Host-Guest Antenna Materials for Light Harvesting, Transport and Trapping

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1 Host-Guest Antenna Materials for Light Harvesting, Transport and Trapping New Building Blocks for Solar Energy Conversion Devices Gion Calzaferri Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern Unidirectional Antenna

2 Table of Contents 1. Host-Guest Antenna Materials, Principles 1.1 Zeolites, a short introduction 1.2 Structure and framework of three important zeolites, A, Y and L 1.3 Some applications 1.4 Ship in a bottle synthesis 1.5 Ion exchange, position of cations, ph inside 1.6 Inner and outer surface 2. Electronic Excitation Energy Migration and The Stopcock Principle 2.1 Radiationless transfer of electronic excitation energy 2.2 Zeolite L is an ideal host for supramolecular organization of dyes 2.3 A Förster energy transfer experiment 2.4 Sequential insertion of dyes 2.5 The stopcock principle - Functional stopcocks 2.6 Organizing supramolecular functional dye-zeolite crystals 2.7 New materials, an overview 3. New Building Blocks for Solar Energy Devices 3.1 New dye-zeolite guest-host antenna materials 3.2 Sensitized thin layer solar cells 3.3 Sensitized thin layer Si-based solar cells 3.4 Sensitized organic solar cells 3.5 Luminescent concentrators 3.6 Summary

3 1.1 Zeolites, a short introduction STILBITE: NaCa 2 Al 5 Si 13 O 36-14H 2 O NATROLITE: Na 2 Al 2 Si 3 O 10-2H 2 O HEULANDITE: (Ca, Na) 2-3Al 3 (Al, Si) 2 Si 13 O 36-12H 2 O Natural zeolites combine rarity, beauty, complexity and unique crystal habits. Typically forming in the cavities, or vesicles, of volcanic rocks, zeolites are the result of very low grade metamorphism. Classical Zeolites are framework silicates consisting of interlocking tetrahedrons of SiO 4 and AlO 4. In order to be a zeolite the ratio (Si +Al)/O must equal 1/2. The alumino-silicate structure is negatively charged and attracts the positive cations that reside within. Zeolites have large vacant spaces or cages in their structures that allow space for cations such as Na +, K +, Ba 2+, Ca 2+, molecules and cation groups such as water, ammonia, carbonate ions and nitrate ions. In many zeolites, the spaces are interconnected and form long wide channels of varying sizes depending on the mineral. These channels allow the easy movement of the resident ions and molecules into and out of the structure.

1.1 Zeolites, a short introduction A L Y Zeolites are formed by the linking together tetrahedral SiO 4 and AlO 4 to give 3-dimensional anionic networks in which each oxygen of a given tetrahedron is

4 1.1 Zeolites, a short introduction A L Y Zeolites are formed by the linking together tetrahedral SiO 4 and AlO 4 to give 3-dimensional anionic networks in which each oxygen of a given tetrahedron is shared between this tetrahedron and one of the four others. Thus there are no unshared oxygen's in the frameworks. This means that (Al + Si):O = 1:2. For every Si +4 which is replaced in the framework by Al +3 a negative charge is created which is neutralized by a charge equivalent of cations. Additionally in zeolites the framework is sufficiently open to accommodate water as well as cations. This openness imparts characteristic zeolite properties, e.g. their ability to lose and absorb water without damage to their crystal structures.

5 1.1 Zeolites, a short introduction Zeolites have been studied by mineralogists for almost 250 years.

6 1.1 Zeolites, a short introduction 1756: A. F. Cronstedt History of zeolites starts with the discovery of Stilbite. Cronstedt described behavior under fast heating conditions. The mineral seemed to boil because of the fast water loss. ζειν = zein = to boil λιϑος = lithos = stone ZEOLITE

7 1.1 Zeolites, a short introduction Until the early 1940 s attempts to synthesize zeolites were made by mineralogists interested in the stability with other minerals. Union Carbide pioneered the synthetic molecular sieve zeolite business, initiating research in 1948 on adsorption for purification, separation and catalysis. 1950: Synthesis of pure zeolite A and X. 1953: Patent filed for zeolite A and X. 1954: Final structure of zeolite A and X. 1956: Zeolite X with high silica/alumina ratios zeolite Y. 1956: Structure of zeolite A published. 1958: Structure of zeolite X published. 1959: Patent granted.

8 1.1 Zeolites, a short introduction Classical and General Definition Classical: Aluminosilicate open network of corner-sharing [AlO 4 ] and [SiO 4 ] tetrahedra (Al, Si T-atoms build framework). Charge of the framework is compensated by mono or divalent cations or protons within the cavities or channels. Exchange capability of cations. Additional water molecules are present in the cavities. General: Three-dimensional framework of tetrahedrally coordinated T-atoms with cavities or channels with the smallest opening larger than six T- atoms. T-atoms: Si, Al, P, As, Ga, Ge, B, Be, etc.

9 1.1 Zeolites, a short introduction The code consists of 3 capital letters. Usually derived from the name of the type materials. For interrupted frameworks the 3-letter code is preceded by a hyphen (-). For intergrown materials, the * denotes a framework of a hypothetical end member. Code Abbreviated NameFull Name LTA Linde Type A Zeolite A (Linde Division, Union Carbide) LTL Linde Type L Zeolite L (Linde Division, Union Carbide) FAU Faujasite MFI ZSM-5 (five) Zeolite Socony Mobil five -CLO Cloverite Four-leafed clover shaped pore opening *BEA Zeolite Beta

10 1.1 Zeolites, a short introduction

11 1.2 Structure and framework of three important zeolites, A, L and Y LTA Sodium zeolite A: Na 12 [(SiO 2 ) 12 (AlO 2 ) 12 ] 27H 2 O 3 μm M + Framework of Zeolite A H 2 O H 2 O H 2 O Al 3+ H 2 O H O 2-2 O H 2 O Si 4+ α-cage: = 11.4 Å

12 1.2 Structure and framework of three important zeolites, A, L and Y LTA Realized by Dr. A. Currao, DCB Univ. of Bern, group Prof. G. Calzaferri

13 1.2 Structure and framework of three important zeolites, A, L and Y LTL Realized by Dr. A. Currao, DCB Univ. of Bern, group Prof. G. Calzaferri

14 1.2 Structure and framework of three important zeolites, A, L and Y FAU Realized by Dr. A. Currao, DCB Univ. of Bern, group Prof. G. Calzaferri

15 1.3 Some applications Purification of gaseous and liquid mixtures and solutions by sorption (activation by evacuation and heating). Reversible sorption capacity for water. Removal of odors and pollutants. Ion exchange. Softening of water for washing (substituted polyphosphates). Removal of heavy metal ions in mine wastewater and radioactive fission products (Cs, Sr). Natural zeolites used for soil fertilizing purposes (Submit ions of potassium, ammonium, phosphate). Catalysis in petrochemical industries (conversion of organic molecules in liquid and gaseous phase). Host material for synthesis in a confined space, new sensor devices, pigments, diagnostics, electronics etc. For applications of zeolites see:

16 1.3 Some applications Inorganic-inorganic host-guest systems Lapis Lazuli (Lazurite) S & 3 in sodalite cages

17 1.3 Some applications

18 1.3 Some applications

19 1.4 Ship in a bottle synthesis of complexes, molecules and quantum dots in the voids and channels of zeolites Zeolites can act as protecting hosts for supramolecular organization of different kinds of atoms, ions, and molecules. This leads to host guest materials with a large variety of challenging properties. A common way to obtain zeolite guest systems is by means of a ship-in-a bottle synthesis. This name is due to artistic bottles containing a ship that is larger than the bottle neck. In chemistry it means the insitu synthesis of compounds occluded in a host material. This is done by inserting sufficiently small molecules and ions into the cavities of the host and allowing further reaction until the product is too large to leave the cavities. A classical example is the synthesis of Ru 2+ (bpy) 3 in zeolite Y. Limits of the in Situ Synthesis of Tris(2,2-bipyridine)ruthenium(II) in the Supercages of ZeoliteY Philippe Laine, Martin Lanz, Gion Calzaferri, Inorg. Chem. 1996, 35, 3514

C NaA Quartz Synthesis of Silver Sulfide Clusters Ag + Na + -H 2 O H 2

20 1.4 Ship in a bottle synthesis Monolayers of Zeolite A containing Luminescent Silver Sulfide Clusters + Quartz Sedimentation at RT Δ 550 C NaA Quartz Synthesis of Silver Sulfide Clusters Ag + Na + -H 2 O H 2 S +H 2 O Ag + Ag 2 S C. Leiggener, G. Calzaferri, ChemPhysChem. 2004, 5, 1593

pseudo unit cell in 6-ring positions, 3 ions in 8-ring positions 1 ion in

21 1.5 Ion exchange, position of cations, ph inside LTA Ion exchange and position of the cations are exemplified for Zeolite Na-A 8 sodium ions per pseudo unit cell in 6-ring positions, 3 ions in 8-ring positions 1 ion in a 4-ring position J.J. Pluth, J. V. Smith, J. Am. Chem. Soc. 1980, 102,

22 1.5 Ion exchange, position of cations, ph inside LTA M. Meyer, C. Leiggener, G.Calzaferri ChemPhysChem 6 (2005) 1071

1.5 Ion exchange, position of cations, ph inside LTA Spectroscopic

23 1.5 Ion exchange, position of cations, ph inside LTA Spectroscopic measurements on dehydrated zeolite Ag + x Na+ 12-x -A: a: x = 0 b: x = 0.5 c: x = 1 d: x = 1.5 e: x = 6 x = 0 x = 0.13 x = 6 Only 4-ring Ag + yields yellow color. 4-ring Na + is first exchanged ion! Absorption band of 8-ring Ag + emerges when x > 1 R. Seifert, A. Kunzmann, G. Calzaferri, Angew. Chem. Int. Ed. 1998, 37, R. Seifert, R. Rytz, G. Calzaferri, J. Phys. Chem. A 2000, 104,

24 1.5 Ion exchange, position of cations, ph inside LTA Na + vs. Ag + exchange in zeolite Na-A: M. Meyer, C. Leiggener, G.Calzaferri, ChemPhysChem 6 (2005) 1071

K + has only position 4 to 6 in the exchange sequence.

25 1.5 Ion exchange, position of cations, ph inside LTA Spectroscopic measurements on dehydrated zeolite Ag + x K+ 12-x -A x = 2 x = 5 x = 6 4-ring K + has only position 4 to 6 in the exchange sequence. First, three to four 6-ring K + are exchanged. M. Meyer, C. Leiggener, G.Calzaferri, ChemPhysChem 6 (2005) 1071

26 1.5 Ion exchange, position of cations, ph inside LTL ph K 9 [Al 9 Si 27 O 72 ] 3.6 monovalent cations per u.c. can be exchanged readily

27 1.5 Ion exchange, position of cations, ph inside LTL K 9 [Al 9 Si 27 O 72 ] X + + (M + 9) Zeol-L (X +,M + 8)Zeol-L+ M + H + + (M + 9) Zeol-L (H +,M + 8)Zeol-L+ M + 1 H + per u.c corresponds to a H 3 O + /H 2 O ratio of 1: M HCl has H 3 O + /H 2 O ratio of 1:21

28 1.5 Ion exchange, position of cations, ph inside LTL K 9 [Al 9 Si 27 O 72 ] X + + (M + 9) Zeol-L (X +,M + 8)Zeol-L+ M + H + + (M + 9) Zeol-L (H +,M + 8)Zeol-L+ M + M X x Y 2+ x [Al 9 Si 27 O 72 ] composition ph inside pk a of ion (zeol in water) K 9 [Al 9 Si 27 O 72 ] 3,4 14 K 5.7 Li 3.3 [Al 9 Si 27 O 72 ] 3,5 13,6 K 4 Cs 5 [Al 9 Si 27 O 72 ] 3,7 - K 5 Ca 2 [Al 9 Si 27 O 72 ] 3,1 12,7 K 5.4 Mg 1.7 [Al 9 Si 27 O 72 ] 2,8 11,2 Host-Guest Antenna Materials, G. Calzaferri, S. Huber, H. Maas, C. Minkowski, Angew. Chem. Int. Ed. 42 (2003) 3733

29 1.5 Ion exchange, position of cations, ph inside LTL H 3 C H 3 C N N + N + CH 3 H + H 3 C + DSM + HDSM ++ H H 3 C N + CH 3 1 HDSM 2+ DSM + A 4 Lithium Kalium Cäsium Magnesium Calcium rel. absorption wavelength / nm Wellenlänge [nm] pk a = 3.4 Host-Guest Antenna Materials, G. Calzaferri, S. Huber, H. Maas, C. Minkowski, Angew. Chem. Int. Ed. 42 (2003) 3733

30 1.5 Ion exchange, position of cations, ph inside LTL pk a1 = 11.3 pk a2 = -1.2 pk* a2 = 1.2 Light-harvesting host-guest antenna materials for photonic devices G. Calzaferri, S. Huber, A. Devaux, A. Zabala Ruiz, H. Li, O. Bossart, L-Q. Dieu, Proc. of SPIE, Organic Optoelectronics and Photonics II, Vol

31 1.5 Ion exchange, position of cations, ph inside LTL HRGG( S ) HRGG( S )* hν 0 1 HRGG( S )* HRGG( S ) + hν ' 1 0 HRGG( S )* + H HRGG H ( S ) + excited state + 1 protonation 1 + HRGG H ( S ) HRGG( S ) very fast 1 thermal relaxation 0 The pk a * is in the order of 2

32 1.5 Ion exchange, position of cations, ph inside LTL O S Mg 2+ K + Cs + Mg 2+ K + Cs + Internal report, research group G. Calzaferri, January 2006

268 d 3 Z 2 Z For a molecule of the size of Ox + which occupies two unit cells, we have: l Z = d Z = 60 nm n c = 960 n uc = 77 10 3 q = 3 l Z = d

33 1.6 Inner and outer surface LTL The concept is exemplified for Zeolite L q = number of molecules to fill the channels of a crystal number of molecules to form a monolayer at the outer surface Number of unit cells n uc : Number of channels n c : n n c uc = d = d 3 Z 2 Z For a molecule of the size of Ox + which occupies two unit cells, we have: l Z = d Z = 60 nm n c = 960 n uc = q = 3 l Z = d Z = 600 nm n c = n uc = q = 30 q = d Z 20 Host-Guest Antenna Materials, G. Calzaferri, S. Huber, H. Maas, C. Minkowski, Angew. Chem. Int. Ed. 42 (2003) 3733

34 1.6 Inner and outer surface LTL Hypochlorite destroys only dye molecules at the outer surface! Host-Guest Antenna Materials, G. Calzaferri, S. Huber, H. Maas, C. Minkowski, Angew. Chem. Int. Ed. 42 (2003) 3733

1.6 Inner and outer surface LTL 6 5 4 3 2 1 Right: absorption spectra measured under the same conditions at different times after mixing an aqueous zeolite suspension with Ox +.

35 1.6 Inner and outer surface LTL Right: absorption spectra measured under the same conditions at different times after mixing an aqueous zeolite suspension with Ox +. 1: 30 s; 2: 9 min; 3: 190 min; 4: 1 d; 5: 7 d. Left: fluorescence spectra of Ox + -zeolite L dispersions at room temperature measured at different times after mixing an aqueous zeolite suspension with the dye: 1: 10 s; 2: 30 s; 3: 90 s; 4: 4 min; 5: 4 h; 6: 18 h. The excitation wavelength was 580 nm.

36 1.7 Summary 1. Host-Guest Antenna Materials, Principles 1.1 Zeolites, a short introduction 1.2 Structure and framework of three important zeolites, A, Y and L 1.3 Some applications 1.4 Ship in a bottle synthesis of complexes, molecules and quantum dots in the voids and channels of zeolites 1.5 Ion exchange, position of cations, ph inside 1.6 Inner and outer surface 1.7 Summary

Helen M. Lang West Virginia University

Zeolites and their Applications Helen M. Lang West Virginia University Zeolite Mineralogy Zeolites are framework silicates, with a completely linked framework of tetrahedra, each consisting of 4 O 2- surrounding