Excellent Adsorption of Lead (II) and Chromium (VI) from Water Using Zwitterions (-NH3+ and -COO-) Functionalized Nano Lanthanum Oxide: Kinetic, Isotherm, Thermodynamic, and Surface Mechanism.

Zwitterion amino acid l-cysteine functionalized lanthanum oxide nanoparticles (l-Cyst-La2O3 NPs) have been synthesized for the first time with lanthanum acetate as the precursor, NH4OH as the base, and l-cysteine as the in situ functionalized mediator. The typical size of l-Cyst-La2O3 NPs was obtained in the range of 15-20 nm from the TEM technique. A cytotoxicity test of l-Cyst-La2O3 NPs was performed in Raw 264.7 cell lines, which were shown to be highly biocompatible. The point zero charge pH (pHPZC) of bare and l-Cyst functionalized La2O3 NPs was obtained at pH 6 and 2. The maximum uptake capacities of l-Cyst-La2O3 NPs at temperatures 25-45 °C were obtained as 137-282 mg/g for Pb2+ and 186-256 mg/g for Cr6+. All of these values are much higher than those reported in the literature with other nanomaterials. The presence of -SH, -NH2, and -COOH functional groups in zwitterion l-cysteine provides multiple binding sites leading to the high adsorption of Pb2+ and Cr6+. Five-cycle desorption studies were successfully performed to regenerate the spent l-Cyst-La2O3 NPs.

Fabrication of Mesoporous Silica Nanoparticle-Decorated Graphene Oxide Sheets for the Effective Removal of Lead (Pb2+) from Water.

Mesoporous silica nanoparticle-decorated graphene oxide nanosheets (MSiO2-GO) were synthesized and characterized for the active removal of lead (Pb2+) from the water. MSiO2 NPs were prepared via an ultrasonication method using tetraethyl orthosilicate (TEOS), and GO sheets were obtained via a modified Hummers' method. X-ray diffraction, UV-vis spectroscopy, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy specified the composition of MSiO2 NPs and GO sheets. The surface charge and texture of the MSiO2-GO nanosheets were obtained using the ζ-potential technique and by field emission scanning electron microscopy. The relative cytotoxicity test of MSiO2 NPs and MSiO2-GO nanosheets was performed on Murine Raw 264.7 cells before implying the treatment of water. Adsorption of Pb2+ ions on MSiO2-GO nanosheets was examined at various parameters such as different aqueous pH values (2.0-10.0), MSiO2-GO nanosheet doses (3, 5, 10, 15, 20 mg L-1), time intervals (2-30 min), and temperatures (25-45 °C). About 90% of Pb2+ ions were removed from water within 30 min (MSiO2-GO dose: 15 mg L-1; initial Pb2+ ions: 50 mg L-1; temperature: 25 °C; shaking speed: 200 rpm). The maximal uptake of Pb2+ was obtained at solution pH 6.0. Pseudo-first- and pseudo-second-order kinetic rate equations describe the sorption dynamic data. Pb2+ sorption isotherms were modeled using the Freundlich and Langmuir isotherm models. The possible mechanism of binding of Pb2+ ions onto MSiO2-GO nanosheets has been discussed. The exhausted MSiO2-GO nanosheets were successfully regenerated using 0.005 M HNO3 as the desorbing agent.

Lead and Chromium Adsorption from Water using L-Cysteine Functionalized Magnetite (Fe3O4) Nanoparticles.

L-Cysteine functionalized magnetite nanoparticles (L-Cyst-Fe3O4 NPs) were synthesized by chemical co-precipitation using Fe2+ and Fe3+ as iron precursors, sodium hydroxide as a base and L-Cysteine as functionalized agent. The structural and morphological studies were carried out using X-ray powder diffraction, transmission electron microscopy, dynamic light scattering, scanning electron microscopy and energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and UV-Vis spectrophotometric techniques. The zeta potential of bare Fe3O4 and functionalized L-Cyst-Fe3O4 NPs were +28 mV and -30.2 mV (pH 7.0), respectively. The positive surface charge changes to negative imply the presence of L-Cyst monolayer at particle interface. Band gap energy of 2.12 eV [bare Fe3O4NPs] and 1.4 eV [L-Cyst-Fe3O4 NPs] were obtained. Lead and chromium removal were investigated at different initial pHs, contact time, temperatures and adsorbate-adsorbent concentrations. Maximum Cr6+ and Pb2+ removal occurred at pH 2.0 and 6.0, respectively. Sorption dynamics data were best described by pseudo-second order rate equation. Pb2+ and Cr6+ sorption equilibrium data were best fitted to Langmuir equation. Langmuir adsorption capacities of 18.8 mg/g (Pb2+) and 34.5 mg/g (Cr6+) at 45 °C were obtained. Regeneration of exhausted L-Cyst-Fe3O4 NPs and recovery of Pb2+/Cr6+ were demonstrated using 0.01 M HNO3 and NaOH. L-Cyst-Fe3O4 NPs stability and reusability were also demonstrated.

L-cysteine capped lanthanum hydroxide nanostructures for non-invasive detection of oral cancer biomarker.

In this paper, we present the result of studies related to the in situ synthesis of amino acid (L-Cysteine) capped lanthanum hydroxide nanoparticles [Cys-La(OH)3 NPs] towards the fabrication of efficient immunosensor for non-invasive detection of oral cancer. The characterization of Cys-La(OH)3 NPs was carried out by different techniques including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fourier transform infrared spectroscopy and electrochemical techniques. These Cys-La(OH)3 NPs were electrophoretically deposited onto an indium-tin-oxide glass substrate and used for immobilization of anti-cytokeratin fragment-21-1 (anti-Cyfra-21-1) for the electrochemical detection of Cyfra-21-1. This immunosensor shows a broad detection range of 0.001-10.2ngmL-1, the low detection limit of 0.001ngmL-1, and high sensitivity of 12.044µA (ng per mL cm-2)-1 with a response time of 5min. This immunosensor was found to be more advanced in terms of high sensitivity and low detection limit as compared to previously reported biosensors and commercially available ELISA kit (Kinesis DX).

Immunosensor based on nanocomposite of nanostructured zirconium oxide and gelatin-A.

We have reported the studies related to the fabrication of a nanocomposite, comprising of sol-gel derived inorganic zirconium oxide nanoparticles (ZrO2 NPs) and organic biopolymer gelatin-A (GA), deposited on indium-tin-oxide (ITO) coated glass substrate by drop casting method. The GA-ZrO2/ITO electrode was used for immobilization of monoclonal antibodies (Ab) specific to antigen Vibrio cholerae (Vc) followed by bovine serum albumin (BSA) for antigen Vc detection using electrochemical techniques. The structural and morphological behaviour of these ZrO2 NPs, GA-ZrO2/ITO electrode and BSA/Ab/GA-ZrO2/ITO immunosensor was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The transmission electron microscopy study exhibited a spherical shape ZrO2 NPs. The average crystalline size of ZrO2 NPs was obtained as 10.3 ± 1 nm from X-ray diffraction measurement and 72 nm hydrodynamic radius measured by dynamic light scattering. GA-ZrO2 nanocomposite provides a porous structure which assists to higher loading of Ab on the matrix surface that improved the biosensing properties. The electrochemical response studies of the fabricated BSA/Ab/GA-ZrO2/ITO immunosensor exhibited good linearity in the range of 50-400 ng mL(-1), low limit of detection of 0.74 ng/mL, sensitivity as 0.03 Ω ng(-1)mL(-1)cm(-2) and reproducibility more than 10 times.