Sudipto Pal | Università Del Salento (original) (raw)
Papers by Sudipto Pal
Talanta, 2011
Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis,... more Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis, but it is mainly employed for quality control in the electronics semiconductor industry. The capability to analyze liquid and uniformly thin solid samples makes this technique suitable for other applications, and especially in the very critical field of environmental analysis. Comparison with standard methods like inductively coupled plasma (ICP) and atomic absorption spectroscopy (AAS) shows that TXRF is a practical, accurate, and reliable technique in occupational settings. Due to the greater sensitivity necessary in trace heavy metal detection, TXRF is also suitable for environmental chemical analysis. In this paper we show that based on appropriate standards, TXRF can be considered for non-destructive routine quantitative analysis of environmental matrices such as air filters. This work has been developed in the frame of the EU-FP6 PHIME (Public Health Impact of long-term, low-level Mixed element Exposure in susceptible population strata) Integrated Project (www.phime.org). The aim of this work was to investigate Mn air pollution in the area of Vallecamonica (Italy).
Talanta, 2011
Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis,... more Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis, but it is mainly employed for quality control in the electronics semiconductor industry. The capability to analyze liquid and uniformly thin solid samples makes this technique suitable for other applications, and especially in the very critical field of environmental analysis. Comparison with standard methods like inductively coupled plasma (ICP) and atomic absorption spectroscopy (AAS) shows that TXRF is a practical, accurate, and reliable technique in occupational settings. Due to the greater sensitivity necessary in trace heavy metal detection, TXRF is also suitable for environmental chemical analysis. In this paper we show that based on appropriate standards, TXRF can be considered for non-destructive routine quantitative analysis of environmental matrices such as air filters. This work has been developed in the frame of the EU-FP6 PHIME (Public Health Impact of long-term, low-level Mixed element Exposure in susceptible population strata) Integrated Project (www.phime.org). The aim of this work was to investigate Mn air pollution in the area of Vallecamonica (Italy).
Nanotechnology, 2010
An empirical evaluation of some critical aspects resulting from aggregation of gold nanorods (AuN... more An empirical evaluation of some critical aspects resulting from aggregation of gold nanorods (AuNRs) used as surface enhanced resonant Raman scattering (SERRS)-active substrates was reported. Two types of AuNR substrates with longitudinal plasmon bands which either match (in-plasmon resonance) or not (off-plasmon resonance) the wavelength of the exciting laser source (λ: 632.8 nm) were tested in resonant Raman detection of methylene blue (MB). The in-plasmon resonance condition proved to be significantly useful for detecting MB at very low concentration (less than 10(-10) M), whereas the off-plasmon resonance setup is more than enough for intermediate-low concentrations (down to 10(-8) M). Differently sized AuNR aggregates, obtained by sequential dilution of the AuNR solutions allowed us to investigate the dependence of for surface enhanced Raman scattering (SERS) intensity on the size of the aggregates, pointing out a simple strategy for preparing AuNR-based SERS substrates.
Bulletin of Materials Science, 2008
Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized... more Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized and characterized. These are pure (Ag, Au, Cu and Pt), mixed/alloy (Ag-Cu, Au-Cu, Au-Ag and Au-Pt) nanoparticles in SiO2, Au in mixed SiO2-TiO2 and SiO2-ZrO2, Au and Ag nanoparticles in inorganic-organic hybrid film matrices etc. This investigation leads to the development of tailor-made coloured coatings by tuning the surface plasmon resonance (SPR) band positions originating from the embedded nanometals by controlling mainly (i) refractive index of the film matrices and (ii) nanoalloy composition. In the later case a new layer-by-layer (two-layer) synthetic protocol has been developed to prepare binary nanoalloy particles with controlled atomic ratios.
Journal of Applied Physics, 2010
Silica films (amorphous and crystalline) doped with erbium were fabricated on silica glass substr... more Silica films (amorphous and crystalline) doped with erbium were fabricated on silica glass substrate and characterized. The inorganic-organic hybrid sol-gel method was used to prepare the films and the Na codoping induced the crystallization of silica film. Photoluminescence (PL) measurements revealed that the Er3+ ions can be excited from the ground state through an energy transfer process mediated by active defective sites in SiO2 film matrix. The annealing temperature and atmospheres have large effects on the local environment of Er3+ and the 1.54 μm PL intensity can be improved significantly by suitable heating treatments. We could correlate Er3+ sensitization effect due to the presence of carbon related species in the films. The PL intensity at nonresonant (476.5 nm) condition can be made as intense as the resonant (488 nm) one, for particular annealing conditions. Noticeable changes in PL emission intensities have not been observed whether the matrix silica film is amorphous or crystalline in nature; however, the defect-related luminescence is almost vanished in case of crystalline silica films.
Journal of Materials Chemistry, 2007
Oriented Au-Cu nanoalloys have been generated in SiO2 films using a new two-layer (TL) coating ap... more Oriented Au-Cu nanoalloys have been generated in SiO2 films using a new two-layer (TL) coating approach. Two successive overlapping coating layers were deposited on silica glass substrate using Au- and Cu-incorporated inorganic-organic hybrid silica sols. The concentrations of the Au and Cu (3 equivalent mol% metal-97% SiO2 in each case) in the respective layers and their individual coating thicknesses were
Journal of Nanoscience and Nanotechnology, 2010
Formation of Au-Ag-Cu ternary alloy nanoparticles (NPs) is difficult mainly because the system Cu... more Formation of Au-Ag-Cu ternary alloy nanoparticles (NPs) is difficult mainly because the system Cu/Ag is immiscible. We present a new synthetic technique to generate such ternary alloy NPs in silica film matrix employing a three-layer (3L) coating design. In this methodology three successive coating layers were deposited on silica glass substrates from separately prepared Cu-, Au- and Ag-ion incorporated inorganic-organic hybrid silica sols by dipping method. The Au layer is kept in the middle because it is miscible with both the Ag and Cu. The 3L film assembly was subjected to UV- and heat-treatment at 450-750 degrees C in H2-N2 atmosphere. UV-treatment generates small Au and Ag NPs in the respective layers and Cu remains as Cu2+; subsequent heat-treatment in H2-N2 induces the formation of ternary alloy NPs by the interlayer diffusion of nanometals. The final heat-treated film (750 degrees C/H2-N2) shows single and sharp plasmon band centered at 480 nm in the UV-visible spectrum indicating the formation of alloy (solid solution) NPs. GIXRD study shows one set of diffraction peaks which are shifted towards higher angle with respect to the Au or Ag diffraction peaks. FESEM, GIXRD, HRTEM, and SAED analyses reveal that the alloy has a composition close to (Au + Ag)0.88Cu0.12. The EDS analyses using the nano probe attached with TEM confirm the presence of Au, Ag and Cu in all the alloy NPs.
Journal of Materials Chemistry, 2007
Oriented Au-Cu nanoalloys have been generated in SiO2 films using a new two-layer (TL) coating ap... more Oriented Au-Cu nanoalloys have been generated in SiO2 films using a new two-layer (TL) coating approach. Two successive overlapping coating layers were deposited on silica glass substrate using Au- and Cu-incorporated inorganic-organic hybrid silica sols. The concentrations of the Au and Cu (3 equivalent mol% metal-97% SiO2 in each case) in the respective layers and their individual coating thicknesses were
Journal of Materials Chemistry, 2010
... Sourav Pramanik, Sudipto Pal and Goutam De*. Nano-Structured Materials Division, Central Glas... more ... Sourav Pramanik, Sudipto Pal and Goutam De*. Nano-Structured Materials Division, Central Glass and Ceramic Research Institute, Council of Scientific and ... Smartlab (operating at 9 kW using the rotating anode and cross-beam optics to enhance the X-ray intensity) using Cu K ...
![Research paper thumbnail of Improved photoluminescence properties of sol-gel derived Er[sup 3+] doped silica films](https://attachments.academia-assets.com/47311935/thumbnails/1.jpg)
](Journal of Applied Physics, 2010
Silica films ͑amorphous and crystalline͒ doped with erbium were fabricated on silica glass substr... more Silica films ͑amorphous and crystalline͒ doped with erbium were fabricated on silica glass substrate and characterized. The inorganic-organic hybrid sol-gel method was used to prepare the films and the Na codoping induced the crystallization of silica film. Photoluminescence ͑PL͒ measurements revealed that the Er 3+ ions can be excited from the ground state through an energy transfer process mediated by active defective sites in SiO 2 film matrix. The annealing temperature and atmospheres have large effects on the local environment of Er 3+ and the 1.54 m PL intensity can be improved significantly by suitable heating treatments. We could correlate Er 3+ sensitization effect due to the presence of carbon related species in the films. The PL intensity at nonresonant ͑476.5 nm͒ condition can be made as intense as the resonant ͑488 nm͒ one, for particular annealing conditions. Noticeable changes in PL emission intensities have not been observed whether the matrix silica film is amorphous or crystalline in nature; however, the defect-related luminescence is almost vanished in case of crystalline silica films.
Bulletin of Materials Science, 2008
Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized... more Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized and characterized. These are pure (Ag, Au, Cu and Pt), mixed/alloy (Ag-Cu, Au-Cu, Au-Ag and Au-Pt) nanoparticles in SiO 2 , Au in mixed SiO 2 -TiO 2 and SiO 2 -ZrO 2 , Au and Ag nanoparticles in inorganic-organic hybrid film matrices etc. This investigation leads to the development of tailor-made coloured coatings by tuning the surface plasmon resonance (SPR) band positions originating from the embedded nanometals by controlling mainly (i) refractive index of the film matrices and (ii) nanoalloy composition. In the later case a new layerby-layer (two-layer) synthetic protocol has been developed to prepare binary nanoalloy particles with controlled atomic ratios.
Science of Advanced Materials, 2012
ABSTRACT Au NPs (average diameter ∼20 nm) incorporated MO2 (M = Ti, Zr and Si) films on glass sub... more ABSTRACT Au NPs (average diameter ∼20 nm) incorporated MO2 (M = Ti, Zr and Si) films on glass substrate were synthesized using an ex situ approach. Au NPs were first synthesized and then incorporated into the respective alkoxide derived sols with control of pH. The Au plasmon band was red-shifted in cases of Au@TiO2 and Au@ZrO2 films after annealing at 300 and 500 C mainly due to the increase of refractive index (RI) with matrix crystallizations. Au@SiO2 film showed decrease in RI after annealing, and consequently the Au plasmon was blue-shifted. All heat-treated films appeared spot-free, optically homogeneous and colorful. The surface hardness of heat-treated Au@TiO2 and Au@ZrO2 films were > 2H and 4H, respectively. The heat-treated Au@TiO2 and Au@ZrO2 films showed strong anatase TiO2 and cubic ZrO2 crystalline phases, respectively whereas in case of Au@SiO2, silica remained amorphous and porous.
Materials Research Bulletin - MATER RES BULL, 2009
Reversible transformation of silver oxide and metallic nanoparticles inside a relatively porous s... more Reversible transformation of silver oxide and metallic nanoparticles inside a relatively porous silica film has been established. Annealing of Ag-doped films in oxidizing (air) atmosphere at 450 °C yielded colorless films containing AgOx. These films were turned yellow when heated in H2–N2 (reducing atmosphere) due to the formation of Ag nanoparticles. This yellow coloration (due to nano Ag0) and bleaching (conversion of Ag0 → Ag+) are reversible. Optical and photoluminescence spectra are well consistent with this coloration and bleaching. The soaking test of the air-annealed film in Na2S2O3 solution supports the presence of Ag+. Grazing incidence X-ray diffraction and transmission electron microscopy studies reveal the formation of Ag-oxides and Ag nanoparticles in the oxidized and reduced films, respectively.
Physical Chemistry Chemical Physics, 2008
Bimetallic Au-Pt nanoparticles have been generated inside a relatively porous SiO2 film matrix by... more Bimetallic Au-Pt nanoparticles have been generated inside a relatively porous SiO2 film matrix by a two-layer (2L) coating methodology. Two overlapping coating layers were deposited on glass substrates from Au- and Pt-doped inorganic-organic hybrid silica sols and air dried at 60 degrees C. The 2L coating assembly was then UV- and followed by heat-treated at 450 and 550 degrees C in air. UV-treatment decomposes AuCl(4)(-) and PtCl(6)(2-) ions in the respective layers and the subsequent heat treatment in air influences the diffusion of Au and Pt nanometals to each other to form bimetallic Au-Pt nanoparticles inside the silica matrix. A UV-visible study showed damping of Au-plasmon after heat treatments. GIXRD and TEM analyses reveal the formation of a partial Au/Pt solid solution with a small fraction of Pt ( approximately 16%), while the major fraction of Pt remains fused with the Au(Pt) solid solution.
Journal of Nanoscience and Nanotechnology, 2007
Au-Ag alloy nanoparticles with tunable atomic ratios have been generated in SiO2 film matrix usin... more Au-Ag alloy nanoparticles with tunable atomic ratios have been generated in SiO2 film matrix using a new two layer (TL) approach. Two successive overlapping coating layers of similar thickness were deposited on silica glass substrates using Au- and Ag-incorporated inorganic-organic hybrid silica sols, respectively. The Au and Ag concentrations in the individual layers were varied to obtain the desired Au-Ag alloys of different compositions. Four sets of such TL coating assemblies were prepared from the following pair of sols: (i) 4 equivalent mol.% Au-96% SiO2 and 2 equivalent mol.% Ag-98% SiO2, (ii) 3 equivalent mol.% Au-97% SiO2 and 2 equivalent mol.% Ag-98% SiO2, (iii) 3 equivalent mol.% Au-97% SiO2 and 3 equivalent mol.% Ag-97% SiO2, and (iv) 2 equivalent mol.% Au-98% SiO2 and 3 equivalent mol.% Ag-97% SiO2 and subjected to UV (2.75 J/cm2) and heat-treatments (450-550 degrees C) in air and H2-N2 atmospheres for the generation of Au-Ag alloy nanoparticles of approximate compositions Au.66Ag0.33, Au0.6Ag0.4, Au0.5Ag0.5, and Au0.4Ag0.6, respectively. After UV-treatment, individual Au and Ag nanoparticles were formed in the respective layers. The heat-treatment (450-550 degrees C) induces interlayer diffusion of Au and Ag to each other with the generation of Au-Ag alloy nanoparticles, and as a result, Au-Ag alloy surface plasmon resonance (SPR) absorptions were observed in between the Ag- and Au-SPR absorption positions in the visible spectra. The expected alloy compositions are formed through several intermediate alloy nanoparticles, which can also be arrested by controlling the annealing parameters. The alloy formations were monitored by UV-VIS, FTIR, XRD, EDAX, and TEM studies.
Journal of Materials Science, 2013
Copper-manganese oxide (CuMnO x ) thin films are proposed as efficient and thermally stable selec... more Copper-manganese oxide (CuMnO x ) thin films are proposed as efficient and thermally stable selective solar absorbers. The coatings were deposited on aluminum, stainless steel, and glass substrates by dip-coating method from the alcoholic solution of the Cu and Mn nitrate. An organic filmogen was introduced in order to get better adherence with the substrate hence to get uniform films even for larger substrates. The coated films were dried and subsequently heat-treated at 500°C. X-ray diffraction spectra of the annealed film showed the formation of pure Cu-Mn oxide spinel structure (Cu 1.5 Mn 1.5 O 4 ) in the film. FTIR spectra show complete removal of the organic species after thermal treatment at 500°C. The solar absorptance and thermal emittance were calculated from the hemispherical reflectance spectra in the UV/Vis/NIR and IR range, respectively. The maximum visible absorptance with minimizing the infrared thermal emittance was optimized by controlling the thickness of the films, choosing substrates, and introducing a SiO 2 overlayer.
Industrial & Engineering Chemistry Research, 2014
ABSTRACT TiO2 microspheres (TMS) with perfect spherical morphology were synthesized by spray dryi... more ABSTRACT TiO2 microspheres (TMS) with perfect spherical morphology were synthesized by spray drying of a hydrothermally cured aqueous suspension of TiO2 nanoparticles. TiO2 powders (TP) obtained by drying the nanoparticle suspension were studied simultaneously to determine which was the most efficient photocatalyst. SEM images and laser granulometry on TMS show spherical morphology with the diameter ranging from 2 to 10 μm. TMS had high specific surface area after annealing as seen from BET analyses. XRD analyses show that TMS consist of anatase and rutile crystalline phases where the rutile fraction increases with annealing temperature and above 500 °C rutile dominates anatase. Raman spectroscopy shows several Raman bands from anatase and rutile phases and supports the XRD results of phase transformation with increasing annealing temperature. Photodegradation of organic pollutants in aqueous solution under UV light irradiation establishes the higher photocatalytic activity of TMS with respect to TP. The highest efficiency was found on the 400 °C annealed TMS.
Journal of Nanoparticle Research, 2011
Cu–Ni fcc alloy nanoparticles (NPs) of tunable atomic ratios were generated in SiO2 films. The fi... more Cu–Ni fcc alloy nanoparticles (NPs) of tunable atomic ratios were generated in SiO2 films. The films were prepared using the Cu(NO3)2 and Ni(NO3)2 co-doped inorganic–organic hybrid silica sols by single dipping. Transparent, crack-free, glassy SiO2 films of 310 ± 10 nm in thickness embedded with high mol percent of Cu–Ni alloy NPs were yielded after annealing at 750 °C in 10% H2-90% Ar atmosphere. Nominal compositions of the films were 20 mol% (Cu–Ni)-80 mol% SiO2. Optical spectral study of the heat-treated films showed disappearance of Cu plasmon bands due to Cu–Ni alloy formation. Grazing incidence X-ray diffraction (GIXRD) studies revealed the formation of Cu–Ni alloy (2:1, 1:1 and 1:2) NPs inside the SiO2 film. GIXRD showed a systematic shifting of the diffraction peaks with respect to the fcc Cu–Ni alloy composition, maintaining the nominal ratios. Transmission electron microscopy (TEM) studies of the representative Cu0.5Ni0.5-doped film showed existence of homogeneously dispersed Cu–Ni alloy NPs of average size 6.35 nm inside the SiO2 matrix. The energy dispersive X-ray scattering (EDX) analysis of the individual NPs using the nano-probe (scanning TEM mode) confirmed the presence of both the Cu and Ni with the desired atomic ratio.
Chemistry of Materials, 2005
ABSTRACT A new synthesis procedure has been developed to prepare Au−Ag alloy nanoparticles inside... more ABSTRACT A new synthesis procedure has been developed to prepare Au−Ag alloy nanoparticles inside glassy SiO2 film matrix. Two successive overlapping coating layers were prepared on glass substrate using Au- and Ag-incorporated inorganic−organic hybrid silica sols, respectively. The concentrations of the Au and Ag (3 equivalent mol % metal − 97% silica in each case) in the respective layers and their individual coating thicknesses were kept similar for the generation of 1:1 Au−Ag (Au0.5Ag0.5) alloy. The dried two-layer (TL) coating assembly after UV (2.75 J/cm2) and followed by thermal treatments (450−550 °C) yielded Au−Ag alloy nanoparticles of controllable molar ratios in a glassy SiO2 matrix. Thus, the UV-treated TL film when heated at 450 °C yielded spherical Au−Ag alloy nanoparticles (Au mol fraction ≈ 0.8) of average diameter (D) 2.5 nm whereas the 550 °C heated film sample showed relatively larger alloy nanoparticles of D 4.5 nm having Au mol fraction of ≈0.5. The alloy nanoparticles were formed through the interlayer diffusion of Ag and Au during the thermal annealing in the solid state.
Science of Advanced Materials, 2012
ABSTRACT Au NPs (average diameter ∼20 nm) incorporated MO2 (M = Ti, Zr and Si) films on glass sub... more ABSTRACT Au NPs (average diameter ∼20 nm) incorporated MO2 (M = Ti, Zr and Si) films on glass substrate were synthesized using an ex situ approach. Au NPs were first synthesized and then incorporated into the respective alkoxide derived sols with control of pH. The Au plasmon band was red-shifted in cases of Au@TiO2 and Au@ZrO2 films after annealing at 300 and 500 C mainly due to the increase of refractive index (RI) with matrix crystallizations. Au@SiO2 film showed decrease in RI after annealing, and consequently the Au plasmon was blue-shifted. All heat-treated films appeared spot-free, optically homogeneous and colorful. The surface hardness of heat-treated Au@TiO2 and Au@ZrO2 films were > 2H and 4H, respectively. The heat-treated Au@TiO2 and Au@ZrO2 films showed strong anatase TiO2 and cubic ZrO2 crystalline phases, respectively whereas in case of Au@SiO2, silica remained amorphous and porous.
Talanta, 2011
Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis,... more Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis, but it is mainly employed for quality control in the electronics semiconductor industry. The capability to analyze liquid and uniformly thin solid samples makes this technique suitable for other applications, and especially in the very critical field of environmental analysis. Comparison with standard methods like inductively coupled plasma (ICP) and atomic absorption spectroscopy (AAS) shows that TXRF is a practical, accurate, and reliable technique in occupational settings. Due to the greater sensitivity necessary in trace heavy metal detection, TXRF is also suitable for environmental chemical analysis. In this paper we show that based on appropriate standards, TXRF can be considered for non-destructive routine quantitative analysis of environmental matrices such as air filters. This work has been developed in the frame of the EU-FP6 PHIME (Public Health Impact of long-term, low-level Mixed element Exposure in susceptible population strata) Integrated Project (www.phime.org). The aim of this work was to investigate Mn air pollution in the area of Vallecamonica (Italy).
Talanta, 2011
Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis,... more Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis, but it is mainly employed for quality control in the electronics semiconductor industry. The capability to analyze liquid and uniformly thin solid samples makes this technique suitable for other applications, and especially in the very critical field of environmental analysis. Comparison with standard methods like inductively coupled plasma (ICP) and atomic absorption spectroscopy (AAS) shows that TXRF is a practical, accurate, and reliable technique in occupational settings. Due to the greater sensitivity necessary in trace heavy metal detection, TXRF is also suitable for environmental chemical analysis. In this paper we show that based on appropriate standards, TXRF can be considered for non-destructive routine quantitative analysis of environmental matrices such as air filters. This work has been developed in the frame of the EU-FP6 PHIME (Public Health Impact of long-term, low-level Mixed element Exposure in susceptible population strata) Integrated Project (www.phime.org). The aim of this work was to investigate Mn air pollution in the area of Vallecamonica (Italy).
Nanotechnology, 2010
An empirical evaluation of some critical aspects resulting from aggregation of gold nanorods (AuN... more An empirical evaluation of some critical aspects resulting from aggregation of gold nanorods (AuNRs) used as surface enhanced resonant Raman scattering (SERRS)-active substrates was reported. Two types of AuNR substrates with longitudinal plasmon bands which either match (in-plasmon resonance) or not (off-plasmon resonance) the wavelength of the exciting laser source (λ: 632.8 nm) were tested in resonant Raman detection of methylene blue (MB). The in-plasmon resonance condition proved to be significantly useful for detecting MB at very low concentration (less than 10(-10) M), whereas the off-plasmon resonance setup is more than enough for intermediate-low concentrations (down to 10(-8) M). Differently sized AuNR aggregates, obtained by sequential dilution of the AuNR solutions allowed us to investigate the dependence of for surface enhanced Raman scattering (SERS) intensity on the size of the aggregates, pointing out a simple strategy for preparing AuNR-based SERS substrates.
Bulletin of Materials Science, 2008
Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized... more Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized and characterized. These are pure (Ag, Au, Cu and Pt), mixed/alloy (Ag-Cu, Au-Cu, Au-Ag and Au-Pt) nanoparticles in SiO2, Au in mixed SiO2-TiO2 and SiO2-ZrO2, Au and Ag nanoparticles in inorganic-organic hybrid film matrices etc. This investigation leads to the development of tailor-made coloured coatings by tuning the surface plasmon resonance (SPR) band positions originating from the embedded nanometals by controlling mainly (i) refractive index of the film matrices and (ii) nanoalloy composition. In the later case a new layer-by-layer (two-layer) synthetic protocol has been developed to prepare binary nanoalloy particles with controlled atomic ratios.
Journal of Applied Physics, 2010
Silica films (amorphous and crystalline) doped with erbium were fabricated on silica glass substr... more Silica films (amorphous and crystalline) doped with erbium were fabricated on silica glass substrate and characterized. The inorganic-organic hybrid sol-gel method was used to prepare the films and the Na codoping induced the crystallization of silica film. Photoluminescence (PL) measurements revealed that the Er3+ ions can be excited from the ground state through an energy transfer process mediated by active defective sites in SiO2 film matrix. The annealing temperature and atmospheres have large effects on the local environment of Er3+ and the 1.54 μm PL intensity can be improved significantly by suitable heating treatments. We could correlate Er3+ sensitization effect due to the presence of carbon related species in the films. The PL intensity at nonresonant (476.5 nm) condition can be made as intense as the resonant (488 nm) one, for particular annealing conditions. Noticeable changes in PL emission intensities have not been observed whether the matrix silica film is amorphous or crystalline in nature; however, the defect-related luminescence is almost vanished in case of crystalline silica films.
Journal of Materials Chemistry, 2007
Oriented Au-Cu nanoalloys have been generated in SiO2 films using a new two-layer (TL) coating ap... more Oriented Au-Cu nanoalloys have been generated in SiO2 films using a new two-layer (TL) coating approach. Two successive overlapping coating layers were deposited on silica glass substrate using Au- and Cu-incorporated inorganic-organic hybrid silica sols. The concentrations of the Au and Cu (3 equivalent mol% metal-97% SiO2 in each case) in the respective layers and their individual coating thicknesses were
Journal of Nanoscience and Nanotechnology, 2010
Formation of Au-Ag-Cu ternary alloy nanoparticles (NPs) is difficult mainly because the system Cu... more Formation of Au-Ag-Cu ternary alloy nanoparticles (NPs) is difficult mainly because the system Cu/Ag is immiscible. We present a new synthetic technique to generate such ternary alloy NPs in silica film matrix employing a three-layer (3L) coating design. In this methodology three successive coating layers were deposited on silica glass substrates from separately prepared Cu-, Au- and Ag-ion incorporated inorganic-organic hybrid silica sols by dipping method. The Au layer is kept in the middle because it is miscible with both the Ag and Cu. The 3L film assembly was subjected to UV- and heat-treatment at 450-750 degrees C in H2-N2 atmosphere. UV-treatment generates small Au and Ag NPs in the respective layers and Cu remains as Cu2+; subsequent heat-treatment in H2-N2 induces the formation of ternary alloy NPs by the interlayer diffusion of nanometals. The final heat-treated film (750 degrees C/H2-N2) shows single and sharp plasmon band centered at 480 nm in the UV-visible spectrum indicating the formation of alloy (solid solution) NPs. GIXRD study shows one set of diffraction peaks which are shifted towards higher angle with respect to the Au or Ag diffraction peaks. FESEM, GIXRD, HRTEM, and SAED analyses reveal that the alloy has a composition close to (Au + Ag)0.88Cu0.12. The EDS analyses using the nano probe attached with TEM confirm the presence of Au, Ag and Cu in all the alloy NPs.
Journal of Materials Chemistry, 2007
Oriented Au-Cu nanoalloys have been generated in SiO2 films using a new two-layer (TL) coating ap... more Oriented Au-Cu nanoalloys have been generated in SiO2 films using a new two-layer (TL) coating approach. Two successive overlapping coating layers were deposited on silica glass substrate using Au- and Cu-incorporated inorganic-organic hybrid silica sols. The concentrations of the Au and Cu (3 equivalent mol% metal-97% SiO2 in each case) in the respective layers and their individual coating thicknesses were
Journal of Materials Chemistry, 2010
... Sourav Pramanik, Sudipto Pal and Goutam De*. Nano-Structured Materials Division, Central Glas... more ... Sourav Pramanik, Sudipto Pal and Goutam De*. Nano-Structured Materials Division, Central Glass and Ceramic Research Institute, Council of Scientific and ... Smartlab (operating at 9 kW using the rotating anode and cross-beam optics to enhance the X-ray intensity) using Cu K ...
Journal of Applied Physics, 2010
Silica films ͑amorphous and crystalline͒ doped with erbium were fabricated on silica glass substr... more Silica films ͑amorphous and crystalline͒ doped with erbium were fabricated on silica glass substrate and characterized. The inorganic-organic hybrid sol-gel method was used to prepare the films and the Na codoping induced the crystallization of silica film. Photoluminescence ͑PL͒ measurements revealed that the Er 3+ ions can be excited from the ground state through an energy transfer process mediated by active defective sites in SiO 2 film matrix. The annealing temperature and atmospheres have large effects on the local environment of Er 3+ and the 1.54 m PL intensity can be improved significantly by suitable heating treatments. We could correlate Er 3+ sensitization effect due to the presence of carbon related species in the films. The PL intensity at nonresonant ͑476.5 nm͒ condition can be made as intense as the resonant ͑488 nm͒ one, for particular annealing conditions. Noticeable changes in PL emission intensities have not been observed whether the matrix silica film is amorphous or crystalline in nature; however, the defect-related luminescence is almost vanished in case of crystalline silica films.
Bulletin of Materials Science, 2008
Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized... more Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized and characterized. These are pure (Ag, Au, Cu and Pt), mixed/alloy (Ag-Cu, Au-Cu, Au-Ag and Au-Pt) nanoparticles in SiO 2 , Au in mixed SiO 2 -TiO 2 and SiO 2 -ZrO 2 , Au and Ag nanoparticles in inorganic-organic hybrid film matrices etc. This investigation leads to the development of tailor-made coloured coatings by tuning the surface plasmon resonance (SPR) band positions originating from the embedded nanometals by controlling mainly (i) refractive index of the film matrices and (ii) nanoalloy composition. In the later case a new layerby-layer (two-layer) synthetic protocol has been developed to prepare binary nanoalloy particles with controlled atomic ratios.
Science of Advanced Materials, 2012
ABSTRACT Au NPs (average diameter ∼20 nm) incorporated MO2 (M = Ti, Zr and Si) films on glass sub... more ABSTRACT Au NPs (average diameter ∼20 nm) incorporated MO2 (M = Ti, Zr and Si) films on glass substrate were synthesized using an ex situ approach. Au NPs were first synthesized and then incorporated into the respective alkoxide derived sols with control of pH. The Au plasmon band was red-shifted in cases of Au@TiO2 and Au@ZrO2 films after annealing at 300 and 500 C mainly due to the increase of refractive index (RI) with matrix crystallizations. Au@SiO2 film showed decrease in RI after annealing, and consequently the Au plasmon was blue-shifted. All heat-treated films appeared spot-free, optically homogeneous and colorful. The surface hardness of heat-treated Au@TiO2 and Au@ZrO2 films were > 2H and 4H, respectively. The heat-treated Au@TiO2 and Au@ZrO2 films showed strong anatase TiO2 and cubic ZrO2 crystalline phases, respectively whereas in case of Au@SiO2, silica remained amorphous and porous.
Materials Research Bulletin - MATER RES BULL, 2009
Reversible transformation of silver oxide and metallic nanoparticles inside a relatively porous s... more Reversible transformation of silver oxide and metallic nanoparticles inside a relatively porous silica film has been established. Annealing of Ag-doped films in oxidizing (air) atmosphere at 450 °C yielded colorless films containing AgOx. These films were turned yellow when heated in H2–N2 (reducing atmosphere) due to the formation of Ag nanoparticles. This yellow coloration (due to nano Ag0) and bleaching (conversion of Ag0 → Ag+) are reversible. Optical and photoluminescence spectra are well consistent with this coloration and bleaching. The soaking test of the air-annealed film in Na2S2O3 solution supports the presence of Ag+. Grazing incidence X-ray diffraction and transmission electron microscopy studies reveal the formation of Ag-oxides and Ag nanoparticles in the oxidized and reduced films, respectively.
Physical Chemistry Chemical Physics, 2008
Bimetallic Au-Pt nanoparticles have been generated inside a relatively porous SiO2 film matrix by... more Bimetallic Au-Pt nanoparticles have been generated inside a relatively porous SiO2 film matrix by a two-layer (2L) coating methodology. Two overlapping coating layers were deposited on glass substrates from Au- and Pt-doped inorganic-organic hybrid silica sols and air dried at 60 degrees C. The 2L coating assembly was then UV- and followed by heat-treated at 450 and 550 degrees C in air. UV-treatment decomposes AuCl(4)(-) and PtCl(6)(2-) ions in the respective layers and the subsequent heat treatment in air influences the diffusion of Au and Pt nanometals to each other to form bimetallic Au-Pt nanoparticles inside the silica matrix. A UV-visible study showed damping of Au-plasmon after heat treatments. GIXRD and TEM analyses reveal the formation of a partial Au/Pt solid solution with a small fraction of Pt ( approximately 16%), while the major fraction of Pt remains fused with the Au(Pt) solid solution.
Journal of Nanoscience and Nanotechnology, 2007
Au-Ag alloy nanoparticles with tunable atomic ratios have been generated in SiO2 film matrix usin... more Au-Ag alloy nanoparticles with tunable atomic ratios have been generated in SiO2 film matrix using a new two layer (TL) approach. Two successive overlapping coating layers of similar thickness were deposited on silica glass substrates using Au- and Ag-incorporated inorganic-organic hybrid silica sols, respectively. The Au and Ag concentrations in the individual layers were varied to obtain the desired Au-Ag alloys of different compositions. Four sets of such TL coating assemblies were prepared from the following pair of sols: (i) 4 equivalent mol.% Au-96% SiO2 and 2 equivalent mol.% Ag-98% SiO2, (ii) 3 equivalent mol.% Au-97% SiO2 and 2 equivalent mol.% Ag-98% SiO2, (iii) 3 equivalent mol.% Au-97% SiO2 and 3 equivalent mol.% Ag-97% SiO2, and (iv) 2 equivalent mol.% Au-98% SiO2 and 3 equivalent mol.% Ag-97% SiO2 and subjected to UV (2.75 J/cm2) and heat-treatments (450-550 degrees C) in air and H2-N2 atmospheres for the generation of Au-Ag alloy nanoparticles of approximate compositions Au.66Ag0.33, Au0.6Ag0.4, Au0.5Ag0.5, and Au0.4Ag0.6, respectively. After UV-treatment, individual Au and Ag nanoparticles were formed in the respective layers. The heat-treatment (450-550 degrees C) induces interlayer diffusion of Au and Ag to each other with the generation of Au-Ag alloy nanoparticles, and as a result, Au-Ag alloy surface plasmon resonance (SPR) absorptions were observed in between the Ag- and Au-SPR absorption positions in the visible spectra. The expected alloy compositions are formed through several intermediate alloy nanoparticles, which can also be arrested by controlling the annealing parameters. The alloy formations were monitored by UV-VIS, FTIR, XRD, EDAX, and TEM studies.
Journal of Materials Science, 2013
Copper-manganese oxide (CuMnO x ) thin films are proposed as efficient and thermally stable selec... more Copper-manganese oxide (CuMnO x ) thin films are proposed as efficient and thermally stable selective solar absorbers. The coatings were deposited on aluminum, stainless steel, and glass substrates by dip-coating method from the alcoholic solution of the Cu and Mn nitrate. An organic filmogen was introduced in order to get better adherence with the substrate hence to get uniform films even for larger substrates. The coated films were dried and subsequently heat-treated at 500°C. X-ray diffraction spectra of the annealed film showed the formation of pure Cu-Mn oxide spinel structure (Cu 1.5 Mn 1.5 O 4 ) in the film. FTIR spectra show complete removal of the organic species after thermal treatment at 500°C. The solar absorptance and thermal emittance were calculated from the hemispherical reflectance spectra in the UV/Vis/NIR and IR range, respectively. The maximum visible absorptance with minimizing the infrared thermal emittance was optimized by controlling the thickness of the films, choosing substrates, and introducing a SiO 2 overlayer.
Industrial & Engineering Chemistry Research, 2014
ABSTRACT TiO2 microspheres (TMS) with perfect spherical morphology were synthesized by spray dryi... more ABSTRACT TiO2 microspheres (TMS) with perfect spherical morphology were synthesized by spray drying of a hydrothermally cured aqueous suspension of TiO2 nanoparticles. TiO2 powders (TP) obtained by drying the nanoparticle suspension were studied simultaneously to determine which was the most efficient photocatalyst. SEM images and laser granulometry on TMS show spherical morphology with the diameter ranging from 2 to 10 μm. TMS had high specific surface area after annealing as seen from BET analyses. XRD analyses show that TMS consist of anatase and rutile crystalline phases where the rutile fraction increases with annealing temperature and above 500 °C rutile dominates anatase. Raman spectroscopy shows several Raman bands from anatase and rutile phases and supports the XRD results of phase transformation with increasing annealing temperature. Photodegradation of organic pollutants in aqueous solution under UV light irradiation establishes the higher photocatalytic activity of TMS with respect to TP. The highest efficiency was found on the 400 °C annealed TMS.
Journal of Nanoparticle Research, 2011
Cu–Ni fcc alloy nanoparticles (NPs) of tunable atomic ratios were generated in SiO2 films. The fi... more Cu–Ni fcc alloy nanoparticles (NPs) of tunable atomic ratios were generated in SiO2 films. The films were prepared using the Cu(NO3)2 and Ni(NO3)2 co-doped inorganic–organic hybrid silica sols by single dipping. Transparent, crack-free, glassy SiO2 films of 310 ± 10 nm in thickness embedded with high mol percent of Cu–Ni alloy NPs were yielded after annealing at 750 °C in 10% H2-90% Ar atmosphere. Nominal compositions of the films were 20 mol% (Cu–Ni)-80 mol% SiO2. Optical spectral study of the heat-treated films showed disappearance of Cu plasmon bands due to Cu–Ni alloy formation. Grazing incidence X-ray diffraction (GIXRD) studies revealed the formation of Cu–Ni alloy (2:1, 1:1 and 1:2) NPs inside the SiO2 film. GIXRD showed a systematic shifting of the diffraction peaks with respect to the fcc Cu–Ni alloy composition, maintaining the nominal ratios. Transmission electron microscopy (TEM) studies of the representative Cu0.5Ni0.5-doped film showed existence of homogeneously dispersed Cu–Ni alloy NPs of average size 6.35 nm inside the SiO2 matrix. The energy dispersive X-ray scattering (EDX) analysis of the individual NPs using the nano-probe (scanning TEM mode) confirmed the presence of both the Cu and Ni with the desired atomic ratio.
Chemistry of Materials, 2005
ABSTRACT A new synthesis procedure has been developed to prepare Au−Ag alloy nanoparticles inside... more ABSTRACT A new synthesis procedure has been developed to prepare Au−Ag alloy nanoparticles inside glassy SiO2 film matrix. Two successive overlapping coating layers were prepared on glass substrate using Au- and Ag-incorporated inorganic−organic hybrid silica sols, respectively. The concentrations of the Au and Ag (3 equivalent mol % metal − 97% silica in each case) in the respective layers and their individual coating thicknesses were kept similar for the generation of 1:1 Au−Ag (Au0.5Ag0.5) alloy. The dried two-layer (TL) coating assembly after UV (2.75 J/cm2) and followed by thermal treatments (450−550 °C) yielded Au−Ag alloy nanoparticles of controllable molar ratios in a glassy SiO2 matrix. Thus, the UV-treated TL film when heated at 450 °C yielded spherical Au−Ag alloy nanoparticles (Au mol fraction ≈ 0.8) of average diameter (D) 2.5 nm whereas the 550 °C heated film sample showed relatively larger alloy nanoparticles of D 4.5 nm having Au mol fraction of ≈0.5. The alloy nanoparticles were formed through the interlayer diffusion of Ag and Au during the thermal annealing in the solid state.
Science of Advanced Materials, 2012
ABSTRACT Au NPs (average diameter ∼20 nm) incorporated MO2 (M = Ti, Zr and Si) films on glass sub... more ABSTRACT Au NPs (average diameter ∼20 nm) incorporated MO2 (M = Ti, Zr and Si) films on glass substrate were synthesized using an ex situ approach. Au NPs were first synthesized and then incorporated into the respective alkoxide derived sols with control of pH. The Au plasmon band was red-shifted in cases of Au@TiO2 and Au@ZrO2 films after annealing at 300 and 500 C mainly due to the increase of refractive index (RI) with matrix crystallizations. Au@SiO2 film showed decrease in RI after annealing, and consequently the Au plasmon was blue-shifted. All heat-treated films appeared spot-free, optically homogeneous and colorful. The surface hardness of heat-treated Au@TiO2 and Au@ZrO2 films were > 2H and 4H, respectively. The heat-treated Au@TiO2 and Au@ZrO2 films showed strong anatase TiO2 and cubic ZrO2 crystalline phases, respectively whereas in case of Au@SiO2, silica remained amorphous and porous.