ABSTRACT
This paper provides a general overview of green synthesis of self heteroatom doped N-carbon dots (N-CDs) from biomass derived pumpkin seeds with an energy gap of 2.35 eV and a quantum ef?ciency of 65.5%. Besides that, they possess graphitic carbon structure with spontaneous heteroatom doping of various metal ions and a size distribution of 5-8 nm and an interplaner distance of 0.334 nm, with an excellent electrochemical property. This work focused on the usage of these N-CDs in the detection of the heavy metal ions 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ such as Hg , Zn , Pb , Ni , Ca , Cu , and Mg and the results have demonstrated a better detection limit of the heavy metal Hg ions among other tested metal ions, owing to its excellent selective and sensitive property of ?uorescencent quenching analysis, resulted in the creation of non- ?uorescent centres, effective charge transfer and overall energy transfer, within a minimum detection threshold limit of 20 nM.
ABSTRACT
Excessive mercury ions have negative effects on individual health. So, it is of great significance to develop a method for rapid, sensitive and specific detection of Hg2+. In this study, the method for detection of Hg2+ was developed based on specific T-Hg-T mismatche and G-quadruplex. The template sequence mainly included the recognition region which could combine with Hg2+ specifically, the rich G region which could form G-quadruplex, and the speacer 18 partition zone. The target sequence mainly included 5' ends combining area and 3' end T-rich region. Templates and targets could be combined and the elongation was triggered only in the presence of Hg2+. Furthermore, the G-rich sequences were stripped off the templates and could form a single-stranded structure, because Spacer 18 had partition function. The G-quadruplex was formed with the K+and hemin, and catalyzed H2 O2-2,2-azinobis (3-ethylbenzothiozoline)-6-sulfonic acid(ABTS) reaction with color variations. The detection could be done within 35 min, and the Hg2+ concentration exhibited a linear correlation with absorbance at 414 nm within range of 20-500 nmol/ L, with a detection limit of 16. 5 nmol/ L (3σ). The recoveries of Hg2+ spiked in tap water were 98. 5％ - 103. 5％ . The method exhibited the advantages such as simple operation, low cost and short time, and operation value in emergency treatment and real-time environmental detection.
ABSTRACT
A colorimetric method was developed for detection of mercury based on the inhibition of oxidation of peroxidase substrates. The as-prepared gold nanoclusters ( Au NCs), which has been stabilized and reduced by Glutathione (GSH), can effectively catalyze the H2 O2-TMB to generate a blue color signal. It is interestingly that Hg2+ can inhibit the oxidation of peroxidase substrates, thus causing a color diminished. Taking advantage of the inhibitive effect of Hg2+, a novel Hg2+ sensor has been developed. In this system, sensing conditions, including pH of the buffer solution, substrate concentration and time, were optimized. Under the optimal conditions, the probe showed a linear range of 10 - 300 nmol/ L ( R2 = 0. 997) with a detection limit of 6. 26 nmol/ L. In addition, this sensor exhibited good selectivity and sensitivity for Hg2+against other common environmental mental ions, providing a new method for water analysis.
ABSTRACT
One-step green synthetic approach,with bovine serum albumin(BSA) as stabilizer and reductant, was developed for preparation of BSA hybrid fluorescence gold nanoclusters (AuNCs@BSA). The prepared AuNCs@BSA exhibited strong red fluorescence under UV light illumination. Upon excited at 360 nm, the fluorescence spectrum of AuNCs@ BSA exhibited maximum emission peak at 635 nm. AuNCs@ BSA was presented as uniform spherical morphology with diameter at (2.0 ±0.05) nm. The fluorescence of AuNCs@BSA could be quenched by Hg2+because of its metallophilic reaction. Based on the fluorescent spectrometry, a rapid detection system was developed for Hg2+detection in tap water. The AuNCs@BSA amount, pH and buffer system were optimized in this study. According to optimization results, ultrapure water (pH 5.0) was selected to dilute the AuNCs@BSA by 100 times, and 50 μL/well of AuNCs@BSA dilution was applied to detect mercury ion in tap water. Under the optimized conditions, the detection could be completed within 3 min,the fluorescence intensity of the system was linearly proportional to the concentration of mercury ion in the range of 0.5–900 μg/L with linear equations y=-26.76lgx+803.1(0.5-75 μg/L,R2=0.9951) and y=-0.27x+762.02 (75-900 μg/L,R2=0.9959). The limit of detection was 0.14 μg/L(3σ). The average recoveries in spiked tape water samples ranged from 86.8%-113.4% with relative standard deviation of less than 15%. The result implied that the developed method was able to apply to detect mercury ion rapidly, sensitively and conveniently.
ABSTRACT
A simple,fast and highly sensitive fluorescence analysis method for detection of mercury ion was developed based on N-methyl-mesoporphyrin IX (NMM)/G-quadruplex DNA system and specific T-Hg-T mismatches.In this strategy,a large number of thymine was introduced into guanine-rich oigonucleotides which could form G-quadruplex.In the presence of Hg2+,guanine-rich oigonucleotides and complementary strand could form double-stranded DNA molecule by specific T-Hg-T mismatch pair,leading to destruction of G-quadruplex DNA structure.In the absence of Hg2+,guanine-rich oigonucleotides spontaneously formed G-quadruplex DNA structure that could bound NMM to generate intense fluorescence.Based on the above facts,a sensitive fluorescence biosensor for determination of Hg2+ was fabricated.And the optimal conditions for Hg2+ determination were as follows:buffer solution pH of 6.7,20 mmol/L KCl and 2.5 μmol/L NMM in buffer and incubation for 2 h.Under the optimal conditions,the fluorescence intensity signal change (F0-F) and the Hg2+ concentration exhibited a linear correlation within 50 nmol/L to 1000 nmol/L range with a low detection limit of 22.8 nmol/L (3σ).The biosensor exhibited good selectivity toward common metal ions.The developed method was successfully employed to detect Hg2+ in tap water with recovery of 106.1％-107.8％.
ABSTRACT
The effects of cetyltrimethylammonium bromide ( CTAB) , ascorbic acid, NaBH4 and AgNO3 , as well as the stirring time and reaction time on the preparation of gold nanorods synthesized with seedless growth method were studied. The optimum preparation conditions were obtained in the process of growth of gold nanorods. The gold nanorods prepared under different conditions were characterized by visible absorption spectroscopy and transmission electron microscopy ( TEM ) . Under the optimum conditions such as room temperature, 0. 1 mol/L CTAB, 96 μmol/L AgNO3 , 0. 97 mmol/L ascorbic acid, 1. 5 μmol/L NaBH4 and stirring for 25 s, micro-sized gold nanorods with uniform morphology, good dispersibility, small shaft width and high aspect ratio were prepared within 6 h. The gold nanorods were expected to be applied to the detection of mercury ion in water environment.
ABSTRACT
Based on the plasmon coupling effect in gold nanoparticles core-satellite nanostructures linked by thymine(T)-rich DNA hybridization and the specific Hg2+-mediated T-Hg2+-T base pair, a novel localized surface plasmon resonance (LSPR) optical fiber sensor was proposed and developed for Hg2+ detection in water.The Hg2+-induced conformational change in T-rich DNA sequence inhibited the DNA hybridization reaction, weakened the plasmon coupling effect and leaded to the change of LSPR resonance wavelength.The concentration of Hg2+ was quantitatively determined by the resonance wavelength redshift.The linear range of Hg2+ detection was about 5-150 nmol/L with LOD about 3.4 nmol/L.The specificity of the sensor was proved great by evaluating the response to other heavy metal ions such as Zn2+, Mg2+, Pb2+ and so on.This sensor was applied in environmental water detection by standard addition method,with the RSD less than 4.8% and recoveries of 94.2%-105.4%.
ABSTRACT
The effects of cetyltrimethylammonium bromide ( CTAB) , ascorbic acid, NaBH4 and AgNO3 , as well as the stirring time and reaction time on the preparation of gold nanorods synthesized with seedless growth method were studied. The optimum preparation conditions were obtained in the process of growth of gold nanorods. The gold nanorods prepared under different conditions were characterized by visible absorption spectroscopy and transmission electron microscopy ( TEM ) . Under the optimum conditions such as room temperature, 0. 1 mol/L CTAB, 96 μmol/L AgNO3 , 0. 97 mmol/L ascorbic acid, 1. 5 μmol/L NaBH4 and stirring for 25 s, micro-sized gold nanorods with uniform morphology, good dispersibility, small shaft width and high aspect ratio were prepared within 6 h. The gold nanorods were expected to be applied to the detection of mercury ion in water environment.
ABSTRACT
A gold nanoparticle ( GNP)-based dynamic light scattering ( DLS) assay has been developed for detecting mercury ion ( Hg2+) in aqueous solution. The GNPs are able to maintain monodisperse state in relative high ionic strength ( 0. 1 mol/L NaCl ) aqueous solution because Hg2+ aptamer 5’-TTTCTTCTTTCTTCCCCCCTTGTTTGTTGTTT-3’( Probe DNA ) can adsorb on the GNP surface by electrostatic interaction. In the presence of Hg2+, the Probe DNA molecules easily desorb from GNP surface because of T-Hg2+-T formation. The unprotected GNPs form aggregates in 100 mmol/L NaCl solution, resulting in increased significantly the average hydrodynamic diameter of GNPs. Under the conditions of pH 7. 43, 110 nmol/L aptamer, 100 mmol/L NaCl and 30 minutes incubation time of Hg2+with aptamer, the difference of average hydrodynamic diameter (△D ) of GNPs was increased linearly with logarithm of Hg2+concentration over the range from 0. 1 nmol/L to 5 μmol/L, with a detection limit of 0. 1 nmol/L. Moreover, satisfactory results were obtained when the proposed method was applied to detect Hg2+ in real samples.
ABSTRACT
A simple and sensitive method was developed for the detection of mercury ions with quartz crystal microbalance(QCM), based on the specific thymine(T)-Hg2+-T structure and gold nanoparticles. The gold nanoparticles were prepared by the citrate reduction method. In a self-assembled way, the particle surface was modified with the probe oligonucleotides which were partially replaced by 6-Mercaptohexan-1-ol to reduce the steric hindrance of hybridization. The sensitivity was optimized by the oligonucleotide with a strand length of 9bp and a T number of 7. The linear range was 5.0-100 nmol/L with a detection limit of 2.0 nmol/L. And Ca2+, Mg2+ and other metal ions had no significant interferences. This method was successfully applied for the detection of Hg2+in environmental water samples, with RSD less than 2.9% and recoveries of 97.3%-101.2%.