Carbon dots (CDs) are 1-10 nm scaled complex nanostructures with a wide range of applications and show unconventional photophysical behavior upon excitation. In this article, we have unveiled some of the underlying mechanisms and excited state dynamics of CDs by perturbing their interface with oxidizing and reducing agents. With no substantial alteration in size of surface treated oxidized ( O CDs), reduced ( R CDs) and untreated CDs ( U CDs), we observe marked changes in their charge transport properties and diverse spectral signatures in singlet and triplet excited states. Fine tuning of the spectral behavior of nanomaterials is often treated as an outcome of quantum confinement of the excitons. Herein with different spectroscopic techniques along with conducting atomic force microscopy and triplet-triplet absorption, we elucidate that, not just confinement, the structural modification at the surface also dictates optoelectronic behavior by altering some properties like energy bandgap, quantum tunneling across metal-CD-metal junction and yield of triplet excitons.
A novel triptycene-based azo polymer (TBAP) was explored as a switching material in an atomic switch showing resistive change under voltage sweep and pulse. Current atomic force microscope (C-AFM) measurements...
Nanoarchitectonics through ionic self‐assembly at interfaces is an attractive approach to obtain advanced functional materials. Here, a novel discotic dimer‐DNA complex hybrid system has been investigated at air‐water and air‐solid interfaces. The ionic discotic liquid crystalline dimer consisted of two triphenylene cores linked via alkyl spacer with a imidazolium moiety. At air‐water interface, the dimer formed a stable monolayer with a reversible collapse. The surface manometry results suggested that the condensed phase of the monolayer consisted of molecules arranged in an edge‐on conformation. To understand the folding behavior of the molecules, DFT calculations were carried out which showed that the quantum chemically optimized folded‐form of the molecule was electronically more stable than its unfolded‐form. Upon adding DNA to the subphase, a complex monolayer was formed with enhanced stability as was indicated by increased collapse pressure and decreased limiting area. Importantly, this complexation enabled an efficient and stable multilayer formation on silicon substrates with layers as many as 40. Since both DNA and discotic dimer molecules share common properties of one‐dimensional charge transport with compatible structures, this complex film could serve as a model system for organic electronics.
Emergence of ordered structures during molecular self‐assembly at interfaces is influenced by a variety of thermodynamic and kinetic factors that are not well understood. Experiments alone can only inform about the final architecture keeping self‐assembly pathways inaccessible. Here with the help of molecular dynamic simulations, the intricate details of the self‐assembly processes and resultant ordered structures of a triphenylene–surfactant complex monolayer at air–water interface are reported. The monolayer is observed to be stable and reversible using surface manometry and real‐time Brewster angle microscopy. Not only that the simulated isotherm and 2D density profiles are in good agreement with experimental observations, the simulation results bespeak the crucial role of specific electrostatic interactions forming the nanostructures at the interface analyzed via orientational structural profiles, radial distribution, and Z‐density profiles. Moreover, real‐space visualization using atomic force microscopy suggests that the molecular packing is preserved in the monolayer even after transferring onto a silicon substrate. Since the rational designing of organic electronics requires nanoscale control of molecular structures on solid substrates, it is anticipated that these results will be of fundamental importance.
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