Use of organic photosensitizers to elucidate mechanisms of solar driven processes on pesticides.

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1 Use of organic photosensitizers to elucidate mechanisms of solar driven processes on pesticides. A. Arques, A.M. Amat, J. Gomis, J. Soler, M.L. Marín, M.A. Miranda Departamento de Ingeniería Textil y Papelera, Universidad Politécnica de Valencia, Campus de Alcoy, Alcoy, Spain Instituto Universitario Mixto de Tecnología Química Departamento de Química (UPV CSIC), Valencia, Spain E mail: aarques@txp.upv.es 1

2 1. Introduction 2

3 Reactive species formed from OM OM has been described to accelerate pollutants removal via an indirect photochemical process OM can generate ROS such as singlet oxygen, hydroxyl radical or superoxide Additionally, excited states of OM can take part in electron transfer of energy tranfer processes with the pollutant 3

4 Reactive species formed from OM atural systems are very complex and obtaining mechanistic information is difficult The composition of OM is also variable, not always well stablished and parallel mechanisms can occur Obtaining information from more simple systems on the reactivity of pollutants with ROS or excited states appears interesting 4

5 Organic photosensitizers Organic dyes and have been reported to participate in electron tranfer and energy transfer processes Uses of organic photocatalysts: Organic synthesis Photopolymerization Photodynamic therapy Solar cells Watewater treatment 5

6 Potential use of sensitizers Organic sensitizers can be employed to generate, selectively, the desired oxidative species The mechanisms is well stablished in some cases or it can be more easily elucidated They might be useful for mechanistical studies A wide range of photosensitizers, with different photochemical/photophysical properties is available 6

7 2. Organic photosensitizers: structures and properties 7

8 Structures of photosensitizers (1) Ph Ph Ph O O Ph X Ph X=O: Triphenylpyrylium (TPP) X=S: Triphenylthiapyrylium (TPTP) R 1 Ph Bipyrylium (BP) O Ph R 2 R 1 R 1 =R 2 =H: Anthracene (AT) R 1 = C, R 2 =H: 9,10-Dicyanoanthracene (DCA) R 1 = C, R 2 =CH 2 OCOH(CH 2 ) 2 CH 3 : (DCAC) R 1 = Me, R 2 =H: 9,10-Dimethylanthracene (DMA) HO O 9,10-Anthraquinone (AQ) OH O O R R O Perylene bisimides (PBI) O a: R=(CH 2 ) 12 HSO 3 H b: R=Ph-CO 2 H c: R=(CH 2 ) 4 (CH 3 ) 3 O Rosolic acid (RA) 8

9 Structures of photosensitizers (2) I I R 1 R 1 O O O R 2 R 2 I I -Methylquinolinium (MQ) R 1 =CH 3, R 2 =H 2 : Acridine Yellow G (AYG) R 1 =H, R 2 =(CH 3 ) 2 : Acridine Orange (AO) Cl COO O Cl Cl H 3 C H R 1 R 1 Cl Rose Bengal (RB) H 3 C O Me 2 S Me 2 CH 2 (CHOH) 3 CH 2 OH R 2 Riboflavin (RF) R 1 =R 2 =H: Methylene Blue (MB) R 1 =H, R 2 =O 2 : Methylene Green (MG) 9

10 Structures of photosensitizers (3) R OH H R R H OH H H H H R R= CO 2 H CO 2 H CO 2 H CO 2 H CO 2 H CH1 CH2 Chlorins (CH) CH3 10

11 Structures of photosensitizers (4) R R= CO 2 H e: M=2H Fe R M R R= SO 3 H f: M=2H g: M=Fe h: M=Cu Cl R PP2 R= a: M=2H b: M=Sn R= i: M=2H Cl CO 2 H PP1 CO 2 H R= c: M=2H Cl j: M=2H R= k: M=Fe l: M=Sn m: M=Zn R= Cl SO 3 H d: M=2H R= H n: M=Sn Porphyrins (PP) 11

12 Structures of photosensitizers (5) R 2 R 1 R 1 R 2 M PC1 R 2 R 1 R 1 R 2 a: R 1 =SO 3 a, R 2 =H; M=2H b: R 1 =R 2 =H; M=Cu c: R 1 =R 2 =H; M=Fe d: R 1 =R 2 =H; M=Mn e: R 1 =R 2 =H; M=Zn f: R 1 =SO 3 a, R 2 =H; M=Al(III)OH g: R 1 =SO 3 a, R 2 =H; M=Al(III)Cl h: R 1 =SO 3 a, R 2 =H; M=Ga i: R 1 =SO 3 a, R 2 =H; M=Co(II) j: R 1 =SO 3 a, R 2 =H; M=Fe(II) k: R 1 =SO 3 a, R 2 =H; M=Pd(II) l: R 1 =SO 3 a, R 2 =H; M=Zn(II) m: R 1 =COOH, R 2 =H; M=2H n: R 1 =COOH, R 2 =H; M=Co(II) o: R 1 =COOH, R 2 =H; M=Zn(II) p: R 1 =R 2 =COOH; M=Al q: R 1 =R 2 =COOH; M=Zn r: R 1 = H 2 CS C (CH 3 ) 2 ; M=Cu (CH 3 ) 2 Phthalocyanines (PC) 12

13 Absorption bands of the photosensitizers in the UVB UVA vis range 13

14 3. Reaction mechanisms 14

15 Alternative mechanistic pathways P= Photocatalyst, Q= Pollutant or model compound P h h ' 1 P* isc Q H 2 O P P + Q + OH + H i ii Q 3 P* P + OH + H H 2 O Q P + Q O 2 P + 1 O 2 iii iv v P Q h P + Q vi P + O 2 P + O 2 vii Q + O 2 Q + O 2 Q + 1 O 2 Q + OH Oxidation products 15

16 Determination of a mechanistic pathway: TPP vs MTDT O S hν O + + MeO S S P OMe OMe Arques, A.; Amat, A.M.; Santos Juanes, L.; Vercher, R.F.; Marín, M.L.; Miranda, M.A. Catal. Today 2009, 144,

17 Possible involvement of 1 P* (pathway i) 17

18 Possible involvement of 1 P* (pathway i): fluorescence measurements Concentration (mm) 18

19 Possible involvement of 1 P* (pathway i): fluorescence measurements Obtained rate constants are above diffusion limits There is no dinamic quenching of the fluorescence (lifetime does not depend on the concentration of pollutant) 19

20 Possible involvement of 3 P * : laser flash photolysis Transient absorption spectrum Pyranil radical 3 TPP, λ max = 470 nm 20

21 Possible involvement of 3 P * : laser flash photolysis Intensidad (UA) Time Tiempo ( s) Lifetimes did not change in the presence of the pollutant 21

22 Photoinduced electron transfer from a ground state complex (pathway vi) Q TPP + δ+ δ'+ [TPP Q] hv Q hv TPP + Q + O 2 Oxidation products Q 1 TPP + 3 TPP +

23 Photoinduced electron transfer from a ground state complex (pathway vi) 23

24 4. Orders of reactivity 24

25 Elimination of pollutants: phenolic acids COOH COOH COOH COOH OH OH OH OH OMe COOH COOH COOH OH OH HO COOH OH OH OH 70 photodegradation (%) Miranda M.A.; Amat A.M.; Arques A., Galindo F. Appl. Catal. B 2000, 28,

26 Comparison among different photocatalysts O + S + Solar degradation of ferulic acid (0.001 M) using six different photocatalysts (10 mg/l). Arques A., Amat A.M., Santos Juanes L., Vercher R., Marin M.L., Miranda M.A. Catal. Today 2007, 129,

Carbaryl (CBR) TPP, MTDT TPTP, MTDT Arques, A.; Amat, A.M.; Santos Juanes, L.

27 Elimination of pollutants: pesticides O S S P OCH 3 S OCH 3 Methidathion (MTDT) AYG, CBR OCOHCH 3 AYG, MTDT TPTP, CBR TPP, CBR OH Carbaryl (CBR) TPP, MTDT TPTP, MTDT Arques, A.; Amat, A.M.; Santos Juanes, L.; Vercher, R.F.; Marín, M.L.; Miranda, M.A. Catal. Today 2009, 144,

respiration of activated sludge Arques, A.; Amat, A.M.

28 Detoxification and enhancement of biodegradability Pollutants: methidathion (blue bars) and carbaryl (red bars) Inhibition of respiration of activated sludge Arques, A.; Amat, A.M.; Santos Juanes, L.; Vercher, R.F.; Marín, M.L.; Miranda, M.A. Catal. Today 2009, 144,

29 5. Involvement of hydroxyl radical 29

30 Generation and detection of OH hv 355 nm OH S -hydroxypyridine-2-thione Pyridinethiyl λ max = 490 nm C 6 H 5 OH OH TS Trans-stilbene Ph TS-OH λ max =390 nm M. L. Marin, V. Lhiaubet Vallet, L. Santos Juanes, J. Soler, J. Gomis, A. Arques, A.M. Amat, M.A. Miranda Appl. Catal B: Environ. 103, 48 53, 2011

31 Competitive kinetics

32 Competitive kinetics

33 Competitive kinetics K (M 1 ) k (M 1 s 1 ) Dimethoate 32.4 (R 2 =0.98) 7.67 x 10 9 Methidathion 30.8 (R 2 =0.99) 7.29 x 10 9 Alachlor 13.6 (R 2 =0.98) 3.29 x 10 9 Pyrimethanyl 11.0 (R 2 =0.97) 2.61 x 10 9 aphthalene 7.6 (R 2 =0.99) 1.80 x 10 9 DIM MET>ALA>PYR

34 Photo-Fenton Similar trend

35 TiO2

36 2,4,6-triphenylpyrylium cation Different trend

37 6. Conclusions 37

38 Conclusions Organic sensitizers can be used for mechanistic investigations on the interaction of OM and pollutants ROS and electron transfer mechanisms can be slectively studied by choosing a given sensitizer Reactivity and kinetic data can be determined Relative participation of different oxidative species might be elucidated by comparing orders of reactivity 38

Supporting Information

Supporting Information Imidazolium-based ionic liquids in water: Assessment of photocatalytic and photochemical transformation Paola Calza a, Davide Vione a,* Debora Fabbri a, Riccardo Aigotti b, and Claudio