Amit Kumar Dutta

Municipal solid waste management in Kolkata, India - a review.

Kolkata is one of four metropolitan cities in India. With an area of 187.33sqkm and a population of about 8 million, it generates around 3,000td(-1) of municipal solid waste (MSW) at a rate of 450-500g per capita per day. With rapid urbanization as a result of planned and unplanned growth and industrialization, the problems associated with handling MSW have increased at an alarming rate over the past few years. No source segregation arrangement exists; there is only limited (60%) house-to-house collection; and 50-55% open vats are used in the present collection system. The operational efficiency of the Kolkata Municipal Corporation (KMC) transport system is about 50%, with a fleet composed of about 30-35% old vehicles. The majority (80%) of these, particularly the hired vehicles, are more than 20 years old. The newly added areas covered by KMC have even lower collection efficiencies, and only an informal recycling system exists. The waste collected has a low energy value (3,350-4,200kJkg(-1)) with high moisture and inert content. A 700td(-1) compost plant set up in 2000 has not been functioning effectively since 2003. Open dumping (without liners and without a leachate management facility) and the threat of groundwater pollution, as well as saturation of an existing landfill site (Dhapa) are the most pressing problems for the city today. KMC spends 70-75% of its total expenditures on collection of solid waste, 25-30% on transportation, and less than 5% on final disposal arrangements. The Kolkata Environmental Improvement Project, funded by the Asian Development Bank, is seen as only a partial solution to the problem. A detailed plan should emphasize segregation at the source, investment in disposal arrangements (including the use of liners and leachate collection), and an optimized transport arrangement, among improvements.

Enhanced photocatalytic activity of Eu-doped Bi2S3 nanoflowers for degradation of organic pollutants under visible light illumination

Europium (Eu)-doped Bi2S3 nanoparticles (NPs) with different Eu contents were successfully synthesized by solvothermal decomposition of the precursor complexes Bi(ACDA)3 and [Eu(ACDA)3·H2O] [ACDA = 2-aminocyclopentene-1-dithiocarboxylic acid] in ethylenediamine (EN). The precursors were characterized by usual techniques such as UV-vis and FT-IR spectroscopy, and CHN and TGA analyses. The prepared nanomaterials were characterized by XRD, EDX, SEM and TEM analyses. The XRD results demonstrate that the particles were highly crystallized. The TEM images ascertain the NPs to be of flower-like structure consisting of ultrathin nanoplates with an average diameter of 9–10 nm. Photocatalytic efficiency of the Eu-doped Bi2S3 NPs was evaluated by monitoring the degradation of methylene blue (MB) in aqueous solution under visible light. It was observed that the rate of photocatalytic degradation of MB increases with an increase in the amount of the dopant ion. In addition, the photocatalytic degradation of various toxic organic pollutants such as phenol, p-cresol, 4-chlorophenol, 4-tert-butylphenol, 2,5-dimethylphenol and 2,6-di-tert-butyl-p-cresol was carried out with doped NPs in visible light. Under identical conditions, the degradation rate of 4-chlorophenol is higher than the corresponding phenol, p-cresol and 4-tert-butylphenol. Finally, the mechanism of the degradation pathway for phenol and the substituted phenols is discussed.

A novel amperometric biosensor for hydrogen peroxide and glucose based on cuprous sulfide nanoplates

A facile, greener and template free route has been developed to produce cuprous sulfide (Cu2S) nanoplates (NPs) with average diameters of 70-150 nm, via one step solvothermal decomposition of a single-source precursor (SSP) Cu(ACDC)2 [ACDC = 2-aminocyclopentene-1-dithiocarboxylate] in the presence of ethylenediamine (EN) and triethylenetetramine (TETA) as structure orienting agents. The precursor complex and nanomaterials were thoroughly characterized by several common techniques and measurements, which give the composition and characteristics of the materials. Amperometric biosensors for hydrogen peroxide (H2O2) and glucose have been constructed by immobilizing the synthesized Cu2S NPs in glutaraldehyde on a glassy carbon (GC) electrode using a direct drop-coating method. The proposed sensor has displayed faster response, high and reproducible sensitivity (64.27 μA mM-1) with linear range of 10 μM to 3.75 mM, towards the electrochemical biosensing of H2O2 at -0.35 V (vs. Ag/AgCl). The sensor also showed high and reproducible sensitivity (61.67 μA mM-1) towards glucose determination with linear range of 10 μM to 3.1 mM. The anti-inference ability of electroactive molecules and favorable stability are some of the advantages of the proposed sensor. Finally, using the sensor we have determined the glucose concentration in a human blood serum sample. The results strongly demonstrate the usefulness of Cu2S NPs for biosensor design and other biological applications.

Assessment of vehicular pollution in Kolkata, India, using CALINE 4 model

CALINE 4 offers several advantages over other models and is chosen as the base model for the purpose of developing a modified line source model for the city of Kolkata. Carbon monoxide is chosen for the model because it is principally emitted from vehicular sources. Average date wise background concentration is developed with the available data in different seasons. It is observed that, under actual conditions at Beleghata and Taratala, shift 1 (6am–2pm) is better correlated than shift 2 (2pm–10pm) without considering canyon option. Results show slightly better correlation coefficient and a lower standard deviation using the available season-wise 8-h average background concentrations rather than the generated average date-wise background concentrations. From the results, correction factors are developed for the city. Validated results near the HUDCO crossing show that CALINE 4, with the correction factors, can be applied reasonably well (mean error 0.37) for the prediction of carbon monoxide (CO) of Kolkata. CALINE 4 predictions with correction factors have revealed that construction of a flyover connecting VIP Road to EM bypass will lead to lessening of CO. The CALINE 4 model with the suitable correction factors should serve as a guide for proper air quality management.

Synthesis of Ag2S quantum dots by a single-source precursor: an efficient electrode material for rapid detection of phenol

Phenol and its derivatives are highly important chemicals in a variety of industrial products. However, their presence in ppm concentrations is extremely toxic for the environment in general and aquatic life specifically. Herein, we report the synthesis of highly mono-dispersed Ag2S quantum dots (QDs) with an average diameter of 11 nm from a single-source precursor, aiming to employ them as electrode materials for the detection of phenol. The as-prepared Ag2S QDs are immobilized on a glassy carbon (GC) electrode, and the electrochemical sensing of phenol using the developed Ag2S QD/GC electrode is observed to be within a wide range (1 μM to 16 mM). As compared with conventional sensing approaches, the present technique shows a much lower detection limit (0.015 μM) and higher sensitivity (61.2 μA mM−1 cm−2) towards phenol. In addition, the Ag2S QD/GC electrode-based sensor also exhibits good stability, repeatability, reproducibility and anti-interference ability. Thus, the sensor presents a great advantage for sensitive, rapid and cost-effective detection and quantification of phenol, indicating a promising potential for practical sensing applications.

Morphological tuning of Eu2O2S nanoparticles, manifestation of peroxidase-like activity and glucose assay use

Eu2O2S nanoparticles have been synthesized by solvothermal decomposition of the precursor complex [NHEt3]+[Eu(acda)4]−, wherein acda− is the anion of 2-aminocyclopentene-1-dithiocarboxylic acid. Oleylamine alone or in combination with surface active agents, such as trioctylphosphine or oleic acid, at 280 °C produced nanoparticles of three different morphologies, namely, ultrathin nanoplates, nanospheres and short rods. The optical band energy of the nanoparticles has been found to be 4.57(8) eV. Eu2O2S particles exhibit strong photoluminescence at room temperature with a quantum yield of about 4% upon excitation at 285 nm. All three forms display peroxidase-like activity towards the oxidation of 3,3′,5,5′-tetramethylbenzidine in the presence of H2O2 and follow a Michaelis–Menten enzymatic pathway. The mechanistic investigation reveals that the Eu3+/Eu2+ redox couple plays a crucial role behind this catalytic process. Catalytic efficiency of the nanoparticles decreases in the order plates > spheres > rod-like particles. Based on peroxidase activity, selective detection and estimation of glucose in the presence of related carbohydrates has been carried out.

Highly active spherical amorphous MoS2: facile synthesis and application in photocatalytic degradation of rose bengal dye and hydrogenation of nitroarenes

Herein, we developed a facile method to prepare amorphous spherical MoS2 via a simple solvothermal decomposition of a precursor complex MoO2(acda)2 (Hacda = 2-aminocyclopentene-1-dithiocarboxylic acid) in the presence of triethylenetetramine (TETA) as a solvent at 200 °C in an inert atmosphere. The as-obtained product was characterized by X-ray diffraction analysis (XRD), electron diffraction X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and UV-vis spectroscopic techniques. The transmission electron microscopic study ascertains the amorphous particles to be of spherical structure. The amorphous MoS2 has shown photocatalytic activity for the degradation of rose bengal (RB) dye under visible light illumination. The kinetics of the decomposition process was also investigated and found to show the pseudo-first-order reaction kinetics with rate constants of 5.0 × 10−2 min−1. Furthermore, amorphous MoS2 was found to be highly effective in catalyzing the reduction of a series of nitroarenes to the corresponding anilines by an eco-friendly protocol.

Observation of enhanced photocurrent response in M–CuInS2 (M = Au, Ag) heteronanostructures: phase selective synthesis and application

We report controlled synthesis of CuInS2 in wurtzite and zinc blende phases by solution based thermal decomposition of dual precursors [In(acda)3] (acda = 2-aminocyclopentene-1-dithiocarboxylic acid) and [Cu(PPh3)2(acda)] (PPh3 = triphenylphosphine) in the presence of appropriate surface-active agents. Furthermore, the preparation of M–CuInS2 (M = Au and Ag) heteronanostructures on both the phases has been achieved successfully by hot injection of respective gold and silver precursor solutions into the reaction mixture. The characterization of both pure and hybrid nanostructures was carried out by X-ray diffraction (XRD), UV-vis spectroscopy, energy dispersive X-ray (EDX) study and transmission electron microscopy (TEM). A detailed photovoltaic study has been performed with both pure materials and the twin structures and their photocurrent and photoresponse behavior have been compared. The study reveals that upon loading Au and Ag, the material exhibits high photocurrent efficiency compared to pure CuInS2. An appreciable increase in the light to dark current density ratio confirms that these materials can be used in the fabrication of promising photovoltaic devices.

Structure, luminescence and antimicrobial properties of mononuclear silver(I) complexes of pyridine 2-carboxamide

AbstractTwo Ag(I) complexes, [Ag(HL)2]ClO4 (1) and [Ag(HL)2]NO3⋅H2O (2), where HL is pyridine 2–carboxamide, have been synthesized and characterized by various spectroscopic techniques. The X-ray crystal structural analyses indicate that both the complexes consist of slightly distorted square planar silver(I) ions and ligand-supported weak Ag ⋯⋅Ag metallophilic interactions. Both the complexes show photoluminescence in solid state and acetonitrile solution at room temperature. Antimicrobial studies have been performed with these silver(I) complexes against various gram + ve, gram −ve bacterial and fungal species. Graphical AbstractSquare planar silver(I) complexes, [Ag(HL)2]ClO4 (1) and [Ag(HL)2]NO3·H2O (2), where HL is pyridine 2–carboxamide, exhibit room temperature photoluminescence and excellent ntimicrobial activity.