Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

When a molecule absorbs a photon of appropriate energy, a chain of photophysical events ensues, such as internal conversion or vibrational relaxation (loss of energy in the absence of light emission), fluorescence, intersystem crossing (from singlet state to a triplet state) and phosphorescence, as shown in the Jablonski diagram for organic molecules (Fig. 1). Each of the processes occurs with a certain probability, characterized by decay rate constants (k). It can be shown that the average length of time τ for the set of molecules to decay from one state to another is reciprocally proportional to the rate of decay: τ = 1/k. This average length of time is called the mean lifetime, or simply lifetime. It can also be shown that the lifetime of a photophysical process is the time required by a population of N electronically excited molecules to be reduced by a factor of e. Correspondingly, the fluorescence lifetime is the time required by a population of excited fluorophores to decrease exponentially to N/e via the loss of energy through fluorescence and other non-radiative processes. The lifetime of photophycal processes vary significantly from tens of femotoseconds for internal conversion1,2 to nanoseconds for fluorescence and microseconds or seconds for phosphorescence.1






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Figure 1


Jablonski diagram and a timescale of photophysical processes for organic molecules.

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Fluorescence Lifetime Measurements and Biological Imaging

Elements Of X Ray Diffraction

The long wavelength (far-red to NIR) analyte-responsive fluorescent probes are advantageous for in vivo bioimaging because of minimum photo-damage to biological samples, deep tissue penetration, and minimum interference from background auto-fluorescence by biomolecules in the living systems. Thus, great interest in the development of new long wavelength analyte-responsive fluorescent probes has emerged in recent years. This review highlights the advances in the development of far-red to NIR fluorescent probes since 2000, and the probes are classified according to their organic dye platforms into various categories, including cyanines, rhodamine analogues, BODIPYs, squaraines, and other types (240 references).

Far-red to near infrared analyte-responsive fluorescent probes based on organic fluorophore platforms for fluorescence imaging

http://nathan.instras.com/documentDB/paper-12.pdf

Applications of functionalized transition metal complexes in photonic and optoelectronic devices

The 1H NMR spectra of a series of disperse monoazo dyes in solution are reported and analysed in terms of electronic effects of the substituents, rotational isomerism and hydrogen bonding.

Guido Viscardi

Papers

1H NMR spectra of a series of disperse azo dyes

Adsorption of 1-alkyl-4-methylpyridinium salts at solid-liquid and water-air interfaces

Structural characterisation of Nitrazine Yellow by NMR spectroscopy

Solution Thermodynamics of highly fluorinated gemini bispyridinium surfactants for biomedical applications

Technical properties and photofading of disperse heterocyclic azo dyes