Photoinduced electron transfer mechanism between green fluorescent protein molecules and metal oxide nanoparticles

Green fluorescent protein (GFP) molecules are attached to titanium dioxide and cadmium oxide nanoparticles via sol-gel method and fluorescence dynamics of such a protein-metal oxide assembly is investigated with a conventional time correlated single photon counting technique. As compared to free fluorescent protein molecules, time-resolved experiments show that the fluorescence lifetime of GFP molecules bound to these metal oxide nanoparticles gets shortened dramatically. Such a decrease in the lifetime is measured to be 22 and 43 percent for cadmium oxide and titanium dioxide respectively, which is due to photoinduced electron transfer mechanism caused by the interaction of GFP molecules (donor) and metal oxide nanoparticles (acceptor). Our results yield electron transferrates of 3.139 x 108 sand 1.182 x 108 s_ 1 from the GFP molecules to titanium dioxide and cadmium oxide nanoparticles, respectively. The electron transfer rates show a marked decrease with increasing driving force energy. This effect represents a clear example of the Marcus inverted region electron transfer process

In situ measurement of humidity induced changes in the refractive index and thickness of polyethylene glycol thin films

6th International Conference on PhotonicsHumidity induced changes in the refractive index and thickness of polyethylene glycol (PEG) thin films are in situ determined by optical waveguide spectroscopy. PEG brushes are covalently attached to the surface of a thin gold film on a borosilicate crown glass (BK7) using a grafting-from chemical synthesis technique. The measurements are carried out in an attenuated total internal reflection setup. At low humidity levels, both the refractive index and the thickness change gradually due to swelling of the PEG thin films upon water intake. At around 80% relative humidity, a steep decrease in the refractive index and a steep increase in the thickness are observed as a result of a phase change from a semicrystalline state to a physical gel state. The hydrogenation of PEG films causes a less pronounced phase change from a semicrystalline state to a gel state. Due to fewer ether oxygen atoms available for the water molecules to make hydrogen bonding, the polymer has a more stable structure than before and the phase change is observed to shift to higher humidity levels. It is discussed that such a humidity induced change in the index of refraction can be utilized in constructing of a PEG based humidity sensor.Czech & Slovak Soc Photonc; Act M Agcy; Czech Tech Univ; Acad Sci Czech Republic; Slovak Acad Sci; Meopta Prerov; SPIE; SPIE Europe; European Opt Soc; Opt Soc Ame

Use of polyethylene glycol coatings for optical fibre humidity sensing

Humidity induced change in the refractive index and thickness of the polyethylene glycol (PEG) coatings are in situ investigated for a range from 10 to 95%, using an optical waveguide spectroscopic technique. It is experimentally demonstrated that, upon humidity change, the optical and swelling characteristics of the PEG coatings can be employed to build a plastic fibre optic humidity sensor. The sensing mechanism is based on the humidity induced change in the refractive index of the PEG film, which is directly coated onto a polished segment of a plastic optical fibre with dip-coating method. It is observed that PEG, which is a highly hydrophilic material, shows no monotonic linear response to humidity but gives different characteristics for various ranges of humidity levels both in index of refraction and in thickness. It undergoes a physical phase change from a semi-crystal line structure to a gel one at around 80% relative humidity. At this phase change point, a drastic decrease occurs in the index of refraction as well as a drastic increase in the swelling of the PEG film. In addition, PEG coatings are hydrogenated in a vacuum chamber. It is observed that the hydrogen has a preventing effect on the humidity induced phase change in PEG coatings. Finally, the possibility of using PEG coatings in construction of a real plastic fibre optic humidity sensor is discussed. (C) 2008 The Optical Society of Japan

Simultaneous measurements of the thermal optical and linear thermal expansion coefficients of a thin film etalon from the reflection spectra of a super-luminescent diode

An experimental determination technique for simultaneous measurements of the thermal optical and linear thermal expansion coefficients of tantalum pentoxide thin films in the infrared wavelength region is described. A tantalum pentoxide thin film deposited directly onto the end face of a single mode optical fibre is illuminated by a super-luminescent diode source and its spectrum on reflection, between 1460 and 1620 nm, is monitored at various temperatures using an optical spectrum analyser. Temperature induced change in the index of refraction and the film thickness are determined from the reflection spectrum to calculate the thermal optical and linear thermal expansion coefficients simultaneously

Three-dimensional optical profilometry using a four-core optical fibre

This paper describes the use of a four-core optical fibre for measurements of three-dimensional rigid-body shapes. A fringe pattern, which is generated by interference of four wavefronts emitted from the four-core optical fibre, is projected on an object's surface. The deformed fringe pattern containing information of the object's Surface topography is captured by a digital CCD camera and is analysed using a two-dimensional Fourier transform profilometry. It is demonstrated for the first time that the use of such a four-core optical fibre increases the compactness and the stability of the fringe projection system

Elastic behaviour of solution cross-linked poly(isobutylene) gels under large compression

Modulus of elasticity of loosely cross-linked poly(isobutylene) gels are measured under large compressive deformations. Gels of perfect spherical shape are prepared by the suspension cross-linking technique of dilute toluene solutions of butyl rubber using sulfur monochloride as a cross-linking agent. Compressive deformation is applied by a calibrated stainless steel cantilever to spherical poly(isobutylene) beads of sizes ca. 1.0-4.0 mm in diameter swollen in toluene. The relationship between force and deformation is obtained by using the constitutive relations from molecular theory of elasticity Moduli are measured immediately after applying compression, and after full relaxation which obtains after solvent exudes the gels under compression. The instantaneous moduli are an order of magnitude larger than equilibrium moduli. Results of mechanical measurements, which are presently of a preliminary type, are compared with those from independent thermodynamic estimates of shear moduli

Decay rate measurement of perylene dye molecules attached to porous silicon nanostructures

Bilen, Bükem (Dogus Author) -- Conference full title: Photonics, Devices, and Systems IV; Prague; Czech Republic; 27 August 2008 through 29 August 2008The radiative decay rates of perylene dye molecules, attached to silicon nano-rods are investigated by means of timeresolved fluorescence experiments. The decay rates of dye molecules in the vicinity of silicon nano-rods are inhibited due to their various diameters and therefore the modification of the surrounding environment. Inhibition is caused by an increased nonradiative rate due to resonant energy transfer described by the Gersten-Nitzan model

Monitoring excimer formation of perylene dye molecules within PMMA-based Nanofiber via FLIM Method

Conference on Nanophotonics VI -- APR 03-07, 2016 -- Brussels, BELGIUMWOS:000378220200013Confocal fluorescence lifetime imaging microscopy method is used to obtain individual fluorescence intensity and lifetime values of aromatic Perylene dye molecules encapsulated into PMMA based nanofibers. Fluorescence spectrum of aromatic hydrocarbon dye molecules, like perylene, depends on the concentration of dye molecules and these dye molecules display an excimeric emission band besides monomeric emission bands. Due to the dimension of a nanofiber is comparable to the monomer emission wavelength, the presence of nanofibers does not become effective on the decay rates of a single perylene molecule and its lifetime remains unchanged. When the concentration of perylene increases, molecular motion of the perylene molecule is restricted within nanofibers so that excimer emission arises from the partially overlapped conformation. As compared to free excimer emission of perylene, time-resolved experiments show that the fluorescence lifetime of excimer emission of perylene, which is encapsulated into NFs, gets shortened dramatically. Such a decrease in the lifetime is measured to be almost 50 percent, which indicates that the excimer emission of perylene molecules is more sensitive to change in the surrounding environment due to its longer wavelength. Fluorescence lifetime measurements are typically used to confirm the presence of excimers and to construct an excimer formation map of these dye molecules.SPIE, B PHOT Brussels Photon Team, Res Fdn Flanders, Visit Brussel