Sujata Pramanik

Facile preparation of polyaniline nanofibers modified bentonite nanohybrid for gas sensor application

We report the preparation of polyaniline (PAni) nanofibers by in situ intercalative polymerization of anilinium salt absorbed onto the nanoclay layers and modification of bentonite to an efficient nanohybrid gas sensor. The nanohybrid exhibited stable dispersion in different organic solvents like tetrahydrofuran, dimethyl acetamide and dimethyl sulphoxide. The Fourier transform infrared (FTIR) spectroscopic analysis indicated the formation of the benzenoid-quinoid structure of PAni in the nanohybrid. The wide angle X-ray diffraction study confirmed the crystallinity of the PAni nanofibers and the increase of d-spacing of the clay gallery on formation of the nanohybrid. The formation of the PAni nanofibers within the porous nanoclay layer was confirmed by the field-emission scanning electron microscopy. The sensitivity of the nanohybrid-based gas sensor towards toxic gases viz., acetone, benzene, ethanol and toluene was investigated. The nanohybrid gas sensor exhibited a high sensitivity to acetone compared to benzene, ethanol and toluene using ruthenium electrode than the silver electrode. Therefore, the prepared nanohybrid has the potential to be used as a promising gas sensor for the detection of toxic gases.

Antimicrobial hyperbranched poly(ester amide)/polyaniline nanofiber modified montmorillonite nanocomposites.

There has been growing interest in the use of nanomaterials featuring potent of antimicrobial activity in the biomedical domain. It still remains a challenge for the researchers to develop an efficient nanocomposite possessing antimicrobial efficacy against broad spectrum microbes including bacteria, fungi as well as algal consortium, posing serious challenges for the human survival. In addressing the above problem, we report the fabrication of bio-based hyperbranched poly(ester amide) (HBPEA)/polyaniline nanofiber modified montmorillonite (MMT) nanocomposites by an ex-situ polymerization technique at varied weight percentages (1, 2.5, 5 wt.%) of the modified MMT (nanohybrid). The Fourier transform infrared spectroscopy confirmed the structural changes upon interaction of the nanohybrid with HBPEA. A probable mechanism is proposed for the formation of nanocomposites with partially exfoliated nanoplatelet structure, which was further confirmed from the high resolution transmission electron microscopic analyses. The prepared nanocomposites exhibited potent efficacy against gram positive bacteria like Bacillus subtilis and Staphylococcus aureus as compared to the gram negative ones like Pseudomonas aeruginosa and Escherichia coli. The nanocomposites showed significant antifungal activity against Aspergillus niger, Fusarium oxysporum and Coleotricum capcii and antialgal activity against algal consortium comprising of Chlorella, Hormidium and Cladophorella species. The formation of thermosetting nanocomposites resulted in the acceptable improvement of desired physico-chemical and mechanical properties including thermostability. Thus pronounced antimicrobial activity of the nanocomposites against a spectrum of bacterial and fungal strains as well as a consortium of algal species along with other desired performance vouched them as potent antimicrobial materials in the realm of health and biomedical industry.

Bio-based hyperbranched poly(ester amide)–MWCNT nanocomposites: multimodalities at the biointerface

There has been a growing interest in the use of nanomaterials featuring potent biocompatibility and biodegradability together with the added facet of antibacterial activity, particularly against drug-resistant bacterial species. Addressing these three features at the biointerface, we report the fabrication of multimodal bio-based hyperbranched poly(ester amide) (HBPEA)-microwave functionalized multiwalled carbon nanotube (f-MWCNT) nanocomposites by incorporation of various weight percentages (1, 2.5, and 5 wt%) of the f-MWCNTs into HBPEA by using an ex situ polymerization technique. Fourier transform infrared spectroscopy confirmed the structural changes upon interaction of the f-MWCNTs with HBPEA. The formation of thermosetting nanocomposites resulted in an acceptable improvement of the desired properties including their mechanical properties (∼170%), instrumental for providing mechanical integrity in cultured cells. The nanocomposite films were found to be biocompatible substrates for the in vitro adhesion and proliferation of peripheral blood mononuclear cells (PBMC) with enhanced cell viability correlating with the increase of the f-MWCNT content. The antibacterial results, monitored by a CFU count and the protein concentration, demonstrated that the prepared nanocomposites were more toxic towards Gram positive bacteria and Mycobacterium smegmatis than the Gram negative ones. The damage of bacterial cells upon interaction with the nanocomposites was validated by UV-visible spectroscopy and a SEM study. The antibacterial and biocompatibility studies suggested that these microporous nanocomposite films (3D interconnected porous structures with pore diameters of 5-105 μm and a porosity of 39.90%) possess concurrent long-term lethal activity against the bacterial cells and biocompatibility with PBMC. Thus, the prepared nanocomposites may find potential bio-medical applications, particularly as antimicrobial dressing materials for infected burn wounds.

Lycopene coupled ‘trifoliate’ polyaniline nanofibers as multi-functional biomaterial

Bio-conjugation seems to be an unparalleled avenue to tailor the shape-size-bioactivity accord of nanomaterials. In this backdrop, conjugation of tomato peel lycopene through the green chemistry tool of sonication, under statistically optimized parameters led to the morphological alteration of polyaniline (PAni) nanofiber from linear to biomimetic ‘runner’ morphology with trifoliate branching as observed under TEM. X-ray diffractogram was suggestive of alterations in the d-spacing and strain in the polymer backbone post lycopene binding. Post bio-conjugation, the semiconducting-behavior of the PAni nanofibers was retained although lycopene coupling resulted in a decrease in the formers conductivity. DMol3 was employed for the quantum molecular calculations of lycopene interacting with PAni (via non-covalent functionalization involving π–π stacking) and its solvation study. The contribution to HOMO came from the lycopene unit whereas the LUMO had contribution from the aromatic ring of PAni in the conjugated system. The bioactivity of the PAni nanofibers post bio-conjugation was attested by free radical scavenging and anti-lipid peroxidation of liver tissue homogenate. Epiflorescence microscopic imaging demonstrated the cytocompatibility with L929 normal cell line while the nuclear fragmentation and membrane blebbing of apoptotic HeLa cells vouched for the anticancer action of the conjugated system. Furthermore, the reported system exhibited a stimulatory effect on Cucumis sativus seed germination. Thus the study marshals in support of modulated morphology and desirable bio-action of nanoscaled biomaterials via bio-conjugation for advanced applications.

Polymer Nanocomposites for Adhesive, Coating, and Paint Applications

The chapter presents a comprehensive account on the flurry of research works engulfing the utility of clay- and C-based polymeric nanocomposites, both the synthetic and bio-based ones undergoing renaissance since the 1990s in the realm of adhesives, coatings, and paints. The chapter focuses on the technological innovations of the nanocomposites and the modulations in the factors affecting the same as a function of shape-size accord of nanomaterials mainly clay- and C-based nanomaterials. In essence, the different physico-mechanical properties and various types of nanocomposites are critically scrutinized to bring out their potentiality in the aforementioned domains. The recent demand for low-temperature, radiation-cured, and waterborne high-solid content coatings gaining commercial importance has been highlighted. The chapter also pens down the scientific endeavor made in the contemporary times to bridge up the gap between the laboratories and the laymen. The present appraisal also intends to provoke a debate in the concluding section on the different strategies for upscaling of the current technologies and their impact on the environment.