Evolution of Silver Nanoparticles within an Aqueous Dispersion of

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Evolution of Silver Nanoparticles Within an Aqueous Dispersion of Nano-Sized Zeolite Y: Mechanism and Applications Michael Severance, and Prabir K Dutta J. Phys. Chem. C, Just Accepted Manuscript • Publication Date (Web): 19 Nov 2014 Downloaded from http://pubs.acs.org on November 20, 2014

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The Journal of Physical Chemistry

Evolution of Silver Nanoparticles Within an Aqueous Dispersion of Nano-Sized Zeolite Y: Mechanism and Applications Michael Severance and Prabir K Dutta * Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210.

*To whom correspondence should be addressed. Email: [email protected], Telephone: (614) 2924532

1 ACS Paragon Plus Environment


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Keywords : dihydroxyphenols, resorcinol, SERS, nitrophenol reduction, silver growth Abstract: Stable aqueous dispersion of silver ion-exchanged nanozeolite Y was reacted with the three common dihydroxyphenols, hydroquinone, catechol and resorcinol. With hydroquinone and catechol, there was rapid reduction of the intrazeolitic silver to form metallic silver with complete destruction of the zeolite framework. Resorcinol, the weakest reducing agent amongst the group behaved differently. The formation of metallic silver was considerably slower, and the zeolite framework was mostly intact. This made it possible to examine the evolution of silver cluster formation with optical spectroscopy and transmission electron microscopy. In the first 135 min of reaction, extinction/fluorescence spectroscopy indicates the formation of Agn4 clusters. The smaller clusters disappear more rapidly with time. For the 1 hr reduced sample, transmission electron microscopy showed uniform distribution of 1.4 nm Ag particles throughout the zeolite. After 2 hr of reduction, the average size of the particles was 2.5 nm, and a fraction of these particles appeared on the zeolite surface. With further time of reduction (3-24 hr), more of the intrazeolitic Ag migrated to the surface, and Ostwald ripening into larger nanoparticles (> 3 nm) was observed at the zeolite-solution interface. We propose that the slow growth of the silver prevented the destruction of the zeolite framework. Two factors are considered important for the slow growth of silver with resorcinol. First, resorcinol is a weak reducing agent. Second, and more importantly, the intrazeolitic pH drops upon initial silver reduction, as measured by an acidochromic dye, which raises the reduction potential of resorcinol, thereby arresting further reduction and particle growth. By removing the resorcinol at any stage of the reduction, stable Ag nanoparticles on nanozeolite samples can be isolated. Such samples were investigated as SERS substrates as well as a heterogeneous 2 ACS Paragon Plus Environment

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catalyst. Optimal SERS enhancement as well as the optimal rate of reduction of nitrophenol by NaBH4 was observed with the sample obtained after reaction with resorcinol for 2 hr.



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1. Introduction Metal-based nanostructures are an active area of research, driven by their unique catalytic, optical, and electrical properties. In particular, silver nanoparticles are extensively studied as substrates for surface enhanced Raman scattering,1 anti bacterial agents,2,3 and catalysts.4 In each of these applications, the surface characteristics of the Ag particle is relevant, e.g., the under coordinated nature of the surface atoms are hypothesized to contribute to active catalytic sites.5 Stabilization of Ag nano particles require capping/stabilizing agents.6 Inclusion of stabilizing agents can modify the surface properties and interfere in certain applications. One approach to this problem is to stabilize nanoparticles on a support that prevents aggregation or dissolution. This general approach has been demonstrated for a variety of metal nanoparticles. In fact, alumina supported silver nanoparticles are used as a catalyst for ethylene oxide production.7 The activity of alumina supported silver nanoparticles ( 20 nm. The rate determining step in the lower temperature regime was considered to be the reduction of Ag+ to Ag0. The formation mechanism of the larger particles (~20 nm) is not well understood.58 A recent study of Ag+-mordenite by H2 proposed a multistep process for Ag nanoparticle growth. Based on PDF analysis, the model noted that Ag+ reduction in 8 versus the 12 numbered channels occur at different rates, and that Ag clusters formed within the 12-ring channels diffuse to the zeolite and aggregate to form nanoparticles.41 The present study is a demonstration of Ag growth in hydrated zeolites using aqueous chemical reducing agents for the first time, with characteristics of nucleation, growth and Ostwald ripening comparable to studies in dehydrated zeolites and in solution. 23 ACS Paragon Plus Environment


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4.3

Properties of Silver Loaded Zeolite as a function of nanoparticle size

We demonstrate two novel characteristics of the resorcinol reduced Ag-Y, especially the sample obtained after 2 hr reduction. Silver nanoparticles and nanostructures are employed as surface enhanced Raman scattering substrates. Much effort in preparing innovative SERS substrates involves engineering electromagnetic "hot-spots" where the plasmons of neighboring metal particles, or surface features, constructively interact to form high electric fields.1 The sample obtained after 2 hr reduction gives the highest, most reproducible SERS enhancements (Figure 8), with enhancement factor of 104. This is comparable to enhancement factors characteristic of silver loaded membranes and colloidal silver sols.60 Densely formed silver particles formed within and outside the ordered 3D array of supercages in nanozeolites thus provide a method of preparing solution dispersed SERS substrates. The reduction of 4-nitrophenol to 4-aminophenol with NaBH4 is known to be catalyzed by silver nanopartilces, and shows a strong size dependent effect, with smaller Ag nanoparticles exhibiting higher rate constants.61–63 Figure 9 shows that the apparent rate constant is maximum for the 2 hr sample. The lower apparent rate constant with the sample beyond 2 hr is due to increasing size of silver particles (dissociated from the zeolite and mostly in the bulk). For the 30 min sample, there was no catalytic activity, as the clusters were not large enough to form nanoparticles. With both the 1- and 2 hr samples, silver nanoparticles are observed in or on the zeolite by TEM (Figure 6ab). The redox potential of Ag nanoparticles (Ep) is predicted to decrease with size, and Ep was calculated according to the following equation:64


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= −

2γν zFr

Where Ebulk = +0.8V, γ = 1.140x10-4 J cm-2 is the surface tension, ν is the molar volume (10.28 cm3/mole), z is the charge (=1), F is Faraday’s constant, and r is the radius of Ag nanoparticles. We found Ep to be +0.45 and +0.60 eV for the 1 and 2 hr sample, suggesting that a faster rate of electron transfer from the Ag nanoparticle to the 4-nitrophenol should be observed with the 1hour sample. The experimental observation is that maximum rate was obtained with the 2-hour sample. It is well recognized, especially with Au nanoparticles, that maximum catalytic activity in a reaction such as CO oxidation peaks with 2-3 nm particle, and then drops off as particles get smaller or larger.65,66 Such a phenomena could be going on with the current study, but more likely is that with the 1-hour sample, the silver nanoparticles are primarily within the zeolite, and the slower reaction rate may just reflect lower diffusion constants of 4-NP within the zeolite. For the 2-hour sample, the silver nanoparticles are primarily on the zeolite surface, readily accessible to 4-NP. Nevertheless, these results with 1-3 nm Ag particles stabilized on the nanozeolite are among the first solution based catalytic studies in this size range with zeolite supported silver.

5. Conclusions This work examines the evolution of silver ions reduced within the micropores of nanozeolite Y using dihydroxyphenols as reducing agents. Zeolite framework destruction was observed in cases utilizing catechol and hydroquinone. With resorcinol, silver can be effectively reduced to nanoparticles while maintaining a uniform dispersion within the zeolite host, and evolution of these particles was investigated. Initial reaction involves transformation of silver ions to silver clusters. A wide range of cluster types varying in the number of silver monomers were detected



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using optical spectroscopy, Agn+ (1≤n≤10) during the first two hours of the reaction. Transmission electron microscopy shows the presence of 1.4 nm Ag nanoparticles distributed throughout the zeolite after one hour. With further reaction time, larger silver particles grew at the zeolite solution interface, and eventually fell off into the bulk solution, keeping the zeolite structure mostly intact. We propose that the slow reaction of silver cluster growth is due to the formation of extraframework protons within the zeolite as redox by-products of resorcinol. The zeolite, by virtue of these charge balancing protons, alters the reduction potential of resorcinol, thereby slowing/stopping the rate of reduction, and regulating the kinetics of growth of intrazeolitic silver nanoparticles. Growth at the zeolite/solution interface is promoted by silver ion exchange that brings a steady supply of silver ions to the surface where they are subsequently reduced to form larger particles. By stopping the reduction reaction at one or two hours, this study provided a method to synthesize and isolate stable highly dispersed nanozeolite supported silver nanoparticles with sizes of 1-3 nm. Product obtained with the two hour reduction is demonstrated to be the most effective colloidal SERS substrate, with enhancement factors of ~104, as well as an efficient catalyst for NaBH4 reduction of nitrophenols.


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Acknowledgements The authors gratefully acknowledge the support of Henk Colijn at the Ohio State University's Center for Electron Microscopy and Analysis and Dr. Jim Ciston along with the staff of the National Center for Electron Microscopy at the Lawrence Berkeley National Laboratory. Supporting Information UV-Vis abosorption spectra of the DSM+ molecule as a function of pH, nitrogen adsorption and desorption isotherms for the silver loaded zeolite materials, growth kinetics of the silver surface plasmon band as a function of resorcinol concentration, and under aerated versus deaerated conditions, silver particle size distributions, HAADF-STEM image of reaction products after 24 hrs., and SERS spectra as a function of the sample cuvette depth are contained in supporting information. This material is available free of charge via the internet at http://pubs.acs.org.



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References 1. Schatz, G. C.; Van Duyne, R. P. Handbook of Vibrational Spectroscopy. John Wiley & Sons, Ltd, 2006 2. Morones, J. R.; Elechiguerra, J. L.; Camacho, A.; Holt, K.; Douri, J. B.; Ramirez, J. T.; Yacaman, M. J. The bactericidal effect of silver nanoparticles. Nanotechnology 2005, 16, 2346–2353 3. Eckhardt, S.; Brunetto, P. S.; Gagnon, J.; Priebe, M.; Giese, B.; Fromm, K. M. Nanobio Silver: Its interactions with peptides and bacteria, and its uses in medicine. Chem. Rev. 2013, 113, 4708-4754 4. Van Santen, R. A.; de Groot, C. P. M. The mechanism of ethylene epoxidation. J. Catal. 1986, 98, 530–539 5. Auffan, M.; Rose, J.; Bottero, J-Y.; Lowry, G. V.; Jolivet, J-P.; Wiesner, M. R. Towards a definition of inorganic nanoparticles from an environmental, health and safety perspective. Nat. Nanotechnol. 2009, 4, 634–641 6. Sun, Y. Controlled synthesis of colloidal silver nanoparticles in organic solutions: empirical rules for nucleation engineering. Chem. Soc. Rev. 2013, 42, 2497-2511 7. Serafin, J. G.; Liu, A. C.; Seyedmonir, S. R. Surface science and the silver-catalyzed epoxidation of ethylene: an industrial perspective. J. Mol. Catal. Chem. 1998, 131, 157–168 8. Lei, Y.; Mehmood, F.; Lee, S.; Greeley, J.; Lee, B.; Seifert, S.; Winans, R. E.; Elam, J. W.; Meyer, R. J.; Redfern, P. C.; et al. Increased silver activity for direct propylene epoxidation via subnanometer size effects. Science 2010, 328, 224–228


Page 28 of 45

Page 29 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


9. Sezin Galiog ˘lu, M. Z. Effect of silver encapsulation on the local structure of titanosilicate ETS-10. Microporous Mesoporous Mater. 2012, 159, 1–8 10. Sasaki, Y.; Suzuki, T. Formation of Ag clusters by electron beam irradiation of Ag-zeolites. Mater. Trans. 2009, 50, 1050–1053 11. Shameli, K.; Mansor Bin Ahmad, M.; Mohsen, Z.; Yunis, W. Z.; Ibrahim, N. A. Fabrication of silver nanoparticles doped in the zeolite framework and antibacterial activity. Int. J. Nanomedicine 2011, 6, 331-341 12. Lin, D.-H.; Jiang, Y.-X.; Wang, Y.; Sun, S.-G. Silver Nanoparticles confined in SBA-15 mesoporous silica and the application as a sensor for detecting hydrogen peroxide. J. Nanomater. 2008, 2008, 1–10 13. Shibata, J.; Takada, Y.; Shichi, A.; Satokawa, S.; Satsuma, A.; Hattori, T. Ag cluster as active species for SCR of NO by propane in the presence of hydrogen over Ag-MFI. J. Catal. 2004, 222, 368–376 14. Sazama, P.; Jirglová, H.; Dědeček, J. Ag-ZSM-5 zeolite as high-temperature water-vapor sensor material. Mater. Lett. 2008, 62, 4239–4241 15. Mazzocut, A.; Coutino-Gonzalez, E.; Baekelant, W.; Sels, B.; Hofkens, J.; Vosch, T. Fabrication of silver nanoparticles with limited size distribution on TiO2 containing zeolites. Phys. Chem. Chem. Phys. 2014, 16, 18690–18693 16. Luchez, F.;Tahri, Z.; De Waele, V.; Yordanov, I.; Mintova, S.; Moissette, A.; Mostafavi, M.; Poizat, O. Photoreduction of Ag+ by diethylaniline in colloidal zeolite nanocrystals. Microporous Mesoporous Mater. 2014, 194, 183–189



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

17. Zaarour, M.; El Roz, M.; Dong, B.; Retoux, R.; Aad, R.; Cardin, J.; Dufour, C.; Gourbileau, F.; Gilson, J-P.; Mintova, S. Photochemical preparation of silver nanoparticles supported on zeolite crystals. Langmuir 2014, 30, 6250–6256 18. De Cremer, G.; Sels, B. F.; Hotta, J-I.; Roeffaers, M. B. J.; Bartholomeeusen, E.; CoutinoGonzalez, E.; Valtchev, V.; De Vos, D. E.; Vosch, T.; Hofkens, J. Optical encoding of silver zeolite microcarriers. Adv. Mater. 2010, 22, 957–960 19. Sayah, E.; Brouri, D.; Massiani, P. A comparative in situ TEM and UV–visible spectroscopic study of the thermal evolution of Ag species dispersed on Al2O3 and NaX zeolite supports. Catal. Today 2013, 218-219, 10-17 20. Nagy, A.; Harrison, A.; Sabbani, S.; Munson Jr., R. S.; Dutta, P. K.; Waldman, W. J. Silver nanoparticles embedded in zeolite membranes: release of silver ions and mechanism of antibacterial action. Int. J. Nanomedicine 2011, 6, 1833-1852 21. Dutta, P. K.; Robins, D. Silver-coated faujasitic zeolite crystals as surface-enhanced Raman spectroscopic substrates. Langmuir 1991, 7, 2004–2006 22. Holmberg, B. A.; Wang, H.; Norbeck, J. M.; Yan, Y. Controlling size and yield of zeolite Y nanocrystals using tetramethylammonium bromide. Microporous Mesoporous Mater. 2003, 59, 13–28 23. Le Ru, E. C.; Blackie, E.; Meyer, M.; Etchegoin, P. G. Surface enhanced raman scattering enhancement factors: A comprehensive study. J. Phys. Chem. C 2007, 111, 13794–13803 24. Koppel, D. E. Analysis of macromolecular polydispersity in intensity correlation spectroscopy: The method of cumulants. J. Chem. Phys. 1972, 57, 4814–4820 25. Provencher, S. CONTIN: A general purpose constrained regularization program for inverting noisy linear algebraic and integral equations. Comput. Phys. Commun. 1982, 27, 229–242


Page 30 of 45

Page 31 of 45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


26. Lowell, S.; Shields, J. E.; Thomas, M. A.; Thommes, M. Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density. p. 58–81, Springer Netherlands, 2004 27. Lowell, S.; Shields, J. E.; Thomas, M. A.; Thommes, M. Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density. p. 101–128, Springer Netherlands, 2004 28. Bartolomeu, R.; Bértolo, R.; Casale, S.; Fernandes, A.; Henriques, C.; da Costa, P.; Ribeiro, F. Particular characteristics of silver species on Ag-exchanged LTL zeolite in K and H form. Microporous Mesoporous Mater. 2013, 169, 137–147 29. Duarte, P.; Ferreira, D. P.; Lopes, T. F.; Pinto, J. V.; Fonseca, I. M.; Ferreira Machado, I.; Vieira Ferreira, L. F. DSM as a probe for the characterization of modified mesoporous silicas. Microporous Mesoporous Mater. 2012, 161, 139–147 30. Valtchev, V.; Rigolet, S.; Bozhilov, K. N. Gel evolution in a FAU-type zeolite yielding system at 90 degrees C. Microporous Mesoporous Mater. 2007, 101, 73–82 31. Gentry, S. T.; Fredericks, S. J.; Krchnavek, R. Controlled particle growth of silver sols through the use of hydroquinone as a selective reducing agent. Langmuir 2009, 25, 2613– 2621 32. De Cremer, G.; Roeffaers, M. B. J.; Moens, B.; Ollevier, J.; Van der Auweraer, M.; Schoonheydt, R.; Jacobs, P. A.; De Schryver, F. C.; Hofkens, J.; De Vos, D. E.; et al. Characterization of fluorescence in heat-treated silver-exchanged zeolites. J. Am. Chem. Soc. 2009, 131, 3049–3056 33. Joo, T. H.; Kim, M. S.; Kim, K. Surface-enhanced Raman scattering of benzenethiol in silver sol. J. Raman Spectrosc. 1987, 18, 57–60 34. Sun, T.; Seff, K. Silver clusters and chemistry in zeolites. Chem. Rev. 1994, 94, 857–870



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

35. Mitchell, S. A.; Ozin, G. A. Silver clusters in rare gas matrixes. Thermal and photochemical silver atom aggregation reactions. J. Phys. Chem. 1984, 88, 1425–1436 36. Gurin, V. S.; Bogdanchikova, N. E.; Petranovskii, V. P. Few-atomic silver clusters in zeolites: Ab Initio MO LCAO calculation and optical spectroscopy. J. Phys. Chem. B 2000, 104, 12105–12110 37. Gurin, V.; Petranovskii, V.; Bogdanchikova, N. Metal clusters and nanoparticles assembled in zeolites: an example of stable materials with controllable particle size. Mater. Sci. Eng. C 2002, 19, 327–331 38. Ozin, G. A.; Hugues, F.; Mattar, S. M.; McIntosh, D. F. Low nuclearity silver clusters in faujasite-type zeolites: optical spectroscopy, photochemistry and relationship to the photodimerization of alkanes. J. Phys. Chem. 1983, 87, 3445–3450 39. Ozin, G. A.; Hugues, F. Silver atoms and small silver clusters stabilized in zeolite Y: optical spectroscopy. J. Phys. Chem. 1983, 87, 94–97 40. Coutino-Gonzalez, E.; Roeffaers, M. B. J.; Dieu, B.; De Cremer, G.; Leyre, S.; Hanselaer, P.; Fyen, W.; Sels, B.; Hofkens, determination and optimization of the luminescence external quantum efficiency of silver-clusters zeolite composites. J. Phys. Chem. C 2003, 117, 6998– 7004 41. Zhao, H.; Nenoff, T. M.; Jennings, G.; Chupas, P. J.; Chapman, K. W. Determining quantitative kinetics and the structural mechanism for particle growth in porous templates. J. Phys. Chem. Lett. 2011, 2, 2742–2746 42. Jacob, J. A.; Mahal, H. S.; Biswas, N.; Mukherjee, T.; Kapoor, S. Role of phenol derivatives in the formation of silver nanoparticles. Langmuir 2008, 24, 528–533


Page 32 of 45

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


43. Wardman, P. Reduction potentials of one‐electron couples involving free radicals in aqueous solution. J. Phys. Chem. Ref. Data 1989, 18, 1637–1755 44. Linnert, T.; Mulvaney, P. Long-lived nonmetallic silver clusters in aqueous solution: preparation and photolysis. J. Am. Chem. Soc. 1990, 112, 4657-4664 45. Land, E. J. Preparation of unstable quinones in aqueous solution via pulse radiolytic oneelectron oxidation of dihydroxybenzenes. J. Chem. Soc. Faraday Trans. 1993, 89, 803–810 46. Panigrahi, S.; Praharaj, S.; Basu, S.; Ghosh, S. K.; Jana, S.; Pande, S.; Vo-Dinh, T.; Jiang, H.; Pal, T. Self-assembly of silver nanoparticles: Synthesis, stabilization, optical properties, and application in surface-enhanced Raman scattering. J. Phys. Chem. B 2006, 110, 13436– 13444 47. Steenken, S.; Neta, P. One-electron redox potentials of phenols. Hydroxy- and aminophenols and related compounds of biological interest. J. Phys. Chem. 1982, 86, 3661-3667 48. Steenken, S.; Neta, P. Electron transfer rates and equilibria between substituted phenoxide ions and phenoxyl radicals. J. Phys. Chem. 1979, 83, 1134-1137 49. Simo, A.; Polte, J.; Pfänder, N.; Vainio, U.; Emmerling, F.; Rademann, K. Formation mechanism of silver nanoparticles stabilized in glassy matrices. J. Am. Chem. Soc. 2012, 134, 18824–18833 50. Mostafavi, M.; Keghouche, N.; Delcourt, M.-O.; Belloni, J. Ultra-slow aggregation process for silver clusters of a few atoms in solution. Chem. Phys. Lett. 1990, 167, 193–197 51. Fedrigo, S.; Harbich, W.; Buttet, J. Collective dipole oscillations in small silver clusters embedded in rare-gas matrices. Phys. Rev. B 1993, 47, 10706–10715



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

52. Naik, B.; Hazra, S.; Prasad, V. S.; Ghosh, N. N. Synthesis of Ag nanoparticles within the pores of SBA-15: an efficient catalyst for reduction of 4-nitrophenol. Catal. Commun. 2011, 12, 1104–1108 53. Yan, S.; Wu, Z.; Yu. H.; Gong, Y.; Tan, Y.; Du, R.; Chen, W.; Xing, X.; Mo, G.; Chen, Z.; et al. Time-resolved small-angle X-ray scattering study on the growth behavior of silver nanoparticles. J. Phys. Chem. C 2014, 118, 11454–11463 54. Takesue, M.; Tomura, T.; Yamada, M.; Hata, K.; Kuwamoto, S.; Yonezawa, T. Size of elementary clusters and process period in silver nanoparticle formation. J. Am. Chem. Soc. 2011, 133, 14164–14167 55. Ott, L. S.; Finke, R. G. Transition-metal nanocluster stabilization for catalysis: A critical review of ranking methods and putative stabilizers. Coord. Chem. Rev. 2007, 251, 1075– 1100 56. Kecht, J.; Tahri, Z.; De Waele, V.; Mostafavi, M.; Mintova, S.; Bein, T. Colloidal zeolites as host matrix for copper nanoclusters. Chem. Mater. 2006, 18, 3373–3380 57. Gentry, S. T.; Kendra, S. F.; Bezpalko, M. W. Ostwald ripening in metallic nanoparticles: stochastic kinetics. J. Phys. Chem. C 2011, 115, 12736–12741 58. Beyer, H.; Jacobs, P. A.; Uytterhoeven, J. B. Redox behaviour of transition metal ions in zeolites. Part 2.—Kinetic study of the reduction and reoxidation of silver-Y zeolites. J. Chem. Soc. Faraday Trans. 1976, 72, 674–685 59. Mondloch, J. E.; Bayram, E.; Finke, R. G. A review of the kinetics and mechanisms of formation of supported-nanoparticle heterogeneous catalysts. J. Mol. Catal. Chem. 2012, 355, 1–38


Page 34 of 45

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


60. Liu, N.; Gong, M.; Zhang, P.; Li, L.; Li, W.; Lee, R. Silver-embedded zeolite crystals as substrates for surface-enhanced Raman scattering. J. Mater. Sci. 2011, 46, 3162–3168 61. Zhang, Z.; Shao, C.; Sun, Y.; Mu, J.; Zhang, M.; Zhang, P.; Guo, Z.; Liang, P.; Wang, C.; Liu, Y. Tubular nanocomposite catalysts based on size-controlled and highly dispersed silver nanoparticles assembled on electrospun silica nanotubes for catalytic reduction of 4nitrophenol. J. Mater. Chem. 2012, 22, 1387 62. Pradhan, N.; Pal, A.; Pal, T. Silver nanoparticle catalyzed reduction of aromatic nitro compounds. Colloids Surf. A 2002, 196, 247–257 63. Guo, M.; Feng, Z.; Hofmann, J. P.; Weckhuysen, B. M.; Fan, F.; Li, C. Synthesis and morphology control of AM-6 nanofibers with tailored -V-O-V- intermediates. Chem. Eur. J. 2013, 19, 14200–14204 64. Plieth, W. J. Electrochemical properties of small clusters of metal atoms and their role in the surface enhanced Raman scattering. J. Phys. Chem. 1982, 86, 3166–3170 65. Falsig, H.; Hvolbaek, B.; Kristensen, I. S.; Jiang, T.; Bligaard, T.; Christensen, C. H.; Norskov, J. K. Trends in the catalytic CO oxidation activity of nanoparticles. Angew. Chem. Int. Ed. 2008, 47, 4835–4839 66. Petkov, V.; Ren, Y.; Shan, S.; Luo, J.; Zhong, C.-J. A distinct atomic structure–catalytic activity relationship in 3–10 nm supported Au particles. Nanoscale 2013, 6, 532–538



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Figure 1: XRD patterns of a standard zeolite Y as simulated from the FAU structure (a), the assynthesized nanozeolite Y (b), silver exchanged nanozeolite Y (c) silver exchanged nanozeolite Y after 24hr of reduction with 0.1M resorcinol (d). ) silver exchanged nanozeolite Y after 24hr of reduction with 0.1M hydroquinone (e) ) silver exchanged nanozeolite Y after 24hr of reduction with 0.1M catechol (f). (Ag peaks marked with an asterisk).


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Figure 2: In-situ emission spectra of the DSM+-Ag+-Y mixed cation system excited at 450nm as a function of reduction time with resorcinol. Inset illustrates the pH dependence of DSM+ emission in solution.



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Figure 3: The evolution of the BET surface area (blue line, black diamonds) and the relative microporosity (red line, black dots) of the silver exchanged nanozeolite materials as a function of reduction time with resorcinol.


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Figure 4: Extinction spectra of an aqueous 0.1wt % silver exchanged nanozeolite dispersion reduced with 0.1M resorcinol after 2hrs. (a), 6hrs. (b), 12hrs. (c), and 24hrs. (d). No observable features were detected in the sample prior to 2hrs. Comparison of the evolution of the intensity of the 445 nm band of a solution of silver nitrate (silver sol) with that of silver exchanged nanozeolite (Ag-nanoY sol) with resorcinol. The major features in each extinction spectrum are labeled with a dotted black line.



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Figure 5: 2D excitation/emission maps of silver exchanged nanozeolite after 30 min (a), 60 min (b), 90 min (c), and 135 min (d) reaction with resorcinol.


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Figure 6: A collection of HAADF-STEM images showing the progress of the silver reduction of silver exchanged nanozeolite with resorcinol after 1hr. (a), 2hr. (b), 3hr. (c), 6hr. (d), 12hr. (e), and 24hr. (f). The bright spots in these images are due to silver particles.



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Figure 7: HAADF-STEM images following migration of silver species through the zeolite matrix toward large surface particles in silver exchanged nanozeolite samples reduced with resorcinol for 12hr. Panel (a) gives a unified view of a large region while panels (b-d) are magnified views of the boxes drawn in (a).


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Figure 8: Surface enhanced Raman spectra as a function of time for reduction of silver exchanged nanozeolite with resorcinol. The inset plots the change in the intensity of the 999cm-1 band of benzenethiol as a function of time. The enhancement factor (EF) calculated for the 2hr reduced sample is listed in the inset (104).



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Figure 9: UV-Vis spectra capturing the conversion of 4-nitrophenol to 4-aminophenol upon reaction with NaBH4 in the presence of silver exchanged nanozeolite reacted with resorcinol for 2 hr (a), a plot of the observed pseudo first order rate constant for several samples isolated at different times after reaction of silver exchanged nanozeolite with resorcinol (b), and the plot of the logarithm of absorbance vs. time for the sample of silver exchanged nanozeolite reduced by resorcinol for 2 hr, the slope being the first order rate constant (c). 44 ACS Paragon Plus Environment

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Evolution of Silver Nanoparticles within an Aqueous Dispersion of

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