| 41. |
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| 42. |
- Chiragwandi, Zackary, 1968, et al.
(författare)
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Properties of a bio-photovoltaic nano-device
- 2008
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:48, s. 18717-18721
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Tidskriftsartikel (refereegranskat)abstract
- Properties of an on-chip photovoltaic nanodevice are demonstrated. The dyes comprise green florescent proteins(GFP). Dependence of recently reported zero external potential bias (ZEPB) photocurrent (I) on temperature,power, and wavelength (λ) is shown. Correlation between UV-vis spectrum of the GFP and the ZEPB I(λ)of the device is reported. The temperature dependence suggests the ZEPB photocurrent to reflect a liquidcrystal type ordering where the current declines monotonically with increasing temperature. The influence ofan external bias on the photocurrent is demonstrated. The resulting light-induced current is analyzed in termsof resistive and quantum mechanical contributions.
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| 43. |
- Choi, S. D., et al.
(författare)
-
Binding Mode of [Ruthenium(II) (1,10-Phenanthroline)2L]2+ with Poly(dT*dA-dT) Triplex. Ligand Size Effect on Third-Strand Stabilization
- 1997
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 1520-4995 .- 0006-2960. ; 36:1, s. 214-223
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Tidskriftsartikel (refereegranskat)abstract
- The binding of homochiral [Ru(II)(1,10-phenanthroline)(2)L](2+) complexes {where L = 1,10-phenanthroline (phen), dipyrido[3,2-a:2',3'-c]phenazine (DPPZ) or benzodipyrido[3,2-a:2',3'-c]phenazine (BDPPZ)} to poly(dT*dA-dT) triplex has been investigated by linear and circular dichroism and thermal denaturation. Analysis of the linear dichroism spectra indicates that the extended DPPZ and BDPPZ ligands lie approximately parallel to the base-pair and base-tripler planes consistent with intercalation which is also supported by strong hypochromism in the interligand absorption bands with either duplex or tripler. The spectral properties of any of the metal complex enantiomers were similar for binding to either duplex or tripler DNA, indicating that the third strand, which occupies the major groove of the template duplex, has little effect on the binding geometries and hence supports the hypothesis that the metal complexes all bind from the minor groove with the DPPZ and BDPPZ ligands intercalated but without intercalation in the case of [Ru(phen)(3)](2+). Third-strand stabilization depended on the nature of the third substituted phenanthroline chelate ligand but was not directly related to its size, with stabilizing power increasing in the order phen
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| 44. |
- Coates, C. G., et al.
(författare)
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Picosecond time-resolved resonance Raman probing of the light-switch states of Ru(Phen)(2)dppz (2+)
- 2001
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 105:50, s. 12653-12664
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Tidskriftsartikel (refereegranskat)abstract
- Picosecond time-resolved resonance Raman (picosecond-TR3) spectroscopy has been used to conduct an extensive photophysical characterization of the light- switch complex [Ru(phen)(2)dppz](2+) as a function of environment, in which studies have been carried out in aqueous and nonaqueous media and in DNA. The results are considered in rotation to a previous report describing environment-sensitive lowest triplet MLCT states. Vibrational marker features and enhancement patterns were used to determine the rapid progression (< 20 ps) between two triplet MLCT states in aqueous environment, followed by subnanosecond, nonradiative deactivation to the ground state. In nonaqueous environment, the long-lived, emissive triplet MLCT state is spectrally identified as the short-lived first triplet MLCT state observed in water, in agreement with the earlier proposed mechanism. The present data are shown to correlate well with previous nanosecond RR findings for the complex in each environment. Interestingly, a precursor state has been identified upon excitation in both nonaqueous solvent and in DNA, which precedes the triplet MLCT state, and the lifetime of which appears to be environment dependent. Observation of this state is discussed in relation to other recent femtosecond spectroscopic studies on this complex.
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| 45. |
- Colmenarejo, G., et al.
(författare)
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Electronic Spectra and Transition Moments of 6-(2’-Pyridiniumyl)phenanthridinium Photoactive DNA Intercalators
- 1997
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Ingår i: Journal of Physical Chemistry B Materials. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 101:26, s. 5196-5204
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Tidskriftsartikel (refereegranskat)abstract
- The electronic transitions giving rise to the UV-visible absorption spectra of two pyridinium-phenanthridinium viologens, 6,7-dihydropyridol[2',1':3,4]pyrazinol[1,2-f]phenanthridinediium dication (1) and 7,8-dihydro-6H-pyrido[2',1':3,4]diazepino[1,2-f]phenanthridinediium dication (2), have been investigated with respect to energies, intensities, and transition moment directions. A combination of methods has been applied: UV-visible absorption, circular dichroism, magnetic circular dichroism, fluorescence anisotropy, Linear dichroism In stretched poly(vinyl alcohol) films, and semiempirical molecular orbital calculations. For both drugs, the lowest energy absorption band, occurring around 400 nm, results from two separate transitions. The corresponding electric transition dipole moments lie in the phenanthridine plane and are polarized, respectively, in the direction of the pyridine moiety (the lower energy transition) and parallel to the phenanthridine long axis (the higher energy transition). Up to four additional different pi --> pi* transitions account for a second band that peaks at 250 nm; they show different polarizations within the phenanthridine plane. The lowest energy transition of the whole spectrum of both drugs corresponds to the promotion of an electron from the HOMO to the LUMO, which are molecular orbitals mainly localized in the phenanthridine and pyridine rings, respectively, thereby implying a charge transfer, upon excitation, from the phenanthridine toward the pyridine ring. The experimental and theoretical results are discussed in relation to the spectroscopic, redox, and photochemical properties of these drugs.
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| 46. |
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| 47. |
- Dahlgren, T., et al.
(författare)
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Electronic spectra of dithieno analogues of phenanthrene
- 1979
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 40:3, s. 397-404
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic circular dichroism (MCD) spectra of some dithieno analogues of phenanthrene: benzo [2,1-b;3,4-b′] dithiophene (I) benzo [1,2-b;4,3-b′] dithiophene (II), benzo [1,2-c;3,4-c′] dithiophene (III) and benzo [1,2-b;3,4-b′] dithiophene (IV) are reported. For I–III the spectra corresponding to two different transition moment directions could be obtained from low-temperature linear dichroism spectra. The results compare well with theoretical energies, oscillator strengths, moment directions and MCD B-terms which were obtained from semi-empirical quantum mechanical calculations in the π-electron approximation.
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| 48. |
- Davidsson, A., et al.
(författare)
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A method for determination of the refractive index in a region of absorption. Anomalous dispersion of CS2 in the UV range
- 1975
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 8:1-2, s. 223-230
-
Tidskriftsartikel (refereegranskat)abstract
- A method is described for determining the refractive index of, e.g., a liquid solution, within an absorption band by studying the linear dichroism generated by different reflections at inclined optical incidence. The method requires a sensitive differential photometric technique, such as that accomplished in a circular dichroism spectrometer.The refractive index of CS2 is reported in the region 260–450 mm. and the result compared to that obtained from a Kramers-Kronig integration on the 320 nm absorption band. Though this band is fairly isolated the experimentally gained result was found more reliable. This was due to difficulties in obtaining an accurate absorption coefficient of liquid CS2 as well as to the fact that the integration had to be restricted to a finite spectral range.
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| 49. |
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| 50. |
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