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Identification of a natural-based sensitizer with optimal stability and efficiency for dye-sensitized solar cell (DSSC) application remains a challenging task. Previously, we proposed a new class of sensitizers based on bio-nano hybrids. These systems composed of natural cyanidin dyes interacting with silver nanoclusters (NCs) have demonstrated enhanced opto-electronic and photovoltaic properties. In this study, we explore the doping of silver nanocluster within a cyanidin-Ag3 hybrid employing Density Functional Theory (DFT) and its time-dependent counterpart (TDDFT). Specifically, we investigate the influence of coinage metal atoms (Au and Cu) on the properties of the cyanidin-Ag3 system. Our findings suggest that cyanidin-Ag2Au and cyanidin-AgAuCu emerge as the most promising candidates for improved light harvesting efficiency, increased two-photon absorption, and strong coupling to the TiO2 surface. These theoretical predictions suggest the viability of replacing larger silver NCs with heterometallic trimers such as Ag2Au or AgAuCu, presenting new avenues for utilizing bio-nano hybrids at the surface for DSSC application. [ABSTRACT FROM AUTHOR]

New materials for transparent luminescent solar concentrators (TLSCs) are of large interest. Therefore, we investigated the optical properties of J-aggregates-like oligomers (hereinafter referred to as J-aggregates) based on covalently bound squaraine dyes in toluene solvent using DFT and TD-DFT methods. In addition, the rate constants needed for the prediction of fluorescence quantum yield (QY) have been calculated using Fermi's Golden rule and vertical harmonic approximation (VH) for ground and excited states. In the context of QY prediction, different broadening of the lineshape has also been employed. We found that J-aggregates based on squaraine dyes exhibit near-infrared (NIR) selective absorption and emission as well as high fluorescence QY. Comparison of the properties obtained for dimers, trimers and tetramers belonging to two classes (SQA and SQB) of J-aggregates allows us to select the tetramer of SQA J-aggregates as suitable for application. The scaling model for N ≥ 4 monomer subunits supports quantitative findings. Therefore, we propose J-aggregates containing N ≥ 4 subunits of SQA with a central squaric acid ring with two oxygen atoms in toluene solvent as a suitable candidate for TLSC application. [ABSTRACT FROM AUTHOR]

For the rational design of new fluorophores, reliable predictions of fluorescence quantum yields from first principles would be of great help. However, efficient computational approaches for predicting transition rates usually assume that the vibrational structure is harmonic. While the harmonic approximation has been used successfully to predict vibrationally resolved spectra and radiative rates, its reliability for non-radiative rates is much more questionable. Since non-adiabatic transitions convert large amounts of electronic energy into vibrational energy, the highly excited final vibrational states deviate greatly from harmonic oscillator eigenfunctions. We employ a time-dependent formalism to compute radiative and non-radiative rates for transitions and study the dependence on model parameters. For several coumarin dyes, we compare different adiabatic and vertical harmonic models (AS, ASF, AH, VG, VGF, and VH), in order to dissect the importance of displacements, frequency changes, and Duschinsky rotations. In addition, we analyze the effect of different broadening functions (Gaussian, Lorentzian, or Voigt). Moreover, to assess the qualitative influence of anharmonicity on the internal conversion rate, we develop a simplified anharmonic model. We address the reliability of these models considering the potential errors introduced by the harmonic approximation and the phenomenological width of the broadening function. [ABSTRACT FROM AUTHOR]

In photodynamic therapy (PDT), light-sensitive photosensitizers produce reactive oxygen species (ROS) after irradiation in the presence of oxygen. Atomically-precise thiolate-protected gold nanoclusters are molecule-like nanostructures with discrete energy levels presenting long lifetimes, surface biofunctionality, and strong near-infrared excitation ideal for ROS generation in PDT. We directly compare thiolate-gold macromolecular complexes (Au10) and atomically-precise gold nanoclusters (Au25), and investigate the influence of ligands on their photoexcitation. With the ability of atomically-precise nanochemistry, we produce Au10SG10, Au10AcCys10, Au25SG18, and Au25AcCys18 (SG: glutathione; AcCys: N-acetyl-cysteine) fully characterized by high-resolution mass spectrometry. Our theoretical investigation reveals key factors (energetics of excited states and structural influence of surface ligands) and their relative importance in singlet oxygen formation upon one- and two-photon excitation. Finally, we explore ROS generation by gold nanoclusters in living cells with one- and two-photon excitation. Our study presents in-depth analyses of events within gold nanoclusters when photo-excited both in the linear and nonlinear optical regimes, and possible biological consequences in cells. Atomically precise thiolate-protected gold nanoclusters present strong near-infrared excitation, long lifetimes, and surface biofunctionality, making them ideal candidates as photosensitizers in photodynamic therapy. Here, the authors evaluate the influence of the ligands and metal core on the efficiency of photoexcited Au10 and Au25 clusters to produce reactive oxygen species, as well as possible biological consequences in living cells. [ABSTRACT FROM AUTHOR]

Noble metal nanoclusters allow for the atomically‐precise control of their composition. However, to create nanoclusters with pre‐defined optical properties, comprehensive description of their structure‐property relation is required. Here, we report the gold atom doping impact on one‐photon and two‐photon absorption (TPA) and luminescence properties of ligated silver nanoclusters via combined experimental studies and time‐dependent density functional theory simulations (TD‐DFT). We synthesized a series of Ag25−xAux(DMBT)18 nanoclusters where x=0, 1 and 5–10. For Ag24Au1(DMBT)18 we demonstrate that the presence of the central Au dopant strongly influences linear and non‐linear optical properties, increasing photoluminescence quantum yield and two‐photon brightness, with respect to undoped silver nanoclusters. With improved TPA and luminescence, atomically‐precise AuAg alloys presented in our work can serve as robust luminescent probes e.g. for bioimaging in the second biological window. [ABSTRACT FROM AUTHOR]

Atomically precise gold nanoclusters are a fascinating class of nanomaterials that exhibit molecule‐like properties and have outstanding photoluminescence (PL). Their ultrasmall size, molecular chemistry, and biocompatibility make them extremely appealing for selective biomolecule labeling in investigations of biological mechanisms at the cellular and anatomical levels. In this work, we report a simple route to incorporate a preformed Au25 nanocluster into a model bovine serum albumin (BSA) protein. A new approach combining small‐angle X‐ray scattering and molecular modeling provides a clear localization of a single Au25 within the protein to a cysteine residue on the gold nanocluster surface. Attaching Au25 to BSA strikingly modifies the PL properties with enhancement and a redshift in the second near‐infrared (NIR‐II) window. This study paves the way to conrol the design of selective sensitive probes in biomolecules through a ligand‐based strategy to enable the optical detection of biomolecules in a cellular environment by live imaging. [ABSTRACT FROM AUTHOR]

Interfacing ultrasmall metal nanoclusters (NCs) with proteins can present a dual opportunity: proteins can be used for protecting NCs, and the surface ligands of NCs may interact with proteins. Here, the authors identify and discuss remaining open questions surrounding the bio-NC interface that call for future research efforts. [ABSTRACT FROM AUTHOR]

Catalytic CO methanation represents an important reaction to improve the feed gas quality for hydrogen fuel cells. Previously, the large potential of small bare and ligated ruthenium clusters as highly selective and active catalysts has been shown by employing gas phase clusters as model systems. Now, density functional theory (DFT) calculations are employed to demonstrate the possibility to translate the gas phase CO methanation reaction mediated by a ligated Ru4(CO)13H2+ complex into the framework of a ZSM‐5 zeolite. Such a translation, manifested by a reaction pathway which is mechanistically and energetically similar to the gas phase analogue, is possible since the zeolite framework does not influence the reactive center. Furthermore, we reveal the important role of the CO ligand environment in protecting the Ru4+ metal core from formation of bonds with the zeolite and in the creation of the reactive center by promoting the cooperatively enhanced adsorption and dissociation of H2. [ABSTRACT FROM AUTHOR]

We present a theoretical approach for the ultrafast nonadiabatic dynamics based on the ab initio molecular dynamics carried out “on the fly” in the framework of the configuration interaction method combined with Tully’s surface hopping algorithm for nonadiabatic transitions. This approach combined with our Wigner distribution approach allows us to perform accurate simulations of femtosecond pump-probe spectra in the systems where radiationless transitions among electronic states take place. In this paper we illustrate this by theoretical simulation of ultrafast processes and nonradiative relaxation in the Na3F cluster, involving three excited states and the ground electronic state. Furthermore, we show that our accurate simulation of the photoionization pump-probe spectrum is in full agreement with the experimental signal. Based on the nonadiabatic dynamics at high level of accuracy and taking into account all degrees of freedom, the nonradiative lifetime for the 1 1B1 excited state of Na3F has been determined to be ∼900 fs. [ABSTRACT FROM AUTHOR]

Gold nanoclusters (Au NCs) are an emerging class of luminescent nanomaterials but still suffer from moderate photoluminescence quantum yields. Recent efforts have focused on tailoring their emission properties. Introducing zwitterionic ligands to cap the metallic kernel is an efficient approach to enhance their one-photon excitation fluorescence intensity. In this work, we extend this concept to the nonlinear optical regime, i.e., two-photon excitation fluorescence. For a proper comparison between theory and experiment, both ligand and solvent effects should be considered. The effects of ligand shell size and of aqueous solvent on the optical properties of zwitterion functionalized gold nanoclusters have been studied by performing quantum mechanics/molecular mechanics (QM/MM) simulations. [ABSTRACT FROM AUTHOR]

The ability of gold(i) thiolates to self-assemble into supramolecular architectures opens the route for a new class of nanomaterials with a unique structure–optical property relationship. However, for a confirmed structure–optical property relationship, a control of the supramolecular architectures is required. In this work, we report a simple synthesis of sub-100 nanometer gold–cysteine and silver doped gold–cysteine supramolecular assemblies. We explore in particular silver-doping as a strategy to enhance the optical properties of these supramolecular assemblies. By an accurate characterization of as-synthesized supramolecular nanoparticles, we have been able to measure for the first time, their absolute two-photon absorption cross-section, two-photon excited fluorescence cross-section and first hyperpolarizabilities at different near-IR wavelengths. Huge values are obtained for silver doped gold–cysteine supramolecular assemblies, as compared to their corresponding undoped counterpart. In addition, we employ DFT and TD-DFT methods to study the geometric and electronic structures of model gold–cysteine and silver doped gold–cysteine compounds in order to address the structure−linear/nonlinear optical property relationship. The aim is to gain insights into the origin of the nonlinear optical enhancement of silver-doped gold supramolecular assemblies. [ABSTRACT FROM AUTHOR]

Here we describe a new conceptual approach for the design of a heterogeneous metal‐organic framework (MOF) catalyst based on UiO‐67 for the selective decarboxylation of formic acid, a reaction with important applications in hydrogen storage and in situ generation of H2. Models for the {CuH} reactive catalytic site at the organic linker are assessed. In the first model system, gas‐phase mass spectrometry experiments and DFT calculations on a fixed charge bathophen ligated copper hydride complex, [(phen*)Cu(H)]2−, were used to demonstrate that it acts as a catalyst for the selective decomposition of formic acid into H2 and CO2 via a two‐step catalytic cycle. In the first step liberation of H2 to form the carboxylate complex, [(phen*)Cu(O2CH)]2− occurs, which in the second step selectively decomposes via CO2 extrusion to regenerate the hydride complex. DFT calculations on four other model systems showed that changing the catalyst to neutral [(LCu(H)] complexes or embedding it within a MOF results in mechanisms which are essentially identical. Thus catalytic active sites located on the organic linker of a MOF appear to be close to a gas‐phase environment, thereby benefitting from the favorable characteristics of gas‐phase reactions and validating the use of gas‐phase models to design new MOF based catalysts. [ABSTRACT FROM AUTHOR]

A novel bisphosphine ligated Ag60 nanocluster, [{Cl@Ag12}@Ag48(dppm)12], has been discovered and characterized by X-ray crystallography. It consists of a central chloride located inside an icosahedral silver core layer, which is further encased by a second shell of 48 silver atoms/ions, which are capped with 12 bis(diphenylphosphino)methane (dppm) ligands. Due to lack of sufficient material the cluster could not be further characterized by other methods. DFT calculations were carried out on the cation [{Cl@Ag12}@Ag48(dppm)12]+ to determine if it corresponds to a superatom with a core count of n=58. The DFT optimized structure is in agreement with X-ray findings, but the low value of the HOMO-LUMO gap does not support superatom stability. [ABSTRACT FROM AUTHOR]

Abstract: Translating a homogenous catalyst into a heterogeneous catalyst requires a fundamental understanding of how the catalyst “fits” into the zeolite and how the reaction is influenced. Previous studies of bimetallic catalyst design identified a potent copper homobinuclear catalyst, [(L)Cu2(H)]+ for the selective decomposition of formic acid. Here, a close interplay between theory and experiment shows how to preserve this selective reactivity within zeolites. Gas‐phase experiments and DFT calculations showed that switching from 1,1‐bis(diphenylphosphino)‐methane ligand to the 1,8‐naphthyridine ligand produced an equally potent catalyst. DFT calculations show that this new catalyst neatly fits into a zeolite which does not perturb reactivity, thus providing a unique example on how “heterogenization” of a homogenous catalyst for the selective catalysed extrusion of carbon dioxide from formic acid can be achieved, with important application in hydrogen storage and in situ generation of H2. [ABSTRACT FROM AUTHOR]

Design of new bimetallic catalysts requires an understanding of how cooperative effects of the metal sites influences reactivity. Here we show how switching one or both of the silver atoms in binuclear silver hydride cations, [dppmAg2(H)]+ (dppm=1,1-Bis(diphenylphosphino)-methane), with all combinations of copper and/or gold maintains selective dehydrogenation of formic acid, enhancing reactivity by up to 2 orders of magnitude. This is a key step in the selective, catalyzed extrusion of carbon dioxide from formic acid, HO2CH, with important applications in hydrogen storage and in situ generation of H2. Decarboxylation of [dppmMM′(O2CH)]+ through collision induced dissociation regenerates [dppmMM′(H)]+. DFT calculations provide insights into these cooperative effects. The copper homobinuclear catalyst performs best overall. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The bis(diphenylphosphino)methane (L = Ph2PCH2PPh2) ligated silver deuteride nanocluster dication, [Ag10D8L6]2+, has been synthesised in the condensed phase via the reaction of bis(diphenylphosphino)methane, silver nitrate and sodium borodeuteride in the methanol : chloroform (1 : 1) mixed solvent system. The photoionisation and photofragmentation of this mass-selected cluster were studied using a linear ion trap coupled to the DESIRS VUV beamline of the SOLEIL Synchrotron. At 15.5 eV the main ionic products observed are [Ag10D8L5]2+, [Ag10D8L4]2+, [Ag10D8L6]3+Ṗ, [Ag9D8L4]2+Ṗ, and [AgL2]+. The later two products arise from fragmentation of [Ag10D8L6]3+Ṗ. An analysis of the yields of these product ions as a function of the photon energy reveals the onset for the formation of [AgL2]+ and [Ag9D8L4]2+Ṗ is around 2 eV higher than that for ionisation to produce [Ag10D8L5]3+Ṗ. The onset of ionisation energy of [Ag10D8L6]2+ was determined to be 9.3 ± 0.3 eV from a fit of the yield of the product ion, [Ag10D8L6]3+Ṗ, as a function of the VUV photon energy. DFT calculations at the RI-PBE/RECP-def2-SVP level of theory were carried out to search for a possible structure of the cluster and to estimate its vertical and adiabatic ionisation energies. The calculated lowest energy structure of the [Ag10D8L6]2+ nanocluster contains a symmetrical bicapped square antiprism as a silver core in which hydrides are located as a mix of triangular faces and edges. Four of the bisphosphines bind to the edges of the cluster core as bidentate ligands, the remaining two bisphosphines bind via a single phosphorus donor atom to each of the apical silver atoms. The DFT calculated adiabatic ionisation energy for this structure is 8.54 eV, in satisfactory agreement with experiment. [ABSTRACT FROM AUTHOR]