SYNTHESIS, CHARACTERIZATION AND APPLICATION OF METAL NANOPARTICLES

Abstract

Improved and size controlled methods were developed for the synthesis of noble metal such as (Au, Ag and Hg) nanoparticles/nanosols. In first phase, spherical 3.5 ± 0.7 nm sized Gel-AuNPs were synthesized using strong reductant NaBH 4 and gelatin as stabilizer in aqueous system at room temperature. At optimum parameters Gel-AuNPs were characterized using UV-visible, HRTEM, STEM, AFM, XRD and DLS. Gel-AuNPs were used as catalyst for reduction of EB, MB and RB in the presence of NaBH 4 . 100% reduction of EB, MB and RB dyes were carried out in just 150 sec. Plot of lnC Vs Time (sec) shows that reaction is undergoing through first order kinetics. Additionally, Gel- AuNPs were also tested for transformation of 4-NP to 4-AP in the presence of NaBH 4. At optimum conditions, complete reduction of 4-NP into 4-AP was carried out in just 120 sec. This study suggested that easier and faster method was developed for fabrication of Gel- AuNPs in aqueous system, synthesized Gel-AuNPs proved excellent catalyst for reduction of various dyes and 4-NP in aqueous medium. The process of catalysis is environmental friendly in terms of recovery of Gel-AuNPs, exceptionally fast and hence extremely economical. In second phase, Ibuprofen reduced/capped AgNPs were fabricated in aqueous medium at 90 0 C; Ibu-AgNPs were characterized by UV-visible, HRTEM, STEM, AFM, XRD and DLS techniques. HRTEM images reveal that stable spherical AgNPs with an average diameter 3.05 ± 0.6 nm were formed. Ibu-AgNps were applied on to surface of GCE and used as voltammetric Pb(II) sensor. The fabricated sensor is simple, highly selective, sensitive, stable and reproducible and works in linear range, 0.1–1500 ppb with lower detection limit (LDL) of 0.01 ppb (50 pM) and regression coefficient of 0.999 for Pb(II) ions. RSD of 1.5% was observed for 20 replicates of 1000 ppb Pb(II) solution which proves its excellent reproducibility. Drinking, tap and river water samples were successfully analyzed for estimation of Pb(II) ions by developed sensor. In addition to, synthesized Ibu-AgNPs were also tested for catalytic reduction of EB, MB and RB in the presence of NaBH 4 . 100% bleaching of EB, MB and RB dyes were carried out in only 100 sec, 150 sec and 150 sec respectively. Moreover synthesized Ibu-AgNPs were used for catalytic reduction of 4-NP to 4-AP in the presence of NaBH 4 , 100% transformation of 4- NP to 4-AP was carried out in just 60 sec. Plot of lnC Vs time (sec) shows that reduction of EB, MB, RB and 4-NP proceeds through first order kinetics. In third phase, spherical 4 nm ±1 average sized Ibu-HgNsols were synthesized in which hydrazine was used as reductant and ibuprofen as stabilizer in aqueous system at room temperature. At optimum parameters Ibu-HgNsols were characterized by UV-visible, AFM, TEM, STEM and DLS. Synthesized Ibu-HgNsols were applied onto GCE and used as voltammetric sensor for simultaneous determination of Zn(II), Cd(II), Pb(II) and Cu(II) with linear response ranging from 0.1 – 600 ppb and R 2 value around 0.999 for all metals with LDL of Zn(II), Cd(II), Pb(II) and Cu(II) as 0.05 ppb, 0.042 ppb, 0.03 ppb and 0.035 ppb respectively. The sensor was successfully used for monitoring Zn (II), Cd(II), Pb(II) and Cu(II) in various types of water samples. In addition to, synthesized Ibu-HgNsols were used as sensor for determination of acrylamide (AA) in aqueous system using SWV; developed sensor displayed an excellent electro sensing response for AA. At optimum parameters calibration graph was plotted in the range 100 - 1300 ppb. Calibration plot describes excellent linearity with R 2 value 0.996, and LDL was calculated as 0.85 ppb. The sensor exhibited high sensitivity, selectivity and stability. The developed sensor was also applied for determination AA in various industrial aqueous real samples.