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Lithography methods are commonly used to create structures in inorganic semiconductors like silicon but have not been widely applied to organic crystals. In this work, electron beam lithography (EBL) is used to pattern structures into single organic photomechanical crystals composed of 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene. The electron beam creates amorphous regions of decomposed molecules, while the reactivity of the unexposed crystal regions is preserved under a removable Au coating. Exposure of the patterned crystal to 365 nm light causes ridges of amorphous material to increase in height by 30–70%. This height increase can be reversed by visible light exposure and undergo multiple cycles. The reversible surface morphology changes are strong enough to rupture a sheet of graphene placed on top of the patterned crystal. Surprisingly, the change in dimensions of the EBL features is an order of magnitude larger than the changes in overall crystal dimensions as deduced from X-ray diffraction experiments and microscopy observations. A dynamic extrusion model is presented to explain how nanoscale features imprinted into single crystals can amplify molecular-level photomechanical changes. This work demonstrates the capability of EBL methods to produce sub-micron structural features on single photomechanical crystals, providing a new route to monolithic light-powered actuator devices.

Previous work has shown that photoisomerization of dopant molecules in a polystyrene film can either enhance or suppress its adhesion to a polar glass surface (Mostafavi, S. H.Macromolecules2018, 51, 2388−2394; Mostafavi, S. H.Macromolecules2019, 52, 6311–6317). In this paper, a different polymer host, Zeonex (ZX), is used in conjunction with the photochrome spiropyran. Nonpolar ZX has a higher glass transition temperature that makes it resistant to nanoscale mechanical deformations, while the spiropyran (SP) → merocyanine (MC) photoisomerization is a reversible reaction with a large polarity change. Ultraviolet light isomerizes SP to the polar MC form, increasing both the shear and pull-off adhesion forces to a clean glass surface by a factor of 5. Visible irradiation switches it back to the nonpolar SP form and returns the film back to its original weak adhesion, in contrast to the previously studied polystyrene films. The ability of visible light to switch off the polymer–glass adhesion is harnessed to make a light-controlled payload release device as well as to accelerate the polymer film delamination rate in water by a factor of 100. The kinetics of the water delamination, as well as the origin of residual adhesion after switching back to the SP form, are investigated. This work demonstrates how light-controlled noncovalent adhesion can be used as a solvent-free method to remove protective coatings or to disassemble structures.

Ultrathin layers of hexagonal boron nitride (h-BN) are used to fully encapsulate single perylene microcrystals. The morphology and chemical stability for samples prepared using different encapsulation methods are characterized using electron, optical, and atomic force microscopies. Only multilayer MBE-grown h-BN could fully protect the organic crystals from dissolution and sublimation. To determine the interaction of the two-dimensional material with the underlying organic chromophores, a polymer film with Lumogen Red dye molecules that act as energy donors was used to characterize the fluorescence quenching ability of the encapsulation layer. Encapsulation using wet-transfer method leads to h-BN layers that have an effective Forster quenching radius of 2.9 nm, as compared to 14.6 nm for graphene. Fluorescence quenching by h-BN can be completely avoided by using dry-transfer methods, suggesting that wet transfer leads to structural defects that act as energy acceptors. Both the type of h-BN and its method of transfer determine its ability to act as an inert coating and avoid fluorescence quenching. Encapsulation of organic molecular crystals using multilayer h-BN is feasible, but attention must be paid to preparation conditions and the nature of the h-BN sample.

The technique of focused ion beam (FIB) milling is used to cut two-dimensional shapes into single crystals composed of the organic semiconductor molecule perylene. The use of an ultrathin Au coating and its removal using a KI/I2etchant solution allow the crystal to be imaged in the FIB apparatus while protecting it from electron beam damage. Using this approach, features with a spatial resolution on the order of 130 nm can be created while retaining 90% of the original photoluminescence intensity in the surrounding crystal regions. These proof-of-principle experiments demonstrate that FIB milling could provide a general way to control the nanoscale morphology of organic molecular crystals.

Photoisomerization of molecules dissolved in a polymer film can modulate its properties. In a previous paper (Mostafavi, S. H.;Macromolecules2018, 51, 2388−2394), it was found that the ultraviolet light-induced photoisomerization of spiropyran dopants could substantially increase adhesion to a glass surface. In this work, a different photochromic reaction, the visible-light-induced cyclization of a donor–acceptor Stenhouse adduct (DASA), leads to the opposite effect: the deadhesion of a polystyrene film from a clean glass surface. Measurements of the shear and pull-off adhesion strengths before and after visible irradiation show a light-induced decrease of 20–30%. The time required for delamination in water shows an even more dramatic decrease of 90%. Changes in the water contact angle and other measurements suggest that molecular-level noncovalent interactions between the polymer and glass are weakened after photoisomerization, possibly due to the molecular contraction of the DASA that disrupts the interaction between its amine groups and the surface silanols. The ability to reduce polymer adhesion using visible light enables the controlled release of dye molecules from a glass container, where these have been stored as a dry powder, into an aqueous solution. Embedding photochromic molecules in a polymer can lead to new effects that may have practical applications in stimuli-responsive materials.

Interconnecting the surfaces of nanomaterials without compromising their outstanding mechanical, thermal, and electronic properties is critical in the design of advanced bulk structures that still preserve the novel properties of their nanoscale constituents. As such, bridging the π-conjugated carbon surfaces of single-walled carbon nanotubes (SWNTs) has special implications in next-generation electronics. This study presents a rational path toward the improvement of the electrical transport in aligned semiconducting SWNT films by deposition of metal atoms. The formation of conducting Cr-mediated pathways between the parallel SWNTs increases the transverse (intertube) conductance while having a negligible effect on the parallel (intratube) transport. In contrast, doping with Li has a predominant effect on the intratube electrical transport of aligned SWNT films. Large-scale first-principles calculations of electrical transport on aligned SWNTs show good agreement with the experimental electrical measurements and provide insight into the changes that different metal atoms exert on the density of states near the Fermi level of the SWNTs and the formation of transport channels.

We discuss advances in the covalent modification of the carbon allotropes, in particular graphene and carbon nanotubes. The main focus is on the organometallic chemistry that affords the possibility to electronically interconnect graphitic surfaces by means of covalent bonding. This mode of functionalization allows the formation of atomic scale interconnects that consist of bis-hexahapto-metal-bonds between benzenoid ring systems, which increases the dimensionality of the electronic structure of the materials leading to enhanced conductivity. The bis-hexahapto bond formation in single walled carbon nanotubes (SWNTs), graphite nanoplatelets and graphene, can be readily accomplished by metal vapor synthesis (e-beam evaporation), solution and photochemical routes.

To develop novel succinate dehydrogenase inhibitors (SDHIs), two series of novel N-4-fluoro-pyrazol-5-yl-benzamide and N-4-chloro-pyrazol-5-yl-benzamide derivatives were designed and synthesized, and their antifungal activities were evaluated against Valsa mali, Sclerotinia sclerotiorum, FusaHum graminearumSehw, Physalospora piricola, and Botrytis cinerea. The bioassay results showed that some of the target compounds exhibited good antifungal activities in vitroagainst V. maliand S. sclerotiorum. Remarkably, compound 9Ipdisplayed good in vitroactivity against V. maliwith an EC50value of 0.58 mg/L. This outcome was 21-fold greater than that of fluxapyroxad(12.45 mg/L) and close to that of the commercial fungicide tebuconazole(EC50= 0.36 mg/L). In addition, in vivo experiments proved that compound 9Iphas good protective fungicidal activity with an inhibitory rate of 93.2% against V. maliat 50 mg/L, which was equivalent to that of the positive control tebuconazole(95.5%). The results of molecular docking indicated that there were obvious hydrogen bonds and p−π interactions between compound 9Ipand succinate dehydrogenase (SDH), which could explain the probable action mechanism. In addition, the SDH enzymatic inhibition assay was carried out to further prove its mode of action. Our studies suggest that compound 9Ipcould be a fungicidal lead to discover more potent SDHIs for crop protection.

We discuss advances in the covalent modification of the carbon allotropes, in particular graphene and carbon nanotubes. The main focus is on the organometallic chemistry that affords the possibility to electronically interconnect graphitic surfaces by means of covalent bonding. This mode of functionalization allows the formation of atomic scale interconnects that consist of bis-hexahapto-metal-bonds between benzenoid ring systems, which increases the dimensionality of the electronic structure of the materials leading to enhanced conductivity. The bis-hexahapto bond formation in single walled carbon nanotubes (SWNTs), graphite nanoplatelets and graphene, can be readily accomplished by metal vapor synthesis (e-beam evaporation), solution and photochemical routes.