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A facile one-pot solvothermal strategy was used to prepare fluorescent carbon nitride nanoparticles (CNNPs) using tartaric acid and urea as carbon and nitrogen sources at relatively low temperatures. The obtained CNNPs were characterized by multiple analytical techniques. The CNNPs with fluorescence (FL) quantum yield up to 17.9% exhibited excellent selectivity and sensitivity of fluorescence quenching for free chlorine. The quenching rate was quick, and the linear response range of free chlorine was from 0 to 30 μM. The limit of detection (LOD) was as low as 13 nM, which was much lower than that of the most widely used N,N -diethyl- p -phenylenediamine (DPD) colorimetric method. This sensing system exhibits many advantages, such as short response time (less than 1 min), excellent selectivity, high sensitivity, and wide linear response range. The results show that this method has promising potential applications in the detection of free chlorine in real water samples. [ABSTRACT FROM AUTHOR]

A metal-organic frameworks (MOFs), cauliflower-like MIL-100(Cr), has been facilely prepared through simple reflux method for the first time and characterized by XRD, FT-IR, SEM and XPS. The MOFs was found to be useful for the simultaneous and selective electrochemical detection of microgram Cd(II), Pb(II), Cu(II), and Hg(II) in aqueous solution. The detection was performed by the square wave anodic stripping voltammetry (SWASV). The MIL-100(Cr) modified electrode showed an excellent selectivity and stability for Cd 2+ , Pb 2+ , Cu 2+ , Hg 2+ determinations. The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as pH, deposition potential and deposition time were optimized for the purpose of determination of traces of metal ions. [ABSTRACT FROM AUTHOR]

Facile and stable nanocomposites, carbon nanocages (CNCs)-reduced graphene oxide (RGO), were developed via one-pot in situ solvothermal reaction in this study. Transmission electron microscope, scanning electron microscope, X-ray diffraction, Raman spectroscopy, energy dispersive X-ray spectroscopy, atomic focus microscope, N 2 adsorption/desorption isotherms, thermogravimetric analysis and Fourier-transform infrared were performed to characterize the CNCs-RGO hybrid material. The electrochemical detections of catechol (CC) and hydroquinone (HQ) were investigated by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The excellent electrocatalytic activity and reversibility have been shown on the modified electrode toward oxidation of both CC and HQ in 0.04 M acetate buffer solution (pH = 4.0). The relationship between the oxidation peak current of CC and its concentration was linear over the range from 1 to 400 μM in the presence of 100 μM HQ, and the linear relationship between the oxidation peak current of HQ and its concentration can be obtained range from 1 to 300 μM in the presence of 100 μM CC. The detection limits (S/N = 3) for CC and HQ were 0.40 and 0.87 μM, respectively. [ABSTRACT FROM AUTHOR]

Non-enzymatic electrochemical sensors for the detection of glucose and hydrogen peroxide (H 2 O 2 ) were designed based on novel nanostructure electrocatalyst of carbon quantum dots (CQDs)/octahedral cuprous oxide (Cu 2 O) nanocomposites. The CQDs/octahedral Cu 2 O nanocomposites has been smoothly by a facile method with ultrasonic treatment and the morphologies of the synthesized materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) with Energy dispersive X-ray spectroscopy (EDS) and powder X-ray diffraction measurements (XRD). Compared to octahedral Cu 2 O, the CQDs/octahedral Cu 2 O exhibited preferable electrocatalysis to the glucose oxidation and H 2 O 2 reduction. Amperometric sensing of glucose was realized with a linear response range from 0.02 to 4.3 mM, a detection limit of 8.4 μM ( S / N = 3). The interferents of ascorbic acid (AA), uric acid (UA), dopamine (DA) and sodium chloride (NaCl) was also detected using the CQDs/octahedral Cu 2 O modified electrode, the results showed good selectivity for glucose detection. Besides, the nonenzymatic sensor also has good performance to the electrocatalytic reduction of H 2 O 2 , with a linear response range from 5 μM to 5.3 mM and a detection limit of 2.8 μM ( S / N = 3). The CQDs/octahedral Cu 2 O nanocomposites have good selectivity for the H 2 O 2 detection with the AA, NaCl and UA. [ABSTRACT FROM AUTHOR]

Abstract: A label-free DNA biosensor for hybridization detection of short DNA species related to the transgenic plants gene fragment of cauliflower mosaic virus (CaMV) 35S promoter was developed in this paper. The nanocomposite containing chitosan (CS) and mutiwalled carbon nanotubes (MWNTs) was first coated on a glassy carbon electrode. Then a highly reactive dialdehyde reagent of glutaraldehyde (GTD) was applied as an arm linker to covalently graft the 5′-amino modified probe DNA to the CS–MWNTs surface via the facile aldehyde–ammonia condensation reaction. The hybridization capacity of the developed biosensor was monitored with electrochemical impedance spectroscopy (EIS) using [Fe(CN)6]3−/4− as an indicating probe, and the experimental results showed that the biosensor had fast hybridization rate and low background interference. A wide dynamic detection range (1.0×10−13–5×10−10 M) and a low detection limit (8.5×10−14 M) were achieved for the complementary sequence. In addition, the hybridization specificity experiments showed that the sensing system can accurately discriminate complementary sequence from mismatch and noncomplementary sequences. [Copyright &y& Elsevier]