An electrochemical daunorubicin sensor based on the use of platinum nanoparticles loaded onto a nanocomposite prepared from nitrogen decorated reduced graphene oxide and single-walled carbon nanotubes.

A glassy carbon electrode (GCE) was modified with a nanocomposite prepared from nitrogen-doped reduced graphene oxide (N-rGO) and single walled carbon nanotubes (SWCNTs), and then loaded with platinum nanoparticles (Pt NPs) to obtain a voltammetric sensor for daunorubicin (DNR). Reductive doping of GO and the crystallization of the Pt NPs were carried out in a one-step hydrothermal process. The modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry. It exhibited high sensitivity compared with unmodified electrode. Some experimental parameters which affected sensor response were optimized. Under optimum conditions and at a working voltage of typically -0.56 V (vs. Ag/AgCl), the sensor has a low detection limit (3 ng mL-1), a wide linear range (0.01-6 µg mL-1) and good long-term stability. The method was successfully applied to the sensitive and rapid determination of DNR in spiked human serum samples. Graphical abstract Platinum nanoparticles were loaded onto a nanocomposite prepared from nitrogen decorated reduced graphene oxide and single-walled carbon nanotubes (N-rGO-SWCNTs-Pt) and then used for electrochemical determination of daunorubicin (DNR).

Voltammetric simultaneous determination of catechol and hydroquinone using a glassy carbon electrode modified with a ternary hybrid material composed of reduced graphene oxide, magnetite nanoparticles and gold nanoparticles.

An electrochemical sensor is described for the simultaneous determination of the pollutants catechol (CC) and hydroquinone (HQ). A glassy carbon electrode (GCE) was modified with reduced graphene oxide, Fe3O4 and gold nanoparticles and then showed a pair of well-defined voltammetric peaks for CC and HQ. Its oxidation peak potentials (located at 0.21 and 0.10 V vs. Ag/AgCl) are well separated, and this makes it suitable for simultaneous determination of the two isomers. Under optimal conditions, the oxidation peak currents of CC and HQ increase linearly in the 0.05-550 µM and 0.1-500 µM concentration ranges, even in the presence of 0.1 mM of the respective other isomer. The detection limits are 0.02 and 0.17 µM (at S/N = 3), respectively. The modified GCE exhibits good selectivity and recovery when applied for the analysis of spiked wastewater. Graphical abstract Ternary hybrid nanomaterials of rGO-Fe3O4-Au was developed for simultaneous electrochemical determination of catechol (CC) and hydroquinone (HQ).

Carbon nanospheres with dual-color emission and their application in ratiometric pyrophosphate sensing.

Herein, we employ pH-dependent solubility equilibrium to develop the one-pot aqueous synthesis of dual-color emission fluorescent carbon nanosphere (DFCSs) with novel physicochemical properties. Unexpectedly, some of the DFCSs have a regular nanosphere shape, containing uniform carbon dots (∼20 nm) on their surface. This may be attributed to the change in the surface composition of the carbon nanospheres under the strong alkaline conditions (pH 13), which results in dual-wavelength emission by single-wavelength excitation. Interestingly, the fluorescence intensities of the two emission peaks of the DFCSs at 315/410 nm can be simultaneously quenched upon the addition of Co2+ due to the strong coordination between Co2+ and the O-containing luminescent groups from the carbon dots and DFCSs. Also, the results demonstrate that one Co2+ simultaneously combines with two chromophoric groups. Furthermore, the quenched DFCSs exhibit high sensitivity for pyrophosphate (PPi) in the range of 0.075-200.0 µM through a fluorescence recovery process, which can be attributed to the stronger Co2+-O[double bond, length as m-dash]P bond. This results in the removal of Co2+ from the surface of DFCSs-Co2+ system via competitive adsorption interactions. Meanwhile, this sensor shows high selectivity for PPi over mercapto amino acid and phosphate in aqueous solution. These results indicate the DFCSs can act as a dual-signal PPi-selective sensor via a ratiometric competitive mechanism.

Photoluminescent coral-like carbon-branched polymers as nanoprobe for fluorometric determination of captopril.

The authors describe the synthesis of fluorescent coral-like carbon nano-branched polymers (PCNBPs) co-doped with nitrogen and phosphorus. Uric acid and phosphoric acid act as nitrogen and phosphorus sources, respectively. The PCNBPs have a coral-like branched structure, are cross-connected, and < 20 nm in skeleton diameter. Their blue fluorescence, best measured at excitation/emission wavelengths of 330/425 nm, is quenched by mercury (II) ions due to the specifically restricted rigid conformation caused by the interaction of phosphorus, nitrogen, and oxygen groups on the surface of the PCNBPs. Fluorescence is selectivity quenched by Hg(II) but restored in addition of the hypertension drug captopril (CAP) in the range 50 nM to 40 µM concentration range. Fluorescence recovery is attributed to the effectively specific interactions between the thiol group of CAP and Hg(II). The method was applied to the determination of the concentration of Cap in pharmaceutical samples, and recoveries were between 97.6 and 105.1%. Graphical abstract Fluorescent coral-like carbon nano-branched polymers (PCNBPs) co-doped with nitrogen and phosphorus are described. Their fluorescence is selectivity quenched by Hg(II) but restored in addition of the hypertension drug captopril (Cap) in the range 50 nM to 40 µM concentration range.

Multiplexed ratiometric photoluminescent detection of pyrophosphate using anisotropic boron-doped nitrogen-rich carbon rugby ball-like nanodots.

The shape of nanoparticles is decisive for their intrinsic physicochemical properties, as well as for the anisotropic behavior of individual particles in many instances. Herein, boron-doped nitrogen-rich carbon rugby ball-like nanodots (BNCRDs) have been synthesized by a heterophase polymerization route at a vital mass ratio of phenylboronic acid and uric acid in the precursor solution. Unexpectedly, the as-prepared BNCRDs showed stable dispersions of ellipsoidal carbonaceous polymer nanodots (rugby ball-like structures that are approximately 150 nm in length) as novel carbon dot derivatives. The anisotropic BNCRDs are water-soluble compounds that have highly enhanced photoluminescence (PL), which is accompanied by a large red shift of the emission peak upon the addition of Hg2+ and is nearly quenched upon the addition of Cu2+. This is due to the chelation-enhanced fluorescence property of the BNCRDs following Hg2+ complexation with sterically efficient heteroaromatics in the BNCRDs and the chelation enhancement quenching effect of the BNCRDs following Cu2+ complexation with the N/O donor atoms of the surface of the BNCRDs, respectively. Importantly, the BNCRD PL, which is changed by Hg2+ and Cu2+, exhibits high selectivity and sensitivity for the pyrophosphate ion (PPi) in the ranges 50 nM-280 µM and 10 nM-100 µM through a photoluminescent reset process, respectively, and could be attributed to the effective coordination/chelation interactions between Hg2+/Cu2+ and the plentiful oxygen groups of PPi. These results indicate that anisotropic BNCRDs can act not only as a ratiometric sensor for Hg2+ but also as a dual-mode PPi-selective sensor via ratiometric displacement and a competitive mechanism. With the broad diversity in the molecular backbone of the carbon dots via rich chemical routes, anisotropic BNCRDs have been developed with unique structural, electrical, and attractive functions, which greatly expands the research horizon of carbon-based composites.

Clinical value of polymerase chain reaction in the diagnosis of joint tuberculosis by detecting the DNA of Mycobacterium tuberculosis.

OBJECTIVE: To assess the clinical value of polymerase chain reaction (PCR) in the diagnosis and differential diagnosis of joint tuberculosis (TB). METHODS: PCR was used blindly to detect the DNA of Mycobacterium tuberculosis (M.TB) in five specimens of M.TB, 5 of BCG, and 10 of other bacteria. Then, M. TB in 98 samples from patients with joint TB and 100 samples from patients with non-tubercular joint disorders were detected by PCR, acid-fast staining and culture,. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of PCR were calculated. The χ2 test was used for statistical analysis of the frequency of various factors. At the same time, some problems with PCR were also systematically analyzed. RESULTS: (1) In the "standard samples", both M. TB and BCG showed positive while other bacteria were negative. (2) In 98 cases from patients with joint TB, 81 were positive by PCR, 6 by acid-fast staining, and 17 by culture. In 100 cases from patients with non-tuberculous joint disorders, 9 were positive by PCR, and none by either acid-fast staining or culture. Sensitivity, specificity, accuracy, positive and negative predictive value of PCR were 82.65% (81/98), 91.00% (91/100), 86.87% (172/198), 90.00% (81/90) and 84.26% (91/108), respectively. (3) The positive rates for PCR, acid-fast staining and culture in detection of M. TB were 82.65% (81/98), 6.12% (6/98), and 17.34% (17/98), respectively. There were statistically significant differences between the three methods (P < 0.001). (4) The process of PCR is automatic, and can be completed within 3 to 6 hours, whereas 4 to 8 weeks are required for the conventional culture of M. TB. CONCLUSION: PCR is a sensitive, specific, rapid, simple and minimally invasive method for detection of M. TB in samples from joint TB, and can play an important role in early and rapid diagnosis and differential diagnosis of joint TB. But it also has some limitations, such as false positivity and false negativity.