various molecular weights. A composite of low molecular weight CS at a CS/GO ratio of 0.1 is shown to have the highest specific surface area (up to 70.5 m2/g) in comparison to the medium and high CS molecular weight, pristine GO, and the CS/GO composite materials. The affinity of the optimized GO/CS composites towards benzene, toluene, and naphthalene was evaluated at 19.3 mg/L of organic matter content while altering pH. Sips and Langmuir adsorption isotherm models well described the adsorption behavior, and benzene adsorption performance was reduced at low pH. Related to the presence of dissolved organic matter (DOM) in solution, lower diffusivity constants (k1) in hydrocarbon systems were recorded. Our results demonstrate the feasibility of CS as a potential pillaring agent in CS/GO composites to increase specific surface area and enhance the capture of soluble hydrocarbons from aqueous solutions.


Assuntos
Grafite , Adsorção , Concentração de Íons de Hidrogênio , Óxidos , Água
19.
Sci Total Environ ; 706: 135725, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31940729

RESUMO

This study reports the preparation of nanobiochar (NBC) via top-down approach of bioenergy waste-derived dendro biochar through mechanised grinding in order to assess its capacity to remove emerging contaminants, such as antibiotics, agrochemicals, and potentially toxic elements from aqueous media. Preconditioned biochar was disc milled in ethanol media, and the resulting colloidal biochar was dispersed in water to obtain the NBC fraction by centrifugation. Adsorption edge and isotherm experiments were carried out at pH 3 to 8 and NBC dosages of 0.5 g/L for oxytetracycline (OTC), glyphosate (GL), hexavalent chromium (CrVI), and cadmium (CdII). NBC was characterised by scanning electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area, and Fourier transform infrared spectroscopy, which demonstrated the flakey and graphitic nature of the NBC particles with a surface area of 28 m2/g and the presence of different functional groups, such as OH, CO, NH, and CH3. The best pH for OTC and Cd(II) was 9, whereas the best pH levels for GL and Cr(VI) were 7 and 4, respectively. Isotherms depicted a positive cooperative adsorption mechanism by providing the best fit to the Hills equation, with high removal capacities for four contaminants. Dendro NBC showed the best performance, demonstrated by the high partition coefficient for the removal of OTC, GL, Cr(VI), and Cd(II) over various types of adsorbents. The overall results indicated that graphitic NBC produced by mechanical grinding of dendro biochar is a promising material for the removal of OTC, GL, Cr(VI), and Cd(II) from aqueous media.


Assuntos
Carvão Vegetal/química , Grafite/química , Poluentes Químicos da Água , Purificação da Água/métodos , Adsorção , Cromo , Química Verde , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Água
20.
J Environ Manage ; 256: 109930, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31989975

RESUMO

To fabricate an efficient, eco-friendly and stable photocatalyst, the current work describes a demonstration of simple synthesis approach of Ag3PO4/MnFe2O4(x wt%)/reduced graphene oxide composites. Ag3PO4/MnFe2O4 (5 wt%) revealed superior activity for decontamination of dye pollutant. Further, rGO was incorporated with Ag3PO4/MnFe2O4 (5 wt%) to investigate its effect on their overall properties. The resultant composites were characterized by various analytical techniques to confirm their structural and physical-chemical features. FESEM analysis showed that morphology of Ag3PO4 varied significantly from orthorhombic dodecahedrons to tripods and tetrapods with the combinations MnFe2O4 (5 wt%), and MnFe2O4 (5 wt%)+rGO respectively. The photocatalytic decontamination of toxic organic dyes tested against Rhodamine B(RhB) and 4-Nitrophenol. The outstanding performance for decontamination of RhB was observed for Ag3PO4/MnFe2O4(5 wt%)/rGO (~99% in 5 min) with the rate of k = 7.28 × 10-1 min-1. The enhanced activity of Ag3PO4/MnFe2O4(5 wt%)/rGO composites credited to co-catalytic effects of MnFe2O4 and physiochemical properties of rGO which leads to making intimate contact with Ag3PO4 to form heterojunction and rGO served as a medium for charge transfer to prevent their recombination. The incorporation of rGO in Ag3PO4/MnFe2O4 (5 wt%) composite leads to a considerable increase in the photocatalytic activity by offering improved surface area and properties, high electron stability and mobility. Based on experiment results, the photocatalytic enhancement mechanism for organic pollutants degradation was discussed. The recyclability of Ag3PO4/MnFe2O4(5 wt%)/rGO hierarchical composite was evaluated by replicated photocatalytic reaction trials. Overall, the morphological transformation of Ag3PO4/MnFe2O4(5 wt%)/rGO composites played a dynamic role in determining their photocatalytic activity towards the organic industrial dye pollutants.


Assuntos
Poluentes Ambientais , Grafite , Descontaminação , Prata
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