Quantum-mechanical tunneling in thin films of chlorophyll a

Simpson, William H.; Reucroft, P. J.

doi:10.1016/0040-6090(70)90037-4

Cited by 15 publications

(4 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Jones et a1 (1980) present arguments to support the view that the photovoltage is generated at the Al,O,/chlorophyll interface. This work extends and confirms the results obtained by Reucroft and Simpson (1969) and Simpson and Reucroft (1970). Miyasaka et a1 (1978,1979,1980) have made similar studies using transparent SnO, as the substrate and a solution of hydroquinone as the other electrode.…”

Section: Photocurrents Through the J L Msupporting

confidence: 88%

The physics of Langmuir-Blodgett films

Tredgold

1987

Rep. Prog. Phys.

View full text Add to dashboard Cite

Langmuir-Blodgett (LB) films are formed by the successive deposition of a series of monolayers of one or more types of amphiphilic molecules initially spread at the interface between water and air. They usually consist of a regular planar array of molecular layers having a well defined and predetermined thickness. Their properties have made them of interest to physicists, electronic engineers, chemists and biologists. This review is mainly addressed to physicists and device engineers but, since the topic is of an interdisciplinary nature, it is hoped that it may also be of use to research workers in other disciplines. The early development and essential technology of the subject are discussed and key papers are referred to. However, the review is mainly devoted to the large amount of recent work in the field. The application of LB films to the study of dye molecules and their interactions is not dealt with in any detail as this topic has been well reviewed elsewhere and leads, in any case, to the general study of dye molecules which is beyond the scope of this review. A wide variety of different types of amphiphilic molecule are discussed ranging from simple carboxylic acids via complex heterocyclic compounds to polymers. The various physical techniques used to determine the crystallographic structure of the films together with the influence of deposition methods on this structure are discussed. The study of the electric and optical properties of various LB films is described both in relation to the physical information which may be gained from these studies and also in respect of possible technical applications. The difficulties inherent in attempting to obtain good threedimensional crystallographic order in films are pointed out together with possible methods of overcoming these difficulties.

show abstract

Section: Photocurrents Through the J L Msupporting

confidence: 88%

The physics of Langmuir-Blodgett films

Tredgold

1987

Rep. Prog. Phys.

View full text Add to dashboard Cite

show abstract

“…The interesting current-voltage curves obtained by Simpson and Reucroft (8) for thin chlorophyll films may also be explained in terms of TAT. By adding a monolayer at a time, these authors were able to move from a virtually temperature independent, low field region in which Fermilevel tunnelling dominated the current-voltage characteristic, to a situation at higher fields which clearly involved a thermally activated process.…”

mentioning

confidence: 69%

“…For solids with ohmic contn-ts we propose that pseudo-intrinsic conduction as described by equation (1) can account for the correlation between the activation energy, E, and the conductivity, d . If a solid is subjected to a disturbance which changes the depth of one of its dominant levels and at the same time alters the densities of its dominant levels from N ml ' N to N N it is straightforward to show from equation (1) that the two activation energy curves obtained before and after the disturbance will intersect at T =provided N physical grounds and probably accounts for several reported curves obeying equation physica status solidi (a) 8 We then obtain the result which may be compared directly with equation (2) non-ohmic configurations, is the following: We propose a model in which a thin potential barrier exists at the interface between the electrode and the solid. We further assume that the transfer of charge carriers across the barrier is via thermally assisted tunnelling (TAT).…”

mentioning

confidence: 98%

Recent theories of electrical conduction in semi-insulators and their experimental observation in organic solids

Roberts

1971

Phys. Stat. Sol. (a)

View full text Add to dashboard Cite

A recent theory discussing all possible interpretations of a simple activation energy for electrical conduction has been given by Roberts and Schmidlin (1). In their paper they show that the density of free carriers, n activation energy in a wide band gap n-type material, can be expressed by the controlling the ohmic C, equation whereas the activation energy of a current in the space charge limited region is Ec -Em. In the above equation the subscripts c, m, and q, correspond to conduction band, dominant electron, and dominant hole states respectively. Although the validity of this equation was exemplified by experiments on inorganic single crystal semiconductors, their theory concerning the statistical occupancy of states

show abstract

“…A number of studies on the functions of Chl- a LB films have been carried out extensively, aiming at developing new molecular devices such as photoelectric cells based upon the Chl- a assemblies. − Most of the studies suggested that Chl- a is not a suitable organic semiconductor and a sufficient photoelectric conversion effect has not been observed. Some research groups investigated energy transfer from/to Chl- a in LB films containing another molecule as well as Chl- a .…”

Section: Introductionmentioning

confidence: 99%

Control of Molecular Arrangement in Langmuir−Blodgett Films of Chlorophyll a Prepared in Various Gas Phases Studied by Ultraviolet−Visible and Infrared Spectroscopies and Atomic Force Microscopy^,

Sato¹,

Ozaki²,

Oishi³

et al. 1997

Langmuir

View full text Add to dashboard Cite

Attenuated total reflection (ATR)/Fourier-transform infrared (FT-IR) spectra were measured for one-monolayer Langmuir−Blodgett (LB) films of chlorophyll a (Chl-a) fabricated in an argon (Ar) atmosphere. The frequencies of CO stretching bands and marker bands for the coordination number of the central Mg atom suggest that Chl-a takes a five-coordinated dimer in the films prepared in the Ar atmosphere. Ultraviolet−visible (UV−vis) as well as IR spectra were obtained for multilayer LB films of Chl-a prepared in air, Ar, nitrogen (N2), and oxygen (O2) atmospheres. In the cases of the multilayer LB films, spectral features in the CO stretching band region suggest that Chl-a exists as a monomer in the film prepared in air while it assumes a dimer in the films prepared in the Ar, N2, and O2 atmospheres. The marker bands for the coordination number of the Mg atom in the IR spectra indicate that Chl-a is in a five-coordinated state. These results imply that one can control the molecular arrangement in the LB films of Chl-a by changing the atmosphere in which they are prepared. Both the UV−vis and IR spectra of the LB films fabricated in the Ar, N2, and O2 atmospheres are almost identical to each other. This means that O2 does not affect the stability and structure of Chl-a in the monolayer on the aqueous subphase. On the basis of the postulate that CO2, which exists only in air, caused a change in pH of the aqueous subphase, we investigated pH-dependent IR spectral changes for the LB films. The results indicate that the dimer of Chl-a changes into pheophytine a (Phe-a) below pH 6.0 and that the monomer species do not exist through pH 6.0−4.0; therefore, it is unlikely that CO2 changes the pH. Probably CO2 coordinates to the central Mg atom as a fifth ligand in the LB films prepared in air, preventing the keto carbonyl group of another Chl-a molecule from coordinating to it.

show abstract

Quantum-mechanical tunneling in thin films of chlorophyll a

Cited by 15 publications

References 9 publications

The physics of Langmuir-Blodgett films

The physics of Langmuir-Blodgett films

Recent theories of electrical conduction in semi-insulators and their experimental observation in organic solids

Control of Molecular Arrangement in Langmuir−Blodgett Films of Chlorophyll a Prepared in Various Gas Phases Studied by Ultraviolet−Visible and Infrared Spectroscopies and Atomic Force Microscopy^,

Contact Info

Product

Resources

About

Quantum-mechanical tunneling in thin films of chlorophyll a

Cited by 15 publications

References 9 publications

The physics of Langmuir-Blodgett films

The physics of Langmuir-Blodgett films

Recent theories of electrical conduction in semi-insulators and their experimental observation in organic solids

Control of Molecular Arrangement in Langmuir−Blodgett Films of Chlorophyll a Prepared in Various Gas Phases Studied by Ultraviolet−Visible and Infrared Spectroscopies and Atomic Force Microscopy,

Contact Info

Product

Resources

About

Control of Molecular Arrangement in Langmuir−Blodgett Films of Chlorophyll a Prepared in Various Gas Phases Studied by Ultraviolet−Visible and Infrared Spectroscopies and Atomic Force Microscopy^,