The Journal of Physical Chemistry Letters最新文献

Broadband nanoextinction images recorded in tip-enhanced optical spectroscopy geometry track the 3D topography of a single layer of WS₂ on Au substrate. The described nano-optical method is complementary to conventional atomic force microscopy and offers additional information about the buried material-metal interface that is not accessible using conventional topographic imaging. Beyond 3D optical imaging, we observe large variations in the junction plasmon resonance on the nanoscale. The latter is important to understand and account for in tip-enhanced Raman and photoluminescence studies that target low-dimensional materials specifically. Our observations and (coherent) optical scattering-based method are also relevant to emerging efforts aimed at exploring strong coupling and Fano interferences in hybrid plasmonic-low dimensional quantum material systems.

Nucleocapsid self-assembly is an essential yet elusive step in virus replication. Using time-resolved small-angle X-ray scattering on a model icosahedral ssRNA virus, we reveal a previously unreported kinetic pathway. Initially, RNA-bound capsid subunits rapidly accumulate beyond the stoichiometry of native virions. This is followed by a disorder-to-order transition characterized by glass-like relaxation dynamics and the release of excess subunits. Our molecular dynamics simulations, employing a coarse-grained elastic model, confirm the physical feasibility of self-ordering accompanied by subunit release. The relaxation can be modeled by an exponential integral decay on the mean squared radius of gyration, with relaxation times varying within the second range depending on RNA type and subunit concentration. A nanogel model suggests that the initially disordered nucleoprotein complexes quickly reach an equilibrium size, while their mass fractal dimension continues to evolve. Understanding virus self-assembly is not only crucial for combating viral infections, but also for designing synthetic virus-inspired nanocages for drug delivery applications.

NMR field cycling relaxometry is a powerful method for determining the rotational and translational dynamics of ions, molecules, and dissolved particles. This is in particular true for ionic liquids (ILs) in which both ions carry NMR sensitive nuclei. In the IL triethylammonium bis(trifluoromethanesulfonyl)imide ([TEA][NTf₂]), there are ¹H nuclei at the [TEA]⁺ cations and ¹⁹F nuclei at the [NTf₂]⁻ anions. Moreover, the high viscosity of this IL leads to frequency-dependent relaxation rates, leaving the so-called extreme narrowing regime. Both the rotational and the translational dynamics of the constituents of ILs can be obtained by separating the contributions of intra- and intermolecular relaxation rates. In particular, the translational dynamics can be obtained separately by applying the so-called “low-frequency approach” (LFA), utilizing the fact that the change in the total relaxation rates at low frequencies results solely from translational motions. However, for systems containing multiple NMR active nuclei, heteronuclear interactions can also affect their relaxation rates. For [TEA][NTf₂], the intermolecular relaxation rate is either the sum of ¹H–¹H cation–cation and ¹H–¹⁹F cation–anion interactions or the sum of ¹⁹F–¹⁹F anion–anion and ¹⁹F–¹H anion–cation interactions. Due to the lack of available experimental information, the ¹H–¹⁹F heteronuclear intermolecular contribution has often been neglected in the past, assuming it to be negligible. Employing a suitable set of ILs and by making use of isotopic H/D substitution, we show that the ¹H–¹⁹F heteronuclear intermolecular contribution in fact cannot be neglected and that the LFA cannot be applied to the total ¹H and total ¹⁹F relaxation rates.

Metal-organic frameworks (MOFs) have been widely used as versatile precursors to fabricate functional nanomaterials with well-defined structures for various applications. Herein, the presynthesized Ni-MOF nanosheets were grown on a Ni foam (NF) substrate, which then guided the nucleation and further growth of Prussian blue analogues (PBA) nanocubes to form MOF-on-MOF of the PBA/Ni-MOF film. This film was subsequently converted into a Co₂P/Ni₂P heterostructure. The NF-supported Co₂P/Ni₂P composites exhibited excellent supercapacitor performance, delivering a high specific capacity of 5124.2 mF cm^-2 at 1 mA cm^-2 and a remarkable capacity retention of 80.69% after 3000 cycles at 10 mA cm^-2. An asymmetric supercapacitor assembled using Co₂P/Ni₂P/NF as the cathode and activated carbon as the anode yielded a maximum energy density of 0.34 mWh cm^-2 at a power density of 1.50 mW cm^-2. The enhanced supercapacitor performance is attributed to the synergistic effects of the Ni₂P and Co₂P components with multiple valence states as well as the unique hierarchical structure, which provides efficient pathways for electron and ion transport while mitigating volume expansion during energy storage. This synthetic strategy demonstrates an effective approach to fabricate phosphide-based hybrid materials for high-performance supercapacitor applications.

Salt-in-water and water-in-salt mixtures are promising for battery applications and fine-tuning of room-temperature ionic liquid (RTIL) properties. Although critical processes take place at interfaces of these systems, including charge transfer and heterogeneous catalytic reactions, the microscopic interfacial structures remain unclear. Here, we apply heterodyne-detected sum-frequency generation spectroscopy to aqueous solutions of imidazolium-based RTILs to unveil the microscopic structure of the interfaces of these solutions with air. Our results show that, under salt-in-water conditions, the orientation of the OH group hydrogen-bonded to the other water molecules flips from the OH group pointing down into the liquid for pure water to up due to the accumulation of anions in the cation-rich interfacial region. However, under the water-in-salt condition, the interfacial water molecules are confined by RTIL, and their orientation is down. Details of the water organization depend critically on the alkyl chain length of the imidazolium cation. Our results demonstrate that the surface structure can be tuned by altering the molecular structure and concentration of the RTIL.