Using microwave irradiation, water soluble, optically active, penicillamine (Pen) capped CdSe nanocrystals with broad spectral distribution (430-780 nm) of photoluminescence have been produced and studied by a range of instrumental techniques including absorption, circular dichroism and both steady state and time resolved photoluminescence spectroscopy. The photoluminescence of these nanocrystals is attributed to emission from surface defect states. The decay of the excited state in the nanosecond region, which can be analysed as a triple exponential, depends strongly on the emission wavelength selected, but only weakly on the excitation wavelength. Graphical Abstract: IntroductionChirality is a common occurrence in the natural world and chiraln compounds are very important in chemistry, biology, pharmacology and medicine. It has also been envisaged that chirality could play an important role in nanotechnology. 1,2 The majority of existing research in this field has been focused on chiral organic, metallorganic and biological molecules and their supramolecular structures, 3 while research in the area of chiral inorganic nanoparticles is still in the very early stage of its development. For example, there has been some work involving chiral optically active metallic gold 4,5 and silver 6,7 nanoparticles, as well as carbon nanotubes. 8,9 However, there are currently only a few recent papers dealing with chiral light emitting semiconducting nanocrystals (quantum dots). [10][11][12][13][14] In general over the last decade much attention has been directed towards II-VI type CdS, CdTe and CdSe quantum dots (QDs). [15][16][17][18][19] It is the ability to fine-tune their optical properties by chemical control of their size and shape (i.e. their degree of quantum confinement) which makes quantum dots particularly interesting. This level of optical control combined with QDs' resistance to photobleaching and their high level of solubility in practically any solvent (depending on the stabiliser used) make these nanomaterials potentially suited for roles as divergent as light emitting diodes, 20 biological sensors 21 and photovoltaic devices. [22][23][24] Thiol group containing amino acids have proved to be excellent stabilisers, with L-cysteine becoming one of the popular surface capping molecules for CdX (X ¼ S, Se, and Te) nanoparticles. 18,[25][26][27][28][29][30][31] In addition this use of stereospecific chiral stabilising molecules opened another avenue of interest in the area of quantum dot research, as chirality is a key factor in biological and biochemical interactions. Due to their unique photophysical properties, we believe that chiral QDs have a range of potential applications in photonics and biochemistry. 13,32,33 The main aim of our work is to develop novel chiral CdSe based QDs by using chiral stabilisers and to investigate the properties of these materials. Here we report the synthesis and detailed spectroscopic studies of new penicillamine stabilised CdSe QDs, which have been prepared using the dextrorota...

The role of N1-substitution in controlling the deactivation processes in photoexcited cytosine derivatives has been explored using picosecond time-resolved IR spectroscopy. The simplest N1-substituted derivative, 1-methylcytosine, exhibits relaxation dynamics similar to the cytosine nucleobase and distinct from the biologically relevant nucleotide and nucleoside analogues, which have longerlived excited-state intermediates. It is suggested that this is the case because the sugar group either facilitates access to the long-lived 1 n O π* state or retards its crossover to the ground state.

The transient IR absorption spectrum for UV-excited i-motif DNA is reported for the first time and found to possess complex dynamics pointing to multiple decay processes, including possible charge transfer between packed hemi-protonated C bases.

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[Cr(phen) 2 (X 2 dppz)] 3+ {X = H, Me, or F} have been synthesised, characterised, and chromatographically resolved into their constituent D and K enantiomers. The DNA-binding interactions of each of the racemic complexes were investigated, with the results of linear dichroism, thermal denaturation, and emission quenching studies indicative of intercalative binding to CT-DNA with a significant electrostatic contribution. UV/Vis absorption titrations suggest strong DNA binding by each of the racemic complexes, with the methylated analogue [Cr(phen) 2 (Me 2 dppz)] 3+ exhibiting the largest equilibrium binding constant. Emission quenching and UV-Vis titrations of the enantiomers of [Cr(phen) 2 (dppz)] 3+ imply similar binding affinities for the D and K isomers, although significant differences between the circular dichroism spectra of the enantiomers in the presence of DNA connote differences in binding orientation and/or conformation between the two.