Mozhdeh Mohammadpour

Recent molecular simulations indicate nanoscale heterogeneity at liquid-solution interfaces, which is expected to significantly impact interfacial processes, such as catalysis and nucleation. We investigate the enhancement of glycine concentration in aqueous solutions at solid interfaces using molecular dynamics (MD) simulations and surface plasmon spectroscopy (SPR) measurements. MD predicts an interfacial concentration enhancement in a nanoscale solution region at the solid surface. SPR shows for the first time direct experimental evidence of such an enhancement in small molecule liquid mixtures. The excess interfacial mass density on gold and polystyrene surfaces for undersaturated glycine solutions reaches up to ∼50 ng/cm², corresponding to a 1 nm layer with over double the glycine saturation concentration. We attribute the interfacial enhancement to omnipresent van der Waals interactions between solution components and surfaces. We expect this effect to be a common phenomenon in solutions that is likely to have profound effects on both natural and industrial interfacial processes.

Heat treatment (115 °C, 24 h) of HDPE film (T) led to higher crystallinities ( cf. untreated, UT). HDPE(T) films yield radiation-grafted AEMs with more consistent ion-exchange capacities, and higher bulk water contents and fuel cell performances.

Perfluorinated sulfonic acid membranes are renowned for their unique proton conduction and chemical/mechanical stability. As water plays a crucial role in their proton conduction that changes with environmental humidity, here we evaluate the robustness of our recently proposed humidity-controlled terahertz time-domain spectroscopy on commercially available membranes with different morphologies to quantify water uptake and states for direct comparison against literature values. We further apply the technique to resolve membrane hygral swelling and shrinkage during humidity cycles towards future dimensional stability evaluation. As a whole, this work highlights the broad applicability of humidity-controlled terahertz time-domain spectroscopy for testing perfluorinated sulfonic acid membranes for future product optimizations.

In the present work, a series of aryl‐cycloplatinated(II) complexes with general formula [Pt(C^{^}N)(Ar)(κ¹‐dppm)], 1, [C^{^}N = 7,8‐benzoquinolinyl (bzq) or 2‐phenylpyridinyl (ppy); Ar = C₆F₅ or p‐MeC₆H₄, dppm = 1,1‐bis(diphenylphosphanyl)methane] was employed in the reaction with AuCl(SMe₂) in order to generate heterobimetallic Pt^II‐Au^I complexes, [Pt(C^{^}N)(Ar)(µ‐dppm)Au(Cl)], 2, featuring a dppm bridge between the metal centers. The expectation was to induce metallophilic character into the excited state and to reduce non‐radiative deactivation pathways of the dangling auxiliary κ¹‐dppm ligand through molecular motions, to improve the photophysical properties. After characterization of the new complexes by means of NMR spectroscopy and X‐ray crystallography technique, the photophysical properties of all the complexes were investigated by UV/Vis and photoluminescence spectroscopy. Both of the monometallic complexes and heterobimetallic products have shown to be luminescent in different states and temperature conditions. However, by addition of Au^I, the impact on the photophysics of the heterobimetallic products in relation to the precursors with dangling dppm is minimal, a finding which can be attributed to the absence of a Pt^II‐Au^I bond in these compounds. Indeed, the character of the excited states of the monomer Pt^II complexes and their corresponding bimetallic Pt^II‐Au^I ones are similar, as confirmed by density functional theory (DFT) and time resolved DFT (TD‐DFT) calculations. The cytotoxic activities of the compounds along with that of [ClAu(µ‐dppm)AuCl] were evaluated against human breast cancer (MCF‐7), human lung cancer (A549), human ovarian cancer (SKOV3) and non‐tumorigenic epithelial breast (MCF‐10A) cell lines. The highest activity was found for the heterometallic Pt‐Au species, suggesting a cooperative effect of both metallic fragments. The most cytotoxic compound, i.e. [Pt(bzq)(p‐MeC₆H₄)(µ‐dppm)Au(Cl)], 2b, effectively causes cell death in MCF‐7 cancer cell line by inducing apoptosis. Fluorescence microscopy experiments for 2a were performed.

We appreciate Aranda's comments on our recent work entitled ‘‘Elucidation of charge-transfer SERS selection rules by considering the excited state properties and the role of electrode potential’’. We would also like to thank the editor of Physical Chemistry Chemical Physics for giving us an opportunity to specify more details of our work in this reply. An important part of our article concerns the role of the electrode potential in charge-transfer SERS spectra and we would like to first address the questions that Aranda et al. posed about our labeling.

The goal of this study is to shed light on the charge-transfer (CT) mechanism of surface-enhanced Raman scattering (SERS) by considering the properties of CT excited states. The calculations have been done by means of an excited-state gradient approximation for a pyridine molecule interacting with a silver cluster, and provided a satisfactory improvement in comparison to previous work. The effect of electrode potential on the SERS-CT spectra has been modelled theoretically by applying an external electric field for selected CT transitions and the enhancement of the ν_6a and ν_9a modes and a decline in the intensity of the ν_8a mode under a negative electric field (which is directed toward the cluster) have been observed. These results match well with the experimental studies and also explain the effect of electrode potentials on the patterns of spectra, as experimental evidence of the CT mechanism. Finally, this study demonstrated that the excited state vector gradient can be used as a distinguishing factor to explain the SERS selection rules.

The prospect of challenges in reproducing and interpretation of resonance Raman properties of molecules interacting with metal clusters has prompted the present research initiative. Resonance Raman spectra based on the time-dependent gradient approximation are examined in the framework of density functional theory using different methods for representing the exchange-correlation functional. In this work the performance of different XC functionals in the prediction of ground state properties, excitation state energies, and gradients are compared and discussed. Resonance Raman properties based on time-dependent gradient approximation for the strongly low-lying charge transfer states are calculated and compared for different methods. We draw the following conclusions: (1) for calculating the binding energy and ground state geometry, dispersion-corrected functionals give the best performance in comparison to ab initio calculations, (2) GGA and meta GGA functionals give good accuracy in calculating vibrational frequencies, (3) excited state energies determined by hybrid and range-separated hybrid functionals are in good agreement with EOM-CCSD calculations, and (4) in calculating resonance Raman properties GGA functionals give good and reasonable performance in comparison to the experiment; however, calculating the excited state gradient by using the hybrid functional on the hessian of GGA improves the results of the hybrid functional significantly. Finally, we conclude that the agreement of charge-transfer surface enhanced resonance Raman spectra with experiment is improved significantly by using the excited state gradient approximation.