Luminescent clusters of noble metals

Transcription

1 Luminescent clusters of noble metals T. Pradeep Manonmaniam Sundaranar University, Tirunelveli, January 28, 2010

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5 Hardcover: 274 pages Publisher: Elsevier Science Ltd (June 1978) Language: English ISBN-10: ISBN-13: Gold Chemistry ISBN: Hardcover 908 pages March 1999

6 Number of papers published per year after the discovery of gold catalysis.

7 5000 Numbe rof publication in gold nanoparticle Publications per year as on December 31, 2009 With the key words, gold and nanoparticle* Year

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9 T. Pradeep

10 Acknowledgements M.A. Habeeb Muhammad E.S. Shibu, P. R. Sajanlal Udayabhaskar Rao Tummu K.V. Mrudula K. Kimura, University of Hyogo, Japan T. Tsukuda, IMS, Okazaki, Japan S.K. Pal, SNBS, Kolkata G.U. Kulkarni, JNCASR, Bangalore R. V. Omkumar, RGCB, Tiruvananthapuram Manzoor Koyakutty, Amrita, Kochi

11 Electro-magnetic rotations (1821) Benzene (1825) Electro-magnetic induction (1831) The laws of electrolysis and coining words such as electrode, cathode, ion (early 1830s) The magneto-optical effect and diamagnetism (both 1845) 400+ papers

12 22/09/ /08/1867 Faraday in his laboratory Royal Institution

13 Faraday s gold preserved in Royal Institution. From the site, 50 nm

14 they are simply cases of pure gold in a divided state; yet I have come to that conclusion, and believe that the differentlycoloured fluids and particles are quite analogous. Experimental Relations of Gold (and Other Metals) to Light, M. Faraday, Philos. Trans. R. Soc. London, 1857, 147, 145

15 Gustav Mie ( ) Surface plasmons 1905 By changing size 1940 Mie G. Beiträge zur Optik trüber Medien speziell kolloidaler Goldlösungen (contributions to the optics of diffuse media, especially colloid metal solutions). Ann Phys 1908;25: This paper, including an English translation, as well as other historic papers on light scattering and absorption can be found at

16 Colours by changing shape Shells Gold shells. Nanoshells designed to absorb various wavelengths of light (the six vials on the right), including infrared (vial at far right) compared to gold colloid (far left). Used with permission from

17 Colours by changing shape Sajanlal

18 Samal

19 Organised nanostructures

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21 E. S. Shibu et al. Adv. Mater. 2008; Nano Res. 2009

22 Mesoflowers Sajanlal and Pradeep Nano Res. 2009

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24 Bimetallic mesoflowers AuAg P. R. Sajanlal.; T. Pradeep. Langmuir 2010, 26, 456.

25 P. R. Sajanlal and T. Pradeep, Unpublished Wire-like meso/nanostructures Ni Wire Ni Wire Ni Wire Au Wire

26 Ni/Au nanotubes P. R. Sajanlal and T. Pradeep, Unpublished

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28 Schematic representation for CO oxidation pathways over Au/TiO2. M. Haruta. When Gold Is Not Noble: Catalysis by Nanoparticles. Chem. Rec. 2003, 3, 75.

29 IR-spectra of 13CO and 15NO adsorbed on Pd30 (Figure 3a/b) and Pd8 (Figure 3c/d) clusters. Figure 3a/c shows the spectra if 13CO was predosed for both cluster sizes. Figure 3b/d shows the spectra if 15NO was predosed. All of the spectra were taken at 90 K after annealing the cluster samples to the indicated temperatures. Wörz, A. S.; Judai, K.; Abbet, S.; Heiz, U. Cluster Size-Dependent Mechanisms of the CO + NO Reaction on Small Pdn (n e 30) Clusters on Oxide Surfaces. J. Am. Chem. Soc. 2003, 125, 7964.

30 Two-dimensional Au20 island (yellow on line) adsorbs on a two layer MgO film (O atoms in red and Mg in green) supported on Mo(100) (blue on line), with a coadsorbed O2 molecule. Superimposed we show an isosurface of the excess electronic charge (light blue on line) illustrating activation of the adsorbed molecule through population of the antibonding 2π* orbital. (a-c) Configurations of the two-dimensional Au20 island shown in Figure 1 (the color scheme is the same as in Figure 1) with coadsorbed O2 (the atoms marked O(1) and O(2)) and CO (C atom in gray online): (a) the initial optimized configuration; d(o(1)-o(2)) ) 1.52 Å, d(c-o(2)) ) 2.85 Å; (b) the transition state (the nearest-neighbor Mg atoms are marked as I and II); distances are d(o(1)-o(2)) ) 1.55 Å, d(c-o(2)) ) 1.60 Å, d(c-o) ) 1.18 Å, d(c-mg(ii)) ) 2.30 Å; (c) a configuration illustrating formation and desorption of CO2; (d) the total energy profile along the C-O(2) reaction coordinate, with the zero of the energy scale taken for configuration a. The sharp drop past the barrier top corresponds to CO2 formation. Zhang, C.; Yoon, B.; Landman, U. Predicted Oxidation of CO Catalyzed by Au Nanoclusters on a Thin Defect- Free MgO Film Supported on a Mo(100) Surface. J. Am. Chem. Soc. 2007, 129, 2228.

31 Au 13 [Au 13 (PPhMe 2 ) 10 C1 2 ] 3+ Briant, C. E.; Theobald, B. R. C.; White, J. W.; Bell, L. K.; Mingos, D. M. P.; Welch, A. J. Synthesis and x-ray structural characterization of the centered icosahedral gold cluster compound [Au 13 (PPhMe 2 ) 10 Cl 2 ](PF 6 ) 3 ; the realization of a theoretical prediction. J. C. S. Chem. Comm. 1981, 5, 201.

32 Gold clusters Au 13 Au 55 Au 55 [P(C 6 H 5 ) 3 ] 12 Cl 6 - a gold cluster of unusual size, Schmid, G.; Pfeil, R.; Boese, R.; Brandermann, F.; Meyer, S.; Calis, G. H. M.; Van der Velden.; Jan W. A. Chemische Berichte 1981, 114, Synthesis and x-ray structural characterization of the centered icosahedral gold cluster compound [ Au 13 (PMe 2 Ph) 10 Cl 2 ](PF 6 ) 3 ; the realization of a theoretical prediction, Briant, C. E.; Theobald, B. R. C.; White, J. W.; Bell, L. K.; Mingos, D. M. P.; Welch, A. J. Chem. Commun. 1981, 5, 201. Synthesis of water-soluble undecagold cluster compounds of potential importance in electron microscopic and other studies in biological systems, Bartlett, P. A.; Bauer, B.; Singer, S. J. Am. Chem. Soc. 1978, 100, 5085.

33 Magic clusters From Gunter Schmidt, Chem. Soc. Rev. 2008, 37,

34 Dendrimer encapsulated clusters Au 3+ reduction Clusters High quantum yield blue emission from water-soluble Au 8 nanodots, Zheng, J.; Petty, J. T.; Dickson, R. M. J. Am. Chem. Soc. 2003, 125, Highly fluorescent, water-soluble, size-tunable gold quantum dots, Zheng, J.; Zhang, C. W.; Dickson, R. M. Phys. Rev. Lett. 2004, 93, Highly fluorescent noble-metal quantum dots, Zheng, J.; Nicovich, P. R.; Dickson, R. M. Annu. Rev. Phys. Chem. 2007, 58, 409. Etching colloidal gold nanocrystals with hyperbranched and multivalent polymers: A new route to fluorescent and water-soluble atomic clusters, Duan, H.; Nie, S. J. Am. Chem. Soc. 2007, 129, 2412.

35 DNA encapsulated clusters DNA-Templated Ag Nanocluster Formation, Petty, J. T.; Zheng, J.; Hud, N. V.; Dickson, R. M. J. Am. Chem. Soc. 2004, 126, 5207.

36 Au 102 Au 102 (p-mba) 44 Jadzinsky, P. D.; Calero, G.; Ackerson, C. J.; Bushnell, D. A.; Kornberg, R. D. Structure of a Thiol Monolayer Protected Gold Nanoparticle at 1.1 Å Resolution Science 2007, 318, 430.

37 Absorbance a b a - Au-citrate b - Au-C 18 c - Au c Wavelength (nm) Optical absorption (extinction) spectrum of (a) 15 nm gold particles in aqueous solution (labeled Au@citrate). The spectrum of (b) 3 nm particles in toluene is also shown. See the broadening of the plasmon feature. The spectrum of (c) Au 25 in water. In this, there is no plasmon excitation and all the features are due to molecular absorptions of the cluster. Das, Choi, Yu and Pradeep, Nanofluids, John Wiley, New York, 2008

38 Polyacrylamide gel electrophoresis (PAGE) Au 3+ μg HO O NH2 O NH O SH NH OH O BH 4 - Negishi, Y.; Nobusada, K.; and Tsukuda, T. Glutathione-Protected Gold Clusters Revisited: Bridging the Gap between Gold(I)-Thiolate Complexes and Thiolate-Protected Gold Nanocrystals. J. Am. Chem. Soc. 2005, 127,

39 Au 25 SG 18 Synthesis: Au 25 clusters can be preferentially populated by dissociative excitation of larger precursors Scheme showing the synthesis of Au 25 SG 18 clusters

40 Characterization of Au 25 SG 18 Optical absorption spectrum with an absorption maximum at 672 nm. Tsukuda et. al. JACS 2005 Photoluminescence profile with excitation and emission maxima at 535 and 700 nm, respectively.

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42 FTIR spectrum: The peak at 2526 cm -1 of glutathione due to SH stretching frequency is absent in IR spectrum of Au 25 suggesting the ligand binding on cluster surface. 1H NMR spectrum: There is one-to-one correspondence between the two spectra, except that the βch 2 resonance (labeled as C) disappears completely in the cluster which is expected as it is close to the cluster surface. All the observed resonances have been broadened in view of their faster relaxation and non-uniform distribution of ligands.

43 F XPS spectrum TEM image: The clusters are seen only faintly since the size is ~1 nm. Some of the individual clusters are shown by circles. There are also cluster aggregates which upon extended electron beam irradiation fuse to form bigger particles

44 Perumal Ramasamy et al. J. Mater. Chem., 2009, 19, With Arindam Banerjee

45 Ligand exchange of Au 25 HO 1 O NH2 O NH (GSH) O SH NH OH O (MB) HS H 3 C CH 3 OH 2 R 1 O HO O NH O NH O NH O OH SH (NAGSH and NFGSH) 3&4

46 Absorbance I(E)=A(W)xW k k 81.00k LUMO 54.00k HOMO 27.00k 0.00 a b c spband Au 25 SG 18 Au 25 -MB Au 25 -SGAN Au 25 -SGFN d-band Energy (ev) Wavelength(nm) E.S. Shibu et al. J. Phys. Chem. C 2008, 112,

47 I(E)=I(W)xW 2 Energy (ev) x x x Au 25 SG 18 Au 25 -MB Au 25 -SGAN Au 25 -SGFN Wavelength (nm)

48 Fluorescence : A comprehensive study between organic dye, gold atoms and molecular clusters of gold 2.0x10 7 Intensity (a. u.) 1.5x x x Wavelength (ev) Lecoultrea, S.; Rydlo, A.; F elixb, C.; Harbich, W. Eur. Phys. J. D, 2009 DOI: /epjd/e

49 Cluster Q.Yield Au 10 (SG) 10 Au 11 (SG) 11 Au 11 (SG) 11 1*10-4 Au 15 (SG) 13 2*10-4 Recently developed clusters using Au 25 as precursor Au 18 (SG) 14 4*10-3 Cluster Q. Yield Au 22 (SG) 16 4*10-3 Au 22 (SG) 17 2*10-3 Au 25 (SG) *10-3 Au 29 (SG) 20 3*10-3 Au 33 (SG) 22 Au 35 (SG) 22 2*10-3 Precursor Using other ligands Au *10-2 Au *10-2 Au *10-2 Au 8 (SG) 8 1.5*10-1 Au 38 (SG) 24, Au 39 (SG) 24 2*10-3 Gold nanoparticles 1* Nano Res., 1(2008) Chemistry A European Journal. (In Press). 3. ACS Applied Materials and Interfaces (in press) Negishi, Y.; Nobusada, K.; Tsukuda, T. J. Am. Chem. Soc. 2005, 127, 5261.

50 Intensity (a. u. ) 50k Au25 SG 18 40k 30k 20k 10k Au 25 -MB Au 25 -SGAN 4f 5/2 4f 7/ Binding Energy (ev)

51 a c d e bound ligand free ligand ppm b Time (min) c Time (min) Peak d ln (Concentration) Peak e ln (Concentration)

52 Au 8 SG 8 Au 8 Au 25

53 Comparison of the optical absorption profiles of Au 25 and Au 8. Comparison of the photoluminescence profiles of the clusters with Traces I and II are the excitation and emission spectra of Au 8, respectively. Traces III and IV are the excitation and emission spectra of Au 25, respectively and trace V is the emission spectrum of Au@MSA. Habeeb Muhammed et al. Nano Res. 2008, 1, 333.

54 6 - GS m/z m/z Habeeb Muhammed et al. Unpublished

55 Au 25 SG 18 Single Phase Etching Bi- Phase Etching OT 55 o C OT 25 o C MPTS 25 o C Au x MPTS y Au Au x SG y (Aqueous Layer) Glutathione (GSH) 3-mercaptopropyl trimethoxy silane (MPTS) Octane thiol (OT) Au x OT y (Organic Layer) Scheme 1. Formation of the three sub-nanoclusters from Au 25 SG 18 by core etching by two routes. Photographs of the cluster aqueous solutions under UV light are also given. Habeeb Muhammed et al. Chem. Euro. J. 2009, 15,

56 Absorbance Wavelength (nm) Comparison of the optical absorption features of Au SG (green trace) with Au OT (grey trace), Au SG (pink trace) and Au MPTS (purple x y x y x y trace). The arrows show the absorption peaks of the clusters due to intra band transitions. The spectra are shifted vertically for clarity. Dotted lines indicate the threshold of absorption. Inset shows the photographs (under white light) of the water-toluene bi-phasic mixture before (A) and after (B) reaction at 55 ºC (interfacial etching) for 1 h.

57 Pattern 1 A 197 B Au 23 S Pattern 2 Figure 2. A) MALDI-MS of Au x SG y which shows bunch of peaks due to Au m S n clusters. B) A group of peaks with m/z spacing of 197 or 229 between the major peaks of the adjacent group of peaks. C) Expanded view of peaks due to Au 23 S

58 Intensity (a. u.) B. E. (ev) 90 Comparison of the Au(4f) XPS spectra of Au 22, Au 23 and Au 33 along with parent Au 25.

59 Intensity (a. u.) Wavelength (nm) Comparison of the photoluminescence profiles of Au 22, Au 23 and Au 33 along with parent Au 25. Photographs of the aqueous solutions of Au 22 and Au 23 under white light (A and C, respectively) and UV light (B and D, respectively) are also given.

60 Au 25 Normalized Intensity Au 33 Au 23 Au 22 IRF Time (ns) Fluorescence decay pattern of Au 25, Au 33, Au 23, and Au 22 collected at 630 nm.

61 3M Intensity (a. u.) 2M 1M.5M Wavelength (nm) 900 Photoluminescene profile of Au 23 cluster before (pink trace) and after (orange trace) phase transfer. Emission of the cluster enhances considerably after the phase transfer. Photographs of the aqueoustoluene mixture containing the cluster before and after phase transfer under white light (A and B, respectively) and UV light (C and D, respectively). In C, only the interface is illuminated as the UV is attenuated as the sample was irradiated from the top

62 A B I II A) Solvent dependent fluorescence of 50 µm Au 23 in ethylene glycol, methanol, water, acetonitrile and dioxane before phase transfer. B) Solvent dependent fluorescence of Au 23 in methanol, ethanol, propanol, butanol and pentanol after phase transfer. Inset of B shows the photograph of phase transferred Au 23 in toluene (I) and butanol (II) under UV light irradiation

63 Solvent τ 1 (ps) % τ 2 (ns) % τ 3 (ns) % Ethylene Glycol Methanol Water Dioxane A) Optical absorption spectra of Au 23 in dioxane, water, methanol and ethylene glycol. B) Fluorescence decay of Au collected at 630 nm in various solvents. Table tabulates the life time of the cluster in various solvents.

64 Plot of fluorescence intensity of Au 23 cluster in water-dmso mixture starting from pure water (blue line) to 1:1 (green line), 1:2 (red line) and 1:3 (black trace) water-dmso mixtures. Inset shows the photographs of the corresponding solutions under UV light irradiation

65 Fluorescence Intensity Millions Temperature 0 C Plot of temperature vs fluorescence intensity of the cluster in the aqueous and toluene layers. While the intensity of emission of aqueous solution of Au 23 decreases with increase in temperature, the emission intensity remains unaltered for phase transferred Au 23.

66 A Streptavidin Au 23 Au EDC 23 EDC :1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide Schematic representation of the conjugation of streptavidin on Au 23 SG 18 by EDC coupling. A B C µm Fluorescence (A), bright field (B) and overlay of fluorescent and bright field images (C) of human hepatoma (HepG2) cells stained with streptavidin conjugated Au 23.

67 A B Bright field (A) and fluorescence (B) images of HepG2 cells stained with unconjugated Au 23 clusters. No fluorescence was observed from the cells after washing

68 Fluorescent microscopic images showing interaction of Au-BSA-FA NCs with different types of cell lines: a1-a2) FRve lung carcinoma A549 after 2 hours of incubation, b1-b2) FR-ve lung carcinoma A549 after 24 hours of incubation, c1-c2) FR+ve KB cells with unconjugated Au clusters, d1-d2) FR+ve KB cells with FA conjugated Au clusters at 2 hrs, e1-e2) 4 hrs and f1-f 2) 24 hrs of incubation [Archana R, Sonali S, Deepthy M et al (2009) Molecular Receptor Specific, Non-toxic, Near-infrared Emitting Au Cluster-Protein Nanoconjugates for Targeted Cancer Imaging. Nanotechnology (in press)]. Nanotechnology 2010

69 Clusters for metal ion detection Water soluble red emitting clusters where treated with various metal ions with a final Concentration of 25 ppm. The emission was shifted to lower wavelength in case of silver ions and quenched completely in case of copper ions. The emission was an altered in case of other ions. Habeeb Muhammed et al. Chem. Euro. J. 2009, 15,

70 FRET between Au 25 and Dansyl Chromophore Approaches Used for the Functionalization of Dansyl Chromophore on the Au 25 Cluster. Habeeb Muhammmed et al. J. Phys. Chem. C 2008, 112,

71 Cluster based patterns N N H H N N OH 1,8-dibromooctane K 2 CO 3 /DMF N N H H N N O Br I II (Me 3 Si) 2 S/ TBAF/THF (H 2 TPPOASH) Toluene Core reduction/ligand exchange N N H H N N O SH [Au 25 SG 18 ] aq [Au 22 (SG) 15 (H 2 TPPOAS) 2 ] aq III H 2 TPPOASH Abosrbance A B Abosrbance Au 25 SG 18 Au 22 H 2 TPPOASH Wavelength (nm) Intensity (cps) 12.0M 8.0M 4.0M Au 25 SG 18 H 2 TPPOASH Au 22 excitation emission B 0.0 Q Wavelength (nm) Wavelength (nm) 25.0M 20.0M excitation emission 5 C C D Intensity 15.0M 10.0M 25 C = (GSH) 5.0M Wavelength (nm) RT 5 C

72 775 (Au n S m ) + A 20.0 K x 9 Au12S7 + Au14S9 + Au16S11 + Au18S13 + Au20S15 + Au22S Intensity 8.0 K K m/z 10k 10k Cluster H 2 TPPOASH Intensity Intensity 1k (IRF) Time (ns) Lifetime (ns) % Lifetime (ns) % A Wavelength (nm) 6x10 6 5x10 6 4x10 6 3x10 6 2x10 6 1x a (0 µl) b (20 µl) c (150 µl) d (300 µl) Intensity (cps) Addition of Zn +2 (mm) Flu.Intensity at 670 nm 4x10 6 3x10 6 2x10 6 1x Concentration of Zn (µm) +2 C 1k (IRF) Time (ns) B Wavelength (nm) 5x10 6 4x10 6 3x10 6 2x10 6 1x a (0 µl) b (50 µl) c (100 µl) d (300 µl) Intensity (cps) Addition of Cu +2 (mm) Flu. Intensity at 670 nm 4x10 6 3x10 6 2x10 6 1x D Concentration of Cu +2 (µm)

73 With G. U. Kulkarni A C 532 nm 10 µm 800 B III I Intensity II 50 0 C A C 0 D Wavelength (nm) 0 CCD Cts 4500 CCD Cts E 304.0k CCD counts 302.0k B 1 µm 1 µm 200 D 300.0k Distance (µm) 150 Height (nm) Distance (µm) E. S. Shibu et al. ACS Appl. Mater. 2009, 1, 2199.

74 glutathione (GSH) protected gold nanoparticle OH 4 OH 6a,b OH 1 n= 6, 7, alpha CD 7---beta CD 8---gamma CD n O O NH OH O H2N NH HO O SH Basic unit of CD is 6 membered glucose Scheme: Au 15 was synthesized inside the cyclodextrin (CD) cavity (in situ). Note: CD and GSH are the abbreviations of cyclodextrin and glutathione, respectively. For our synthesis we have used all 3 CDs (alpha, beta and gamma) E. S. Shibu and T. Pradeep. Unpublished 3D image of CD showing the nanometer cavity

75 150.0k 100.0k Au 15 -α CD Au 15 -β CD Au 15 -γ CD 1.5x10 6 I= A(W)x W k 50.0k I= A(W)x W k Wavelength (nm) Intensity (cps) 1.0x x Wavelength (nm) Wavelength (nm) E. S. Shibu and T. Pradeep. Unpublished

76 Glass coating and fluorescence Au 15 Clusters have a tendency to self paint on glass surface while dipping in cluster solution. Figure shows the photograph of a glass plate coated with Au 15 cluster. Fluorescence from the Au 15 cluster solution shown in inset The red fluorescence coming from glass after decanting the cluster solution Photograph shows the red fluorescence coming from glass plate after the self painting of Au 15 cluster.

77 E. S. Shibu and T. Pradeep. Unpublished

78 Magnetism in Au 15 cluster K 60 K 130 K 240 K M (emu/g) H (K Oe) E. S. Shibu and T. Pradeep. Unpublished

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80 Silver clusters

81 350 nm 550 nm 550 nm 640 nm

82 Absorbance A) 0.6 C) M 4M 0 Intensity (a.u.)12m λ/nm Ag@MSA 10 min 60 min 360 min 24 hours 48 hours λ exi 350 λ exi λ/nm B) Absorbance D) Udaybhaskar Rao and Pradeep, Submitted a st band 2 nd band λ/nm b 20 nm 10 nm d c 20 nm

83 a b c d e f g h m/z

84 Ag 5 (H 2 MSA) 3 (HMSA) - e) f) Ag 6 (H 2 MSA) 3 (HMSA) - g) Ag 7 (H 2 MSA) 3 (HMSA)

85 Na{(Ag 4 (H 2 MSA) 2 (HMSA) 2 } Na 2 {Ag 4 (H 2 MSA)(HMSA) 3 } Na 3 {Ag 4 (HMSA) 4 } - {Ag 4 (H 2 MSA) 3 (HMSA)} Na 4 {Ag 4 (HMSA) 3 (MSA)} - Na 5 {Ag 4 (HMSA) 2 (MSA) 2 } - Na 6 {Ag 4 (HMSA)(MSA) 3 } m/z

86 Intensity (a.u.) Intensity (a.u.) B.E (ev) Ag 7 Ag 8 Crude Ag NP Ag@MSA NP Crude cluster Ag 8 (H 2 MSA) 5 Ag 7 (H 2 MSA) 4 Intensity (a.u.) Intensity (a.u.) Ag@MSA NP Crude cluster Ag 8 (H 2 MSA) 5 Ag 7 (H 2 MSA) Binding energy (ev) Ag@MSA NP Crude cluster Ag 8 (H 2 MSA) 5 Ag 7 (H 2 MSA) Binding energy (ev) Binding energy (ev)

87 White light RT UV light T

88 A Intensity (a.u.) 9x10 3 6x10 3 3x10 3 Ag 5 S 4 Ag 7 S 4 B Ag 9 S 5 C Ag 11 S 6 Ag 13S 7 Ag 15 S 8 Ag 17S m/z

89 A 5x10 5 Intensity (a.u.) 4x10 5 2x10 5 1x10 5 I II Ag 4 (H 2 MSA) 4 in toluene Ag 4 (H 2 MSA) 4 in water λ/nm

90 Clusters in proteins Lourdu Xavier, Kamalesh Choudhari

91 E. F. Schumacher

92 Nano Mission, Department of Science and Technology Thanks! IIT Madras