Sushanta Debnath

Development of a polyaniline-lignocellulose composite for optimal adsorption of Congo red

A polyaniline lignocellulose composite (PLC) was synthesized and used in the removal of Congo red (CR) from aqueous solution. The adsorption process showed good fits to both the pseudo-second-order and pseudo-first-order models and the Redlich Peterson isotherm. Boundary layer diffusion was the rate-limiting step. The adsorption was spontaneous and endothermic. The combined effect of pH and initial dye concentration was antagonistic; the combined effect of initial dye concentration and temperature was synergistic, while the combined effect of pH and temperature was reciprocal. The maximum CR adsorption capacity of PLC was evaluated as 1672.5 mg g(-1). The optimal removal was calculated as 99.85% at pH 4.29, initial dye concentration of 28.5 mg L(-1) and adsorbent dosage of 0.69 g L(-1). The predicted removal capacity showed a good correlation to the experimental results. PLC has demonstrated a superior adsorption capacity to many other adsorbents reported and could be used as an efficient adsorbent for CR removal from industrial wastewater.

Rapid and efficient removal of fluoride ions from aqueous solution using a polypyrrole coated hydrous tin oxide nanocomposite.

Polypyrrole/hydrous tin oxide nanocomposites (PPy/HSnO NC 1, 2, 3, 4 and 5) were synthesized through encapsulating HSnO by the PPy via an in situ polymerization for fluoride removal. The optimized adsorbent i.e. PPy/HSnO NC 3 was characterized using FE-SEM, HR-TEM, ATR-FTIR, XRD, BET, TGA and zeta sizer. Microscopic images revealed the encapsulation of HSnO by precipitating PPy during polymerization. The FTIR and XRD studies confirmed the presence of both constituents. The BET surface area and pHpzc of the adsorbent were estimated to be 65.758m(2)/g and 7.6, respectively. The fluoride adsorption followed pseudo-second-order model and was commendably rapid. The monolayer adsorption capacity was found to be 26.16-28.99mg/g at pH 6.5±0.1. The thermodynamic parameters indicated the sorption of F(-) was spontaneous, endothermic and that physisorption occurred. The calculated activation energy (Ea∼20.05kJ/mol) provided further evidence of a physisorption mechanism. Moreover, the adsorbent performed very well over a considerably wide pH range of 3.5-8.5 and in the presence of other co-existing ions. The regeneration of the F(-) laden PPy/HSnO NC 3 showed a high desorption efficiency of 95.81% up to 3 cycles. Ground water tested results also demonstrate the potential utility of the PPy/HSnO NC as an effective adsorbent.

Single stage batch adsorber design for efficient Eosin yellow removal by polyaniline coated ligno-cellulose.

Polyaniline-coated lignin-based adsorbent (PLC) was synthesized and used for uptake of reactive dye eosin yellow (EY) from aqueous solution. The adsorption capability of the adsorbent was found to be more effective than the unmodified adsorbent (LC). In particular, the adsorption capability of the PLC was effective over a wider pH range. This could be owing to its higher point of zero charge, which is more favorable for the uptake of the anionic dye. Adsorption isotherm models suggested a monolayer adsorption was predominant. The mean free energy of adsorption (E(DR)) was found to have values between 8 and 16 kJ mol(-1) which suggests that an electrostatic mechanism of adsorption predominated over other underlying mechanisms. The adsorption process was also found to be spontaneous, with increasing negative free energy values observed at higher temperatures. Chemisorption process was supported by the changes in enthalpy above 40 kJ mol(-1) and by the results of desorption studies. This new adsorbent was also reusable and regenerable over four successive adsorption-desorption cycles. The single stage adsorber design revealed that PLC can be applicable as an effective biosorbent for the treatment of industrial effluents containing EY dye.

A real time colorimetric ‘two in one’ kit for tracking ppb levels of uric acid and Hg2+ in live HeLa S3 cells and Hg2+ induced keto–enol tautomerism

A TBET based ‘turn-on’ fluorescent reagent with high Stokes shifts, exhibits selective and colorimetric detection of biologically important uric acid as well as toxic Hg2+. A new Hg2+ induced keto–enol tautomerism phenomenon associated with a solvatochromic effect was reported. The sensor has proved its real time application as an accurate ‘two in one’ kit for tracking uric acid and Hg2+ in live HeLa cells via a fluorescence bio-imaging technique.

Photoinduced Dynamics and Toxicity of a Cancer Drug in Proximity of Inorganic Nanoparticles under Visible Light.

Drug sensitization with various inorganic nanoparticles (NPs) has proved to be a promising and an emergent concept in the field of nanomedicine. Rose bengal (RB), a notable photosensitizer, triggers the formation of reactive oxygen species under green-light irradiation, and consequently, it induces cytotoxicity and cell death. In the present study, the effect of photoinduced dynamics of RB upon complexation with semiconductor zinc oxide NPs is explored. To accomplish this, we successfully synthesized nanohybrids of RB with ZnO NPs with a particle size of 24 nm and optically characterized them. The uniform size and integrity of the particles were confirmed by high-resolution transmission electron microscopy. UV/Vis absorption and steady-state fluorescence studies reveal the formation of the nanohybrids. ultrafast picosecond-resolved fluorescence studies of RB-ZnO nanohybrids demonstrate an efficient electron transfer from the photoexcited drug to the semiconductor NPs. Picosecond-resolved Förster resonance energy transfer from ZnO NPs to RB unravel the proximity of the drug to the semiconductor at the molecular level. The photoinduced ROS formation was monitored using a dichlorofluorescin oxidation assay, which is a conventional oxidative stress indicator. It is observed that the ROS generation under green light illumination is greater at low concentrations of RB-ZnO nanohybrids compared with free RB. Substantial photodynamic activity of the nanohybrids in bacterial and fungal cell lines validated the in vitro toxicity results. Furthermore, the cytotoxic effect of the nanohybrids in HeLa cells, which was monitored by MTT assay, is also noteworthy.

Hydrous TiO2@polypyrrole hybrid nanocomposite as an efficient selective scavenger for the defluoridation of drinking water

An adsorptive process for the defluoridation of drinking water was performed using a hybrid nanocomposite of hydrous titanium oxide@polypyrrole (HTiO2@PPy), as a scavenger. The adsorbent was successfully fabricated via facile in situ chemical oxidative polymerization of pyrrole monomer in aqueous media in which HTiO2 nanoparticles were suspended. The developed adsorbent was characterized using various spectro-analytical techniques viz. BET, FTIR, FE-SEM, STEM, EDX, TGA and ZETA SIZER. Relatively high BET surface area (98.17 m2 g−1) and pHpzc (∼8.4) values were obtained for HTiO2@PPy. The synergistic effect of both the counterparts (PPy and HTiO2) of the nanocomposite rapidly enhanced the F− adsorption process. A noteworthy rapid fluoride uptake best described by the pseudo-second-order kinetic model was observed (equilibrium attainment within 5–30 min). The Langmuir model best described the isotherm data with a maximum adsorption capacity of 31.93 mg g−1 at 25 °C and pH 6.5 (±0.2). Thermodynamic and activation parameters provided evidence of the spontaneous, endothermic and physical nature of the adsorption process. The selectivity of HTiO2@PPy for F− sorption was significant in the presence of Cl−, NO3−, HCO3−, SO42− and PO43− co-existing ions and noteworthy reusability for up to three regeneration cycles was achieved. Electrostatic interactions and ion-exchange were proposed to be the possible underlying mechanisms for the adsorption of F− by HTiO2@PPy nanocomposite. Thus, HTiO2@PPy is anticipated to serve as an efficient scavenger for the defluoridation of drinking water.

Hydrous ZrO2 decorated polyaniline nanofibres: Synthesis, characterization and application as an efficient adsorbent for water defluoridation

A new hybrid material comprising hydrous zirconium oxide (HZrO2) supported onto polyaniline (PANI) nanofibres (HZrO2@PANI NFs) was prepared via the precipitation of HZrO2 onto as-synthesized PANI NFs and tested for its defluoridation capabilities. The developed adsorbent (HZrO2@PANI NFs) was fully characterized by FTIR, BET, XRD, SEM-EDX, TEM-(S)TEM, XPS, and zeta potential measurements. HZrO2@PANI NFs achieved 2-fold BET surface area ∼86.64 m2/gas compared to PANI NFs ∼44.72 m2/g, implying that the incorporation of HZrO2 onto the PANI nanofibres enhanced the available surface area for effective fluoride adsorption. Moreover, HZrO2@PANI NFs was found to be effective over a wide pH range (3-9) as designated by its high pHpzc ∼9.8. The adsorption kinetics obeyed the pseudo-second-order model well with equilibrium attainment in 30min. Adsorption isotherm was best described by the Langmuir model and the maximum adsorption capacities obtained were 83.23 and 28.77mg/g at pH 3 and 6.5, respectively, which is superior to most ZrO2 based adsorbents reported in the literature and better than that of native PANI. Furthermore, the developed adsorbent manifested quite a selective fluoride uptake at pH 3 as compared to pH 6.5±0.1 wherein significant chemical affinity competition was presented by phosphate ions followed by bicarbonate and sulfate. The recyclability of HZrO2@PANI NFs for four cycles and its applicability to fluoride spiked ground water has also been demonstrated. The adsorption mechanism was interpreted with the help of FTIR, XPS and Zeta potential analysis and the results revealed the involvement of both anion exchange and electrostatic attraction in the adsorption of F- ions. Thus, a new efficient adsorbent with reasonably high adsorption capacity and superior pH tolerance has been developed for fluoride removal.

Study of Gallium Oxide Nanoparticles Conjugated with β-Cyclodextrin: An Application To Combat Cancer

Bioactive nanomaterials, namely, gallium oxyhydroxide GaO(OH), also surface-conjugated GaO(OH) with a giant sugar molecule β-cyclodextrin (CD), have been prepared through a simple wet chemical route such that the same could be suitably used in biomedical diagnostics as well as therapeutic applications. Several physical methods were used for their characterization: powder X-ray diffraction pattern of GaO(OH) NPs for their grain size determination, optical spectroscopic absorption (UV-vis and FT-IR), and fluorescence properties of these NPs to ascertain surface conjugation and also their wide band-gap properties. Besides these, morphological properties of these NPs were studied by transmission electron microscopic (TEM) investigation, justifying the elemental constitution through energy dispersive X-ray analysis (EDX). Further, biological cellular uptake of these nanoparticles have been demonstrated on cancerous HeLa cells and reported with total fetal effect after 72 h, with CD templated GaO(OH) nanoparticles, a fact that has not been reported so far.

l-Cysteine-Conjugated Ruthenium Hydrous Oxide Nanomaterials with Anticancer Active Application

Bioactive nanomaterials, namely: ruthenium hydrous oxide (or ruthenium oxy-hydroxide), RuOx(OH)y and also a surface-conjugated novel material of the same within the template of an amino acid molecule, l-cysteine, have been studied. These compounds have been prepared through a simple wet chemical route, under physiological conditions, such that they could be suitably used in anticancer applications. Several physical methods were used for the nanomaterial characterization, e.g.: thermal analysis of the as prepared ruthenium hydrous oxide by differential scanning calorimetry (DSC) followed by thermal gravimetric analysis (TGA). This confirms that the material is a precursor for anhydrous nanocrystalline ruthenium oxide (RuO2), as is affirmed by powder X-ray diffraction pattern. Also, optical spectroscopic absorption (UV-vis and FT-IR) study of these nanoparticles (NPs) to ascertain their surface conjugation with l-cysteine have been performed. Besides these, surface morphology of the NPs were studied by field emission scanning electron microscopy (FE-SEM) along with their elemental purity check through energy dispersive X-ray analysis (EDX). Their surface chemical microenvironments were examined by X-ray photo electron spectroscopy (XPS). The hydrodynamic size of the prepared NPs were measured through dynamic light scattering (DLS) studies. Further, biological consequences of these NPs on cancerous HeLa cells and their cytotoxicity effects have been reported with MTT assay, such an application has not been reported so far.

Ultrasound assisted adsorptive removal of hazardous dye Safranin O from aqueous solution using crosslinked graphene oxide-chitosan (GO CH) composite and optimization by response surface methodology (RSM) approach

Chitosan (CH) was crosslinked with graphene oxide (GO) by combining solutions of CH and GO. Characterisations by ATR-FTIR, FE-SEM and XRD confirmed the formation of the GOCH composite. Removal of the dye Safranin Orange (SO) by ultrasonic adsorption from aqueous solution was tested by the composite. The removal of the cationic dye was more favourable at pH values greater than 5.2 and the optimum pH was found to be 6.5. The adsorption kinetics followed a pseudo-first order model and the rate-limiting step was identified as boundary layer diffusion from the Intraparticle diffusion model. The sonication assisted adsorption kinetic data were compared with the non-sonicated one and it was found that sonication has a marked effect on the adsorption kinetics. The Redlich Peterson adsorption isotherm described the adsorption with more resemblance to the Langmuir Model than the Freundlich Model suggesting that monolayer adsorption predominated. From Response Surface Methodology it was noted that the combined effect of pH and initial concentration was antagonistic while that of sonication time was synergistic. The optimum parameters from the RSM model were found to be pH 6.82, initial SO concentration 425mgL-1 and sonication time 25min. This was in good agreement with the experimental results.