Transcription

1

2

3

4

5

6

7

8 Retinal photoisomerization 11-cis all-trans

9

10 R = Rhodopsin T = Transducin PDE = Phosphodiesterase 5 -GMP = guanosine monophosphate GMP = cyclic guanosine monophosphate GTP/GDP = guanosine tri/diphosphate

11 3,5 -GMP cycl 5 -GMP

12

13

14

15

16 PHTN WRITES DEVICES signal signal Information Storage ptical Memories ptical Switches

17 DATA STRAGE DENSITY - book 5x10-2 cm 2 /char 20 char/cm 2 - CD 1x10-7 cm 2 /char 1x10 7 char/cm 2 - molecular memory (10 Å) 2D cm char/cm 2 3D cm char/cm 3 - if light is used to write, x λ e. g., for λ = 500 nm 2D 2x10 9 cm 2 3D cm 3

18 Information Storage (Write/Read/Erase) with Photochromic Systems

19 Photochromic Diarylethenes CF 2 F 2 C CF 2 UV CF 2 F 2 C CF 2 N N 2 2 S S 0.9 vis N 2 S S N absorbance Closed pen wavelength, nm Drawback: destructive readout

20 A lock/unlock write-read-erase molecular system write erase unlock lock

21 Fluorescence Readout Memory: Fluorophore + Photochromic unit F = Fluorophore P = Photochromic unite hν quenching F* P F* P

22 Fluorescence Readout Memory: Dyad with Fluorophore + Photochromic unit Selective quenching by closed form. Quenching mechanism: energy transfer Drawback: destructive readout

23 Fluorescence Readout Memory: Dyad with Fluorophore + Photochromic unit Selective quenching by closed form. Quenching mechanism: electron transfer Advantage: non-destructive readout

24 Non-destructive Readout Fluorescence Memory: Triplet Quenching by Photochromic Unit hν UV An(S 1 ) DAn(S 1 ) Ru(S 1 ) Ru(T 1 ) An(T 1 ) DAn(T 1 ) Ru(T 1 ) Ru(S 1 ) Ru(S 0 ) An(S 0 ) DAn(S 0 ) Ru(S 0 )

25 Functional Materials Luminescent ptical Memories write 450 nm 390 nm 450 nm FF M P M P N no emission X 600 nm Fluorescent microscope image written with a frequency doubled Ti:Sapphire laser through a TEM grid (10 µm resolution)

26 Bacteriorhodopsin from Halobacterium Halobium

27 Bacteriorhodopsin A natural photochromic system

28

29 Bacteriorhodopsin: a natural photochromic system R Q

30 3D ptical Memory based on BacterioRhodopsin

31

32 PHTN READS DEVICES hν hν Sensors Luminescent Probes

33 Chemical sensors (Chemosensors) Chemosensor (molecular sensor) A A chemosensor isi molecule of abiotic origin that signals the presence of matter or energy (A. W. Czarnick) UNITA DI TRASDUZINE UNITA DI SEGNALAZINE SIT DI RICNSCIMENT ANALITA SEGNALE Fluorescent chemosensor It is a chemosensor that generate a fluorescence signal Why fluorescence? Sensitivity (even single molecule detection is possible) High spatial and temporal resolution Low cost and easily performed instrumentations

34 Fluorescent Sensor based on ET quenching e - e - Sensor P* R Analyte P* R Fluorophore quenched by free receptor No quenching by receptor-analyte. Fluorescence switched on

35 Fluorophore-Receptor Supermolecules FF state: S 1 state of fluorophore quenched by ET from amino group of receptor

36

37 Intrinsic chemosensors 1 Ca 2+ C - C - N -C N C - H 3 C N N C - C - FURA-2 (Tsien 1980) N C - H 3 C N Quin-2 (Tsien 1985) C - C - Mg 2+ N C - C - NH C - C C N Na + N C C C - Me Me Mag-Indo-1 (London 1989) (Tsien 1989)

38 Excimers formation M + M* E* excimer emission monomer emission C 2 Et C 2 Et Na + Et Et calix[4]arene calix[4]arene Jin et al. J. Chem. Soc., Chem. Commun., 1992, 499.

39 Molecular Recognition/Sensing

40 Intrinsic chemosensors 2 J.K. Tusa, H. He

41 Special Fluorophores: Greeen Fluorescent Protein chromophore: 4-(p-hydroxybenzylidene)imidazolidin-5-one (HBI) Martin Chalfie, samu Shimomura,Roger Y. Tsien 2008 Nobel Prize in Chemistry

42

43 Special Fluorophores: Semiconductor Quantum Dots Quantum Size Effects hν hν bulk material nanocrystal decreasing size molecular cluster

44 The atoms on the surface of a crystal facet are incompletely bonded within the crystal attice and leave dangling orbitals pointed outward from the crystal. If these surface energy states are within the semiconductor band gap, they can trap charge carriers at the surface, thereby increasing the probability of nonradiative recombination To minimize intraband gap surface states and reduce surface atomic reconstruction, the surface must be passivated with (i) organic ligands or (ii) insulating inorganic shell an. trap CB cat. trap VB

45 Special Fluorophores: Semiconductor Quantum Dots

46 Functionalized with biological conjugates bio-conjugate = enzyme, antibody, etc. fluorescent sensors, cell imaging, etc.

47 Study of enzyme activity Protease Protein kinase DNA polymerase

48 p-n light emitting diode (LED) p-n photodiode

49 Quantum dot light emitting diode (QDLED)

50 Displays, TV screens.