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About OMICS Group OMICS Group International is an amalgamation of Open Access publications and worldwide international science conferences and events.

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Presentation on theme: "About OMICS Group OMICS Group International is an amalgamation of Open Access publications and worldwide international science conferences and events."— Presentation transcript:

1 About OMICS Group OMICS Group International is an amalgamation of Open Access publications and worldwide international science conferences and events. Established in the year 2007 with the sole aim of making the information on Sciences and technology ‘Open Access’, OMICS Group publishes 400 online open access scholarly journals in all aspects of Science, Engineering, Management and Technology journals. OMICS Group has been instrumental in taking the knowledge on Science & technology to the doorsteps of ordinary men and women. Research Scholars, Students, Libraries, Educational Institutions, Research centers and the industry are main stakeholders that benefitted greatly from this knowledge dissemination. OMICS Group also organizes 300 International conferences annually across the globe, where knowledge transfer takes place through debates, round table discussions, poster presentations, workshops, symposia and exhibitions.

2 About OMICS Group Conferences OMICS Group International is a pioneer and leading science event organizer, which publishes around 400 open access journals and conducts over 300 Medical, Clinical, Engineering, Life Sciences, Phrama scientific conferences all over the globe annually with the support of more than 1000 scientific associations and 30,000 editorial board members and 3.5 million followers to its credit. OMICS Group has organized 500 conferences, workshops and national symposiums across the major cities including San Francisco, Las Vegas, San Antonio, Omaha, Orlando, Raleigh, Santa Clara, Chicago, Philadelphia, Baltimore, United Kingdom, Valencia, Dubai, Beijing, Hyderabad, Bengaluru and Mumbai.

3 Toshio Naito Ehime University Giant Photoconductivity in Organic Materials by UV Irradiation

4 Photoconductors Applied to various imaging & sensor devices ex. CdS, PbS, etc Battery Photoconductor Battery Valence Band Conduction Band h (> E g ) e-e- e-e- New (additional) Functions Information / Communication Technology ex.) Laser Printer, Photocopy, Solar Cell, Sensor, CMOS, etc ・ Found in Se (1870’s) ・ Explained (1930’s) ・ Applied to Electronics (1950’s)

5 Purpose Standard mechanism of photoconductivity e-e- h+h+ Cation A or Anion X Cation A or Anion X LUMO HOMO (e.g.) AX New PCs with additional functions* Wavelength-selectivity of response Different responses to different wavelengths Photo-magnetic-conductors etc A 2+ A A A A A A ee - A (2+  )+ A A (2-  )+ A (2+  )+ A (2-  )+ A (2+  )+ A (2-  )+ h * h Charge disproportionation New Mechanism

6 e-e- h+h+ Cation or Anion or Cation Our strategy Proposed (New) mechanism e-e- h+h+ Cation or Anion Cation or Anion Standard mechanism NO disproportionation (for high conductivity) Merits C-A Charge Transfer (CT) h h Cat (1-  )+ (1+  )+ An (1+  )- Cat (1+  )+ (Localized spins) A-A or C-C Charge Transfer (CT)

7 C (= Cations)X ref BPY 2, 6 NMQ 1 ( ,  ) DiCC 1 ( ,  ) 2 ( ,  ) MV Adv. Mater., 6153 (2012) JACS (2012) Eur. J. Inorg. Chem. (2014) Chem. Lett (2014) Abbre. C[Ni(dmit) 2 ] X

8 C-A CTA-A CT(Almost) No CT MV BPY NMQ DiCC (n-C 4 H 9 ) 4 N Ru(bpy) 3 ・・・・ < 2-3 [Ni(dmit) 2 ] - salts RCRC Cations Photoconductivity (  ph ) Dark conductivity (  dark ) Conductivity Ratio ( R C ) = RCRC Carrier Doping (A - C + A (1-  )- C (1-  )+ ) e-e- Charge Disproportionation (A - A - A (1-  )- A (1+  )- ) e-e-

9 BPY 2+ [Ni(dmit) 2 ] - [Ni(dmit) 2 ] - = conduction C-A CT

10 Black ; ~ 100% [Ni(dmit) 2 ] - Green ; ~ 100% BPY 2+ Red ( 16 bands ); ( e.g. )~ 37% [Ni(dmit) 2 ] - UV ( ~ a few eV) Anion-Cation Mixed Bands BPY[Ni(dmit) 2 ] 2 Band Calculation ( Extended Hückel Method )

11 BPY[Ni(dmit) 2 ] 2 Solid State & Solution Spectra Solution ( Absorption ) Solid State ( Diffuse Reflection )

12 A[Ni(dmit) 2 ] 2 MV ++ ( Single Crystal ) Ground state = insulating (A = BPY, MV) E a = 0.28 eV (  RT = 2×10 5  cm) E a = 0.12 eV (  RT = 63  cm) Thermally activated behavior ( dark ) Conduction

13 E g (cond) = 0.24 eV A[Ni(dmit) 2 ] 2 Conduction MV ++ ( Single Crystal ) Ground state = insulating (A = BPY, MV) E a = 0.28 eV (  RT = 2×10 5  cm) cf. E g (band) ~ 0.06 eV E g (cond) = 0.56 eV cf. E g (band) ~ 0.05 eV E a = 0.12 eV (  RT = 63  cm) Thermally activated behavior ( dark )

14 A[Ni(dmit) 2 ] 2 Ground state = diamagnetic (non-magnetic) ( Polycrystal ) (A = BPY, MV) J AF ~ 110 K    1 × emu mol -1 MV + + dark Mag. Susceptibility

15 A[Ni(dmit) 2 ] 2 Mag. Susceptibility Ground state = diamagnetic (non-magnetic) ( Polycrystal ) (A = BPY, MV) E g (cond) = 0.56 eV E g (mag) ~ 0.02 eV J AF ~ 110 K E g (band) ~ 0.05 eV    1 × emu mol -1 (e.g.) MV MV + + dark

16 UV ( 375 nm, 11.6 mW cm -2, 300 K, in vacuo ) A = BPY 2+ (n-C 4 H 9 ) 4 N salt ( BPY salt ) 200 K 300 K A = MV 2+ A[Ni(dmit) 2 ] 2 ; photoconductivity ( Single Crystal ) Comparison  S (  ph /  dark  2 ) Photoconduction is negligible in many Ni(dmit) 2 salts. UV (375 nm)

17 A[Ni(dmit) 2 ] 2 ESR H  [010] 153 K ( single crystal, ) A = BPY 2+ [Ni(dmit) 2 ] - BPY 2+ [Ni(dmit) 2 ] - BPY 2+ h (integrated) under dark under UV h

18 A[Ni(dmit) 2 ] 2 ESR H  [010] 153 K ( single crystal, ) A = BPY 2+ [Ni(dmit) 2 ] - BPY 2+ [Ni(dmit) 2 ] - BPY 2+ h (integrated) [Ni(dmit) 2 ] - + BPY 2+ [Ni(dmit) 2 ] (1-  ) - + BPY (2-  )+ UV (Consistent with band calc. & UV spectra) e -   0.1 h

19 A[Ni(dmit) 2 ] 2 ; photoconductivity – I - & T -dependences ( Single Crystal )( 375 nm, in vauo ) (1)  =  dark + aI + bI 2 (2)Wavelength selectivity (Responsive ONLY to ~ nm) Photoconduction mechanism is different from the known mechanism New Features in Photoconduction  (I : light intensity) C-A CT bands C-A CT type salts

20 C-A CTA-A CT(Almost) No CT MV BPY NMQ DiCC (n-C 4 H 9 ) 4 N Ru(bpy) 3 ・・・・ < 2-3 Photoconductivity (  ph ) Dark conductivity (  dark ) Conductivity Ratio ( R C ) [Ni(dmit) 2 ] - salts RCRC Cations RCRC (RT) (200 K)

21 A-A CT-based PC Sharp wavelength-selectivity Large  UV /  dark (eg. ~ K, ~ K) (Only ~ 375 nm) Unique PC NMQ[Ni(dmit) 2 ]* * (in regard to synthesis, crystal structure, and dark conductivity) J. P. Cornelissen, et al. Inorg. Chim. Acta 1991, 185, (A) (C) ( A = Anion, C = Cation ) unusually

22 Crystal Structure [Ni(dmit) 2 ]  NMQ  ca eV ca eV Negligible C-A interactions

23 Band Structure & Conductivity NMQ band Ni(dmit) 2 band 300 K 375 nm 11.6 mWcm -2 DC 2 V 2-probe 375 nm (3.3 eV) E a (dark) = 0.20 eV E a (UV) = 0.12 eV X 40

24 XPS & UV-Vis-NIR Spectra NMQ[Ni(dmit) 2 ] (powder) (C 4 H 9 ) 4 N[Ni(dmit) 2 ] (in CH 3 CN) NMQ·I (in CH 3 CN) CT between A-A (not C-A or C-C) XPS (Ni, S, E F ) do NOT change (under dark and UV) S 2s S 2p Ni 2p EFEF Under UV-irradiation (375 nm) Under dark (375 nm) A-A C-A C-C

25 New contribution in PC dark  Ph, std  Ph, new  dark  Ph, std  Ph, new  R C  nd photoconduction ( I = mW cm -2 ) R C = dark  sq   (I)(I) = 0

26 Summary; A-A CT Coexistence of three kinds of (photo)conduction NMQ[Ni(dmit) 2 ]  (ph)   (dark)  40 (RT)  880 (200 K) dark  Ph, std  Ph, new  (15.7 mWcm -2 ) On the verge (or in the middle) of melting of charge-ordered state? Remains to be clarified

27 YBa 2 Cu 3 O 7-  (T C = 90 K) Chemical doping → Metastable State ( 930 ºC 、 5 h ) → Oxygen deficiency ( irrev. ) Irradiation → Photoexcited State → CT trans. ( rev. ) MV[Ni(dmit) 2 ] 2 Optical Doping

28 PHOTOMAGNETIC CONDUCTORS  log T  T 2 T. Naito et al, Adv. Mater., 24 (46), (2012) T. Naito et al, J. Am. Chem. Soc., 134(45), (2012) (Possible Kondo Effect under UV)

29 Acknowledgments Financial Support JSPS (No ) Ito Science Foundation Japan Securities Scholorship Ehime Univ. GP Ehime Univ. Grant for Interdisciplinary Research Collaborators Mr. T. Karasudani, Dr. S. Mori, Porfs. K. Ohara, K. Konishi & T. Yamamoto (Ehime University) Mr. T. Takano, Dr. Y. Takahashi, Prof. T. Inabe (Hokkaido University) Profs. S. Nishihara & K. Inoue (Hiroshima University) Profs. K. Furukawa* & T. Nakamura (IMS) (*present Niigata Univ.) Thank you

30 Synthesis ( Crystallization ) A[Ni(dmit) 2 ] X AX (BPY 2+ ) 2, 6 (n-C 4 H 9 ) 4 N[Ni(dmit) 2 ] (10 mg) / CH 3 CN (20 ml) BPY·Br 2 (10 mg) / CH 3 CN (20 ml) filtration Container ( 50 ml ; sealed ) Stand still ( 20 º C, dark ) Step 1 Step 2 ( shiny platelets ) a few days – a few weeks 2 (MV 2+ ) T. Naito et al, Adv. Mater. 24, 6153 (2012) T. Naito et al., J. Am. Chem. Soc. 134, (2012) BPY·Br 2

31 Case 1; D-A CT (3) 153 K Ni(dmit) 2 BPY Non-linear behavior New Features for PC 375 nm T. Naito et al, J. Am. Chem. Soc., 134(45), (2012)

32 BPY MV e = x  n = 0  n!n! x n

33 A[Ni(dmit) 2 ] 2 ; photoconductivity – I - & T -dependences ( Single Crystal )( 375 nm, in vauo ) A = BPY b I 2 : Nearly T-independent 1. Thermally inaccessible to the dark states 2. Metallic conduction * Yonemitsu, K. J. Phys. Soc. Jpn. 2004, 73, Importance of cooperative effect*  : Non-linear dependence on I  sq =  dark + aI + bI 2 aI : known/standard mechanism bI 2 : a new mechanism

34 ~ 3.4 Å ~ 3.5 Å BPY[Ni(dmit) 2 ] S = 0 S = 1/2 a a (0) b c 0 b c 0 a b c JACS, (2012) Monoclinic, P2 1 /c (#14) (MV) a = (5) Å ( (9) Å) b = 7.466(2) Å  = (4) o c = (7) Å V = 3624(2) Å 3 (1882.7(3) Å 3 ) Z = 4 (Z = 2)

35 BPY[Ni(dmit) 2 ] 2 c b a 0 b a c 0 a c b 0 a c 0 b JACS, (2012)

36 S 3 ~ 0.015S 2, S 6 ~ Ni(dmit) 2 -Ni(dmit) 2 S 9 ~ S 5, S 8 ~ S 11, S 13, S 14  BPY-Ni(dmit) 2 S 7 ~ S 10 ~ BPY[Ni(dmit) 2 ] 2 Intermolecular Interactions ( Extended Hückel Method )

37 3 eV (400 nm) BPY[Ni(dmit) 2 ] 2 Band Calculation ( Extended Hückel Method ) JACS, (2012) Red :( e.g. )~ 37% Ni(dmit) 2 Green :~ 100% BPY Black :~ 100% Ni(dmit) 2 (Fermi level) Feat. 1) Anion-Cation Mixed Bands

38 BPY[Ni(dmit) 2 ] 2 Band Structure ( Calc. Extended Hückel Method ) [Ni(dmit) 2 ] -  [Ni(dmit) 2 ] (1-  )- Feat. 2) Interband transitions = CT between anion and cation

39 BPY[Ni(dmit) 2 ] 2 Band Structure ( Calc. Extended Hückel Method ) Black : Ni(dmit) 2 Green : BPY Primary contribution e.g.) 3 eV (400 nm) Feat. 3) CT  UV region ( ~ a few eV)

40 BPY[Ni(dmit) 2 ] 2 Band Structure ( Calc. Extended Hückel Method ) Feat. 4) Narrow and relatively isotropic band at E F Black : Ni(dmit) 2 Green : BPY Primary contribution

41 A[Ni(dmit) 2 ] 2 ; photoconductivity – I - & T -dependences ( Single Crystal )( 375 nm, in vauo ) A = BPY A = MV Non-linear

42 A[Ni(dmit) 2 ] 2 ; photoconductivity – I - & T -dependences ( Single Crystal )( 375 nm, in vauo ) A = BPY b I 2 : Nearly T-independent 1. Thermally inaccessible to the dark states 2. Metallic conduction * Yonemitsu, K. J. Phys. Soc. Jpn. 2004, 73, Importance of cooperative effect*  : Non-linear dependence on I  sq =  dark + aI + bI 2 aI : known/standard mechanism bI 2 : a new mechanism

43 Photoconductivity – I -dependence (General behavior) ( Single Crystal ) Pentacene

44 Spin #1 (on Ni(dmit) 2 )2 (on BPY) Relative Intensity Nuclear Spin I1/2 ( 1 H)1 ( 15 N) Electron Spin S1/2 gxgx gygy gzgz A x [mT] A y [mT] A z [mT]  x [mT]  y [mT]  z [mT] Gaussian/Lorenzian0/100100/0 Table S3. ESR simulation parameters for BPY[Ni(dmit) 2 ] 2 (measured on the single crystal with H // [010] at 153 K). integrated

45 under continuous UV irradiation  log T  T 2 Metallic conduction (Possible) Kondo Effect Non-linear dependence on I T. Naito et al, Adv. Mater., 24 (46), (2012) New Features for PC 375 nm cf. T. Naito et al, J. Am. Chem. Soc., 134(45), (2012) e - Our previous work; C-A CT

46 MV[Ni(dmit) 2 ] 2 Evidence for Interaction between carriers and localized spins Kondo Effect ? UV  log T dark Semiconducting Metallic T-dependence of R ( single crystal ) under continuous UV irradiation  log T  T 2 [Ni(dmit) 2 ]  [Ni(dmit) 2 ] 0.98  UV ( Estimated from band calc. & UV spectra )

47 Metallic electronic system (unpaired electrons for Conduction) Localized spin system (unpaired electrons for Magnetism) Kondo Effect INTERACTION Dilute localized spin system (on MV) Carriers (on Ni(dmit) 2 )

48 D-A 相互作用で混じったバンド (各寄与がバンド毎に異なる) (例) ドナー( D )分子 [Ni(dmit) 2 ] ([Ni]) アクセプター( A )分子 BPY 2+ (BPY) - 電荷移動= Charge Transfer (CT)

49 A[Ni(dmit) 2 ] 2 ( A = MV, BPY ) ; 光応答(単結晶) ( ESR 応答の強さは、 光の単位強度当たりとして表示) 照射条件(強度, 波長, 温度, 雰囲気) を検討  主に紫外光~ nm にのみ応答 (E g  nm) CT が集中 ( 300 K, 375 nm, 11.6 mW cm -2 ) ESR 光電流 伝導性の光応答と 局在スピンの光応答が 連動 Ni(dmit) 2 BPY MV 2+ [Ni(dmit) 2 ] - e-e- MV 2+ MV[Ni] 2 [Ni] - UV

50 Summary & ConclusionA[Ni(dmit) 2 ] 2 (A = BPY, MV) Crystal Structure3D closely packed [Ni(dmit) 2 ] - accommodating photochemical redox active BPY 2+ / MV 2+ Electronic StructureIsotropic Strongly correlated (Narrow bands around E F ) strong Ni(dmit) 2 ―cation interaction Electronic Properties Dark semiconducting & diamagnetic UV irradiated Unpaired electrons on both of cation & Ni(dmit) 2 ( cation  Loc. Spins, Ni(dmit) 2  Carriers ) cf. Kondo effect (MV salt)

51 Let Us Meet Again We welcome you all to our future conferences of OMICS Group International Please Visit: Contact us at


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