Stability of radical-functionalized gold surfaces by self-assembly and on-surface chemistry

We have investigated the radical functionalization of gold surfaces with a derivative of the perchlorotriphenylmethyl (PTM) radical using two methods: by chemisorption from the radical solution and by on-surface chemical derivation from a precursor. We have investigated the obtained self-assembled monolayers by photon-energy dependent X-ray photoelectron spectroscopy. Our results show that the molecules were successfully anchored on the surfaces. We have used a robust method that can be applied to a variety of materials to assess the stability of the functionalized interface. The monolayers are characterized by air and X-ray beam stability unprecedented for films of organic radicals. Over very long X-ray beam exposure we observed a dynamic nature of the radical–Au complex. The results clearly indicate that (mono)layers of PTM radical derivatives have the necessary stability to withstand device applications.

We have investigated the radical functionalization of gold with a derivative of the perchlorotriphenylmethyl radical using two methods: by chemisorption from the radical solution and by on surface chemical derivation from a precursor.     

Gold Complexes with Difunctional Perfluoroalkyl Chains: Quantifying the Energy of Aurophilic Interactions in Flexible Open‐Chain Complexes

The first binuclear Au^I compounds containing bridging (CF₂)_n chains (n=4, 6, 8) and Au^III metallaperfluorocyclopentanes have been obtained by photoinitiated reactions of LAuMe (L=PPh₃, PMe₃, PCy₃, or IPr) with α,ω‐diiodoperfluorocarbons. Complexes LAu(CF₂)₄AuL present an unusual looped structure stabilized by an aurophilic interaction for L=PMe₃, PPh₃, and PCy₃. The study of their dynamic behaviour has provided new insights about the strength of aurophilic interactions in solution, allowing quantification of the energy of a single Au???Au interaction.     

Symmetry‐Breaking Charge‐Transfer Chromophore Interactions Supported by Carbon Nanodots

Carbon dots (CDs) and their derivatives are useful platforms for studying electron‐donor/acceptor interactions and dynamics therein. Herein, we couple amorphous CDs with phthalocyanines (Pcs) that act as electron donors with a large extended π‐surface and intense absorption across the visible range of the solar spectrum. Investigations of the intercomponent interactions by means of steady‐state and pump‐probe transient absorption spectroscopy reveal symmetry‐breaking charge transfer/separation and recombination dynamics within pairs of phthalocyanines. The CDs facilitate the electronic interactions between the phthalocyanines. Thus, our findings suggest that CDs could be used to support electronic couplings in multichromophoric systems and further increase their applicability in organic electronics, photonics, and artificial photosynthesis.     

Optimization,Stability, and Entropy in Endoreversible Heat Engines

The stability of endoreversible heat engines has been extensively studied in the literature. In this paper, an alternative dynamic equations system was obtained by using restitution forces that bring the system back to the stationary state. The departing point is the assumption that the system has a stationary fixed point, along with a Taylor expansion in the first order of the input/output heat fluxes, without further specifications regarding the properties of the working fluid or the heat device specifications. Specific cases of the Newton and the phenomenological heat transfer laws in a Carnot-like heat engine model were analyzed. It was shown that the evolution of the trajectories toward the stationary state have relevant consequences on the performance of the system. A major role was played by the symmetries/asymmetries of the conductance ratio σhc of the heat transfer law associated with the input/output heat exchanges. Accordingly, three main behaviors were observed: (1) For small σhc values, the thermodynamic trajectories evolved near the endoreversible limit, improving the efficiency and power output values with a decrease in entropy generation; (2) for large σhc values, the thermodynamic trajectories evolved either near the Pareto front or near the endoreversible limit, and in both cases, they improved the efficiency and power values with a decrease in entropy generation; (3) for the symmetric case (σhc=1), the trajectories evolved either with increasing entropy generation tending toward the Pareto front or with a decrease in entropy generation tending toward the endoreversible limit. Moreover, it was shown that the total entropy generation can define a time scale for both the operation cycle time and the relaxation characteristic time.     

Theoretical developments and applications of polarization propagators

The Argentinian studies of response properties by applying polarization propagators started more than 35 years ago. It began when the research group led by Professor Ruben Contreras in Buenos Aires started to apply it to the study of NMR spectroscopic parameters on top of semiempirical methods. Novel theoretical developments and its successful early applications make that this group quickly grew up with students from different regions of Argentina. In this review, we shall expose some Argentinian developments of that formalism, including its extension to the relativistic regime and also its latest formal development, which shows how can it be derived from the more fundamental path integral formalism. The interpretative power and the analysis of different electronic effects, that influence the NMR spectroscopic parameters, will be shown with few selected examples. They include molecules with light and heavy atoms, and also hydrogen-bonded systems. Novel results and analysis of earlier and latest developments will also be given. One of the main advantages of the formalism of polarization propagators is its flexibility for being applied in both regimes, relativistic and nonrelativistic in the same manner. One can go from one to the other framework, by only scaling the velocity of light.     

Residuality of Sets of Hypercyclic Operators

We prove a criterion that guarantees that in a given class of operators the set of hypercyclic ones is residual. We also prove the existence of quasinilpotent Volterra composition operators, V_j{V_\varphi} , such that both V_j{V_\varphi} and V_j^*{V_\varphi^\star} are supercyclic and both I + V_j{I + V_\varphi} and I + V_j^*{I + V_\varphi^\star} are hypercyclic.     

Multi-physics design of microvascular materials for active cooling applications

This paper describes a framework for the design of microvascular polymeric components for active cooling applications. The design of the embedded networks involves complex and competing objectives that are associated with various physical processes. The optimization tool includes a PDE solver based on advanced finite element techniques coupled to a multi-objective constrained genetic algorithm. The resulting Pareto-optimal fronts are investigated in the optimization of these materials for void volume fraction, flow efficiency, maximum temperature, and surface convection objective functions.     

Photoinitiated Reactions of Haloperfluorocarbons with Gold(I) Organometallic Complexes: Perfluoroalkyl Gold(I) and Gold(III) Complexes

The study of perfluoroalkyl metal complexes is key to understand and improve metal-promoted perfluoroalkylation reactions. Herein, we report the synthesis of the first gold complexes with primary or secondary perfluoroalkyl ligands by photoinitiated reactions between Au^I organometallic complexes and iodoperfluoroalkanes. Complexes of the types LAuR_F (L=PPh₃ or N,N-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; R_F=n-C₄F₉, n-C₆F₁₃, i-C₃F₇, c-C₆F₁₁) and [Au(R_F)(Ar)I(PPh₃)] (Ar=2,4,6-trimethylphenyl) have been isolated and characterized. Alkynes R_FC≡CR were formed by reaction of Ph₃PAuC≡CR (R=Ph, nHex) with IR_F (R_F=n-C₄F₉, i-C₃F₇). According to the evidences obtained, this transformation undergoes through a photoinitiated radical mechanism. Au^III complexes [Au(n-C₄F₉)(X)(Y)L] (X=Y=Cl, Br, I, Me; X=Me, Y=I) have been prepared or in situ generated, and their thermal or photochemical decomposition reactions have been studied.