RESUMEN
Here, we report the synthesis of MoS2/graphene heterostructure in single-stage, liquid-phase exfoliation using a 7:3 isopropyl alcohol/water mixture. Further, the synthesized heterostructure was characterized using UV-visible and micro-Raman spectroscopies, transmission electron microscopy (TEM), and dynamic light scattering (DLS) analysis. UV-visible and micro-Raman analyses confirmed that the synthesized heterostructure had mostly few-layered (two-to-four sheets) MoS2. The photophysical properties of the heterostructure were analyzed using steady-state and time-resolved luminescence techniques. Enhanced photoluminescence was observed in the case of the heterostructure probably due to an increase in the defect sites or reduction in the rate of nonradiative decay upon formation of the sandwiched heterostructure. Applications of this heterostructure for fluorescence live-cell imaging were carried out, and the heterostructure demonstrated a better luminescence contrast compared to its individual counterpart MoS2 in phosphate-buffered saline (PBS).
RESUMEN
The dynamics and structural characteristics of polymethacrylic acid bound rhodamine-123 (PMAA-R123) and its interpolymer complex formed through hydrogen bonding between the monomeric units with poly(vinylpyrrolidone) were investigated using single molecular fluorescence studies. The time resolved fluorescence anisotropy decay of PMAA-R123 under acidic pH exhibits an associated anisotropy decay behavior characteristic of two different environments experienced by the fluorophore with one shorter and another longer rotational correlation time. The anisotropy decay retains normal bi-exponential behavior under neutral pH. Fluorescence correlation spectroscopic investigation reveals that the attached fluorophore undergoes hydrolysis under basic condition which results in the release of the fluorophore from the polymer backbone. Shrinkage in the hydrodynamic radius of PMAA is observed on addition of the complementary polymer PVP which is attributed to the formation compact solubilized nanoparticle like aggregates. The size of particle further decreases on the addition of NaCl. The detailed results show that these complexes have potential for use as drug-delivery system under physiological conditions.
RESUMEN
The efficient intense field double detachment of molecular anions observed in SF6() is studied by 3D coincidence imaging of the dissociation products. The dissociation anisotropy and kinetic energy release distributions are determined for the energetically lowest double detachment channel by virtue of disentangling the SF5(+) + F fragmentation products. The observed nearly isotropic dissociation with respect to the linear laser polarization and surprisingly high kinetic energy release events suggest that the dissociation occurs on a highly excited state. Rydberg (SF6(+))* states composed of a highly repulsive dication core and a Rydberg electron are proposed to explain the observed kinetic energy release, accounting also for the efficient production of all possible cationic fragments at equivalent laser intensities.
RESUMEN
Interaction of molecular SF6(-) anions with intense near-IR laser pulses is found to produce cationic fragments by nonsequential multiple detachment. Dissociative ionization channels that lie more than 20 eV above the threshold energy for double detachment are observed. Mass-resolved product yields are presented and analyzed as a function of the femtosecond laser pulse energy, pulse shape, and polarization ellipticity. The observed strong suppression of multiple detachment by pre-pulses, induced with negative third-order dispersion of the transform-limited fs laser pulse, is interpreted as suppression of a nonsequential process by early single detachment. However, in contrast to the relatively simple picture of a rescattering mechanism characterized by acute sensitivity to polarization ellipticity that dominates double ionization of neutral species and was reported for the atomic F(-) anion, multiple detachment of the molecular anion is found to exhibit only mild ellipticity dependence.