Shahid Ali Khan

Antibacterial nanocomposites based on chitosan/Co-MCM as a selective and efficient adsorbent for organic dyes

Chitosan/cobalt-silica (Co-MCM) nanocomposites were synthesized for the purification of effluent by adding 5, 15 and 25mL of Co-MCM solution to the aqueous chitosan solution for the formation of chitosan/Co-MCM-5, chitosan/Co-MCM-15 and chitosan/Co-MCM-25, respectively. These different nanocomposites were characterized by FESEM, EDS, X-ray crystallography and IR spectrophotometer and employed for the adsorption of various dyes (methyl orange, acridine orange, indigo carmine and congo red). The respective nanocomposites showed good adsorption toward methyl orange, indigo carmine and congo red while all nanocomposites were inactive for acridine orange dye. Among the nanocomposites, chitosan/Co-MCM-15 showed the highest adsorption performance which might be due to ideal dispersion of Co-MCM inside the chitosan polymer host. Chitosan/Co-MCM-15 exhibited high adsorption for methyl orange as compared to indigo carmine. We have further checked the biological potential of chitosan/Co-MCM nanocomposites against gram positive and negative bacteria as well as multi drug resistant bacteria. The results favor the strongest bioactivities of chitosan/Co-MCM-15 against various gram positive and gram negative bacteria as well as multi drug resistant bacteria, which further suggest the ideal dispersion of Co-MCM in chitosan polymer host and is responsible for the improvement of both adsorption as well as biological performance.

Recent Development of Chitosan Nanocomposites for Environmental Applications.

BACKGROUND Potable, clean and safe water is the basic need for all human beings. Major portion of the earth is occupied by water, however, this is contaminated by rapid industrialization, improper sewage and natural calamities and man-made activates, which produce several water-borne and fetal diseases. In this review we presented some recent patent for environmental remediation. METHODS Various technologies have been developed for the treatment of waste water consist of chemical, membrane, filtration, sedimentation, chlorination, disinfection, electrodialysis, electrolysis, reverse osmosis and adsorption. Among these entire phenomenons, adsorption was the most efficient method for wastewater treatment, because it is a quick and cheap technology which signifies extensive practical applications. Adsorption phenomenon has been tactfully used for the removal of biological waste as well as soluble and insoluble material with a removal efficacy of 90-99%. RESULTS Clean water supply is limited to human beings. The people in the developing countries have less or no access to the clean and potable water. The shortage of potable water resources and long term safe water deficiencies are some of the leading problems worldwide. In this review, we have explained in the detail adsorption phenomena of chitosan, pharmaceutical importance and other applications. It is worth to say that adsorption technologies using chitosan and its derivative is one of the quickest and cost effective methods for the wastewater treatment. The review comprises of ninety eight references. This review also covers various patents vis-a-vis the role of chitosan-nanocomposite in environmental application for wastewater treatment. CONCLUSION Chitosan is a pseudo-neutral cationic polymer which is formed by the de-acetylation of chitin polymer. Various patent on chitosan and chitosan-nanocomposite were taken into account related to wastewater purification. We have found that chitosan and chitosan-nanocomposite are used for the removal of viruses, bacteria, cryptosporidium oocysts and giardia cysts, soluble and insoluble organic pollutants, poly aromatic hydrocarbons and heavy metals from wastewater. In this study, we also found that chitosan and chitosan-nanocomposite are selected for the removal of transition metals.

Toward the design of Zn–Al and Zn–Cr LDH wrapped in activated carbon for the solar assisted de-coloration of organic dyes

Designing of materials for the extraction of organic toxins are the critical factors for environmental remediation. In the present study, a layered double hydroxide (LDH) of the binary compounds Zn–Al and Zn–Cr wrapped in activated carbon were synthesized through the co-precipitation method. These catalysts were characterized by FESEM, XRD, EDS, XPS, FTIR, PL and DRS. These catalyst were evaluated for the adsorption-assisted photodegradation of acridine orange (AO), malachite green (MG), crystal violet (CV), congo red (CR) and methyl orange (MO) dyes. The adsorption-assisted photodegradation was studied in four different parameters: dark, visible, ultraviolet and sunlight exposure conditions. Under various light effects, AO was selectively removed and Zn–Al/C-LDH showed stronger activity then Zn–Cr/C-LDH. Both catalysts showed approximately 90% removal efficiency of AO in sunlight. PL and DRS data showed prominent bands for the respective catalysts in the visible region. Zn–Al/C-LDH and Zn–Cr/C-LDH showed band gaps of 2.97 eV and 2.91 eV, respectively. Zn–Al/C-LDH showed very good recyclability and durability until the fourth cycle and still remained active after the fourth cycle as compared to Zn–Cr/C-LDH, which also showed good recyclability until the fourth cycle, but remained inactive after the fourth cycle. It was also observed that the specific light intensity and the substrate-catalyst specificity required equal consideration during the development of these new catalysts.

Core–shell cobalt oxide mesoporous silica based efficient electro-catalyst for oxygen evolution

In the last few decades, renewable resources received considerable attention for the production of hydrogen. Herein, we present oxygen evolution from water using cobalt oxide based nanomaterials (Co3O4, Co3O4@SiO2, Co3O4/TiO2, Co3O4/Fe2O3 and ZnO@SiO2). These nanomaterials were grown in a controlled size and were characterized by various spectroscopic techniques. The Co3O4, Co3O4@SiO2, Co3O4/TiO2, Co3O4/Fe2O3, and ZnO@SiO2 were screened for their electro-catalytic properties towards H2O oxidation. All cobalt oxide based nanomaterials showed good oxygen evolution activity and high stability in alkaline conditions. However, Co3O4@SiO2 showed a higher current density at lower overpotentials and a lower Tafel slope (107.7 mV dec−1) as compared to Co3O4/TiO2, Co3O4/Fe2O3, ZnO@SiO2, and Co3O4. At 1.0 V (overpotential 735 V versus Ag/AgCl), Co3O4@SiO2 supplied a current density of 63.0 mA cm−2 in 0.3 M KOH solution. This indicated a superior electrocatalytic performance then the other electrocatalyst. The excellent electrocatalytic performance of Co3O4@SiO2 might be due to certain structural features, which elevate its electrical conductivity, its oxidizing aptitude, and the affinity between OH− ions and the Co3O4@SiO2 surface and ultimately enhance smooth mass transports, which give superior oxygen evolution activity to Co3O4@SiO2.

Layered double hydroxide of Cd-Al/C for the Mineralization and De-coloration of Dyes in Solar and Visible Light Exposure

Cd-Al/C layered double hydroxide (Cd-Al/C-LDH) and Cd-Sb/C nanocatalyst are reported here for the de-coloration and mineralization of organic dyes. These catalysts were largely characterized by FESEM, EDS, XRD, FTIR, XPS, PL and DRS. The diffuse reflectance data showed a band gap at 2.92 and 2.983 eV for Cd-Al/C-LDH and Cd-Sb/C respectively. The band gap suggested that both catalysts work well in visible range. The photoluminescence spectra indicated a peak at 623 nm for both the catalysts which further support the effectiveness of the respective catalyst in visible range. Both catalysts also showed good recyclability and durability till 4th cycle. Five dyes, acridine orange (AO), malachite green (MG), crystal violet (CV), congo red (CR) and methyl orange (MO) were used in this experiment. Various parameters of different light intensity such as visible, ultraviolet, sunlight and dark condition are observed for the de-coloration of these dyes. The de-coloration phenomenon was proceeded through adsorption assisted phot-degradation. The low cost, abundant nature, good recyclability and better dye removal efficiency make these catalysts suitable candidates for the de-coloration and mineralization of organic dyes.

Anti-bacterial PES-cellulose composite spheres: dual character toward extraction and catalytic reduction of nitrophenol

Polyethersulfone (PES) based hybrid adsorbents were used for the removal of different phenols from aqueous solutions, which are categorized as major aquatic organic pollutants. In an effort to develop adsorbents with high surface area, PES, PES-silica (PES-SiO2), PES-carbon black (PES-CB) and PES-cellulose acetate-CB (PES-CA-CB) were prepared in the form of spheres and characterized by using FESEM, TEM, EDS, XRD, FTIR, and TGA. All the hybrid spheres were selective toward adsorption of 4-nitrophenol (4-NP) and among different hybrid spheres, PES-CA-CB spheres possessed high affinity and competent selectivity toward 4-NP. Therefore, different adsorption parameters have been optimized for PES-CA-CB spheres. The adsorption uptake of 4-NP onto PES-CA-CB spheres was highly dependent on pH and concentration of 4-NP. The highest adsorption was recognized at a pH around 6. The adsorption isotherm of 4-nitrophenol on PES-CA-CB obeyed the Langmuir model with an adsorption capacity of 128.79 mg g−1. Further, all hybrid spheres were utilized as supporting materials for Cu nanoparticles. Hybrid spheres supported Cu nanoparticles were applied for the catalytic reduction of 4-NP. Among all the hybrid spheres supported Cu nanoparticles, PES-CA-CB spheres supported Cu (Cu@PES-CA-CBspheres) nanoparticles exhibited high catalytic activity. Finally, Cu@PES-CA-CBspheres showed excellent antibacterial activity compared to all the hybrid spheres and hybrid spheres supporting Cu nanoparticles. All these adsorbents and catalysts can be prepared by a very simple method, are easily recovered by just removing the pellet from the solution and can be used several times.

Performance of cellulose acetate-ferric oxide nanocomposite supported metal catalysts toward the reduction of environmental pollutants

Water contamination by toxic compounds has become one of the most serious problems worldwide. Catalytic reduction using metal nanoparticles offer opportunities for environmental benefits. In this study, cellulose acetate-ferric oxide nanocomposite (CA/Fe2O3) was prepared and used as support for metal nanoparticles. After adsorption of Ag, Cu or Ni ions from aqueous solutions, metal ions associated with CA/Fe2O3 were treated with sodium borohydride to prepare Ag, Cu and Ni nanoparticles loaded CA/Fe2O3. The CA/Fe2O3 supported Ag, Cu or Ni nanoparticles was evaluated as a catalyst for pollutants degradation. Silver nanoparticles (Ag@CA/Fe2O3) exhibit remarkable decomposition for methyl orange dye and p-nitrophenol in short time. The rate constant for methyl orange and p-nitrophenol were 8.58×10-3 and 4.77×10-3s-1, respectively. Besides the good catalytic activities of Ag@CA/Fe2O3, the catalyst could be easily recovered from the reaction medium by pulling the catalyst after completion of the reduction reaction. The recovered catalyst can be recycled several times if their exposure time to air was minimal.

Antiproliferation and antibacterial effect of biosynthesized AgNps from leaves extract of Guiera senegalensis and its catalytic reduction on some persistent organic pollutants

The study concentrate on the biosynthesis of silver nanoparticles (AgNps) from the leaves extract of Guiera senegalensis with focus on its; antiproliferation effect on prostate (PC3), breast (MCF7) and liver (HepG2) cancer cell lines, antibacterial effect on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) and the degradation on 4-nitrophenol (4-NP) and congo red dye (CR). The synthesized AgNps were characterized by FTIR, TEM, FESEM, XRD and EDX analysis. The EDS spectrum revealed that the synthesized nanoparticles (Nps) were composed of 55.45% Ag atoms of spherical shape with approximately 50nm size, identified from TEM and FESEM data. The antiproliferation effect of the AgNps varies with cell lines in a concentration dependent manner. The result showed that the AgNps were more effective on PC3 (IC50 23.48μg/mL) than MCF7 (29.25μg/mL) and HepG2 (33.25μg/mL) by the virtue of their IC50 values. The AgNps were highly effective against E. coli and S. aureus by killing 99% colonies. The AgNps also shows a good catalytic reduction of the toxic organic pollutants in which only 3mg of the AgNps degraded 95% of both CR dye and 4-NP in 22 and 36min respectively. Therefore, the green synthesis of AgNps may have potential applications in pharmacology and industries for the treatment of cancers, bacterial infections and in degrading toxic organic pollutants in water.

2-[(2-Chloro­benzyl­idene)amino]-4,5,6,7-tetra­hydro-1-benzothio­phene-3-carbonitrile

In the title compound, C16H13ClN2S, the mean planes fitted through all non-H atoms of the heterocyclic five-membered and the benzene rings are oriented at a dihedral angle of 5.19 (7)°. In the crystal, a weak C—H⋯π interaction occurs, along with weak π–π interactions [cenroid–centroid distance = 3.7698 (11) Å].

2-[(3,5-Dimethyl-1-phenyl-1H-pyrazol-4-yl)methylidene]Indan-1,3-dione

In the title compound, C21H16N2O2, the five-membered heterocyclic ring makes a dihedral angle of 47.06 (6)° with the attached benzene ring, whereas the indan-1,3-dione ring system and the benzene ring are oriented at a dihedral angle of 21.92 (7)°. In the crystal, inversion dimers linked by pairs of C—H⋯O hydrogen bonds generate R 2 2(22) loops. Aromatic π–π stacking interactions [centroid–centroid distances = 3.8325 (12)–3.8600 (12) Å] also occur.