Separation and Purification Technology, May 1, 2016
Utilization of solar energy is an energy efficient process for dye wastewater treatment. Photocat... more Utilization of solar energy is an energy efficient process for dye wastewater treatment. Photocatalytic degradation of toxic azo dyes was carried out using modified semiconductors under direct sun light. Concerning this, the different wt% of CdS loaded Ag-ZnO catalysts were prepared by the simple precipitation-thermal decomposition method and used for degradation studies. Cadmium sulfide (CdS) is a kind of semiconductor with fine band gap of 2.4 eV, and its valence electron can be effortlessly evoked to conduction band under solar or visible light illuminations. Among the different CdS prepared catalysts, highly efficient 2 wt% of CdS loaded Ag-ZnO was characterized by different characterization techniques. Metal sulfide loading increases the absorbance of ZnO into the entire visible region. XPS reveals that the presence of metallic silver in the catalyst. The photocatalytic activity of 2 wt% CdS loaded Ag-ZnO was compared with single metal doped, undoped, and other commercial catalysts, especially Degussa P25, a standard bench mark photocatalyst. The photodegradation of RR 120, RO 4, and RY 84 had been analyzed in detail. Mineralization of these dyes has been confirmed by chemical oxygen demand (COD) measurements. A dual mechanism has been proposed for the higher efficiency of CdS-Ag-ZnO at neutral pH under solar light. Antiphotocorrosive study reveals that bare ZnO suffers more dissolution by photocorrosion than our prepared photocatalyst CdS-Ag-ZnO. This catalyst is found to be more stable and reusable.
Journal of Environmental Sciences-china, Jul 1, 2018
One of today's major challenges is to provide green materials for a cleaner environment. We 19 ha... more One of today's major challenges is to provide green materials for a cleaner environment. We 19 have conducted studies on carbon dioxide (CO 2) adsorption and conversion to valuable 20 products by an ecofriendly approach based in chitosan/graphene oxide (CSGO) nanocomposite 21 film. Rheological behavior indicates that the CSGO has a better solvation property than the 22 pure chitosan. An adsorption capacity of 1.0152 mmol CO 2 /g of CSGO nanocomposite at 23 4.6 bar was observed. The catalytic behavior of the CSGO nanocomposite in the presence of 24 tetra-n-butylammonium iodide (n-Bu 4 NI) as co-catalyst was evaluated for the cycloaddition of 25 CO 2 to epoxides, to give cyclic carbonates, in the absence of any solvent. These results strongly 26 suggest that the CSGO nanocomposite may open new vistas towards the development of 27 ecofriendly material for catalytic conversion and adsorption of CO 2 on industrial scale.
Higher CO2 adsorption capacity compared to pure chitosan and pure zeolite. Catalytic activity... more Higher CO2 adsorption capacity compared to pure chitosan and pure zeolite. Catalytic activity in chemical fixation of CO2.
Separation and Purification Technology, Aug 1, 2018
Abstract Although noble metals were used as dopants, the synthesized composite is an economically... more Abstract Although noble metals were used as dopants, the synthesized composite is an economically and environmentally friendly photocatalyst, based on very low concentrations (Au-1 wt% and Ag-5 wt%) of both metals and its reusability in degradation experiments. The bimetallic photocatalyst was characterized by different techniques. Photocatalytic activity of Ag loaded Au/ZnO was evaluated by irradiating the sample solution under solar light and taking Acid Red 18 (AR 18) as an organic dye. The photocatalytic trials confirmed that the Ag-Au/ZnO composite exhibited improved photocatalytic efficiency compared with Ag-ZnO, Au-ZnO, commercial ZnO, bare ZnO, TiO2-P25 and TiO2 (Aldrich) at pH 11 for the mineralization of Acid Red 18 dye. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photomineralization of AR 18 dye have been analyzed. Degradation intermediates were analyzed by GC–MS, and a degradation pathway was proposed. A mechanism is proposed for the degradation of AR 18 under solar light. Moreover, the Ag-Au/ZnO sample showed excellent stability after four photodegradation cycling runs. The antifungal activity of the prepared materials was tested against Aspergillus flavus, Aspergillus niger, Penicillim chryogenum, Trigoderma veride and Fusarium oxysporum and their antibacterial activity was tested against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, streptococcus pyogenes. All doped ZnOs have moderate to good activity compared with bare ZnO.
Journal of environmental chemical engineering, Aug 1, 2018
For a visible light active photocatalyst, the band alignment of coupled semiconductors is a key s... more For a visible light active photocatalyst, the band alignment of coupled semiconductors is a key step. In here, we present a semiconductor heterostructure obtained between TiO 2 and BiOI. Gelatin assisted g-TiO 2 /BiOI nanocomposites were prepared in a two step synthetic method. Tetrabutylammonium iodide (TBAI) was used as the iodide source for BiOI. The prepared materials have been characterized by XRD, FE-SEM, DRS and PL measurements. FE-SEM measurements confirmed the presence of sphere like TiO 2 particles embedded on the BiOI plates. BiOI loading increases the absorbance of g-TiO 2 into the entire visible region, and make these composites more photoactive under visible light. PL measurements confirm the suppression of electron-hole recombination in g-TiO 2 /BiOI samples. The prepared materials were used for the azo dye Acid Black 1 (AB 1) degradation under visible light, and it was found that BiOI loading effectively enhances the degradation ability of the TiO 2. The degradation mechanism was proposed based on the energy levels of TiO 2 and BiOI. The reusability of the g-TiO 2 / BiOI was studied.
An increasingly level of one of the important greenhouse gas, CO 2 , in the atmosphere from anthr... more An increasingly level of one of the important greenhouse gas, CO 2 , in the atmosphere from anthropogenic human activities has several adverse consequences and thus, chemical transformation of carbon dioxide into useful, renewable and environmentally friendly products is becoming an important research problem. In the present investigation, we have developed photocatalyst of graphene oxide modified with cobalt metallated aminoporphyrin (GO-Co-ATPP) for conversion of CO 2 to formic acid under visible light. The efficiency of nanohybrid photosynthetic conversion of formic acid from carbon-dioxide is 96.49 μmol for 2 h. We have used XRD, SEM, HR-TEM, AFM, thermogravimetric analysis, BET measurement to establish the structural and physical properties along with infrared spectroscopy and Raman spectroscopy for chemical properties of GO-Co-ATPP. The photocatalyst was significantly effective for NADH photoregeneration with cumulative 48.53% over time and photoelectrochemical measurement showed photocurrent properties. These results strongly suggest that the GO-Co-ATPP photocatalyst materials may open new vistas in conversion of CO 2 into useful and environmentally friendly products as well as energy applications.
Journal of Industrial and Engineering Chemistry, 2016
Environmental tribulations such as air and water pollution have provided the impetus for sustaine... more Environmental tribulations such as air and water pollution have provided the impetus for sustained fundamental and applied research in the area of environmental remediation. Photocatalytic degradation of organic pollutants by using nanostructured semiconductors offers great potential for the complete elimination of toxic chemicals. It has been established that the wide-bandgap semiconductor metal oxides (SMOs) such as TiO 2 and ZnO can degrade variety of organic dyes under UV light irradiation [1-3]. ZnO was reported to be more active than TiO 2 in several processes, including the treatment of toxic dyes, the photooxidation of phenol and the photocatalysed oxidation of 2-phenyl phenol [4-6]. Nevertheless, application of ZnO has been limited due to its photocorrosion and fast electron-hole recombination [7]. Suppression of the recombination of photogenerated electronhole pairs in the semiconductors is crucial for enhancing the efficiency of photocatalyst [8]. Doping or loading is a more useful way to get better charge separation in semiconductor systems and dopants such as Ag, Pt, Au, Mg and Fe enhance the charge separation by reducing the electron-hole recombination [9-13]. 27 Additionally coupling of semiconductor photocatalyst with 28 other semiconductor oxide, such as ZnO-Fe 2 O 3 [14], ZnO-WO 3 29 [15], ZnO-SnO 2 [16], AgBr-ZnO [4], Ag 2 S-ZnO [17], ZrS 2-ZnO [18] 30 and TiO 2-WO 3 [19], have been reported for efficiencies photo-31 degradation. Nanocrystalline SnO 2 is an n-type semiconductor 32 with a large band gap (3.6 eV). Due to its unique electrical and 33 optical properties and its chemical stability, SnO 2 is used in dye-34 sensitized solar cells [20], as a photocatalyst [21], in gas sensors 35 [22], etc. In the present study, the Sn loaded Au-ZnO photocatalyst 36 has been prepared through the precipitation-decomposition 37 method. The photocatalytic activity of Sn-Au-ZnO was studied 38 using Acid Red 18 as a model organic pollutant. 39 2. Experimental 40 2.1. Materials 41 The commercial Acid Red (18) dye, obtained (molecular 42 formula = C 20 H 11 N 2 Na 3 O 10 S 3 ; molecular weight 604.47 and dye 43 content 80%) from s.d. fine was used as such. Oxalic acid dihydrate 44 (99%) and zinc nitrate hexahydrate (99%) were obtained from 45 Himedia chemicals. SnCl 2 Á2H 2 O (S.d.fine chem.), TiO 2 (Aldrich) and 46 AuCl 3 (Sigma Aldrich) were used as received. A gift sample of 47 Degussa TiO 2-P25 was obtained from Evonik (Germany). It is a 48 80:20 mixture of anatase and rutile. It has a particle size of 30 nm 49 and BET surface area 50 m 2 g À1. AnalaR grade H 2 O 2 (30 w/w%), 50 KIO
Highlights CS/PVA/ZnO nanocomposites films were prepared via a greener approach. Physicochemi... more Highlights CS/PVA/ZnO nanocomposites films were prepared via a greener approach. Physicochemical properties of CS/PVA/ZnO nanocomposites films were investigated. CS/PVA/ZnO nanocomposites films were found to be thermally stable.
Journal of Thermal Analysis and Calorimetry, Jul 6, 2014
In this work, 3,5-bis(decyloxy)benzaldehyde, a precursor of long chain amphiphilic BODIPYs, was s... more In this work, 3,5-bis(decyloxy)benzaldehyde, a precursor of long chain amphiphilic BODIPYs, was synthesized and its polymorphic behavior was characterized by differential scanning calorimetry, polarized light thermo microscopy, infrared spectroscopy, and XRPD. From the combined use of these techniques, an interesting polymorphic behavior was observed, and four polymorphs were identified. The initial compound melts around room temperature, ca. 30°C, and several polymorphic forms of lower melting point are obtained by cooling the melt. A thermal program could be developed that allows obtaining each form independently. Keywords 3,5-bis(decyloxy)benzaldehyde Á Polymorphism Á Calorimetry Á Thermomicroscopy Experimental General Chemicals were obtained from Sigma-Aldrich Chemical Co. and used without further purification.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Acta Crystallographica Section E-structure Reports Online, May 21, 2008
This work was supported by Fundaçã o para a Ciê ncia e a Tecnologia (FCT) under project POCI/FIS/... more This work was supported by Fundaçã o para a Ciê ncia e a Tecnologia (FCT) under project POCI/FIS/57876/2004. Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT2705).
Tetrazoles are incredibly useful organic molecules with a wide range of applications from medicin... more Tetrazoles are incredibly useful organic molecules with a wide range of applications from medicinal chemistry as carboxylic acid isosteres to high energy density materials in space research. In an effort to develop an easy protocol for the synthesis of tetrazoles from nitriles, we used nano-Ag-TiO 2 as an efficient heterogeneous catalyst for the reaction of various nitriles and sodium azide to afford 5-substituted tetrazoles in excellent yields. By this method, a wide variety of aryl nitriles underwent [3 + 2] cycloaddition to afford tetrazoles in excellent yields. Further reaction of tetrazoles with ethylchloroacetate resulted in the formation of expected products, except for a bis-tetrazole, which underwent ring opening and subsequent reaction to afford an unusual product. The bis-tetrazole also formed an unusual polymeric sodium complex in aq. NaOH solution. X-ray crystallography revealed a distorted octahedral geometry for the complex, which forms a three-dimensional network of chains interlinked by bis-tetrazole moieties through a network of H-bonds.
TiO 2-P25 supported Pd/C (P25@Pd/C) composite was prepared by the solid state dispersion method. ... more TiO 2-P25 supported Pd/C (P25@Pd/C) composite was prepared by the solid state dispersion method. The prepared composite was characterized by XRD, Raman, PL, SEM and DRS measurements. The photocatalytic activity of the composite was tested towards Naphthol Blue Black (NBB) azo dye degradation under visible light. The photocatalytic activity of P25 was highly influenced by Pd/C. Almost complete degradation was achieved with P25@Pd/C in 120 min, and found to be more efficient when compared with pristine Degussa-P25. The composite was reused in four cycles without loss of activity. A mechanism was proposed for NBB degradation by P25@Pd/C composite under visible light.
Eriocephalus africanus, an Asteraceae plant endemic from South Africa and naturalized in the Medi... more Eriocephalus africanus, an Asteraceae plant endemic from South Africa and naturalized in the Mediterranean region, is commonly used in culinary and in traditional medicine. Despite the claimed health benefits attributed to this plant by the folk medicine, there is still a lack of scientific data to support this information. The present study describes the main phenolic composition of hydroethanolic extracts from stems and leaves of E. africanus, along with the assessment of their antioxidant properties. The identification of the phenolic constituents on the stems and leaves from E. africanus was carried out by LC-DAD-ESI/MS n , and the structures of the two major HPLC-eluted compounds were further confirmed by NMR analysis. Both extracts were rich in mono-and di-caffeoylquinic acids, which accounted for approximately 90% and 74% of total quantified phenolics, for the stems and leaves extracts, respectively. Besides, eriodictyol-hexuronide was found in considerable amounts in the extract from the leaves. One must highlight that these compounds together with other minor phenolic acids (namely other caffeoyl, ferulic and protocatechuic acid derivatives) and flavonoids (including hesperetin and eriodictyol) were herein identified for the first time. Furthermore, through three in vitro methods, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH Å) radical scavenging, ferric reducing antioxidant power and lipid peroxidation inhibition capacity assays,
Abstract We report on the straightforward synthesis, characterization and photovoltaic and light-... more Abstract We report on the straightforward synthesis, characterization and photovoltaic and light-emission applications of two series of BODIPY molecules with aryloxy or alkoxy groups bonded to the boron centre. The crystal structures of two of these new dyes are also presented. The BODIPYs have absorption features similar to those of the analogous boron-fluorinated BODIPYs used as starting materials. However, the fluorescence properties vary significantly with the nature of the aryloxy/alkoxy group. The photovoltaic performance in bulk heterojunction solar cells of the newly synthesized compounds does not, however, outperform that of the parent boron-fluorinated BODIPYs. The maximum power conversion efficiency was obtained with two non-fluorescent BODIPYs, reaching 0.9%, compared with 2.79% obtained for the cells based on the corresponding boron-fluorinated precursor. The fluorine replacement by aryloxy/alkoxy groups had instead a positive effect on the light-emitting properties of the compounds of one of the series, leading to higher maximum luminance (114 cd/m2) and efficiency (0.057 cd/A), compared to devices based on the corresponding boron-fluorinated dye (35 cd/m2 and 0.015 cd/A, respectively).
A new perlite supported Bismuth Chloride (BiCl 3) was used as an efficient heterogeneous catalyst... more A new perlite supported Bismuth Chloride (BiCl 3) was used as an efficient heterogeneous catalyst for the synthesis of heterocyclic compounds viz., quinoxalines and dihydropyrimidinones. Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, energy dispersive spectra, X-ray diffractometry, thermogravimetric analysis and Brunauer-Emmett-Teller surface area analytical techniques were employed to characterize the prepared catalyst. Initially, the catalytic activity of the prepared BiCl 3-Perlite was tested towards synthesis of simple quinoxaline derivatives at room temperature. The effect of solvent in the preparation of quinoxaline was also examined. The formed products were confirmed by their physical (melting point) and spectral data (FT-IR, 1 H and 13 C-NMR). In order to implement the activity of the BiCl 3-Perlite catalyst, a multicomponent reaction was adopted for synthesis of dihydropyrimidinones under solvent free conditions in a micro oven. The use of recyclable heterogeneous solid acid catalyst makes the reaction simple with minimum chemical waste, shorter reaction time, easy workup and products in good yield.
Special attention is directed to design and synthesize antimicrobial drug candidates by the compl... more Special attention is directed to design and synthesize antimicrobial drug candidates by the complexation of bioactive ligands with transition metals. In this pursuit a ligand with imidazole ring was synthesized and treated with Cu II , Co II and ,Ni II salts to afford the mononuclear metallic complexes IHC1, IHC2 and IHC3, respectively, being assigned the general formula [M(L) 2 ]. Physical and spectral characterization supported octahedral geometry for the complexes. Both the ligand and the synthesized metal complexes were evaluated for their antifungal activity against three different strains of Candida, by determining the minimum inhibitory concentrations and minimum fungicidal concentrations. The antifungal activity results showed that the target compounds display remarkable antifungal activity, with metal complex IHC1 showing the most potent antifungal activity. Mechanism of action of the ligand and metal complexes appears to originate from membrane disruption as revealed by confocal scanning laser microscopy.
The distinct nanocrystalline CS-ZnX (X = O or S) were achieved through Costus speciosus Koen leaf... more The distinct nanocrystalline CS-ZnX (X = O or S) were achieved through Costus speciosus Koen leaf extract assisted precipitation cum hydrothermal method. The formation of the materials was confirmed by different characterization techniques such as XRD, FT-IR, Raman, FE-SEM, EDS, HR-TEM, DRS, and PL measurements. The photocatalytic activity of the prepared materials was tested on the decolourization of Reactive Red 120 dye (RR 120) aqueous solution. The photocatalytic activity was further confirmed by Acid Black 1 (AB 1) dye degradation. The dye photocatalytic process was investigated by considering the influence of test parameters such as catalyst concentration and initial dye pH. Moreover, complete decolourization of 50 ppm of RR 120 solution was achieved within 180 min at pH 5. Both catalysts were found to be reusable. The photocatalytic degradation of RR 120 by CS-ZnX (X = O or S) were confirmed GC-MS analysis, and suitable degradation pathways were proposed based on molecular ion and fragmentation peak values. The probable degradation mechanism was proposed and discussed.
Pt nanoparticles were synthesized through bioreduction process Costus speciosus (CS) leaf extract... more Pt nanoparticles were synthesized through bioreduction process Costus speciosus (CS) leaf extract was used as reducing and capping agent CS-Pt-TiO 2 nanocomposites show good visible absorbance
Separation and Purification Technology, May 1, 2016
Utilization of solar energy is an energy efficient process for dye wastewater treatment. Photocat... more Utilization of solar energy is an energy efficient process for dye wastewater treatment. Photocatalytic degradation of toxic azo dyes was carried out using modified semiconductors under direct sun light. Concerning this, the different wt% of CdS loaded Ag-ZnO catalysts were prepared by the simple precipitation-thermal decomposition method and used for degradation studies. Cadmium sulfide (CdS) is a kind of semiconductor with fine band gap of 2.4 eV, and its valence electron can be effortlessly evoked to conduction band under solar or visible light illuminations. Among the different CdS prepared catalysts, highly efficient 2 wt% of CdS loaded Ag-ZnO was characterized by different characterization techniques. Metal sulfide loading increases the absorbance of ZnO into the entire visible region. XPS reveals that the presence of metallic silver in the catalyst. The photocatalytic activity of 2 wt% CdS loaded Ag-ZnO was compared with single metal doped, undoped, and other commercial catalysts, especially Degussa P25, a standard bench mark photocatalyst. The photodegradation of RR 120, RO 4, and RY 84 had been analyzed in detail. Mineralization of these dyes has been confirmed by chemical oxygen demand (COD) measurements. A dual mechanism has been proposed for the higher efficiency of CdS-Ag-ZnO at neutral pH under solar light. Antiphotocorrosive study reveals that bare ZnO suffers more dissolution by photocorrosion than our prepared photocatalyst CdS-Ag-ZnO. This catalyst is found to be more stable and reusable.
Journal of Environmental Sciences-china, Jul 1, 2018
One of today's major challenges is to provide green materials for a cleaner environment. We 19 ha... more One of today's major challenges is to provide green materials for a cleaner environment. We 19 have conducted studies on carbon dioxide (CO 2) adsorption and conversion to valuable 20 products by an ecofriendly approach based in chitosan/graphene oxide (CSGO) nanocomposite 21 film. Rheological behavior indicates that the CSGO has a better solvation property than the 22 pure chitosan. An adsorption capacity of 1.0152 mmol CO 2 /g of CSGO nanocomposite at 23 4.6 bar was observed. The catalytic behavior of the CSGO nanocomposite in the presence of 24 tetra-n-butylammonium iodide (n-Bu 4 NI) as co-catalyst was evaluated for the cycloaddition of 25 CO 2 to epoxides, to give cyclic carbonates, in the absence of any solvent. These results strongly 26 suggest that the CSGO nanocomposite may open new vistas towards the development of 27 ecofriendly material for catalytic conversion and adsorption of CO 2 on industrial scale.
Higher CO2 adsorption capacity compared to pure chitosan and pure zeolite. Catalytic activity... more Higher CO2 adsorption capacity compared to pure chitosan and pure zeolite. Catalytic activity in chemical fixation of CO2.
Separation and Purification Technology, Aug 1, 2018
Abstract Although noble metals were used as dopants, the synthesized composite is an economically... more Abstract Although noble metals were used as dopants, the synthesized composite is an economically and environmentally friendly photocatalyst, based on very low concentrations (Au-1 wt% and Ag-5 wt%) of both metals and its reusability in degradation experiments. The bimetallic photocatalyst was characterized by different techniques. Photocatalytic activity of Ag loaded Au/ZnO was evaluated by irradiating the sample solution under solar light and taking Acid Red 18 (AR 18) as an organic dye. The photocatalytic trials confirmed that the Ag-Au/ZnO composite exhibited improved photocatalytic efficiency compared with Ag-ZnO, Au-ZnO, commercial ZnO, bare ZnO, TiO2-P25 and TiO2 (Aldrich) at pH 11 for the mineralization of Acid Red 18 dye. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photomineralization of AR 18 dye have been analyzed. Degradation intermediates were analyzed by GC–MS, and a degradation pathway was proposed. A mechanism is proposed for the degradation of AR 18 under solar light. Moreover, the Ag-Au/ZnO sample showed excellent stability after four photodegradation cycling runs. The antifungal activity of the prepared materials was tested against Aspergillus flavus, Aspergillus niger, Penicillim chryogenum, Trigoderma veride and Fusarium oxysporum and their antibacterial activity was tested against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, streptococcus pyogenes. All doped ZnOs have moderate to good activity compared with bare ZnO.
Journal of environmental chemical engineering, Aug 1, 2018
For a visible light active photocatalyst, the band alignment of coupled semiconductors is a key s... more For a visible light active photocatalyst, the band alignment of coupled semiconductors is a key step. In here, we present a semiconductor heterostructure obtained between TiO 2 and BiOI. Gelatin assisted g-TiO 2 /BiOI nanocomposites were prepared in a two step synthetic method. Tetrabutylammonium iodide (TBAI) was used as the iodide source for BiOI. The prepared materials have been characterized by XRD, FE-SEM, DRS and PL measurements. FE-SEM measurements confirmed the presence of sphere like TiO 2 particles embedded on the BiOI plates. BiOI loading increases the absorbance of g-TiO 2 into the entire visible region, and make these composites more photoactive under visible light. PL measurements confirm the suppression of electron-hole recombination in g-TiO 2 /BiOI samples. The prepared materials were used for the azo dye Acid Black 1 (AB 1) degradation under visible light, and it was found that BiOI loading effectively enhances the degradation ability of the TiO 2. The degradation mechanism was proposed based on the energy levels of TiO 2 and BiOI. The reusability of the g-TiO 2 / BiOI was studied.
An increasingly level of one of the important greenhouse gas, CO 2 , in the atmosphere from anthr... more An increasingly level of one of the important greenhouse gas, CO 2 , in the atmosphere from anthropogenic human activities has several adverse consequences and thus, chemical transformation of carbon dioxide into useful, renewable and environmentally friendly products is becoming an important research problem. In the present investigation, we have developed photocatalyst of graphene oxide modified with cobalt metallated aminoporphyrin (GO-Co-ATPP) for conversion of CO 2 to formic acid under visible light. The efficiency of nanohybrid photosynthetic conversion of formic acid from carbon-dioxide is 96.49 μmol for 2 h. We have used XRD, SEM, HR-TEM, AFM, thermogravimetric analysis, BET measurement to establish the structural and physical properties along with infrared spectroscopy and Raman spectroscopy for chemical properties of GO-Co-ATPP. The photocatalyst was significantly effective for NADH photoregeneration with cumulative 48.53% over time and photoelectrochemical measurement showed photocurrent properties. These results strongly suggest that the GO-Co-ATPP photocatalyst materials may open new vistas in conversion of CO 2 into useful and environmentally friendly products as well as energy applications.
Journal of Industrial and Engineering Chemistry, 2016
Environmental tribulations such as air and water pollution have provided the impetus for sustaine... more Environmental tribulations such as air and water pollution have provided the impetus for sustained fundamental and applied research in the area of environmental remediation. Photocatalytic degradation of organic pollutants by using nanostructured semiconductors offers great potential for the complete elimination of toxic chemicals. It has been established that the wide-bandgap semiconductor metal oxides (SMOs) such as TiO 2 and ZnO can degrade variety of organic dyes under UV light irradiation [1-3]. ZnO was reported to be more active than TiO 2 in several processes, including the treatment of toxic dyes, the photooxidation of phenol and the photocatalysed oxidation of 2-phenyl phenol [4-6]. Nevertheless, application of ZnO has been limited due to its photocorrosion and fast electron-hole recombination [7]. Suppression of the recombination of photogenerated electronhole pairs in the semiconductors is crucial for enhancing the efficiency of photocatalyst [8]. Doping or loading is a more useful way to get better charge separation in semiconductor systems and dopants such as Ag, Pt, Au, Mg and Fe enhance the charge separation by reducing the electron-hole recombination [9-13]. 27 Additionally coupling of semiconductor photocatalyst with 28 other semiconductor oxide, such as ZnO-Fe 2 O 3 [14], ZnO-WO 3 29 [15], ZnO-SnO 2 [16], AgBr-ZnO [4], Ag 2 S-ZnO [17], ZrS 2-ZnO [18] 30 and TiO 2-WO 3 [19], have been reported for efficiencies photo-31 degradation. Nanocrystalline SnO 2 is an n-type semiconductor 32 with a large band gap (3.6 eV). Due to its unique electrical and 33 optical properties and its chemical stability, SnO 2 is used in dye-34 sensitized solar cells [20], as a photocatalyst [21], in gas sensors 35 [22], etc. In the present study, the Sn loaded Au-ZnO photocatalyst 36 has been prepared through the precipitation-decomposition 37 method. The photocatalytic activity of Sn-Au-ZnO was studied 38 using Acid Red 18 as a model organic pollutant. 39 2. Experimental 40 2.1. Materials 41 The commercial Acid Red (18) dye, obtained (molecular 42 formula = C 20 H 11 N 2 Na 3 O 10 S 3 ; molecular weight 604.47 and dye 43 content 80%) from s.d. fine was used as such. Oxalic acid dihydrate 44 (99%) and zinc nitrate hexahydrate (99%) were obtained from 45 Himedia chemicals. SnCl 2 Á2H 2 O (S.d.fine chem.), TiO 2 (Aldrich) and 46 AuCl 3 (Sigma Aldrich) were used as received. A gift sample of 47 Degussa TiO 2-P25 was obtained from Evonik (Germany). It is a 48 80:20 mixture of anatase and rutile. It has a particle size of 30 nm 49 and BET surface area 50 m 2 g À1. AnalaR grade H 2 O 2 (30 w/w%), 50 KIO
Highlights CS/PVA/ZnO nanocomposites films were prepared via a greener approach. Physicochemi... more Highlights CS/PVA/ZnO nanocomposites films were prepared via a greener approach. Physicochemical properties of CS/PVA/ZnO nanocomposites films were investigated. CS/PVA/ZnO nanocomposites films were found to be thermally stable.
Journal of Thermal Analysis and Calorimetry, Jul 6, 2014
In this work, 3,5-bis(decyloxy)benzaldehyde, a precursor of long chain amphiphilic BODIPYs, was s... more In this work, 3,5-bis(decyloxy)benzaldehyde, a precursor of long chain amphiphilic BODIPYs, was synthesized and its polymorphic behavior was characterized by differential scanning calorimetry, polarized light thermo microscopy, infrared spectroscopy, and XRPD. From the combined use of these techniques, an interesting polymorphic behavior was observed, and four polymorphs were identified. The initial compound melts around room temperature, ca. 30°C, and several polymorphic forms of lower melting point are obtained by cooling the melt. A thermal program could be developed that allows obtaining each form independently. Keywords 3,5-bis(decyloxy)benzaldehyde Á Polymorphism Á Calorimetry Á Thermomicroscopy Experimental General Chemicals were obtained from Sigma-Aldrich Chemical Co. and used without further purification.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Acta Crystallographica Section E-structure Reports Online, May 21, 2008
This work was supported by Fundaçã o para a Ciê ncia e a Tecnologia (FCT) under project POCI/FIS/... more This work was supported by Fundaçã o para a Ciê ncia e a Tecnologia (FCT) under project POCI/FIS/57876/2004. Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT2705).
Tetrazoles are incredibly useful organic molecules with a wide range of applications from medicin... more Tetrazoles are incredibly useful organic molecules with a wide range of applications from medicinal chemistry as carboxylic acid isosteres to high energy density materials in space research. In an effort to develop an easy protocol for the synthesis of tetrazoles from nitriles, we used nano-Ag-TiO 2 as an efficient heterogeneous catalyst for the reaction of various nitriles and sodium azide to afford 5-substituted tetrazoles in excellent yields. By this method, a wide variety of aryl nitriles underwent [3 + 2] cycloaddition to afford tetrazoles in excellent yields. Further reaction of tetrazoles with ethylchloroacetate resulted in the formation of expected products, except for a bis-tetrazole, which underwent ring opening and subsequent reaction to afford an unusual product. The bis-tetrazole also formed an unusual polymeric sodium complex in aq. NaOH solution. X-ray crystallography revealed a distorted octahedral geometry for the complex, which forms a three-dimensional network of chains interlinked by bis-tetrazole moieties through a network of H-bonds.
TiO 2-P25 supported Pd/C (P25@Pd/C) composite was prepared by the solid state dispersion method. ... more TiO 2-P25 supported Pd/C (P25@Pd/C) composite was prepared by the solid state dispersion method. The prepared composite was characterized by XRD, Raman, PL, SEM and DRS measurements. The photocatalytic activity of the composite was tested towards Naphthol Blue Black (NBB) azo dye degradation under visible light. The photocatalytic activity of P25 was highly influenced by Pd/C. Almost complete degradation was achieved with P25@Pd/C in 120 min, and found to be more efficient when compared with pristine Degussa-P25. The composite was reused in four cycles without loss of activity. A mechanism was proposed for NBB degradation by P25@Pd/C composite under visible light.
Eriocephalus africanus, an Asteraceae plant endemic from South Africa and naturalized in the Medi... more Eriocephalus africanus, an Asteraceae plant endemic from South Africa and naturalized in the Mediterranean region, is commonly used in culinary and in traditional medicine. Despite the claimed health benefits attributed to this plant by the folk medicine, there is still a lack of scientific data to support this information. The present study describes the main phenolic composition of hydroethanolic extracts from stems and leaves of E. africanus, along with the assessment of their antioxidant properties. The identification of the phenolic constituents on the stems and leaves from E. africanus was carried out by LC-DAD-ESI/MS n , and the structures of the two major HPLC-eluted compounds were further confirmed by NMR analysis. Both extracts were rich in mono-and di-caffeoylquinic acids, which accounted for approximately 90% and 74% of total quantified phenolics, for the stems and leaves extracts, respectively. Besides, eriodictyol-hexuronide was found in considerable amounts in the extract from the leaves. One must highlight that these compounds together with other minor phenolic acids (namely other caffeoyl, ferulic and protocatechuic acid derivatives) and flavonoids (including hesperetin and eriodictyol) were herein identified for the first time. Furthermore, through three in vitro methods, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH Å) radical scavenging, ferric reducing antioxidant power and lipid peroxidation inhibition capacity assays,
Abstract We report on the straightforward synthesis, characterization and photovoltaic and light-... more Abstract We report on the straightforward synthesis, characterization and photovoltaic and light-emission applications of two series of BODIPY molecules with aryloxy or alkoxy groups bonded to the boron centre. The crystal structures of two of these new dyes are also presented. The BODIPYs have absorption features similar to those of the analogous boron-fluorinated BODIPYs used as starting materials. However, the fluorescence properties vary significantly with the nature of the aryloxy/alkoxy group. The photovoltaic performance in bulk heterojunction solar cells of the newly synthesized compounds does not, however, outperform that of the parent boron-fluorinated BODIPYs. The maximum power conversion efficiency was obtained with two non-fluorescent BODIPYs, reaching 0.9%, compared with 2.79% obtained for the cells based on the corresponding boron-fluorinated precursor. The fluorine replacement by aryloxy/alkoxy groups had instead a positive effect on the light-emitting properties of the compounds of one of the series, leading to higher maximum luminance (114 cd/m2) and efficiency (0.057 cd/A), compared to devices based on the corresponding boron-fluorinated dye (35 cd/m2 and 0.015 cd/A, respectively).
A new perlite supported Bismuth Chloride (BiCl 3) was used as an efficient heterogeneous catalyst... more A new perlite supported Bismuth Chloride (BiCl 3) was used as an efficient heterogeneous catalyst for the synthesis of heterocyclic compounds viz., quinoxalines and dihydropyrimidinones. Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, energy dispersive spectra, X-ray diffractometry, thermogravimetric analysis and Brunauer-Emmett-Teller surface area analytical techniques were employed to characterize the prepared catalyst. Initially, the catalytic activity of the prepared BiCl 3-Perlite was tested towards synthesis of simple quinoxaline derivatives at room temperature. The effect of solvent in the preparation of quinoxaline was also examined. The formed products were confirmed by their physical (melting point) and spectral data (FT-IR, 1 H and 13 C-NMR). In order to implement the activity of the BiCl 3-Perlite catalyst, a multicomponent reaction was adopted for synthesis of dihydropyrimidinones under solvent free conditions in a micro oven. The use of recyclable heterogeneous solid acid catalyst makes the reaction simple with minimum chemical waste, shorter reaction time, easy workup and products in good yield.
Special attention is directed to design and synthesize antimicrobial drug candidates by the compl... more Special attention is directed to design and synthesize antimicrobial drug candidates by the complexation of bioactive ligands with transition metals. In this pursuit a ligand with imidazole ring was synthesized and treated with Cu II , Co II and ,Ni II salts to afford the mononuclear metallic complexes IHC1, IHC2 and IHC3, respectively, being assigned the general formula [M(L) 2 ]. Physical and spectral characterization supported octahedral geometry for the complexes. Both the ligand and the synthesized metal complexes were evaluated for their antifungal activity against three different strains of Candida, by determining the minimum inhibitory concentrations and minimum fungicidal concentrations. The antifungal activity results showed that the target compounds display remarkable antifungal activity, with metal complex IHC1 showing the most potent antifungal activity. Mechanism of action of the ligand and metal complexes appears to originate from membrane disruption as revealed by confocal scanning laser microscopy.
The distinct nanocrystalline CS-ZnX (X = O or S) were achieved through Costus speciosus Koen leaf... more The distinct nanocrystalline CS-ZnX (X = O or S) were achieved through Costus speciosus Koen leaf extract assisted precipitation cum hydrothermal method. The formation of the materials was confirmed by different characterization techniques such as XRD, FT-IR, Raman, FE-SEM, EDS, HR-TEM, DRS, and PL measurements. The photocatalytic activity of the prepared materials was tested on the decolourization of Reactive Red 120 dye (RR 120) aqueous solution. The photocatalytic activity was further confirmed by Acid Black 1 (AB 1) dye degradation. The dye photocatalytic process was investigated by considering the influence of test parameters such as catalyst concentration and initial dye pH. Moreover, complete decolourization of 50 ppm of RR 120 solution was achieved within 180 min at pH 5. Both catalysts were found to be reusable. The photocatalytic degradation of RR 120 by CS-ZnX (X = O or S) were confirmed GC-MS analysis, and suitable degradation pathways were proposed based on molecular ion and fragmentation peak values. The probable degradation mechanism was proposed and discussed.
Pt nanoparticles were synthesized through bioreduction process Costus speciosus (CS) leaf extract... more Pt nanoparticles were synthesized through bioreduction process Costus speciosus (CS) leaf extract was used as reducing and capping agent CS-Pt-TiO 2 nanocomposites show good visible absorbance
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Papers by Abilio Sobral