The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Charge-Transfer and Energy-Transfer Processes in π-Conjugated Oligomers and Polymers: A Molecular Picture

Synthetic Principles for Bandgap Control in Linear pi-Conjugated Systems.

Inorganic colloidal nanoparticles are very small, nanoscale objects with inorganic cores that are dispersed in a solvent. Depending on the material they consist of, nanoparticles can possess a number of different properties such as high electron density and strong optical absorption (e.g. metal particles, in particular Au), photoluminescence in the form of fluorescence (semiconductor quantum dots, e.g. CdSe or CdTe) or phosphorescence (doped oxide materials, e.g. Y(2)O(3)), or magnetic moment (e.g. iron oxide or cobalt nanoparticles). Prerequisite for every possible application is the proper surface functionalization of such nanoparticles, which determines their interaction with the environment. These interactions ultimately affect the colloidal stability of the particles, and may yield to a controlled assembly or to the delivery of nanoparticles to a target, e.g. by appropriate functional molecules on the particle surface. This work aims to review different strategies of surface modification and functionalization of inorganic colloidal nanoparticles with a special focus on the material systems gold and semiconductor nanoparticles, such as CdSe/ZnS. However, the discussed strategies are often of general nature and apply in the same way to nanoparticles of other materials.

https://faculty.washington.edu/mzhang/mse599/Surface-modification.full.pdf

Surface modification, functionalization and bioconjugation of colloidal inorganic nanoparticles

The current status of the use of nanoparticles for photothermal treatments is reviewed in detail. The different families of heating nanoparticles are described paying special attention to the physical mechanisms at the root of the light-to-heat conversion processes. The heating efficiencies and spectral working ranges are listed and compared. The most important results obtained in both in vivo and in vitro nanoparticle assisted photothermal treatments are summarized. The advantages and disadvantages of the different heating nanoparticles are discussed.

Nanoparticles for photothermal therapies.

Fundamental frequencies, normal coordinates, and force constants were calculated using an Overlay technique for CH3NH2, CD3NH2, CH3ND2, CD3ND2, (CH3)2NH, (CH3)2ND, (CH3)3N, and (CD3)3N. Both valence and Urey–Bradley force fields were adopted. The vibrational assignments previously reported on all these molecules have been partly confirmed and partly modified. The usefulness and limitations of normal coordinate calculations in problems of vibrational assignments is discussed.

Normal Coordinate Calculations as a Tool for Vibrational Assignments. I. Fundamental Vibrations of Simple Aliphatic Amines

We present a simple seed-less synthesis procedure to fabricate stable gold nanostars (AuNSs) with tunable extinction properties from the visible up to 1800 nm, depending on the average values of core size and branch length. The experimental results are compared with data from Finite Elements Method computations by using an approximated model of the fabricated branched systems. The theoretical computations highlight the existence of hot spots located on the tips of the nanostars even up to 1800 nm wavelength, which opens the way to the improvement of IR diagnostics or chemical sensing.

Synthesis and modelling of gold nanostars with tunable morphology and extinction spectrum

The time scale of covalent state relaxation and singlet fission into triplet pairs is determined in a solution of isolated polydiacetylene chains showing a remarkably sharp excitonic transition by applying the transient transmission difference spectroscopy technique with sub-10 fs optical pulses. Photoexcitation into the band of ionic states is followed by a branching within the first 100 fs which populates the band of covalent states. The latter start to dissociate into triplet excitations, completing the process in about 300 fs.

Triplet-Exciton Generation Mechanism in a New Soluble (Red-Phase) Polydiacetylene

Photoinduced absorption is observed for the polydicarbazolyldiacetylene in the microcrystalline state. The absorption spectrum shows well-defined excitonic features, very similar to those observed for the same polymer in the single-crystal form. Photoexcitation at 2.54 eV gives rise to a structured luminescence emission with the maximum around 1.7 eV. The photoinduced absorption spectrum shows three well-resolved peaks at 0.81, 0.96, and 1.26 eV, a shoulder at 1.04 eV, and a band with a maximum below 0.3 eV. By analyzing the dependence of the photoinduced signals on temperature, laser intensity, phase detection, and chopper frequency, we demonstrate that the long-lived photocarriers associated with the peaks at 0.81 eV and below 0.3 eV are charged bipolarons. The 0.96- and 1.04-eV bands are tentatively assigned to vibronic excitations of the bipolarons. Moreover, the 1.26-eV band has been assigned here to a triplet exciton transition. The existence of a correlation between the type of long-lived photogenerated defects and the polymer disorder is also discussed.

Giovanna Dellepiane

Papers

Normal Coordinate Calculations as a Tool for Vibrational Assignments. I. Fundamental Vibrations of Simple Aliphatic Amines

Synthesis and modelling of gold nanostars with tunable morphology and extinction spectrum

Triplet-Exciton Generation Mechanism in a New Soluble (Red-Phase) Polydiacetylene

Long-lived photoexcited states in symmetrical polydicarbazolyldiacetylene

Optical constants of highly stretch-oriented poly( p -phenylene-vinylene): A joint experimental and theoretical study