# Fileset

[■ApplClaySci_UC-clay SI.pdf](https://mdr.nims.go.jp/filesets/35e36f20-7428-4c4a-accb-f70a1127205b/download)

## Creator

Akihiko Yamagishi, [Kenji Tamura](https://orcid.org/0000-0001-6578-0923), Shohei Yamamoto, Fumi Sato, Jun Yoshida, Hisako Sato

## Rights

[Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International](https://creativecommons.org/licenses/by-nc-nd/4.0/)

## Other metadata

[Up-conversion of photon energy in colloidal clay systems](https://mdr.nims.go.jp/datasets/fa88be60-66c4-442e-933d-dbfd6842c378)

## Fulltext

Microsoft Word - ■4 Revised Manuscript with no change1  Up-conversion of Photon Energy in Colloidal 1 Clay Systems 2  3 Akihiko Yamagishi,a Kenji Tamura,*b Shohei Yamamoto,c Fumi Sato,a Jun Yoshidad and 4 Hisako Sato* c 5  6 a School of Medicine, Toho University, Ohta-ku, Tokyo 143-8540, Japan  7 b Environmental Circulation Composite Materials Group, Research Center for Electronic 8 and Optical Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-9 0044, Japan  10 c Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, 11 Japan 12 d Department of Chemistry, College of Humanities & Sciences, Nihon University, 13 Setagaya-ku, Tokyo 156-8550, Japan 14  15 * TAMURA.Kenji@nims.go.jp 16  17  18  19  20  21  22 2  Abstract 23 The up-conversion (UC) of photon energy was attempted for the system of a 24 colloidal clay dispersion through the mechanism of triplet-triplet annihilation. Tris(1,10-25 phenanthroline)ruthenium(II) ([Ru(phen)3]2+) and 9, 10-diphenylanthracne (DPA) were 26 used as a donor and an acceptor, respectively. A used clay mineral was synthetic saponite. 27 A medium was 1:1:0.1 (v/v) methanol/dichloromethane/water. -[Ru(phen)3]2+ (4.9×10-28 5 M) was adsorbed by SAP (3.8×10-4 M) to 26 % CEC. The dispersion was irradiated by 29 a laser light (0.5 mW) at 450 nm in the presence of DPA (4.2×10-3 M). An emission with 30 the peak around 430 nm was observed under air. It implied the Ru(II) complex adsorbed 31 by a colloidal clay acted as a donor to achieve UC. Quantum yield of UC was estimated 32 to be 0.009 ± 0.003. The effect of stereoselectivity was investigated when a chiral 33 donor/acceptor pair was employed.  34  35  36  37 Keywords  38 Up-conversion; Synthetic saponite; Ruthenium(II) complex; 9,10-Diphenylanthracne; 39 Stereoselectivity 40   41 3  1. Introduction 42 The up-conversion of photon energy is the process that an incident light is converted 43 to an emission at shorter wavelength. The processes are investigated extensively with a 44 purpose of achieving the conversion of solar light to shorter wavelength, the chemical 45 reactions driven by visible light and the in situ sensing of biological samples (Yanai and 46 Kimizuka, 2017; Joarder et al., 2018; Liu et al., 2018; Schmidt et al., 2014; Sasaki et al., 47 2017). 48 One approach for up-conversion is the sensitized triplet–triplet annihilation 49 (denoted as TTA), in which two acceptor molecules having been excited to triplet states 50 collide to be disproportionated to the generation of one molecule at a higher singlet level 51 (Han et al., 2017; Li et al., 2021; Lu et al., 2017; Yanai and Kimizuka, 2017; Zhou, et al., 52 2020). Compared to the related approach of absorbing two photons simultaneously, 53 sensitized TTA-based technologies do not necessarily require extremely high light 54 intensities (Duan et al., 2013; El Roz and Castellano, 2017; Kerzig and Wenger, 2018; 55 Singh-Rachford et al., 2008; Wu et al., 2011). They are much more promising for solar 56 energy harvesting.  57 Recently a number of works have been reported to perform the up-conversion 58 process by use of various macromolecules as a host fixing either a donor or an acceptor 59 or both. The used hosts are organic polymers, gels and inorganic colloids (Kageshima et 60 al., 2021; Kashino et al., 2021; Lee et al., 2022; Yang et al., 2021). Among the attempts, 61 there is one paper reporting the use of a natural clay mineral (or montmorillonite) used as 62 a host (Kishimoto, et al., 2020). The present work uses a synthetic saponite as a 63 macromolecular host for the up-conversion. Comparing with montmorillonite, a synthetic 64 4  saponite includes no heavy metal ion, eliminating their quenching effects. The present 65 attempt was motivated by our works demonstrating the unique role of clay minerals in 66 photochemical reactions (Suzuki et al., 2009; Yamagishi et al., 1996a; Yamagishi and 67 Sato, 2012; Yoshida et al., 2020; Yoshida et al., 2021). As a two-dimensional adsorbent, 68 for example, a layered clay mineral is characterized by the following properties: (i) the 69 surface density of an adsorbed molecule is high when it is ion-exchanged with a photo-70 reactive cation and (ii) the surface arrangement of such cations exhibits two-dimensional 71 regularity. Due to these properties, photochemical reactions occurring on a clay surface 72 attain the high efficiency of energy conversion, energy transfer and molecular recognition. 73 It is demonstrated that the harvesting of photon energy is achieved at high efficiency when 74 two kinds of emitting metal complexes are adsorbed on a clay surface (Sato et al., 2014; 75 Tamura et al., 2015). This is due to the rapid energy transfer among adsorbed molecules. 76 Some metal complexes such as cyclomethalated Ir(III) complexes increase their emission 77 efficiency when they are adsorbed by a clay mineral (Takimoto et al., 2018). Quenching 78 by oxygen or solvent molecules is inhibited by the presence of exfoliated clay layers.  79 The above backgrounds motivated us to use a clay mineral as a medium for up-80 conversion. Using a colloidal dispersion of synthetic saponite, a laser light at 445 or 450 81 nm was up-converted to an emission at 430 nm by using tris(1,10-82 phenanthroline)ruthenium(II) as a donor and 1, 10-diphenylanthracene as an acceptor. 83 Moreover, the use of a clay mineral was found to increase UC efficiency under the low 84 concentration of an acceptor. Purposes of the present work are following: (i) to achieve 85 UC under air atmosphere; (ii) to introduce molecular recognition for UC to be utilized for 86 molecular sensing. 87 5   88 2. Experimental 89 2.1. Materials: Racemic tris(1,10-phenanthlorine)ruthenium chloride (denoted as 90 [Ru(phen)3]Cl2) was purchased from Tokyo Kasei Industries, Japan (Chart 1, right). Δ-91 [Ru(phen)3](ClO4)2 and Λ-[Ru(phen)3](ClO4)2 were obtained as described previously 92 (Yamagishi et al., 1996b). 9, 10-Diphenylanthracene (DPA) was purchased from Tokyo 93 Kasei Industries, Japan (Chart 1, left). Synthetic saponite (SAP) was purchased Kunimine 94 Industries (Japan). SAP was dissolved in an acid or alkali, and inductively coupled plasma 95 optical emission spectrometry (ICP-OES) (SPS3520UV-DD, Hitachi High–96 Technologies) was then used to determine the composition formula of the smectites from 97 the results of composition analysis for estimation of the absolute value of negative charge 98 per unit. The composition formula was determined to be 99 Na0.45(Mg3.11)(Si3.53Al0.40)O10(OH)2, and the measured cation exchange capacity (CEC) 100 was 65 cmol(+)/kg. The synthesis and identification of a chiral acceptor (denoted as SS-101 DPA-BINOL) was described in Supporting Information (Fig. S4). 102  103  104 Chart 1. Molecular structures of DPA (left) and [Ru(phen)3]2+ (phen = 1,10-105 phenanthroline) (right).  106 6   107 2.2 Instruments:  UV-vis spectra were measured with a U-3810 spectrometer (Hitachi, 108 Japan). Electronic circular dichroism spectra were measured a polarimeter J-720 (JASCO, 109 Japan). Emission spectra were recorded with a RF-5300 fluorometer (Shimazu, Japan). 110 Two systems were employed for the experiments of up-conversion. For recording the 111 emission spectra from a sample containing a donor and an acceptor, the UC system (LSP-112 1000, Unisoku, Japan) was used. Excitation light at 445 nm was incident continuously 113 from a CW laser at the emission power of 0.5 ~ 78 mW. 200 L of a sample solution was 114 mounted in a glass tube of 4 mm in diameter. The signal was accumulated by averaging 115 36 scans. For taking a photograph, 2 mL of a sample solution was mounted in a four-wall 116 quartz cell. The excitation light at 450 nm was incident from a continuous laser, GPD 117 Laser diode module (Power Technology, USA) at the emission power of 0.5 mW. 118 Emission spectra were recorded by a high-resolution spectrometer BIM-6001 (BroLight 119 Technology, China). The concentration of oxygen dissolved in a sample was measured 120 with an optical oxygen meter FSO2-C1(Pyroscience, Germany). The oxygen sensor tip 121 was placed at the bottom of a sample solution. 122  123 3. Results and Discussion 124 3.1. Quenching of emission from Δ-[Ru(phen)3]2+ by DPA: TTA involves the process 125 of energy transfer from an excited donor to an acceptor. The efficiency of the process was 126 studied by quenching the emission from a donor by an acceptor. As a donor and an 127 acceptor, Δ-[Ru(phen)3](ClO4)2 and DPA were used, respectively. The reason of using 128 7  the enantiomer (or Δ-[Ru(phen)3]2+) instead of the racemic mixture is described later 129 (Section 3.4). A solvent was a 1:1:0.1 (v/v) mixture of methanol, dichloromethane and 130 water. A medium was a 1:1:0.1 (v/v) mixture of methanol, dichloromethane and water. 131 The medium was selected from the viewpoints that [Ru(phen)3]2+ ions and DPA were 132 soluble and that SAP was well dispersed before adding [Ru(phen)3]2+ ions. The excitation 133 of Δ-[Ru(phen)3]2+ was performed by irradiating its solution sample by a light at 450 nm. 134 Under nitrogen atmosphere, excited Δ-[Ru(phen)3]2+ emitted a light with the peak at 570 135 nm as shown in Fig. 1 (curve a). The intensity of the emission lowered by replacing 136 nitrogen with air (curve b). Under air, oxygen molecules quenched excited Δ-137 [Ru(phen)3]2+. On adding SAP, the intensity of emission recovered partially (curve c). 138 This was because the exfoliated layers of SAP acted as a barrier against the attacking of 139 oxygen molecules. 140  141 8  Fig. 1. Emission spectra of Δ-[Ru(phen)3](ClO4)2 (1.9×10-5 M): (a) under nitrogen 142 atmosphere (black curve); (b) under air (red curve); (c) under air in the presence of 143 SAP (3.8×10-4 M in CEC) (blue curve). An excitation wavelength was 450 nm. A 144 medium was 1:1:0.1 (V/V) of dichloromethane/methanol/water. 145  146 The emission intensity decreased on adding DPA, indicating the occurrence of 147 energy transfer from excited Δ-[Ru(phen)3]2+ to DPA. The results are analyzed in terms 148 of the Stern-Volmer plots as below:  149 𝑰𝟎 𝑰⁄ 𝟏 𝑲𝐒𝐕 𝐃𝐏𝐀             (1) 150 Here Io and I are the intensity of the emission at 570 nm in the absence and presence of 151 DPA. KSV is the Stern-Volmer constant. In the absence of O2, KSV is expressed by: 152 𝑲𝐒𝐕 𝒌𝐪 𝒌𝐫⁄               (2) 153 Here kr and kq are the rate constants of spontaneous emission and quenching by DPA, 154 respectively. In the presence of O2, KSV is expressed by: 155 𝑲𝐒𝐕 𝒌𝐪 𝒌𝐫⁄ 𝟏 𝒌𝐪𝐪 𝐎𝟐 /𝒌𝐫𝟏                       𝟑  156 Here kqq is the rate constant of quenching by O2. The concentration of oxygen (denoted 157 as [O2]s) was obtained to be 2.2 mM, when the solvent was saturated with air. Figs. 2 (A), 158 (B) and (C) are the results of quenching experiments under nitrogen atmosphere, air and 159 air in the presence of SAP, respectively. For (B) and (C), the medium contained 2.2 mM 160 of oxygen molecules. In the investigated three cases, the plots followed a linear relation. 161 Table 1 gives the values of slopes (or KSV). The results implied that the energy transfer 162 from exited Δ-[Ru(phen)3]2+ to DPA proceeded predominantly under air, when [DPA] 163 was two times higher than [O2]s or c.a. 4 mM. 164 9   165  166 Fig. 2. The Stern-Volmer plots of the quenching of the emission from Δ-[Ru(phen)3]2+ 167 (1.9 × 10-5 M) excited at 450 nm: (a) under nitrogen atmosphere; (b) under air; (c) 168 under air in the presence of SAP (3.8 × 10-4 M in CEC). A medium was 1:1:0.1 (V/V) 169 of dichloromethane/methanol/water. 170 10   171 Table 1. Stern-Volmer constants for the quenching of emission from excited Δ-172 [Ru(phen)3]2+ by DPA under various conditions. 173 System Δ-[Ru(phen)3]2+ / M SAP / M in CEC KSV / M-1 kqq/kr Under nitrogen 1.9 × 10-5  0 2100 ― In air 1.9 × 10-5 0 490 1500 Under nitrogen (SAP) 1.9 × 10-5 3.9 × 10-4 450 ― In air (SAP)  1.9 × 10-5 3.9 × 10-4 210 490 (*) Excitation wavelength 450 nm 174 (**) [DPA] = 2×10-4 ~ 6×10-3 M 175 (***) Temperature = 300 K 176  177 3.2. Up-conversion of photon energy for a pair of Δ-[Ru(phen)3]2+ and DPA: Up-178 conversion of photon energy was investigated for a pair of Δ-[Ru(phen)3]2+ (donor) and 179 DPA (acceptor). Firstly, the homogeneous solution system of 1:1:0.1 (v/v) 180 methanol/dichloromethane/water was investigated under air. A solution containing Δ-181 [Ru(phen)3](ClO4)2 (4.9×10-5 M) was irradiated by a laser light at 445 nm. It gave an 182 emission with a peak at 570 nm (Fig. 3 (a)). When DPA (4.2×10-3 M) was added, a peak 183 at 430 nm appeared (Fig. 3(b)). The emission was assigned to the transition from the 184 singlet excited state of DPA. The intensity of the peak increased nearly quadratically with 185 the intensity of a laser light (Fig. S1). The results implied that the up-conversion of photon 186 energy from 445 nm to 430 nm was achieved for the used donor-acceptor pair. The 187 photographic images of Figs. S2 (a) and (b) confirmed the color change of emission light 188 from orange to blue on adding DPA.  189 11  Secondly the laser-irradiation experiments were performed on a colloidally 190 dispersion of Δ-[Ru(phen)3](ClO4)2 (4.9×10-5 M), DPA (4.2×10-3 M) and SAP (3.8×10-4 191 M in CEC) under air. The peak at 430 appeared on adding DPA, confirming the 192 occurrence of up-conversion in the presence of SAP (Fig. 3(c)). For the system containing 193 colloidal particles of SAP, the emission spectra were recorded within 10 minutes after 194 preparing the sample. SAP particles coagulated to a negligible extent within this period. 195 When the dispersion was left for more than 1 hour, yellow-colored colloidal particles 196 precipitated at the bottom of the cell (Fig. S2 (c)). The upper solution was nearly colorless, 197 indicating that the whole Ru(II) complexes were bound to clay particles. When a laser 198 light at 450 nm was irradiated onto the yellow-colored particles, white emission was 199 observed (Fig. S2 (d)). The results confirmed that the up-conversion took place through 200 excited Ru(II) complexes bound to clay particles. 201  202 12   203 Fig. 3. The emission spectra recorded in the up-conversion experiments: (a) a laser light 204 at 445 nm was incident on a solution containing Δ-[Ru(phen)3]2+ (4.9×10-5 M) under 205 air: (b) DPA (4.2×10-3 M) was added to a sample (a); (c) SAP (3.8×10-4 M in CEC) 206 was added to a sample (b). A medium was 1:1:0.1 (v/v) of 207 dichloromethane/methanol/water. 208  209 13  The quantum yield of up-conversion was calculated according to the following 210 equation (Ji et. al., 2011): 211 Φuc = 2 Φstd (Astd/Asam)(Istd/Isam)(Esam/Estd)(ηsam /ηstd)2     (4) 212 Here Φuc and Φstd are the quantum yields of Δ-[Ru(phen)3]2+ and the standard 213 compound ([Ru(4,4’-dimethylbypyridine)3]2+) used as a donor, Astd and Asam the 214 absorbances of the standard and samples solutions at 445 nm, respectively, Estd and Esam 215 the band areas with the peak at 430 nm, Istd and Isam the intensities of a laser light irradiated 216 on the standard and sample solutions, and ηstd and ηsam the refractive indexes of the 217 standard and sample solutions, respectively. The difference of the refractive indexes was 218 neglected. Taking a dichloromethane solution of tris(4,4-dimethylbipyridine) 219 ruthenium(II) chlorides as a standard solution and Φstd = 0.015 ± 0.005 from the literature 220 (Ji et. al., 2011), the quantum yield of up-conversion for Δ-[Ru(phen)3]2+ was obtained to 221 be 0.018 ± 0.005 and 0.009 ± 0.003 in the absence and in the presence of SAP (3.8×10-4 222 M in CEC), respectively. Thus the adsorption of a used donor by SAP resulted in the 223 decrease of the quantum yield of up-conversion to 50%. The lowering of the quantum 224 yield might be caused by the situations that a part of bound Δ-[Ru(phen)3]2+ complexes 225 were not accessible to DPA, since they were intercalated between SAP layers. 226  227 3.3. Effects of clay adsorption on up-conversion efficiency: The effects of clay 228 adsorption on up-conversion efficiency were investigated. Under the constant 229 concentration of Δ-[Ru(phen)3](ClO4)2 (4.9×10-5 M), the intensity of emission at 430 nm 230 (denoted as I430) was measured on adding DPA in the absence or presence of SAP. As 231 shown in Fig. 4 (a), the quantum yield as measured in terms of I430 started to rise at [DPA] 232 = 1.5×10-3 M in the absence of SAP. I430 continued to increase until [DPA] was 6.0×10-3 233 14  M. Contrarily I430 rose already at [DPA] = 5.0×10-4 M in the presence of SAP (3.8×10-4 234 M in CEC) (Fig. 4 (b)). I430 attained the saturated value at [DPA] = 1.5×10-3 M. The 235 results indicated that SAP had the effect of lowering the critical concentration of DPA to 236 realize the up-conversion. One plausible mechanism is that DPA was attracted to SAP 237 particles due to its hydrophobic properties. This resulted in the increase of the effective 238 concentration of DPA around excited Δ-[Ru(phen)3]2+ on a clay surface. The tendency 239 was particularly prominent in the vicinity of the SAP surface ion-exchanged with Δ-240 [Ru(phen)3]2+. The situations are schematically shown in Fig. S3. 241  242  243 Fig. 4. The dependence of the quantum yield of up-conversion, when DAP was added to 244 the following samples: (a) a solution containing Δ-[Ru(phen)3](ClO4)2 (4.9×10-5 M); 245 (b) a dispersion containing Δ-[Ru(phen)3](ClO4)2 (4.9×10-5 M) and SAP (3.8×10-4 M 246 in CEC). A medium was 1:1:0.1 (v/v) of dichloromethane/methanol/water. 247  248 3.4 Effect of optical purity of [Ru(phen)3]2+ on up-conversion efficiency: Figs. 5 (a) and 249 (b) compared the emission spectra, when the complex was adsorbed by SAP in the form 250 15  of either a pure enantiomer (or Δ-form) or a racemic mixture. A medium was 1:1:0.1 251 (V/V) dichloromethane/methanol/water. For both cases, the emission intensity at 570 nm 252 from excited [Ru(phen)3]2+ (1.90×10-5 M) increased on adding SAP (3.8×10-4 M in CEC) 253 under air. The degree of increase was larger for Δ-[Ru(phen)3]2+ (80% increase) than for 254 racemic [Ru(phen)3]2+ (40 % increase). The difference was rationalized in terms of the 255 mechanism that racemic [Ru(phen)3]2+ tended to form a tight pair of Δ- and Λ-256 enantiomers, while enantiomeric [Ru(phen)3]2+ exists as an isolated species on a clay 257 surface. In case of a racemic mixture, the formation of a tight ΔΛ pair resulted in 258 lowering emission intensity due to self-quenching. The observe chirality effect on 259 adsorption was assisted by the previous theoretical simulations (Sato et. al., 1992).  260  261 Fig. 5. Emission spectra of [Ru(phen)3](ClO4)2 (1.9×10-5 M) in the presence of SAP 262 (3.8×10-4 M in CEC): (a) [Ru(phen)3](ClO4)2 added as a Δ-formed enantiomer; (b) 263 [Ru(phen)3](ClO4)2 added as a racemic mixture. Excitation wavelength was 450 nm. 264 A medium was 1:1:0.1 (v/v) of dichloromethane/methanol/water. Black curve: no 265 SAP added, red curve: SAP (3.8×10-4 eq/L) added. 266 16   267 Figs. 6 (A) and (B) compares the efficiency of up-conversion, when [Ru(phen)3]2+ 268 (4.9×10-5 M) was adsorbed by SAP (3.8×10-4 M in CEC) as a donor in the form of either 269 a pure enantiomer (or Δ-form) or a racemic mixture. A medium was a 1:1:0.1 (v/v) 270 dichloromethane/methanol/water. In case of Δ-[Ru(phen)3]2+, the up-conversion was 271 realized at [DPA] = 2.0×10-3 M, while, in case of racemic [Ru(phen)3]2+, the up-272 conversion occurred at the concentration of DPA higher than 5.0×10-3 M. I430 was higher 273 for Δ-[Ru(phen)3]2+ than for racemic [Ru(phen)3]2+ in the range of [DPA] = 2 ~ 10 ×10-3 274 M. One possibility for the observed effects was that the energy transfer from excited 275 [Ru(phen)3]2+ to DPA took place less effectively when [Ru(phen)3]2+ formed a tight 276 racemic pair on a clay surface than when the molecule formed an isolated enantiomeric 277 species. The present results implied that a donor is preferred to be used as a pure 278 enantiomer when it has a tendency of forming a racemic pair.  279  280 Fig. 6. The dependence of the quantum yield of up-conversion on [DPA], when 281 [Ru(phen)3]2+ (4.9×10-5 M) was added as a pure enantiomer or a racemic mixture 282 in the presence of SAP (3.8×10-4 M in CEC): (a) Δ-[Ru(phen)3](ClO4)2; ■, (b) 283 17  racemic-[Ru(phen)3](ClO4)2; ●. A medium was 1:1:0.1 (v/v) of 284 dichloromethane/methanol/water.  285  286 3.5 Stereoselectivity in the up-conversion for a chiral donor/acceptor pair: In order to 287 pursue the possibility to achieve stereoselectivity, the up-conversion was investigated for 288 the pair of a chiral donor and a chiral acceptor in the presence of SAP. Δ- or Λ-289 [Ru(phen)3]2+ was used as a chiral donor. As a chiral acceptor, a molecule with two DPA 290 moieties connected to 1,1’-binaphthol was used (Fig. S4). The compound is denoted as 291 SS- or RR-DPA-BINOL, depending on the chirality of a central binaphthyl group, 292 respectively. Here a 1,1’-binaphthyl group was chosen because 1,1’-binaphthol was 293 known to interact with [Ru(phen)3]2+ stereoselectively on a clay surface (Yamagishi et. 294 al., 1996).  295 Up-conversion was studied for the donor/acceptor pair of Δ- or Λ-[Ru(phen)3]2+ and 296 SS-DPA-BINOL. The quantum yield of up-conversion was measured on increasing the 297 concentration of SS-DPA-BINOL. The results are shown in Figs. 7 (a) and (b). In the 298 absence of SAP, no significant difference was observed in the up-conversion efficiency 299 between Δ-[Ru(phen)3]2+/SS-DPA-BINOL and Λ-[Ru(phen)3]2+/SS-DPA-BINOL (Fig. 7 300 (a)). In the presence of SAP (3.8×10-4 M in CEC), the up-conversion efficiency was 301 higher by 20 ~ 40 % for Δ-[Ru(phen)3]2+/SS-DPA-BINOL than for Λ-[Ru(phen)3]2+/SS-302 DPA-BINOL (Fig. 7 (b)). The results implied that the fixation of a donor molecule on a 303 clay surface resulted in enhancing chiral selectivity during the courses of donor/acceptor 304 energy transfer and/or TTA of excited acceptors. The results might open the possibility 305 of developing chiral sensing on the basis of the up-conversion of colloidal clay systems. 306  307 18   308 Fig. 7. The dependence of the quantum yield of up-conversion on the concentration of 309 SS-DPA-BINOL as a chiral acceptor, when Δ- or Λ-Ru(phen)3]2+ (4.9×10-5 M) was 310 used as a chiral donor: (a) no SAP added; (b) SAP added to 3.8×10-4 M in CEC). A 311 medium was 1:1:0.1 (v/v) of dichloromethane/methanol/water. 312  313 4. Conclusions 314 The possibility of achieving the up-conversion of photon energy in systems 315 containing colloidal particles of synthetic saponite was explored. As a donor-acceptor 316 pair, Δ-tris(1,10-phenanthroline)rutheniuim(II)/1,10-diphenylanthracene was used. It 317 was confirmed that an incident laser light at 450 nm was converted to emission at 430 nm 318 through the triplet-triplet annihilation of excited donors in the presence of a clay mineral. 319 The effects of the optical purity of the used Ru(II) complex were examined. 320 Stereoselctivity was pursued through the use of a synthesized chiral acceptor molecule.  321  322  323 19  Acknowledgements 324 This work was financially supported by the Japan Society for the Promotion of 325 Science (JSPS) KAKENHI Grant No. 17H03044, 20K21090 and 22H02033.  326  327 References 328 Duan, P., Yanai, N., Kimizuka. N., 2013, Photon upconverting liquids: matrix-free 329 molecular up-conversion systems functioning in air, J. Am. Chem. Soc. 135, 19056-330 19059. https://doi.org/10.1021/ja411316s 331 Han, J., Duan, P., Li, X., Liu, M., 2017. Amplification of circularly polarized 332 luminescence through triplet–triplet annihilation-based photon upconversion. J. Am. 333 Chem. Soc. 139, 9783-9786. https://doi.org/10.1021/jacs.7b04611 334 Ji, S., Wu, W., Wu, W., Guo, H., Zhao, J. 2011. Ruthenium(II) polyimine complexes with 335 a long-lived 3IL excited state or a 3MLCT/3IL equilibrium: efficient triplet sensitizers 336 for low-power up-conversion, Angew. Chem. Int. Ed., 50, 1626–1629. 337 https://doi.org.10.1002/anie.201006192 338 Joarder, B., Yanai, N., Kimizuka, N., 2018. Solid-state photon upconversion materials: 339 structural integrity and triplet–singlet dual energy migration, J. Phys. Chem. Lett. 9, 340 4613–4624. https://doi.org/10.1021/acs.jpclett.8b02172 341 Kageshima, Y., Tateyama, S., Kishimoto, F., Teshima, K., Domen, K., Nishikiori, H., 342 2021, Photocatalytic oxygen evolution triggered by photon upconverted emission 343 based on triplet–triplet annihilation. Phys. Chem. Chem. Phys. 23, 5673-5679. 344 https://doi.org/10.1039/D0CP06139E  345 20  Kashino, T., Hosoyamada, M., Haruki, R., Harada, N., Yanai, N., Kimizuka, N., 2021. 346 Bulk transparent photon upconverting films by dispersing high-concentration ionic 347 emitters in epoxy resins, ACS Appl. Mater. Interf. 13, 13676−13683. 348 https://doi.org/10.1021/acsami.0c23121 349 Kerzig, C., Wenger, O. S., 2018, Sensitized triplet–triplet annihilation up-conversion in 350 water and its application to photochemical transformations, Chem. Sci. 9, 6670–6678. 351 https://doi.org/10.1039/c8sc01829d  352 Kishimoto, F., Wakihara, T. Okubo, T. 2020. Water-dispersible triplet–triplet 353 annihilation photon up-conversion particle: molecules integrated in hydrophobized 354 two–dimensional interlayer space of montmorillonite and their application for 355 photocatalysis in the aqueous phase, ACS Appl. Mater. Interf. 12, 7021–7029. 356 https://doi.org/10.1021/acsami.9b15957 357 Lee, H., Lee, M-S., Uji., M., Harada, N., Park, J-M., Lee, J., Seo, S. E., Park, C. S., 358 Kim, J., Park, S. J., Bhang, S. H., Yanai, N., Kimizuka, N., Kwon, O. S., Kim, J-H. 359 2022, Nanoencapsulated phase-change materials: versatile and air-tolerant 360 platforms for triplet−triplet annihilation up-conversion, ACS Appl. Mater. Interf. 361 14, 4132−4143. https://doi.org/10.1021/acsami.1c21080. 362 Li, C., Duan, P. 2021. Recent advances of circularly polarized luminescence in photon 363 up-conversion systems. Chem. Lett., 50, 546–552. 364 https://doi.org/10.1246/cl.200771. 365 Liu, Q., Xu, M., Yang, T., Tian, B., Zhang, X., Li, F., 2018, Highly photostable near-Ir-366 excitation upconversion nanocapsules based on triplet-triplet annihilation for in 367 21  vivo bioimaging application, ACS Appl. Mater. Interfaces. 10, 9883-9888. 368 https://doi.org/10.1021/acsami.7b17929 369 Lu, Y., Conway-Kenny, R., Twamley, B., McGoldrick, N., Zhao, J., Draper, S. M. 370 2017. 1,10-phenanthroline ruthenium(Ⅱ) complexes as model systems in the search 371 for high-performing triplet photosensitisers: addressing ligand versus metal effects. 372 ChemPhotoChem, 1, 544–552. https://doi.org/10.1002/cptc.201700158 373 El Roz, K. A., Castellano, F. N. 2017, Photochemical upconversion in water. Chem. 374 Commun. 53, 11705-11708. https://doi.org/10.1039/C7CC07188D.  375 Sasaki, Y., Amemori, S., Kouno, H., Yanai, N., Kimizuka, N. 2017, Near infrared-to-376 blue photon upconversion by exploiting direct S–T absorption of a molecular 377 sensitizer, J. Mater. Chem. C. 5, 5063–5067. https://doi.org/10.1039/C7TC00827A 378 Sato, H., Kato, S., Yamagishi, A. 1992. Monte-carlo simulations for interactions of 379 metal complexes with the silicate sheets of a clay: comparison of binding states 380 between tris(1,10-phenanthroline)metal(Ⅱ) and tris(2,2'-bipyridyl) metal(II) 381 chelates, J. Am. Chem. Soc. 114, 10933-10940. 382 https://doi.org/10.1021/ja00053a034 383 Sato, H., Tamura, K., Taniguchi, M., Yamagishi, A. 2014. Efficient energy transfer of 384 cationic iridium(III) complexes on the surface of a colloidal clay. Appl. Clay Sci., 385 97-98, 84-90. https://doi.org/10.1016/j.clay.2014.05.008 386 Schmidt, T. W., Castellano, F. N., 2014, Photochemical Up-conversion: the primacy of 387 kinetics, J. Phys. Chem. Lett. 5, 4062−4072. https://doi.org/10.1021/jz501799m 388 22  Singh-Rachford, T. N., Islangulov, R. R., Castellano, F. N. 2008, Photochemical 389 upconversion approach to broad-band visible light generation J. Phys. Chem. A, 112, 390 3906-3910. https://doi.org/10.1021/jp712165h 391 Suzuki, Y., Matsunaga, R., Sato, H., Kogure, T., Yamagishi, A. Kawamata, J., 2009. 392 Non-centrosymmetric behavior of a clay film ion-exchanged with chiral metal 393 complexes, Chem. Commun. 6964–6966, https://doi.org/10.1039/B908806G  394 Takimoto, K., Tamura, K., Watanabe, Y., Yamagishi, A., Sato, H., 2018, Microscopic 395 chiral pockets in a tris(chelated) iridium(III) complex as sites for dynamic 396 enantioselective quenching. New J. Chem. 42, 4818-4823. 397 https://doi.org/10.1039/C7NJ04688J.  398 Tamura, K., Yamagishi, A., Kitazawa, T. Sato, H., 2015. Harvesting light energy by 399 iridium(III) complexes on a clay surface. Phys. Chem. Chem. Phys. 17, 18288-400 18293. https://doi.org/10.1039/C5CP02414E 401 Wu, W., Wu, W., Ji, S., Guo, H., Zhao, J. 2011. Accessing the long-lived emissive 3IL 402 triplet excited states of coumarin fluorophores by direct cyclometallation and its 403 application for oxygen sensing and upconversion, Dalton Trans. 40, 5953–5963, 404 https://doi.org/10.1039/C1DT10344J 405 Yamagishi, A. Goto, Y., Taniguchi, M.,1996. Stereochemical effects on monolayer 406 formation of [Ru(dpp)3]2+ (dpp = 4,7-Diphenyl-1,10-phenanthroline) at an air-water 407 interface, J. Phys. Chem. 100, 1827-1832. https://doi.org/10.1021/jp952181a 408 Yamagishi, A., Taniguchi, M., Imamura, Y., Sato, H., 1996, Clay column 409 chromatography for optical resolution: selectivities of L-[Ru(phen)3]2+ and D-410 23  [Ru(bpy)3]2+ laponite columns towards 1, l'-binaphthol, Appl. Clay Sci. 11, 1-10. 411 https://doi.org/10.1016/0169-1317(96)00010-5 412 Yamagishi, A., Sato, H., 2012. Stereochemistry and molecular recognition on the surface 413 of a smectite clay.  Clay. Clay Miner. 60, 411-419. 414 https://doi.org/10.1346/CCMN.2012.0600407. 415 Yanai, N., Kimizuka N., 2017, New triplet sensitization routes for photon up-conversion: 416 thermally activated delayed fluorescence molecules, inorganic nanocrystals, and 417 singlet-to-triplet absorption, Acc. Chem. Res. 2017, 50, 2487–2495. 418 https://doi.org/10.1021/acs.accounts.7b00235 419 Yang, D., Han, J., Sang, Y., Zhao, T., Liu, M., Duan, P., 2021, Steering triplet−triplet 420 annihilation up-conversion through enantioselective self-assembly in a 421 supramolecular gel, J. Am. Chem. Soc. 143, 13259−13265. 422 https://doi.org/10.1021/jacs.1c05927 423 Yoshida, J., Tateyama, K., Kasahara, Y., Yuge, H. 2020. Stabilization of oxidized 424 ruthenium complexes by adsorption on clay minerals. Appl. Clay Sci. 199, 105869. 425 https://doi.org/10.1016/j.clay.2020.105869 426 Yoshida, Y., Shimada, T., Ishida, T., Takagi, S. 2021, Effects of the surface charge 427 density of clay minerals on surface-fixation induced emission of acridinium 428 derivatives, ACS Omega, 6, 21702−21708. 429 https://doi.org/10.1021/acsomega.1c03157 430 Zhou, Y., Castellano, F. N. Schmid, T. W., Hanson, K., 2020, On the quantum yield of 431 photon upconversion via triplet–triplet annihilation. ACS Energy Lett. 5, 432 2322−2326. https://doi.org/10.1021/acsenergylett.0c01150 433 24    434 25  Supporting Information 435 Up-conversion of Photon Energy in Colloidal 436 Clay Systems 437  438 Akihiko Yamagishi,a Kenji Tamura,*b Shohei Yamamoto,c Fumi Sato,a Jun Yoshidad and 439 Hisako Sato* c 440  441 a School of Medicine, Toho University, Ohta-ku, Tokyo 143-8540, Japan  442 b Environmental Circulation Composite Materials Group, Research Center for Electronic 443 and Optical Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-444 0044, Japan  445 c Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, 446 Japan 447 d Department of Chemistry, College of Humanities & Sciences, Nihon University, 448 Setagaya-ku, Tokyo 156-8550, Japan  449  450  451  452  453  454  455  456 26   457  458 Contents 459  460  461 S1. The dependence of the up-conversion efficiency on the intensity of an incident 462 light 463  464 S2. The phtographic images of the experiments on the up-conversion of homogenous 465 and clay-dispersion systems 466  467 S3. The shcematic drawing showing the effects of clay exfoliated layuers on 468 concentrating DPA molecules 469  470 S4. The synthesis of a chiral acceptor for stereoselective up-conversion 471  472  473  474  475  476  477  478  479 27   480 S1. The dependence of the up-conversion efficiency on the intensity of an incident 481 light 482  483  484  485  486  487  488  489  490 Fig. S1. The dependence of the up-conversion efficiency on the intensity of an incident 491 light. The vertical axis is the laser power at 450 nm and the horizontal axis the 492 area of the band at 430 nm (in aubitrary unit). The experimental conditions are 493 following: Δ-[Ru(phen)3]2+ (4.9×10-5 M), DPA (4.2×10-3 M) and a medium 1 : 1 : 494 0.1 (V/V) of dichloromethane/methanol/water. The atmosphere was under air. 495  496  497  498  499  500 28   501 S2. The phtographic images of the experiments on the up-conversion of 502 homogenous and clay-dispersion systems 503  504  505  506 Fig. S2. The photographic images of the samples in the up-conversion experiments: (a) a 507 laser light at 450 nm was incident on sample (a) in Figure3; (b) a laser light at 450 508 nm was incident on sample (b) in Figure 3; (c) sample (c) in Figure 3 was left for 509 one hour; (d) a laser light at 450 nm was incident on sample (c) in this figure. 510  511  512  513  514  515  516  517  518 29   519 S3. The shcematic drawing showing the effects of clay exfoliated layuers on 520 concentrating DPA molecules 521  522  523  524  525 Fig. S3. The schematic image showing the gathering of PDA molecules around a SAP 526 particles ion-exchanged with Δ-[Ru(phen)3]2+. 527  528  529  530  531  532  533  534  535  536 30   537 S4. The synthesis and identification of a chiral acceptor for stereoselective up-538 conversion 539  540  541 S-9-phenyl-10-(4-((7'-((4-(10-phenylanthracen-9-yl)benzyl)oxy)-[1,1'-binaphthalen]-7-542 yl)oxy)phenyl)anthracene 543  544 Fig. S4. The molecular structure of a chiral acceptor (abbreviated as SS-DPA-BINOL in 545 the text). The compound was identified by means of 1H-NMR, 13C-NMR and 546 mass spectrum. The results are following: 547  548 δH(400 MHz : CDCl3) 5.29 (4H, d, J = 6.8 Hz), 7.20-7.32 (20H, m),7.36 (3H, m), 7.45 549 (3H, d, J = 6.8 Hz), 7.54-7.66 (16H, m), 7.92 (2H, d, J = 9.2 Hz), 8.04 (2H, d, J = 9.2 550 Hz) 551 δC(100 MHz : CDCl3) 71.7, 116.5, 121.2, 124.1, 125.1, 125.2, 125.3, 125.8, 126.6, 552 126.8, 126.9, 127.0, 127.2, 127.6, 127.7, 128.1, 128.5, 129.7, 129.8, 129.9, 130.0, 553 131.2, 131.3, 134.5, 136.9, 137.0, 137.2, 138.2, 139.2, 154.5  554 FAB-MS m/z = 970 (Calc. for : 970.38 555  556