RESUMO
Photochemical reactions that produce a detectable change in the spectroscopic properties of organic chromophores can be exploited to harness the principles of Boolean algebra and design molecule-based logic circuits. Moreover, the logic processing capabilities of these photoactive molecules can be directed to protect, encode, and conceal information at the molecular level. We have designed a photochemical strategy to read, write and encrypt data in the form of optical signals. We have synthesized a supramolecular system based on the known dye resazurin, and investigated a series of photochemical transformations that can be used to regulate its absorption and emission properties upon illumination with ultraviolet or visible light. We have then examined the logic behaviour of the photochemistry involved, and illustrated its potential application in data encryption.
RESUMO
Molecules that respond to input stimulations to produce detectable outputs can be exploited to mimic Boolean logic operators and reproduce basic arithmetic functions. We have designed a two-state fluorescent probe with tunable emission wavelength for the construction of a molecular logic gate with reconfigurable single- or dual-output capability. The system is based on a BODIPY skeleton coupled with 4-(dimethylamino)benzaldehyde. The behavior of the molecular logic gate can be easily investigated in solution with fluorescence spectroscopy, and the optical readout (fluorescence) can be monitored in one (green) or two (green and red) channels. Depending on the solvent of choice, single INHIBIT or dual INHIBIT/IMPLY logic functions can be achieved using chemical inputs (acid and base). Reconfiguration from single- to dual-output is thus made possible by operating the system in acetonitrile (single output) or toluene (dual output), respectively. The logic gate can be switched by manipulating the fluorescence emission via protonation or deprotonation, even when immobilized onto a glass substrate. At the solid state, the resulting output can be stored for extended periods of time. This feature provides two added benefits: (i) memory function and (ii) "set/reset" capability of the logic gate. Our design thus provides a proof-of-concept interface between the molecular and electronic domains.
RESUMO
We designed a hybrid nanoparticle-molecular system composed of silver nanostructures (AgNP) and a fluorogenic boron dipyrromethene (BODIPY) that can be selectively activated by UVA or UVC light in the presence of an appropriate photoacid generator (PAG). Light irradiation of the PAG encourages the release of p-toluenesulfonic, triflic or hydrobromic acid, any of which facilitate optical 'writing' by promoting the formation of a fluorescent species. Metal-enhanced fluorescence (MEF) by AgNP was achieved through rational design of the nano-molecular system in accordance with the principles of radiative decay engineering. In addition to increasing signal to noise, AgNP permitted shorter reaction times and low irradiance - all of which have important implications for applications of fluorescence activation in portable fluorescence patterning, bioimaging and super-resolution microscopy. Single molecule fluorescence microscopy provided unique insights into the MEF mechanism which were hidden by ensemble-averaged measurements, demonstrating that single molecule 'reading' is a valuable tool for characterizing particle-molecule interactions such as those responsible for the relative contributions of increased excitation and plasmophoric emission toward overall MEF. This work represents a step forward in the contemporary design of synergistic nano-molecular systems, and showcases the advantage of fusion between classic spectroscopic techniques and single molecule methods in terms of improved quantitative understanding of fluorophore-nanoparticle interactions, and how these interactions can be exploited to the fullest extent possible.
