Phosphinic acid functionalized carbon nanotubes for sensitive and selective sensing of chromium(VI)

Single-walled carbon nanotubes (SWCNTs) have been functionalized with a phosphinic acid derivative 'bis(2,4,4-trimethylpentyl) phosphinic acid' (PA/d). It has been achieved by treating the chlorinated SWCNTs with PA/d at 80°C. Successful functionalization and different nanomaterial properties have been investigated by UV-vis-NIR, FTIR, Raman spectroscopy, AFM and FE-SEM. PA/d conjugated SWCNTs (CNT-PA) are dispersible in some common organic solvents, e.g. CH2Cl2, DMF, CHCl3, and THF. The 'CNT-PA' complex was spin-casted on boron doped silicon wafer. Thus fabricated sensing electrode is demonstrated for sensitive and selective electrochemical sensing of chromium(VI) ions. A linear response is obtained over a wide range of Cr(VI) concentration (0.01-10 ppb). The sensor's sensitivity and the limit of detection are observed to be 35 ± 4 nA/ppb and 0.01 ppb, respectively. The practical utility of the proposed sensor is demonstrated by determining the Cr(VI) concentration in an industrial effluent sample and an underground water sample

Synthesis and Characterization of Silica-Coated Silver Nanoprobe for Paraoxon pesticide Detection

Metal enhanced fluorescence assay-based sensitive detection of a neurotoxic organophosphates pesticide, Paraoxon, is reported. The experimental approach involves the bio-interfacing of organophosphorus hydrolase with a high quantum yield fluorophore, pyranine (8-hydroxyl pyrene-1,3,6-trisulfonic acid trisodium salt), followed by the conjugation of the OPH-pyranine derivative with silica-coated silver nanoparticles (Ag NPs). The above bio-nanoprobe was used for the analysis of the organophosphate pesticide, wherein the induced hydrolysis of the pesticide cause the decrease in pH in the vicinity. An excitation light of 460 nm wavelength was used to monitor the changes in the resulting emission (at 510 nm) with respect to the changing pesticide concentrations (1–100 ppb). The introduction of the silica-coated AgNPs into the nanoprobe system was observed to deliver metal enhanced effect, leading to almost10-fold intensification of the fluorescence signal. The enhanced fluorescence assay format offers linear detection of Paraoxon in the concentration range of 1–100 ng mL−1 with the limit of detection 1 ng mL−1 (1 ppb)

Graphene-gated biochip for the detection of cardiac marker Troponin I

We report lithium ion intercalation mediated efficient exfoliation of graphite to form monolithic graphene sheets which have subsequently been investigated for the development of highly sensitive label-free electrochemical detection platform for cardiac biomarker, Troponin I (cTnI). The spectroscopic and morphological analysis demonstrated the formation of defect free graphene sheets which were successfully employed to fabricate an inter-digited microdevice in a drain-source configuration on a silicon biochip. The graphene gated biochip functionalized with anti-cTnI antibodies used in label free detection of cTnI which exhibited an excellent sensitivity in the picogram range (~1 pg mL(-1)) for cTnI without the use of any enzymatic amplification that promises its potential applicability for bio-molecular detection in clinical diagnosis

Biofunctionalized rebar graphene (f-RG) for label-free detection of cardiac marker troponin I

One-step microwave-assisted unscrolling of carbon nanotubes to form functionalized rebar graphene (f-RG) is reported. The well-characterized f-RG on an interdigitated electrode biochip in a FET configuration showed enhanced electronic properties, as demonstrated with I-V characteristics. The developed device was biofunctionalized with specific anti-cTnI antibodies exhibiting a shift of threshold voltage from -2.15 V to -0.5 V and decrease in electron mobility from 3.609 × 10(4) to 8.877 × 10(3) cm(2) V(-1) s(-1). The new sensing strategy holds great promise for its applicability in diagnostics exhibiting high sensitivity (∼ 1 pg/mL) and specificity toward cardiac marker (cTnI)