Highly luminescent carbon dots (C-dots) were synthesized by the one-pot simple hydrothermal method directly from lemon juice using different temperatures, time, aging of precursors, and diluted ...solvents to control the luminescence of C‐dots. The obtained C-dots were characterized by high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrophotometry, dynamic light scattering, ultraviolet-visible spectrophotometry, and photoluminescent spectrophotometry. The results show that C‐dots had strong green light emission with quantum yield in the range of 14.86 to 24.89% as a function of hydrothermal temperatures. Furthermore, light emission that is dependent on hydrothermal time, aging of precursor, and diluted solvent was observed. These results suggest that the C‐dots have potential application in optoelectronics and bioimaging.
In this study, we investigate the electrochemical behavior of palladium nanoparticles (PdNP) deposition on glassy carbon electrode (GCE) in two deep eutectic solvents, namely, reline and ethaline, ...and its application in DNA sensors. The electrochemical behaviors of PdNP deposition are investigated by cyclic voltammetry and chronoamperometry. The obtained results indicate that the PdNP deposition on GCE in reline was dominated by the progressive 3D nucleation mechanism, while that in ethaline was dominated by the instantaneous nucleation mechanism. The structural, morphological, and compositional characteristics are also investigated through X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. A PdNP-based DNA sensor is constructed for
Mycobacterium tuberculosis
detection. Results indicate a significant difference between the DNA sensing responses based on the PdNPs synthesized in reline (PdNP-RE) and ethaline (PdNP-ET). The PdNP-ET–based DNA sensor has higher sensitivity than the PdNP-RE–based DNA sensor. This study serves as a reference for the development of improved nanomaterials for bioanalysis and the elaborate design of biosensors for practical applications.
The weak emission intensity of rare-earth element-doped dual-mode materials leads to low-sensor sensitivity, which is a challenge in optical sensor applications. The present work achieved high-sensor ...sensitivity and high green color purity based on the intense green dual-mode emission of Er/Yb/Mo-doped CaZrO3 perovskite phosphors. Their structure, morphology, luminescent properties, and optical temperature sensing properties have been investigated in detail. Phosphor shows a uniform cubic morphology with an average size of approximately 1 μm. Rietveld refinement confirms the formation of single-phase orthorhombic CaZrO3. Under the excitation of 975 and 379 nm, the phosphor emits pure green up and down-conversion (UC and DC) emission at 525/546 nm corresponding to 2H11/2/4S3/2–4I15/2 transitions of Er3+ ions, respectively. Intense green UC emissions were achieved because of energy transfer (ET) from the high-energy excited state of Yb3+–MoO42− dimer to the 4F7/2 level of Er3+ ion. Furthermore, the decay kinetics of all obtained phosphors confirmed ET efficiency from Yb3+–MoO42− dimer to Er3+ ions, leading to strong green DC emission. Moreover, the DC of the obtained phosphor shows that a sensor sensitivity value of 0.697% K−1 at 303 K is higher than the UC (0.667% K−1 at 313 K) because the thermal effect generated by the DC excitation source light is ignored compared with UC luminescence. CaZrO3:Er–Yb–Mo phosphor shows intense green dual-mode emission with high green color purity, 96.50% of DC and 98% of UC emissions, and high sensitivity, making it suitable for optoelectronic devices and thermal sensor applications.
This paper reports single-walled carbon nanotube-based biosensors for genetically modified organism (GMO) detection. Electrochemical electrode and single-walled carbon nanotube field effect ...transistor (SWCNT-FET)-based biosensors are used to determine the CaMV 35S promoter of Roundup Ready soybean. Given optimal conditions, both biosensors can effectively detect full complementarity with concentration as low as 1nM. The sensitivity of the electrode-based biosensor is approximately 0.6kΩ/nM while that of the SWCNT-FET-based biosensor is 0.32nA/nM. Both biosensors were also used to determine a polymerase chain reaction-amplified sample. The obtained results showed that both sensors determined transgenic organisms well, thereby providing a useful tool for screening analysis of food samples.
Schematic diagram of device: (a) optical image of microelectrode on wafer, (b) single sensor was separated from wafer, (c) magnification of microelectrode sensor, (d) Cartoon of CNTFET device, (e) FE-SEM image of CNTs on surface of FET. Display omitted
•A single-walled carbon nanotube-based biosensor for genetically modified organism detection was developed.•Detection limit as low as 1nM.•The sensitivity of the SWCNT-FET-based biosensor is 0.32nA/nM.•The polymerase chain reaction-amplified samples were determined by biosensors.
•Carbon dots (C-dots) was synthesized successfully by hydrothermal method using lemon juices as carbon sources.•The obtained C-dots were found to emit bright green luminescence.•The C-dots were used ...for detection of V5+ ions in water and serum.
A simple approach for the synthesis of luminescent carbon dots (C-dots) has been developed by the hydrothermal treatment of lemon juice as carbon precursor at 240 °C in 12 h. The obtained C-dots were found to emit bright green luminescence. Meanwhile, the C-dots exhibited excitation-dependence, photo-stability, and well dispersibility. The C-dots were used for detection of ion V5+ in water and serum, which was based on V5+ induced luminescence quenching of C-dots. The selectivity experiments revealed that the luminescent sensor was specific for V5+ ions even with interference by high concentrations of other metal ions. Detection limits for V5+ ions was 3.2 ppm. These results suggest that the present C-dots are potential application in optoelectronic, imaging and luminescent probing of V5+ ions.
By century XX, the Central Highlands was being the traditional residence of indigenous ethnic minorities. In 1858, the French colonialists established plantations of industrial crops all over the ...area, which ended up forming the first wave of the Kinh people's migration to the Central Highlands. In 1957, the Republic of Vietnam government created the second wave of Kinh emigration to the Central Highlands through the Land Development Program. In the period 1965-1975, the violent escalation of the Vietnam War prompted the 3rd wave of war refugees migrating to the Central Highlands. The 4th wave (1976-1989) was the result of the efforts of the Socialist Republic of Vietnam to redistribute human resources throughout the country, in which a large part of the population from the plains was moved to the Central Highlands to build new economic zones. By early 1990s, with the worldwide 'coffee boom' and the legal recognition of private economic sector, the wave of free migration to the Central Highlands to plant coffee trees exploded - this was the 5th wave. The continuum of the above five waves of migration has completely changed the population and land ownership structure of the Central Highlands as well as brought great alterations to the socio-economic life of this region. While investigating such changes, our article seeks to provides a comprehensive explanation on the process in which the Kinh gained their dominance on the Central Highlands over the five waves of their migration to the plateau.
This paper presents insights on the thermodynamics and kinetics of the cobalt electronucleation and growth mechanisms onto glassy carbon electrode from a eutectic mixture of choline chloride and ...urea. The behavior of the current density transients can be described by a model capable of considering the cobalt three-dimensional nucleation and diffusion-controlled growth from metallic nuclei and the induction-time. Using the proposed model, typical kinetic parameters such as nucleation frequency A, number density of nuclei, N0, and diffusion coefficient, D, were determined at different temperatures and applied potentials. It was found that the residual water has some effects on the early stage of the Co electrodeposition, especially on the nucleation types. Thus, at low temperature it is predominant by progressive nucleation, while at high temperature it is governed by instantaneous nucleation mechanism. Furthermore, from the temperature-dependent relationship of the diffusion coefficient, the Gibbs free energy for cobalt nucleation in DES was able to be estimated.
•Mechanisms and kinetics of cobalt nucleation and growth from DES were investigated.•Chemical species of DES containing Co (II) were established using UV–vis spectra.•A model comprising (3D) nucleation and growth and induction-time was proposed.•Gibbs free energy for nucleation was determined through a model fitting method.
Gold nanoflowers (AuNF) were synthesized on a glassy carbon electrode via a one-step, eco-friendly protocol in deep eutectic solvent (DES) of choline choloride and urea, called reline, for label-free ...detection of DNA hybridization. DES is eco-friendly, low-cost, biocompatible, and nontoxic, and it can be used as an electrolyte to synthesize nanomaterials by using the electrochemical method. In this protocol, highly branched and stable AuNFs were obtained without using any surfactants for DNA sensor application. The electrochemical performance of the AuNF-modified electrode was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Under optimal conditions, the AuNF-based DNA biosensor exhibited a sensitivity of 294.9 Ω nM−1cm−2 and 218 μA nM−1cm−2 and a limit of detection (LOD) of 10−9 M. The remarkable sensitivity and low LOD could be attributed to the good conductivity of AuNFs for accelerating electron transfer, resulting in obvious signal amplification. The DNA biosensor showed good reproducibility (RSD <3.65 %) and acceptable stability and selectivity. Its excellent performance in DNA detection suggested that the proposed electrochemical DNA sensor has great application potential in clinical diagnosis.
Display omitted
•Gold nanoflowers (AuNF) were synthesized via a green protocol for label-free DNA hybridization detection.•AuNF-based DNA sensor exhibited a sensitivity of 294.9 Ω.nM−1cm−2 and 218 μA.nM−1cm−2, limit of detection of 10−9 M.•Proposed DNA sensor has great application potential in clinical diagnosis.
This study investigated a highly sensitive nonenzymatic biosensor based on ZnO nanorods (NRs) for cholesterol concentration monitoring. The electrochemical behavior of the biosensor was studied by ...cyclic voltammetry, electrochemical impedance spectroscopy, and amperometric response in a 20 mM phosphate-buffered saline solution containing cholesterol. Results showed that this behavior was influenced by cholesterol oxidation, which occurs at the allylic position and is controlled by the electron transfer rate. The experimental parameters (pH, cholesterol concentration, and scan rate) influencing the output signal of the sensor were optimized. Under optimum conditions, the nonenzymatic cholesterol biosensor showed a linear response range of 1–9 mM, and the biosensor sensitivity was 4.2 μA mM
−1
cm
−2
for the ZnO-NRs-based biosensor and 135.5 μA mM
−1
cm
−2
for the Ag-nanoparticles (NPs)/ZnO-NRs-based biosensor. The detection limit was 1.78 mM and 0.184 mM, respectively. The reproducibility, stability, and reusability of the nonenzymatic cholesterol sensor were also investigated.
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