Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 56.797
Filtrar
1.
Talanta ; 233: 122526, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215029

RESUMO

Herein, a novel magnetic porous carbon nanocomposite derived from a cobalt based-metal-organic framework was synthesized and evaluated for simultaneous preconcentration of homo and hetero-polycyclic aromatic hydrocarbons. Briefly, magnetite nanoparticles (MNPs) were synthesized and then were coated with a metal-organic framework layer. Finally, the magnetic nanocomposite was carbonized under an inert atmosphere to obtain the magnetic porous carbon (MPC). Various characterization techniques such as FT-IR spectroscopy, transmission and scanning electron microcopies, vibrating sample magnetometry, and X-ray diffraction were employed. Applicability of the MPC was explored using benzothiophene, dibenzothiophene, 9,10-dimethylanthracene, and benz[α]anthracene as the model analytes. Limits of detection and linearities were achieved in the range of 0.06-0.18 µg L-1 and 0.25-500 µg L-1, respectively. Precision of the method as RSDs was evaluated which was in the range of 4.2-7.0% (within-day, n = 5) and 8.2-11.3% (between-day, n = 3). Ultimately, the method was applied to analyze two seawater samples and satisfactory results (RSDs%, 5.0-9.0%; relative recoveries, 89-104%) were obtained.


Assuntos
Estruturas Metalorgânicas , Nanocompostos , Hidrocarbonetos Policíclicos Aromáticos , Poluentes Químicos da Água , Carbono , Cobalto , Limite de Detecção , Fenômenos Magnéticos , Hidrocarbonetos Policíclicos Aromáticos/análise , Porosidade , Extração em Fase Sólida , Espectroscopia de Infravermelho com Transformada de Fourier , Poluentes Químicos da Água/análise
2.
Talanta ; 233: 122541, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215044

RESUMO

The relative humidity (RH) determination is crucial in many fields. Based on the phosphorescent properties of room-temperature phosphorescent (RTP) carbon dots, the RTP carbon dots as a probe are expected to be used to rapidly detect relative humidity. In this study, matrix-free room-temperature phosphorescent N-doped carbon dots (N-CDs) were successfully prepared from urea, succinic acid, and acrylamide using a hydrothermal method. The as-synthesized N-CDs had good biocompatibility and water solubility. The N-CDs emitted blue fluorescence and green phosphorescence. Moreover, the N-CD powder exhibited stable phosphorescence with a phosphorescence lifetime of 158 ms (afterglow time to the naked eye for ~7 s). Because H2O molecules affected the afterglow time, the as-prepared N-CD test paper for the first time could be applied as a probe to monitor RH, the afterglow time of the N-CD test paper is linearly related to the RH (y = -0.0729x+7.042, R2 = 0.998) and the RH detection range is 0%-85%. And the results were consistent with those obtained using a hygrometer. In addition, the N-CD solution could also be used as an encryption ink in the advanced information security field.


Assuntos
Carbono , Fluorescência , Umidade , Temperatura
3.
Talanta ; 233: 122542, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215045

RESUMO

The tailor-prepare solid phase microextraction (SPME) coatings with stable and excellent properties to effectively extract analytes from sample matrix still remains a challenge. Herein, a nitrogen doped graphitic carbon networks (NG-CNTW) coated fiber was fabricated by direct carbonization of nanosized ZIF-67 crystals (nano-ZIF-67) that grown on stainless steel wire. The NG-CNTW coated fiber coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was applied for enrichment and determination of pyrethroids. The NG-CNTW coating exhibited high surface area and hierarchical porous structures that facilitate diffusion and accessibility of target molecules. Simultaneously, the nitrogen doped and highly graphitic structures endow the coating with high adsorption affinity for aromatic compounds. Under optimum conditions, the SPME-GC-MS/MS method presented wide range of linearity performance (0.08-200.0 ng g-1), low limits of detection (0.02-0.5 ng g-1) and good repeatability (RSD < 9.6%) for 8 kinds of pyrethroids. Furthermore, the proposed method was successfully applied in the determination of pyrethroids in grape and cauliflower samples, as the results were in the range of 3.16-15.06 ng g-1and 2.08-9.29 ng g-1, respectively. This work not only provides a new method by fabricating carbon nanomaterial coatings in situ derived from MOFs, but also shows great potential of MOFs derivative materials in environmental analysis field.


Assuntos
Grafite , Praguicidas , Piretrinas , Poluentes Químicos da Água , Carbono , Cromatografia Gasosa-Espectrometria de Massas , Nitrogênio , Praguicidas/análise , Microextração em Fase Sólida , Espectrometria de Massas em Tandem , Poluentes Químicos da Água/análise
4.
Talanta ; 233: 122545, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215048

RESUMO

A nanocomposite of ordered mesoporous carbon/nickel oxide (OMC-NiO) was synthesized by hard-templating method. The nanocomposite remained ordered mesostructure and high surface area with the NiO nanocrystals embedded in the wall of the OMC. A sensitive sensor for electrochemical detection of epinephrine (EP) was developed with GCE modified by OMC-NiO nanocomposite. Cyclic voltammogram (CV) and differential pulse voltammetry (DPV) were used as the techniques to explore the electrochemical behavior of EP on OMC-NiO/GCE surface. The result showed that the electrode demonstrated better electrocatalytic performance to EP compared to that seen at OMC/GCE. Under the optimum condition, DPV measurements of the electrode response displayed a linear detection range for 8.0 × 10-7 to 5.0 × 10-5 M with a detection limit of 8.5 × 10-8 M (S/N = 3). It is worth noting that the electrocatalytic redox mechanism of EP on the electrode have studied through experiments and calculations (cyclic voltammetry and molecular electrostatic potential distribution). Moreover, the electrocatalytic behavior for the oxidation of EP and uric acid (UA) on OMC-NiO/GCE surface was investigated. The result showed that the sensor can be used to selectively determinate EP in the presence of an excesses of UA. Finally, the developed sensor was successfully applied to the determination of EP in spiked human blood serum and EP injection with satisfactory results.


Assuntos
Carbono , Nanocompostos , Técnicas Eletroquímicas , Eletrodos , Epinefrina , Humanos , Níquel
5.
Talanta ; 233: 122583, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215075

RESUMO

Carbon nanospheres (CNSs) were derived hydrothermally from biomass (orange peels) and decorated by manganese dioxide (MnO2) nanosheets. The MnO2/CNSs nanocomposite was intercalated into polypyrrole (PPy) during flow-through in-situ electropolymerization of pyrrole on the surface of the inner wall of a stainless-steel needle to prepare an inside-needle capillary adsorption trap (INCAT) device. The surface morphology, thermogravimetric behavior, sorption characteristics, and structure of the MnO2/CNSs@PPy nanocomposite were characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), nitrogen physisorption by the Brunauer-Emmett-Teller (BET) method, dynamic light scattering (DLS) size distribution, and Fourier-transform infrared spectrometry (FT-IR). The INCAT device was coupled with GC-FID and applied for dynamic headspace analysis of linear alkyl benzenes (LABs) in wastewater samples. The effective experimental variables on the extraction efficiency was optimized using a central composite design (CCD) based on response surface methodology (RSM). Under the optimal conditions, the limits of detection (LODs) were in the range of 0.5-1.0 ng mL-1. The calibration plots were linear over the range of 0.01-10 µg mL-1. The relative standard deviations (RSDs%) for intra-day, inter-day, and inter-INCAT precision were calculated 5.3-8.3%, 9.4-13.5%, and 13.6-16.9%, respectively. The developed technique was employed successfully for the analysis of LABs in water and wastewater samples with average recovery values ranging from 92 to 109%. A single INCAT device was used more than 90 times without significant change in its extraction capability.


Assuntos
Nanosferas , Polímeros , Adsorção , Biomassa , Carbono , Cromatografia Gasosa-Espectrometria de Massas , Compostos de Manganês , Óxidos , Pirróis , Espectroscopia de Infravermelho com Transformada de Fourier
6.
Talanta ; 233: 122498, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215116

RESUMO

Carbon dots have been a promising nano-carbon material with many advantages, and attracted many more attentions. This study designed a new chemosensor integrating the strong fluorescent property of carbon dots and the magnetism of amino-functionalized magnetic core-shell nanomaterial, Fe@SiO2-NH2 for determination of 2,4,6-trinitrotoluene (TNT). In this system, fluorescent carbon dots interacted with amino groups on the surface of amino-functionalized magnetic core-shell nanomaterial leading to fluorescence quenching of carbon dots, appearance of TNT competitively replaced of carbon dots on the surface of the magnetic material through forming a Meisenheimer complex. This sensor exhibits excellent selectivity and sensitivity for TNT, and which provided a good dynamic linear range for TNT from 10 to 2000 ng mL-1. The experiments demonstrate a low detection limit of 2.15 ng mL-1. The intra-day precisions for 25, 100 and 500 ng mL-1 were 4.6, 2.3 and 0.5% (RSD, n = 6), inter-day precisions for 25, 100 and 500 ng mL-1 were 4.2, 2.5 and 0.9% (RSD, n = 6), respectively. The developed sensor was validated with river water, dust, and soil samples, and the achieved spiked recoveries were immensely satisfied from 98.1% to 102.0%. The Fe@SiO2-NH2 possessed excellent reusability. This sensor exhibits that it is simple, sensitive and selective, and will be a vital analytical tool for TNT in many fields.


Assuntos
Nanoestruturas , Pontos Quânticos , Trinitrotolueno , Carbono , Limite de Detecção , Dióxido de Silício
7.
Talanta ; 233: 122513, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34215128

RESUMO

In this work, 1-vinyl-3-octadecylimidazolium bromide ionic liquids ([C18VIm]Br) and their derived carbon dots (ImC18CDs) were prepared, [C18VIm]Br and ImC18CDs were grafted on the silica to obtain Sil-ImC18 and Sil-ImC18CDs, respectively, and they were also co-grafted on silica which named Sil-ImC18/CDs. Compared with Sil-ImC18 and Sil-ImC18CDs columns, Sil-ImC18/CDs column exhibited enhanced selectivity for separation of tetracyclic/tricyclic polycyclic aromatic hydrocarbon (PAH) isomers, and butylbenzene isomers in reversed-phase liquid chromatography, which may be due to the synergistic effect between ImC18CDs and [C18VIm]Br, the π-π interaction between imidazolium and analytes, etc. Meanwhile, the retention behavior of Sil-ImC18/CDs was further evaluated and compared with the commercial C18 column using different classes of analytes, including standard test mixtures of Tanaka, Engelhardt, SRM869b, SRM870. The results demonstrated that co-grafted column exhibited superior separation performance. And this column was applied to determine the contents of calycosin-7-glucoside, ononin, calycosin and formononetin in the extract of Radix Astragali, which were found that the concentration was 0.25 mg mL-1, 0.15 mg mL-1, 0.13 mg mL-1 and 0.30 mg mL-1, respectively.


Assuntos
Líquidos Iônicos , Carbono , Cromatografia de Fase Reversa , Interações Hidrofóbicas e Hidrofílicas , Dióxido de Silício
8.
J Environ Sci (China) ; 106: 83-96, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34210442

RESUMO

In this work, we employed waste activated sludge (WAS) as carbon source to prepare ultrahigh specific surface area (SSA) biopolymers-based carbons (BBCs) through alkali (KOH) treatment coupled to pyrolysis strategy. Before the pyrolysis process, the involvement of KOH made a great recovery of soluble biopolymers from WAS, resulting in highly-efficient catalytic pyrolysis. The Brunner-Emmett-Teller and pore volume of BBCs prepared at 800°C (BBC800) reached the maximum at 2633.89 m2·g-1 and 2.919 m3·g-1, respectively. X-ray photoelectron spectroscopy suggested that aromatic carbon in the form of C=C was the dominant fraction of C element in BBCs. The N element in BBCs were composed of pyrrolic nitrogen and pyridinic nitrogen at 700°C, while a new graphitic nitrogen appeared over 800°C. As a refractory pollutant of wastewater treatment plants, tetracycline (TC) was selected to evaluate adsorption performance of BBCs. The adsorption behavior of BBCs towards TC was conformed to the pseudo-second-order kinetic and the Langmuir models, signifying that chemisorption of monolayers was dominant in TC adsorption. The adsorption capacity of BBC800 reached the maximum at 877.19 mg·g-1 for 90 min at 298 K. Thermodynamic analysis indicated that the adsorption process was endothermic and spontaneous. Hydrogen bonding and π-π stacking interaction were mainly responsible for TC adsorption, and interfacial diffusion was the main rate-control step in adsorption process. The presence of soluble microbial products (SMPs) enhanced TC removal. This work provided a novel strategy to prepare bio-carbon with ultrahigh SSA using WAS for highly-efficient removal of organic pollutants.


Assuntos
Esgotos , Poluentes Químicos da Água , Adsorção , Álcalis , Biopolímeros , Carbono , Carvão Vegetal , Cinética , Pirólise , Poluentes Químicos da Água/análise
9.
Ying Yong Sheng Tai Xue Bao ; 32(6): 1919-1927, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34212595

RESUMO

Understanding the changes of natural abundance of stable carbon and nitrogen isotopes (δ13C and δ15N) along soil profile is of great importance in revealing the mechanisms of soil carbon and nitrogen cycling in terrestrial ecosystems. Based on a comprehensive review on the distribution of δ13C and δ15N along soil profile, the mechanisms underlying their vertical distribution were mainly introduced here. There were three mechanisms driving the δ13C vertical distribution in soil profile: 1) historical changes of vegetation δ13C value, 2) changes of C3-C4 species dominance in plant communities, 3) accumulation of 13C-enriched microbial-derived carbon during decomposition. The effects of 13C Suess effect on the vertical distribution of δ13C in soil profile were also discussed. There were four mechanisms underlying the vertical distribution of δ15N in soil profile: 1) 15N-depletion gas loss during denitrification, 2) accumulation of 15N-enriched microbial-derived nitrogen during decomposition, 3) accumulation of 15N-encriched mycorrhizal fungi residues in deep soil as a result of transferring 15N-depleted nitrogen compounds to plants by mycorrhizae, 4) intera-ction between soil organic matter and mineral substance. We proposed important concerning points for the future study on vertical distribution of natural abundance of stable carbon and nitrogen isotopes in soil profile.


Assuntos
Carbono , Solo , Isótopos de Carbono/análise , Ecossistema , Nitrogênio/análise , Isótopos de Nitrogênio
10.
Ying Yong Sheng Tai Xue Bao ; 32(6): 1963-1970, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34212600

RESUMO

Before the measurement of stable carbon isotope signatures (δ13C), plant samples should be well homogenized. Using a ball-mill fitted with poly tetra fluoroethylene (PTFE) plastic tubes is one of the most efficient and convenient methods. However, sample-tube plastic might contaminate plant samples during milling. In this study, a two-factor experiment was carried out using four growth chambers, with different relative humidity of the air (50% and 80%) and δ13C of the air (13C depleted and enriched). Leaf samples of Cleistogenes squarrosa (C4) were milled and homogenized using a ball-mill fitted with PTFE tubes and measured for δ13C, and the results were compared with that of leaf samples milled using metal tubes. Due to plastic contamination, 13C discrimination (Δ13C) of the two groups of plants, which were grown in CO2 with different δ13C and could be assumed as replicates, were significantly different (with an offset of 4.8‰ on average). The contamination led to errors in δ13C of individual leaves up to 8‰. Given the lower Δ13C value of C4 plants (normally about 1‰-8‰) compared with that of C3 plants, such an error caused by plastic contamination far exceeded the acceptable error range. By using a two-member mixing model that was similar to the 'Keeling plot', such errors could be effectively eliminated, and the δ13C of plant samples and pollutants were accurately estimated. Our results showed that the widely applied method of using PTFE tubes for ball-mill homogenization is not suitable for examining Δ13C of C4 plants, as it might lead to large errors. For studies with high precision requirements, samples should be milled in stainless-steel tubes.


Assuntos
Carbono , Compostos de Vinila , Isótopos de Carbono , Plásticos
11.
Ying Yong Sheng Tai Xue Bao ; 32(6): 2138-2146, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34212620

RESUMO

We investigated the plant species richness both in cespitose Carex mires (C. schmidtii, C. meyeriana) and non-cespitose Carex mire (C. lasiocarpa) in Changbai Mountain. A total of 83 species (36 families, 59 genuses) was recorded in three sites. Among which, 71 species occurred in the C. meyeriana site, 61 species in the C. schmidtii site, and 26 species in the C. lasiocarpa site. The total species number and species richness in the two cespitose Carex mires were much higher than that in the non-cespitose Carex mire, while those on tussocks were much higher than between tussocks in the two cespitose Carex mires. Plant species richness on tussocks was positively related to the height, basal circumference and surface area of the tussocks, suggesting that tussocks were important for plant species diversity in Carex mires. Results of the canonical correspondence analysis indicated that the differences in soil water content, nutrient (soil organic carbon, total N, total P and C/N), and litter layer depth were the main factors influencing the differences of plant community composition on tussocks and between-tussocks. In the cespitose Carex mires, the hummock-hollow microtopography could foster high diversity by increasing surface area and creating multiple micro-habitats. Given its function in maintaining high species diversity, cespitose Carex could be a preferred species for vegetation restoration in degraded peat mires.


Assuntos
Carex (Planta) , Carbono , China , Humanos , Solo , Áreas Alagadas
12.
Ying Yong Sheng Tai Xue Bao ; 32(6): 2217-2226, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34212628

RESUMO

Biomass conditioner made from agricultural and animal husbandry waste for resource disposal could be used to improve desertified soil, which is one of the effective ways of ecological management on desertified grasslands in northwest Sichuan. To clarify the effects of different raw material conditioners on alpine desertified grassland in northwest Sichuan, we analyzed the effects of three conditioners on soil nutrients and microbial community characteristics. With no conditioner as the control (CK), three different biomass conditioners were set up with an application rate of 12 t·hm-2, including mushroom dregs (JZ), straw (JG) and biochar (SWT). The results showed that all biomass conditioners could significantly increase soil available nutrients and active organic carbon by 23.0%-521.6%. Among the three conditioners, JG had the best effect, with an improvement range for soil nutrient and organic carbon of 65.1%-521.6%. Because biomass conditioner was only applied in the first year, soil available nutrients and active organic carbon in the second year decreased by 4.5%-92.3% compared with that of the first year, while soil organic carbon and microbial biomass carbon content of the second year increased by 5.6%-458.0%. The biomass conditioners changed the relative abundance of the dominant bacteria in the microbial community. JG significantly affected bacterial flora, while JG and JZ affected fungal flora. Compared with CK, JG significantly reduced the diversity of soil bacteria and fungi. The Shannon index was decreased by 2.9% and 31.8%, while the Simpson index was increased by 175.0% and 320.9%, respectively. Results of the redundancy analysis showed that the contents of soil available nutrients and active organic carbon were important factors affecting microbial community composition. The contents of soil nitrate and microbial biomass carbon had greater impacts on bacterial community composition, explaining 65.9% of community variations. The contents of soil available potassium and microbial biomass carbon had a greater impact on fungal community composition, explaining 83.2% of community variation. According to the comprehensive comparison, straw conditioner could significantly increase soil available nutrients and active organic carbon, and benefit the growth of beneficial bacteria and fungi, which could be used as a promotion measure to improve soil quality of alpine desertified grassland in northwest Sichuan.


Assuntos
Microbiota , Solo , Animais , Biomassa , Carbono/análise , China , Pradaria , Nutrientes , Microbiologia do Solo
13.
Anal Chim Acta ; 1174: 338737, 2021 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-34247735

RESUMO

The discharge of plastic waste and subsequent formation and global distribution of microplastics (MPs) has caused great concern and highlighted the need for dedicated methods to characterise MPs in complex environmental matrices like seawater. Single particle inductively coupled plasma - mass spectrometry (SP ICP-MS) is an elegant method for the rapid analysis of nano- and microparticles and to characterise number concentrations, mass, and size distributions. However, the analysis of carbon (C)-based microstructures such as MPs by SP ICP-MS is at an early stage. This paper investigates various strategies to improve figures of merit to detect and characterise MPs in complex matrices, such as seawater. Ten methods operating distinct acquisition modes with various collision/reaction gases, tandem MS (ICP-MS/MS) and targeting 12C or 13C were developed and compared for the analysis of polystyrene-based MPs standards in ultra-pure water and seawater. The robust analysis of MPs in seawater was accomplished by on-line aerosol dilution enabling repeatable size calibration while minimising drift effects. However, the direct analysis of seawater decreased ion transmission and required matrix-matching for accurate size calibration. Analysis of the 12C isotope instead of 13C improved the size detection limits (sDL) to 0.62 µm in ultra-pure water and to 0.96 µm in seawater. ICP-MS/MS methods decreased ion transmission but also reduced background signal and increased selectivity, particularly in the presence of spectral interferences. In the second part of this study, it was demonstrated that the developed methods were applicable for the analysis of C in unicellular organisms and allowed calibration of physical dimensions. This is relevant for the investigation and understanding of phenotypical traits associated, for example, with climate change resilience as well as oceanic C storage. SP/SC ICP-MS was employed to target five different intact Symbiodiniaceae algae strains with diverse life-histories in seawater and polystyrene-based MPs were used to calibrate cellular C masses, which were between 51 and 83 pg. The C mass distribution across the analysed unicellular cells was used for modelling cell sizes, which were in the range of 7.6 and 10.1 µm. Determined values were in line with values obtained with complementary techniques (Coulter-counting, total organic C analysis and microscopic analysis).


Assuntos
Microplásticos , Plásticos , Carbono , Água do Mar , Espectrometria de Massas em Tandem
14.
Anal Chim Acta ; 1174: 338743, 2021 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-34247738

RESUMO

Quick and visual detection of component contents, such as water, in a mixed solvent is important for many practical applications, and a full range detection is especially preferred. In this work, a carbon dots based ratiometric fluorescent sensor was synthesized by grafting fluorescent group (Rhodamine B, RhB) on carbon dots, and the dual emission peaks exhibited a linear ratiometric response with the change of polarity and hydrogen bond of Solvent Hansen solubility parameters. This responsive behavior is attributed to surface state photoluminescence mechanisms, and has been used for the quantitative detection of water content in ethanol with an excellent linear relationship (R2 = 0.996), a low detection limit (0.2%), and a full detection range (0-100%). Furthermore, a paper-based ratiometric fluorescence sensing strip is also demonstrated, which exhibits good storage stability and sensitivity. This study suggests that RhB grafted carbon dots could be feasibly and effectively used as ratiometric fluorescent sensors for solvent content detection.


Assuntos
Carbono , Pontos Quânticos , Corantes Fluorescentes , Rodaminas , Solventes
15.
Analyst ; 146(14): 4418-4435, 2021 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-34195700

RESUMO

There has been an explosion of interest in the use of nanomaterials for biosensing applications, and carbonaceous nanomaterials in particular are at the forefront of this explosion. Carbon dots (CDs), a new type of carbon material, have attracted extensive attention due to their fascinating properties, such as small particle size, tunable optical properties, good conductivity, low cytotoxicity, and good biocompatibility. These properties have enabled them to be highly promising candidates for the fabrication of various high-performance biosensors. In this review, we summarize the top-down and bottom-up synthesis routes of CDs, highlight their modification strategies, and discuss their applications in the fields of photoluminescence biosensors, electrochemiluminescence biosensors, chemiluminescence biosensors, electrochemical biosensors and fluorescence biosensors. In addition, the challenges and future prospects of the application of CDs for biosensors are also proposed.


Assuntos
Técnicas Biossensoriais , Nanoestruturas , Carbono , Tamanho da Partícula
16.
Nat Commun ; 12(1): 4065, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-34210971

RESUMO

Strategies that enable intermolecular site-selective C-H bond functionalisation of organic molecules provide one of the cornerstones of modern chemical synthesis. In chloroalkane synthesis, such methods for intermolecular site-selective aliphatic C-H bond chlorination have, however, remained conspicuously rare. Here, we present a copper(I)-catalysed synthetic method for the efficient site-selective C(sp3)-H bond chlorination of ketones, (E)-enones and alkylbenzenes by dichloramine-T at room temperature. A key feature of the broad substrate scope is tolerance to unsaturation, which would normally pose an immense challenge in chemoselective aliphatic C-H bond functionalisation. By unlocking dichloramine-T's potential as a chlorine radical atom source, the product site-selectivities achieved are among the most selective in alkane functionalisation and should find widespread utility in chemical synthesis. This is exemplified by the late-stage site-selective modification of a number of natural products and bioactive compounds, and gram-scale preparation and formal synthesis of two drug molecules.


Assuntos
Domínio Catalítico , Cobre/química , Cetonas/química , Sulfonamidas/química , Produtos Biológicos/química , Carbono/química , Catálise , Halogenação , Hidrogênio/química , Temperatura
17.
Soft Matter ; 17(28): 6765-6772, 2021 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-34196338

RESUMO

Recently, carbon dots (CDs) have attracted wide attention for their potential use as fluorescence probes in biological and analytical chemistry due to their great stability and high fluorescence quantum yields. In our work, norepinephrine (NE)-derived CDs with green luminescence and an average size of 10 nm were fabricated using a one-step hydrothermal route. As-prepared CDs show a strong emission at a wavelength of 520 nm when excited at 420 nm, and demonstrate pH and concentration dependent fluorescence behaviour. Multiple functional groups on the CDs allow their protonation/deprotonation and thus alter fluorescence intensity and peak position in different pH conditions. Prepared CDs show significant potential to be used as a live-cell imaging agent with long-term photostability. Furthermore, a simple but effective method to determine the concentration of hemoglobin (Hb) in diluted human blood samples was also developed based on the inner filter effect (IFE). The method demonstrates good linearity from 0.01-10 µM, with a limit of determination (LOD) of 52 nM.


Assuntos
Carbono , Pontos Quânticos , Corantes Fluorescentes , Hemoglobinas , Humanos , Norepinefrina , Espectrometria de Fluorescência
18.
Artigo em Inglês | MEDLINE | ID: mdl-34208506

RESUMO

Black carbon is one of the riskiest particle matter pollutants that is harmful to human health. Although it has been increasingly investigated, factors that depend on black carbon distribution and concentration are still insufficiently researched. Variables, such as traffic density, wind speeds, and ground levels can lead to substantial variations of black carbon concentrations and potential exposure, which is even riskier for people living in less-airy sites. Therefore, this paper "fills the gaps" by studying black carbon distribution variations, concentrations, and oscillations, with special emphasis on traffic density and road segments, at multiple locations, in a small city located in a basin, with frequent temperature inversions and infrequent low wind speeds. As wind speed has a significant impact on black carbon concentration trends, it is critical to present how low wind speeds influence black carbon dispersion in a basin city, and how black carbon is dependent on traffic density. Our results revealed that when the wind reached speeds of 1 ms-1, black carbon concentrations actually increased. In lengthy wind periods, when wind speeds reached 2 or 3 ms-1, black carbon concentrations decreased during rush hour and in the time of severe winter biomass burning. By observing the results, it could be concluded that black carbon persists longer in higher altitudes than near ground level. Black carbon concentration oscillations were also seen as more pronounced on main roads with higher traffic density. The more the traffic decreases and becomes steady, the more black carbon concentrations oscillate.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Carbono , Cidades , Monitoramento Ambiental , Humanos , Material Particulado/análise , Emissões de Veículos/análise , Vento
19.
J Nanosci Nanotechnol ; 21(12): 5795-5811, 2021 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-34229776

RESUMO

Widespread usage of pesticides in agricultural practice caused their residues to appear in water and food products intended for human consumption. The potential toxicity of these resources has raised awareness about pesticide tracking in the environment. Development of reliable electrochemical sensors for the on-site determination of pesticide concentrations is envisioned as an alternative to conventional chromatographic methods which are robust, expensive and require skilled work force. Modification of the working electrode surface can result in enhanced electrochemical response towards selected pesticide making such electrode convenient sensor for facile and efficient determination of pesticides in low concentrations. New generation of nanomaterials is applied in electrode modification in order to improve its sensitivity and selectivity. The present review summarizes significant advances in voltammetric detection of pesticides for the period of the past five years. The major focus of this review is set to the types of carbon and oxide based materials, metal nanoparticles, composites and other materials employed to upgrade standard electrode configurations such as glassy carbon and carbon paste electrodes, boron doped diamond electrodes, screen printed and film electrodes, metal and amalgam, and other kinds of electrodes.


Assuntos
Praguicidas , Boro , Carbono , Diamante , Técnicas Eletroquímicas , Eletrodos , Humanos , Praguicidas/análise
20.
Molecules ; 26(12)2021 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-34208688

RESUMO

This study aimed to examine the extract of barks of Tamarix aphylla as a corrosion inhibitor. The methodology briefly includes plant sample collection, extraction of the corrosion inhibitor, gravimetric analysis, plotting potentiodynamic polarization plots, electrochemical impedance spectroscopic measurements, optimization of conditions, and preparation of the inhibitor products. The results show that the values of inhibition efficiency (IE%) increased as the concentrations of the inhibitor increased, with a maximum achievable inhibition efficiency of 85.0%. Potentiodynamic polarization (PP) tests revealed that the extract acts as a dual-type inhibitor. The results obtained from electrochemical impedance spectroscopy (EIS) measurements indicate an increase in polarisation resistance, confirming the inhibitive capacity of the tested inhibitor. The adsorption of the inhibitor on the steel surface follows the Langmuir adsorption isotherm model and involves competitive physio-sorption and chemisorption mechanisms. The EIS technique was utilized to investigate the effect of temperature on corrosion inhibition within the 298-328 K temperature range. Results confirm that the inhibition efficiency (IE%) of the inhibitor decreased slightly as the temperature increased. Lastly, the thermodynamic parameters for the inhibitor were calculated.


Assuntos
Aço/química , Tamaricaceae/química , Tamaricaceae/metabolismo , Carbono , Corrosão , Espectroscopia Dielétrica , Casca de Planta/química , Casca de Planta/metabolismo , Extratos Vegetais/química , Propriedades de Superfície , Termodinâmica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...