SciresolSciresolhttps://indjst.org/author-guidelinesIndian Journal of Science and Technology0974-564510.17485/IJST/v13i30.586Synthesis and characterization of gold (Au): Fullerene (C60)-Poly (vinyl pyrrolidone) nanofluids in an alcoholic mediumBeheraMmano.silicon@gmail.com1RamS2Silicon Institute of TechnologyBhubaneswar, OdishaIndiaEx-professor, Materials Science Centre, IIT KharagpurIndia13302020Abstract
Objectives: To synthesize gold (Au) doped fullerene (C60)-Poly (vinyl pyrrolidone) PVP nanofluids in an alcoholic medium. Methods: A simple chemical reduction method was adopted to synthesize Au nanoparticles and then these NPs were doped into the C60-PVP NFs by ultra-sonication. The samples were characterized using spectrophotometer, rheometer and microscope. Findings: We reported Surface Plasmon Resonance enhanced π→π*C60sp2 electron transition in PVP molecules upon insertion of NG into C60 NFs with PVP in butanol. Electron transfer PVP→Au(NG) causes a drastic decrease in the light emission in PVP moieties in a Au:C60-PVP complex. A noticeable red shift of the C=O stretching band of PVP reveals surface interaction between “>C=O and Au-atom. Rheological study of NFs reveals non-Newtonian behavior with an enhanced yield stress and follows a typical Bingham type flow characteristics. High resolution transmission electron micrograph shows formation of Au-C60 metal-non metal NPs of hexagonal shape. Novelty: Decrease in light emission intensity of PVP molecules in presence of Au NPs hints that it could be a candidate for sensing applications.
Fullerene (C60) nanofluids (NFs) are engineered colloidal suspensions of C60 nanoparticles (NPs) dispersed in medium such as water, mineral oils, ethylene glycol, polymer solutions, and biofluids. C60 NFs finds applications in various areas like photovoltaics, catalysis, sensors, biomedicals, etc. 1, 2, 3, 4, 5, 6, 7, 8. Usually, four strategies were widely used in developing C60 in aqueous or non-aqueous medium: (1) surface functionalization; (2) solvent exchange method; (3) mechano-chemical method; and (4) surface modification method 2, 3, 4, 5, 6, 7, 8, 9, 10. Since the last seven years, we are actively involved in developing C60 NFs with and without gold NPs in aqueous and non-aqueous media using method-4 2, 3, 4, 5, 6, 7, 8, 9, 10. Owing to possession of excellent properties by C60 and noble metal NPs like gold (Au), fullerene-gold NP combination is preferred to harvest the unique electron or energy transfer properties useful for photovoltaics, sensing and biomedicals that cannot be obtained either with individual metals or with C60 in an efficient manner.
A lot of research is going on in developing C60-Au NPs by various routes 11, 12, 13, 14, 15, 16. In 11 reported that 3D-nano-assembled Au-C60 clusters are capable of efficient electro-catalytic reduction of hydrogen peroxide in an aqueous solution as they get chemisorbed on the surface of NG. C60-Au NPs synthesiszed by 12 via chemical modification route are capable of enhancing photovoltaic efficiency by providing a large number of donor-acceptor interfaces of large surface area. In 13 synthesized highly stable ogano-soluble thiol-protected Au-nanorods via a functionalization route which exhibits exceptional optical properties different from their corresponding spherical ones. They further reported that thiol compounds not only acts a stabilizer but also provides space for inclusion of insertion of C60 molecules to develop hybrid nanostructures. The thin films prepared by 14reaches a maximum value quantum yield of light emission and results in huge enhancement in the signal of film because of a strong local field induced by surface plasmon resonance (SPR) excitation in the NG. The synthesized piperdine-based Au-C60 nano-composites by15 reported to perform catalytic oxidation of some selected primary & secondary alcohols to their corresponding aldehyde and ketone derivatives. In 16 synthesized graphene/C60-capped Au nanocomposite film which can be used to construct supercapacitor electrodes. In 17 stabilized NG with C60 molecules via multiple binding modes and van der Waals interactions.
In this report we discuss on synthesis of Au doped C60-PVP NFs in a non aqueous medium by a simple chemical method and studied their optical, microstructural and reological properties.
Synthesis route and characterization techniques
Toluene was obtained from Merck and was used as received. Fullerene (C60) of 99.9% purity and gold hydroxide Au(OH)3 of 79% Au were obtained from Alfa Aesar. Poly(vinyl pyrrolidone) PVP was purchased from Alfa Aesar. At first we prepared three stock solutions, i.e., C60 solution, PVP solution and water soluble Au(NO3)3 solution. C60 solution is prepared by dissolving 10.0 mg of C60 in 5.0 mL of toluene by stirring in a beaker covered with a watch glass and then stirring for 1 h at room temperature. PVP solution was prepared by dissolving PVP powder in water and then stirring for 3h at 60 0C. As Au(OH)3 is very difficult to dissolve in water or other common solvents, it was dissolved in HNO3 to form water soluble gold nitrate Au(NO3)3. We prepared a 5 mL stock solution of 1.27 mM Au(NO3)3 solution by dissolving 2.43 mg of Au(OH)3 salt in 5.0 mL HNO3 (5 N). Then we prepared PVP-C60 NFs in butanol and to this we added Au(NO3)3 solution in various volume (e.g., 0.10 mL, 0.15 mL, 0.2 mL, 0.25 mL, 0.30 mL, 0.35 mL, 0.40 mL) to obtain a series of C60-Au-PVP NFs in butanol. UV-Vis spectra were recorded in the wavelength region of 300 to 1000 nm using UV-Vis spectrophotometer from Thermo Scientific. The FTIR data studied in this work were measured in the 400 to 4000 cm-1 region of the vibrational frequencies for the various samples. Liquid solutions were studied in an attenuated total reflectance (ATR) mode using a ZnSe crystal as a sample holder with a Perkin-Elmer FTIR Spectrometer (Spectrum 65). The rheological properties of the synthesized Au:C60-PVPNFs of varied compositions in butanol were measured using a rotational rheometer (TA instruments, model: AR-1000) of parallel plate geometry, with a upper plate of diameter 40 mm. The morphology and size of obtained NFs were studied from micrographs obtained using a Libra Transmission Electron Microscope TEM (Carl Zeiss) operating at 120 kV.
Results and Discussion3.1 Absorption and infrared spectra in Au:C60-PVP NFs
We studied absorption spectra (Figure 1 A) in the 250-900 nm region in the NFs, which consists of (a) 0, (b) 1, (c) 2, (d) 3, (e) 5, (f) 10.0, (g) 30.0, and (h) 50.0 μM Au along with 10.0 μM C60 in the presence of 40.0 g/L PVP in butanol. The optical absorption spectrum exhibits surface plasmon resonance (SPR) enhanced dipole allowed transition near 300 nm in C(sp2) electrons when Au attached to C60/PVP 3, 4, 5, 6, 7, 8, 9, 10, 18.In the presence of Au, a characteristic Au-SPR band group exhibits over 500−900 nm with an average wavelength maxima λmax = 535 nm. FTIR results show that a non-covalent interaction occurs between Au and “>C=O” (PVP) sites.It can be seen from the spectra in Figure 1B that the Au brings a substantial change and red-shift in the PVP (>C=O) vibrational band. It shows that Au interacts with carbonyl group in an Au:C60-PVP complex 5.
(A) Absorption spectra of Au:C60-PVP NFs consisting of (a) 0, (b) 1, (c) 2, (d) 3, (e) 5, (f) 10.0, (g) 30.0, and (h) 50.0 μM Au along with 10.0 μM C60 in the presence of 40.0 g/L PVP in butanol and (B) Infrared spectra of Au:C60-PVP NFs consisting of (a) 0, (b) 1, (c) 2, (d) 3, (e) 5, (f) 10.0, (g) 30.0, and (h) 50.0 μM Au along with 10.0 μM C60 in the presence of 40.0 g/L PVP in butanol.
3.2 Emission spectra and rhelogy in Au:C60-PVP NFs
(A) Emission spectra of Au:C60-PVP NFs consisting of (a) 0, (b) 1, (c) 2, (d) 3, (e) 5, (f) 10.0, (g) 30.0, and (h) 50.0 μM Au along with10.0 μM C60 in the presence of 40.0 g/L PVP in butanol and(B) Rheogram of Au:PVP-C60 NFs consisting of (a) 0, (b) 1, (c)2, (d) 3, (e) 5, (f) 10.0, (g) 30.0, and (h) 50.0 μM Au along with 10.0 μM C60 in the presence of 40.0 g/L PVP in butanol.
Figure 2A shows the emission spectra in the 350-600 nm region in the NFs, which consists of (a) 0, (b) 1, (c) 2, (d) 3, (e) 5, (f) 10.0, (g) 30.0, and (h) 50.0 μM Au along with 10.0 μM C60 in the presence of 40.0 g/L PVP in butanol. Spectra shows that a small doping of 1 μM Au decreases the light intensity of PVP band by nearly ~30% as a consequence of energy transfer from PVP to Au-surface 2, 3, 4, 5, 6, 7, 8. Doping of 50 μM Au almost vanish (~0%) the light emission from PVP.
Figure 2B shows the rheograms i.e., variation of viscosity measured as a function of shear rate (γ-value) in Au:C60-PVP NFs consisting of (a) 0, (b) 1, (c) 2, (d) 3, (e) 5, (f) 10.0, (g) 30.0, and (h) 50.0 μM NG with 10.0 μM C60 with 40.0 g/L PVP molecules in butanol. From the Figure 2B it is observed that the initially shear viscosity drops rapidly over initial γ≤50s-1 values before achieving a stable η-value over the larger γ-values (~200 s-1). All the eight plots exhibit typical non-Newtonian behavior of viscosity. From the rheograms it is further observed that the base h-value in a base C60:PVP NF has been increased (shown in the Figure 2B as an upward arrow). It is due to formation of cross-linked network structures between NG and PVP-capped C60 particles 5.
3.3 Microstructures in Au:C60-PVP NFs
Transmission electron microscopic image inFigure 3 taken from a sample of 1 µM Au in 10.0 µM C60 with 40.0 g/L PVP displays core-shell structures of hexagonal platelets of sizes varies between 5–25 nm. A lattice image in Figure 3B suggests that crystalline Au atom are present in the complex with a 0.235 nm interplanar spacing, which results from the (111) planes of an fcc Au 5.
Micrographs of 1 µM Au in 10.0 µM C60 with 40.0 g/LPVP.
Conclusion
UV-Vis spectra confirm the formation of NG and attachment of NPs to PVP-C60 NPs. IR spectra confirm interaction between Au and >C=O group of PVP. Rheological study reveals that all the NFs follow non-Newtonian flow characteristics. Morphological study reveals that NFs consists of hexagonal platelets of Au-PVP-C60 NPs. Decrease in the light emission of PVP-molecules in presence of NG suggests that Au-PVP-C60 NFs could find applications in bio-sensing.
Acknowledgement
The authors acknowledge the support provided by Silicon Institute of Technology, Bhubaneswar, India in carrying out this research work.
ReferencesDasS KChoiSusYuWPradeepTWiley2007BeheraMRamSSolubilization and stabilization of fullerene C60 in presence of poly(vinyl pyrrolidone) molecules in water2012721-22332390923-0750, 1573-1111Springer Science and Business Media LLChttps://dx.doi.org/10.1007/s10847-011-9957-yBeheraMRamSMechanism of Solubilizing Fullerene C60in Presence of Poly(Vinyl pyrrolidone) Molecules in Water2015239069161536-383X, 1536-4046Informa UK Limitedhttps://dx.doi.org/10.1080/1536383x.2015.1041109BeheraMRamSPoly(vinyl pyrrolidone) Mediated Solubilization and Stabilization of Fullerene C60in the Form of Nanofluid in an Alcoholic Medium201523106410721536-383X, 1536-4046Informa UK Limitedhttps://dx.doi.org/10.1080/1536383x.2015.1068295BeheraMRamSTuning the Optical and Rheological Properties of Fullerene C60/Poly (Vinyl Pyrrolidone) Nanofluids via Inclusion of Nanogold2016114105710651557-1955, 1557-1963Springer Science and Business Media LLChttps://dx.doi.org/10.1007/s11468-015-0142-9BeheraMRamSVariation of optical properties, rheology, and microstructure in fullerene/poly(vinyl pyrrolidone) nanofluids with fullerene content inn-butanol2016241541611536-383X, 1536-4046Informa UK Limitedhttps://dx.doi.org/10.1080/1536383x.2015.1130703BeheraMRamSStrongly optical absorptive nanofluids and rheology in bonded fullerene C60 via poly(vinyl pyrrolidone) molecules in water2017251431501536-383X, 1536-4046Informa UK Limitedhttps://dx.doi.org/10.1080/1536383x.2016.1271788BeheraMRamSInteraction between poly(vinyl pyrrolidone) PVP and fullerene C60 at the interface in PVP-C60 nanofluids–A spectroscopic study20183301757-8981, 1757-899XIOP Publishinghttps://dx.doi.org/10.1088/1757-899x/330/1/012016BeheraManoranjanRamShankerEffect of Fullerene (C60) on Vibrational Spectra, Hydrodynamic Diameter, Zeta Potential and Microstructures of C60/Poly(vinyl pyrrolidone) Nanofluids in Aqueous Medium20183011247224760970-7077, 0975-427XAsian Journal of Chemistryhttps://dx.doi.org/10.14233/ajchem.2018.21470BeheraM.Effect of fullerene content on the thermal, microstructure, and electrokinetic properties of fullerene/poly(vinyl pyrrolidone) nanofluids and nanocomposites20184101757-899XIOP Publishinghttps://dx.doi.org/10.1088/1757-899x/410/1/012009LiuWGaoXReducing HAuCl4 by the C60 dianion: C60-directed self-assembly of gold nanoparticles into novel fullerene bound gold nanoassemblies20081940GengMZhangYHuangQZhangBLiQLiWLi JFunctionalization of C60 with gold nanoparticles20104835703574XueChenmingXuYongqianPangYiYuDingshanDaiLimingGaoMinUrbasAugustineLiQuanOrgano-Soluble Porphyrin Mixed Monolayer-Protected Gold Nanorods with Intercalated Fullerenes201228140743-7463, 1520-5827American Chemical Society (ACS)https://dx.doi.org/10.1021/la300096nYeshchenkoO AKondratenkoS VKozachenkoV VSurface plasmon enhanced photoluminescence from fullerene C60 film on Au nanoparticles array: Resonant dependence on excitation frequency2012111120021-8979, 1089-7550AIP Publishinghttps://dx.doi.org/10.1063/1.4731228PiotrowskiPiotrPawłowskaJoannaSadłoJarosław GrzegorzBilewiczRenataKaimAndrzejTEMPO functionalized C60 fullerene deposited on gold surface for catalytic oxidation of selected alcohols20171951388-0764, 1572-896XSpringer Science and Business Media LLChttps://dx.doi.org/10.1007/s11051-017-3857-zYongVirginiaHahnH. ThomasSynergistic Effect of Fullerene-Capped Gold Nanoparticles on Graphene Electrochemical Supercapacitors20130201152169-0510, 2169-0529Scientific Research Publishing, Inc.https://dx.doi.org/10.4236/anp.2013.21001IslamMd TariqulMoluguK SudheerCookeH PeterNoveronC JuanFullerene stabilized gold nanoparticles2015398592359261144-0546, 1369-9261Royal Society of Chemistry (RSC)https://dx.doi.org/10.1039/c5nj01367dBeheraMAn intensive study on the optical, rheological, and electrokinetic properties of polyvinyl alcohol-capped nanogold201553161169