Second optical harmonic generation by a layered plasmon nanoparticle

The features of second harmonic generation by a spherical nanoparticle with a plasmon shell are theoretically studied. In the framework of the quasistatic perturbation theory, expressions for the oscillating at a doubled frequency induced dipole and quadrupole moments of a particle were obtained. The second harmonic radiation power was calculated, which showed the resonance nature of the dependence of power on the exciting wavelength. Moreover, the positions of the radiation power resonances significantly depend on the dielectric permittivity of the particle core and its size.

Study on Spatial Distribution of UVA Radiant Intensity for Ballast Water Treatment

UVA is seldom applied in UV inactivation or disinfection, however, it may be more suitable for underwater photo-catalysis treatment. Since the wavelength of UVA is longer than UVC, the former has higher transmission ability and encounter less disturbance of suspending substances in water. Also, the exciting wavelength of UVA is between 365nm and 413nm which coincides with the wavelength of UVA. Hence, the spatial distribution of UVA radiation is studied for a 15W UVA lamp. The decaying tendencies of UVA radiation intensity were probed over horizontal and vertical distance, behind large amounts of experimental data. Optimal radiation conditions plan to be detected based on the research to guide the UVA treatment.

Study of Silver Nanoparticles Sensitized Fluorescence and Second-Order Scattering of Terbium(III)-Pefloxacin Mesylate Complex and Determination of Pefloxacin Mesylate

α-Keto acid of pefloxacin mesylate (PFLX) can form the complex with Terbium(III). The intramolecular energy from PFLX to Terbium(III) ion takes place when excited, and thus Terbium(III) excited state is formed and then emits the characteristic fluorescence of Terbium(III), locating at 490, 545, 580, and 620 nm. The second-order scattering (SOS) peak at 545 nm also appears for the complex with the exciting wavelength of 273 nm. When the silver nanoparticles are added to the system, the luminescence intensity at 545 nm greatly increased. So, with the adding of nanoparticles to the Terbium(III)-PFLX complex, not only is the intramolecular energy promoted but also the SOS intensity is enhanced. The experimental results show that it is the silver nanoparticles with certain size and certain concentration which can greatly enhance the fluorescence-SOS intensity, and the relative intensity at 545 nm is proportional to the amount of PFLX. Based on this phenomenon, a novel method for the determination of PFLX has been developed and applied to the determination of PFLX in capsule and serum samples.

Photoactivatable Fluorophores

Photoactivatable fluorophores switch from a nonemissive to an emissive state upon illumination at an activating wavelength and then emit after irradiation at an exciting wavelength. The interplay of such activation and excitation events can be exploited to switch fluorescence on in a defined region of space at a given interval of time. In turn, the spatiotemporal control of fluorescence translates into the opportunity to implement imaging and spectroscopic schemes that are not possible with conventional fluorophores. Specifically, photoactivatable fluorophores permit the monitoring of dynamic processes in real time as well as the reconstruction of images with subdiffraction resolution. These promising applications can have a significant impact on the characterization of the structures and functions of biomolecular systems. As a result, strategies to implement mechanisms for fluorescence photoactivation with synthetic fluorophores are particularly valuable. In fact, a number of versatile operating principles have already been identified to activate the fluorescence of numerous members of the main families of synthetic dyes. These methods are based on either the irreversible cleavage of covalent bonds or the reversible opening and closing of rings. This paper overviews the fundamental mechanisms that govern the behavior of these photoresponsive systems, illustrates structural designs for fluorescence photoactivation, and provides representative examples of photoactivatable fluorophores in actions.

The Resonance Raman Spectra Of Biologically Relevant Polyene Derivatives in T1: A Theoretical Investigation

The vibrational structure of the T1 resonance Raman spectra of β-ionylidene acetaldehyde (C15 aldehyde) and retinal are analyzed with the help of semiempirical quantum chemical calculations. The T1 equilibrium structures and vibrational force fields, along with the structure in the Tn state which is in resonance with the exciting wavelength, are obtained and employed to model the spectra under the assumption of a dominant Franck–Condon mechanism.