The immobilization of fluorescent photoinduced electron transfer (PET) switches/sensors into solid state, which usually cannot maintain their identical properties in solution, has remained a big challenge. Herein, a water-stable anthracene and maleimide appended zirconium-based-metal-organic framework (Zr-MOF; UiO-68-An/Ma) is reported. Unlike the regular intramolecular "fluorophore-spacer-receptor" format, the separated immobilization of fluorescent (anthracene) and acceptor (maleimide) groups into the framework of a multivariate MOF can also favor a pseudo-intramolecular fluorescent PET process, resulting in UiO-68-An/Ma with very weak fluorescence. Interestingly, after Diels-Alder reaction or thiol-ene reaction of maleimide groups, the pseudo-intramolecular fluorescent PET process in UiO-68-An/Ma fails and the solid-state fluorescence of the crystals is recovered. In addition, UiO-68-An/Ma shows an interesting application as solid-state fluorescent turn-on sensor for biothiols, with the naked eye response at a low concentration of 50 µmol L within 5 min. This study represents a general strategy to enable the efficient tuning of fluorescent PET switches/sensors in solid state, and considering the fluorescence of the PET-based MOFs can be restored after addition of analyte/target species, this research will definitely inspire to construct stimuli-responsive fluorescent MOFs for interesting applications (e.g., logic gate) in future.
Physical and chemical technologies have been continuously progressing advances in neuroscience research. The development of research tools for closed-loop control and monitoring neural activities in behaving animals is highly desirable. In this paper, we introduce a wirelessly operated, miniaturized microprobe system for optical interrogation and neurochemical sensing in the deep brain. Via epitaxial liftoff and transfer printing, microscale light-emitting diodes (micro-LEDs) as light sources and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-coated diamond films as electrochemical sensors are vertically assembled to form implantable optoelectrochemical probes for real-time optogenetic stimulation and dopamine detection capabilities. A customized, lightweight circuit module is employed for untethered, remote signal control, and data acquisition. After the probe is injected into the ventral tegmental area (VTA) of freely behaving mice, in vivo experiments clearly demonstrate the utilities of the multifunctional optoelectrochemical microprobe system for optogenetic interference of place preferences and detection of dopamine release. The presented options for material and device integrations provide a practical route to simultaneous optical control and electrochemical sensing of complex nervous systems.
We construct a variational explicit-solute implicit-solvent model for the solvation of molecules. Central in this model is an effective solvation free-energy functional that depends solely on the position of solute-solvent interface and solute atoms. The total free energy couples altogether the volume and interface energies of solutes, the solute-solvent van der Waals interactions, and the solute-solute mechanical interactions. A curvature dependent surface tension is incorporated through the so-called Tolman length which serves as the only fitting parameter in the model. Our approach extends the original variational implicit-solvent model of Dzubiella, Swanson, and McCammon [Phys. Rev. Lett. 2006, 96, 087802 and J. Chem. Phys. 2006, 124, 084905] to include the solute molecular mechanics. We also develop a novel computational method that combines the level-set technique with optimization algorithms to determine numerically the equilibrium conformation of nonpolar molecules. Numerical results demonstrate that our new model and methods can capture essential properties of nonpolar molecules and their interactions with the solvent. In particular, with a suitable choice of the Tolman length for the curvature correction to the surface tension, we obtain the solvation free energy for a benzene molecule in a good agreement with experimental results.
Whether or not the topology of three-dimensional
covalent organic
frameworks (3D COFs) can be tuned via steric control remains a big
question and has never been reported. Herein, we describe the designed
synthesis of two highly crystalline 3D COFs (3D-TPB-COF-OMe and 3D-TPB-COF-Ph),
through the polycondensation of tetra(p-aminophenyl)methane
and methoxy- or phenyl- substituted 1,2,4,5-tetrakis(4-formylphenyl)benzene
on the 3- and 6-positions. Amazingly, by using the continuous rotation
electron diffraction technique, 3D-TPB-COF-OMe is determined to have
a 5-fold interpenetrated structure with a reported pts net, while 3D-TPB-COF-Ph adopts an unprecedented self-penetrated ljh topology (ljh = Luojia Hill) that does not
exist in the database of ToposPro. Therefore, by altering the substituents
from methoxy to phenyl groups, the topology of designed 3D COFs changes
accordingly, and a rare net is now available. This result clearly
demonstrates that such COF structures need to be carefully determined
due to its complexity, and moreover, it is promising to design 3D
COFs with new topology for interesting application by increasing the
steric hindrance of molecular building blocks.
Optogenetic methods provide efficient cell-specific modulations, and the ability of simultaneous neural activation and inhibition in the same brain region of freely moving animals is highly desirable. Here we report bidirectional neuronal activity manipulation accomplished by a wireless, dual-color optogenetic probe in synergy with the co-expression of two spectrally distinct opsins (ChrimsonR and stGtACR2) in a rodent model. The flexible probe comprises vertically assembled, thin-film microscale light-emitting diodes with a lateral dimension of 125 × 180 µm2, showing colocalized red and blue emissions and enabling chronic in vivo operations with desirable biocompatibilities. Red or blue irradiations deterministically evoke or silence neurons co-expressing the two opsins. The probe interferes with dopaminergic neurons in the ventral tegmental area of mice, increasing or decreasing dopamine levels. Such bidirectional regulations further generate rewarding and aversive behaviors and interrogate social interactions among multiple mice. These technologies create numerous opportunities and implications for brain research.
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