S. Krishnamoorthi

A promising electrochemical sensing platform based on a silver nanoparticles decorated copolymer for sensitive nitrite determination

In this paper, we report a facile route to synthesize silver nanoparticles (Ag NPs) incorporated into a copolymer of methyl methacrylate (MMA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) (abbreviated as P(MMA-co-AMPS)) and its application to construct an electrochemical nitrite (NO2−) sensor. The copolymer nano-composite material (Ag–P(MMA-co-AMPS) is characterized by means of transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, UV-vis spectroscopy, X-ray powder diffraction methods, thermogravimetric analysis and electrochemical impedance spectroscopy. Further, Ag–P(MMA-co-AMPS) is used to prepare an electrochemical sensing platform (ESP) on a glassy carbon electrode (GC) surface. NO2− is electrocatalytically oxidized at the ESP (GC/Ag–P(MMA-co-AMPS), which leads to a sensitive determination of NO2−. The oxidation current of NO2− is linear to its concentration in the range of 1.0–100 000.0 μM and the detection limit is found to be 0.2 μM with a sensitivity 104.6 μA mM−1 cm−2. The observed analytical parameters such as wide linear range, low detection limit, high sensitivity and short response time are comparable or superior to other previously reported NO2− sensors. Kinetic parameters are evaluated using cyclic voltammetry and chronoamperometry. Finally it is demonstrated that the proposed sensor can be used for the selective determination of NO2− present in water samples and the results are quite promising.

Synthesis and Characterization of Graft Copolymer of Dextran and 2-Acrylamido-2-methylpropane Sulphonic Acid

A novel biodegradable graft copolymer of dextran (Dx) and 2-acrylamido-2-methyl-1-propane sulphonic acid (AMPS) was synthesized by grafting poly-AMPS chains onto dextran backbone by free radical polymerization using ceric ammonium nitrate (CAN) as an initiator. Different amounts of AMPS were used to synthesize four different grades of graft copolymers with different side chain lengths. These grafted polymers were characterized by elemental analysis, FTIR, 1HNMR, rheological technique, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffractometry (XRD). They exhibited efficient flocculation performance in kaolin suspension.

Trimerization of β-cyclodextrin through the click reaction.

Triprop-2-ynyl benzene-1,3,5-tricarboxylate (A) is synthesized by the reaction of 1,3,5-benzenetricarbonyl trichloride with propargyl alcohol and (A) is clicked with mono-6-deoxy-6-azido-β-cyclodextrin (N3-β-CD) in the presence of copper(I) bromide catalyst. N3-β-CD has been prepared from β-cyclodextrin (β-CD) on treatment with toluenesulfonyl chloride (TsCl) and then with sodium azide (NaN3) in two consecutive steps. Further trimer of β-CD is characterized by (1)H NMR and FTIR studies. Solubility of β-cyclodextrin (β-CD) in water can be increased by increasing the number of alcoholic OH functionalities and hydrophobic cavities in a molecule by the trimerization of β-CD.

Dendrimer like star polymer based on β-cyclodextrin with ABC type miktoarms

The present article reports the synthesis and self aggregation study of a novel dendrimer like star polymer based on β-cyclodextrin (β-CD), in which the primary alcoholic arms of β-CD have been linked to ABC type miktoarm star polymers. Initially, 6-heptaazido-6-deoxy-β-cyclodextrin (7N3-β-CD) has been clicked with alkyne terminated poly(methyl methacrylate) (alkynyl-PMMA-Br), which has been synthesized through atom transfer radical polymerization technique. Subsequently, azidation has been done in order to prepare β-CD(PMMA-N3)7. Parallelly, an amphiphilic block copolymer (alkynyl-PDLL-b-PNIPAAm), having an alkyne end group, has been synthesized by employing a mikto functional initiator having alcohol, xanthate and alkyne functionalities, in ring opening polymerization (ROP) of D,L-lactide (DLL) from –OH end, and reversible addition-fragmentation chain-transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm) from xanthate end. Then, the desired star polymer has been synthesized by the click reaction between β-CD(PMMA-N3)7 and alkynyl-PDLL-b-PNIPAAm. The polymers have been characterized by 1H NMR, and gel permeation chromatography. Self aggregation of the star polymers has been investigated by 1H NMR and fluorescence spectroscopy. Size of the micelles formed has been analyzed by dynamic light scattering and transmission electron microscopic techniques.

Synthesis, characterization and application of novel cationic and amphoteric flocculants based on amylopectin.

The synthesis of novel cationic flocculants based on amylopectin (AP), acrylamide (AM) and (3-acrylamidopropyl) trimethylammonium chloride (ATMAC) were done by free radical polymerization using ammonium persulphate (APS) as an initiator. Three different grades of novel cationic flocculants (AP-g-C 1 to AP-g-C 3) were synthesized by varying the proportion of acrylamide and (3-acrylamidopropyl) trimethylammonium chloride monomers. Through the hydrolysis of these flocculants, in presence of NaOH, three different grades of amphoteric polymers (AP-AT-C 1 to AP-AT-C 3) were synthesized. The synthesized polymers were characterized by various methods, namely, infrared spectroscopy, NMR spectroscopy, thermal analysis, viscosity measurement, scanning electron microscopy and X-ray diffractometry. The flocculation performance of AP-g-C and AP-AT-C were studied in kaolin suspension using jar test and settling test methods at neutral pH. Dye (Methylene blue) removal tests were performed using polymer beads and analysed by UV-vis spectroscopy.

Synthesis, characterization and cyclic voltammetric study of copper(II) and nickel(II) polymer chelates.

Graft copolymers based on dextran (Dx) and 2-acrylamido-2-methyl-1-propane sulphonic acid (AMPS) were synthesized by free radical initiated solution polymerization technique using ceric ammonium nitrate as initiator. These graft copolymers were used to prepare Cu(II) and Ni(II) chelates by reactions with Cu(II) and Ni(II) metal ions respectively. Graft copolymer and metal chelates were characterized by elemental analysis, intrinsic viscosity, FT-IR, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD). Elemental analysis, intrinsic viscosity and FT-IR studies revealed the incorporation of metal ions to form metal chelates. SEM studies showed the change in morphology due to metal incorporation. From AFM studies it was observed that there was increase in Root mean square (RMS) roughness values in case of metal complexes. Metal chelates were observed to be thermally more stable than graft copolymer from TGA. UV-vis spectroscopy study revealed increase in absorbance values and cyclic voltammetric (CV) studies showed more than tenfold increase in redox current due to formation of Cu(II) and Ni(II) metal chelates. The binding constants of each complex determined by using UV-visible spectroscopy revealed that Cu(II) has more binding ability than Ni(II).

Dendritic star polymer of polyacrylamide based on a β-cyclodextrin trimer: a flocculant and drug vehicle

The present investigation involves a water treatment study of polyacrylamide (PAM), and star polymers of polyacrylamide based on β-cyclodextrin (β-CD-PAM) and β-cyclodextrin trimer (3-β-CD-PAM). Studies on the drug loading and in vitro drug release of diclofenac sodium (DS) and doxorubicin (DOX), separately, using β-CD-PAM and 3-β-CD-PAM have also been conducted. β-CD-PAM and 3-β-CD-PAM, synthesized by grafting PAM onto β-cyclodextrin (β-CD) and β-cyclodextrin trimer (3-β-CD), respectively, have been employed as flocculants for kaolin suspensions and in the removal of methylene blue (MB) dye. In flocculation and dye removal tests 3-β-CD-PAM has exhibited the better performance among the three polymers. β-CD-PAM and 3-β-CD-PAM have been loaded with DS to prepare drug loaded polymers viz. β-CD-PAM-DS and 3-β-CD-PAM-DS respectively, and with DOX to prepare β-CD-PAM-DOX and 3-β-CD-PAM-DOX respectively. The loading of the drugs has been examined by UV analysis, dynamic light scattering and atomic force microscopy (AFM) techniques. Furthermore, the drug loaded polymers have been employed in an in vitro drug release study in phosphate buffer solution (PBS) at 37 ± 0.5 °C and pH 7.4.

Solution and microwave assisted synthesis of β-Cyclodextrin grafted polyacrylamide: Water treatment and In-vitro drug release study

The present article reports the application of β-cyclodextrin grafted polyacrylamides synthesized through solution and microwave assisted polymerization techniques as flocculants and then the employment of partially hydrolyzed products of best grade of each technique in-vitro drug release study of diclofenac sodium. Five different grades of β-cyclodextrin grafted polyacrylamides by each of solution and microwave assisted polymerization techniques have been synthesized, by varying the monomer concentration. The synthesized polymers have been well characterized and their flocculation performances have been evaluated in kaolin suspension through settling and jar test methods Then the best performing grades of both the techniques have been partially hydrolyzed to prepare three different grades each technique by varying the concentration aqueous NaOH solution. Flocculation efficiencies of these polymers have been investigated in kaolin suspension. Thus best grades of partially hydrolyzed grafted polymers of each technique have been chosen for further study of drug delivery. In-vitro drug release study has been done using diclofenac sodium loaded microbeads prepared by ionic gelation method with two partially hydrolyzed grafted polymers (one from each technique) in phosphate buffer solution (PBS) at 37±0.5 ○C and pH 7.4. The drug load and release have been analyzed by UV-vis spectroscopy.