Why Do Silver Trimers Intercalated in DNA Exhibit Unique Nonlinear Properties That Are Promising for Applications?

Our investigation of one-photon absorption (OPA) and nonlinear optical (NLO) properties such as two-photon absorption (TPA) of silver trimer intercalated in DNA based on TDDFT approach allowed us to propose a mechanism responsible for large TPA cross sections of such NLO-phores. We present a concept that illustrates the key role of quantum cluster as well as of nucleotide bases from the immediate neighborhood. For this purpose, different surroundings consisting of guanine-cytosine and adenine-thymine such as (GCGC) and (ATAT) have been investigated that are exhibiting substantially different values of TPA cross sections.

pH-Induced transformation of ligated Au to brighter Au nanoclusters.

Thiolate-protected gold nanoclusters have recently attracted considerable attention due to their size-dependent luminescence characterized by a long lifetime and large Stokes shift. However, the optimization of nanocluster properties such as the luminescence quantum yield is still a challenge. We report here the transformation of Au25Capt18 (Capt labels captopril) nanoclusters occurring at low pH and yielding a product with a much increased luminescence quantum yield which we have identified as Au23Capt17.

Au(SG): A Chiral Gold Catenane Nanocluster with Zero Confined Electrons. Optical Properties and First-Principles Theoretical Analysis.

We report facile synthesis of the Au(SG) nanoclusters, where SG stands for glutathione, found to be promising as a new class of radiosensitizers for cancer radiotherapy. The homoleptic catenane structure with two AuSG interconnected rings, among different isomer structures, gives the best agreement between theoretical and experimental optical spectra and XRD patterns. This catenane structure exhibits a centrosymmetry-broken structure, resulting in enhanced second harmonic response and new characteristic circular dichroism signals in the spectral region of 250-400 nm.

Ligand-core NLO-phores: a combined experimental and theoretical approach to the two-photon absorption and two-photon excited emission properties of small-ligated silver nanoclusters.

We report a combined experimental and theoretical study of the two-photon absorption and excited emission properties of monodisperse ligand stabilized Ag, Ag and Ag nanoclusters in aqueous solutions. The nanoclusters were synthesized using a cyclic reduction under oxidative conditions and separated by vertical gel electrophoresis. The two-photon absorption cross-sections of these protected noble metal nanoclusters measured within the biologically attractive 750-900 nm window are several orders of magnitude larger than that reported for commercially available standard organic dyes.

Two-photon absorption of ligand-protected Ag15 nanoclusters. Towards a new class of nonlinear optics nanomaterials.

We report theoretical and experimental results on two-photon absorption (TPA) cross section of thiolated small silver cluster Ag15L11 exhibiting extraordinary large TPA in red. Our findings provide the responsible mechanism and allow proposing new classes of nanoclusters with large TPAs which are promising for biological and medical applications.

Tuning Ag29 nanocluster light emission from red to blue with one and two-photon excitation.

We demonstrate that the tuning of the light emission from red to blue in dihydrolipoic acid (DHLA) capped Ag29 nanoclusters can be trigged with one and two photon excitations. The cluster stoichiometry was determined with mass spectrometry and found to be Ag29(DHLA)12. In a detailed optical investigation, we show that these silver nanoclusters exhibit a strong red photoluminescence visible to the naked eye and characterized by a quantum yield of nearly ∼2% upon one-photon excitation.

UV photodissociation of proline-containing peptide ions: insights from molecular dynamics.

UV photodissociation of proline-containing peptide ions leads to unusual product ions. In this paper, we report laser-induced dissociation of a series of proline-containing peptides at 213 nm. We observe specific fragmentation pathways corresponding to the formation of (y-2), (a + 2) and (b + 2) fragment ions.

The nature of electronic excitations at the metal-bioorganic interface illustrated on histidine-silver hybrids.

We present a joint theoretical and experimental study of the structure selective optical properties of cationic and anionic histidine-silver complexes with Ag and Ag3 which were prepared in the gas phase using mass spectroscopy coupled to electrospray ion source. Our TDDFT calculations provide general insight into the nature of electronic excitations at the metal-bioorganic interface that involve π-π* excitation within bioorganic subunits, charge transfer between two subunits and intrametallic excitations. The binding of silver to histidine, one of the most important amino acids, induces red shift in the optical absorption of protonated histidine particularly for anionic species.

Formation and characterization of thioglycolic acid-silver cluster complexes.

Gas phase reactivity observed in an ion trap was used to produce silver clusters protected with thioglycolic acid. Fragmentation pathways as well as optical properties were explored experimentally and theoretically. Sequential losses of SCH2 and CO2 in the ion trap lead to redox reactions with charge transfers between the metal part and the carboxylate and thiolate groups.