Electron transport across the transition metal dichalcogenide (TMD)-metal interface plays an important role in determining the performance of TMD-based optoelectronic devices. However, the robustness of this process against structural heterogeneities remains unexplored, to the best of our knowledge. Here, we employ a combination of time-resolved photoemission electron microscopy (TR-PEEM) and atomic force microscopy to investigate the spatially resolved hotelectron transfer dynamics at the monolayer (1L) MoS2/Au interface. A spatially heterogeneous distribution of 1L-MoS2/Au gap distances, along with the sub-80-nm spatial-and sub-60-fs temporal resolution of TR-PEEM, permits the simultaneous measurement of electron transfer rates across a range of 1L-MoS2/Au distances. These decay exponentially as a function of distance, with an attenuation coefficient đœ ~ 0.06 ± 0.01 â« -1 , comparable to molecular wires.Ab Initio simulations suggest that surface plasmon-like states mediate hot-electron transfer, hence accounting for its weak distance dependence. The weak distance dependence of the interfacial hot-electron transfer rate indicates that this process is insensitive to distance fluctuations at TMD-metal interfaces, thus motivating the further exploration of optoelectronic devices based on hot carriers.
This paper reports an effective method to prepare patterned polymer brushes on surfaces with tailored graft densities. High-density (concentrated), moderate-density (semidilute), and low-density (dilute) polymer brushes were fabricated in patterned manners, offering defined 3D-patterned structures. This method uses a middle/near-UV (℠250 nm) lamp and needs only a short time (†10 min) to fabricate pre-patterns of the initiator, in sharp contrast to the previous high-energy lithography and time-consuming processes. The obtained patterned brush served as a molecular (protein) repellent/adsorptive interface based on a graft-density dependent size-exclusion effect. This method is facile and accessible to wide ranges of tunable density and pattern shape, which are attractive for extensive use.
Soft nanoparticles continue to offer a promising platform for the encapsulation and controlled delivery of poorly waterâsoluble drugs and help enhance their bioavailability at targeted sites. Linear amphiphilic block copolymers are the most extensively investigated in formulating delivery vehicles. However, more recently, there has been increasing interest in utilizing branched macromolecules for nanomedicine, as these have been shown to lower critical micelle concentrations, form particles of smaller dimensions, facilitate the inclusion of varied compositions and functionâbased entities, as well as provide prolonged and sustained release of cargo. In this review, it is aimed to discuss some of the key variables that are studied in tailoring branched architectureâbased assemblies, and their influence on drug loading and delivery. By understanding structureâproperty relationships in these formulations, one can better design branched star polymers with suitable characteristics for efficient therapeutic interventions. The role played by polymer composition, chain architecture, crosslinking, stereocomplexation, compatibility between polymers and drugs, drug/polymer concentrations, and selfâassembly methods in their performance as nanocarriers is highlighted.
Targeted drug delivery based on polymeric nanoparticles has been a longâstanding interest in nanomedicine for its beneficial traits including controlled and localized drug release. Gasâresponsive polymers offer an advantageous platform and have been slowly gaining attention in spatially locating and displaying unique interactions of specific responsive chemical entities in polymeric chains with endogenous gaseous stimuli. In this review, we highlight recent developments in polymeric nanoformulations with stimulant chemical entities for gasotransmittors such as NO, CO, H2S, SO2, O2 and CO2 in enhancing efficacy in therapeutic interventions. We underline some challenges and limitations of exploring these systems for clinical applications, and how we can further tap into the potential of these emerging materials. © 2021 Society of Industrial Chemistry.
Branched star polymers offer exciting opportunities in enhancing the efficacy of nanocarriers in delivering biologically active lipophilic agents. It is demonstrated that the star polymeric architecture can be leveraged to yield soft nanoparticles of vesicular morphology with precisely located stimuliâsensitive chemical entities. Amphiphilic stars of AB2 (A = PEG, B = PCL) composition with/without oxidative stress or reduction responsive units at the core junction of A and B arms, are constructed using synthetic articulation. Fisetin, a natural flavonoid with remarkable antiâinflammatory and antioxidant properties, but of limited clinical value due to its poor aqueous solubility, is physically encapsulated into miktoarm starâderived aqueous polymersomes. Polymersomes and fisetin are evaluated separately, and in combination, in human microglia (HMC3), to show if i) polymersomes are toxic; ii) fisetin reduces the abundance of reactive oxygen species (ROS); and iii) fisetin modulates the activation of ERK1/2. These signaling molecules and pathways are implicated in inflammatory processes and cell survival. Fisetin, both incorporated and nonincorporated into polymersomes, reduces ROS and ERK1/2 phosphorylation in lipopolysaccharideâtreated human microglia, normalizing excessive oxidative stress and ERKâmediated signaling.
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