Search

We report an efficient photo-induced covalent modification (PICM) of graphene by short-chain fatty acids (SCFAs) with an alkyl chain at the liquid-solid interface for spatially resolved chemical functionalization of graphene. Light irradiation on monolayer graphene under an aqueous solution of the SCFAs with an alkyl chain efficiently introduces sp(3)-hybridized defects, where the reaction rates of PICM are significantly higher than those in pure water. Raman and IR spectroscopy revealed that a high density of methyl, methoxy, and acetate groups is covalently attached to the graphene surface while it was partially oxidized by other oxygen-containing functional groups, such as OH and COOH. A greater downshift of the G-band in Raman spectra was observed upon the PICM with longer alkyl chains, suggesting that the charge doping effect can be controlled by the alkyl chain length of the SCFAs. The systematic research and exploration of covalent modification in SCFAs provide new insight and a potentially facile method for bandgap engineering of graphene.

We report an efficient photo-induced covalent modification (PICM) of graphene by short-chain fatty acids (SCFAs) with an alkyl chain at the liquid-solid interface for spatially resolved chemical functionalization of graphene. Light irradiation on monolayer graphene under an aqueous solution of the SCFAs with an alkyl chain efficiently introduces sp(3)-hybridized defects, where the reaction rates of PICM are significantly higher than those in pure water. Raman and IR spectroscopy revealed that a high density of methyl, methoxy, and acetate groups is covalently attached to the graphene surface while it was partially oxidized by other oxygen-containing functional groups, such as OH and COOH. A greater downshift of the G-band in Raman spectra was observed upon the PICM with longer alkyl chains, suggesting that the charge doping effect can be controlled by the alkyl chain length of the SCFAs. The systematic research and exploration of covalent modification in SCFAs provide new insight and a potentially facile method for bandgap engineering of graphene.

Organic materials have attracted considerable attention in nonlinear optical (NLO) applications as they have several advantages over inorganic materials, including high NLO response, and fast response time as well as low-cost and easy fabrication. Lithium-containing C-60 (Li@C-60) is promising for NLO over other organic materials because of its strong NLO response proven by theoretical and experimental studies. However, the low purity of Li@C-60 has been a bottleneck for applications in the fields of solar cells, electronics and optics. In 2010, highly purified Li@C-60 was finally obtained, encouraging further studies. In this study, we demonstrate a facile method to fabricate thin films of Li@C-60 and their strong NLO potential for high harmonic generation by showing its comparatively strong emission of degenerate-six-wave mixing, a fifth-order NLO effect.

Metal-organic frameworks (MOFs) are interesting candidates for applications in nonlinear optics (NLO). However, current design strategies for MOFs in NLO are typically limited to either engineering the MOF itself or using the MOF to align NLO-active molecules within its pores. But more design factors can be considered when engineering MOFs and choosing guest molecules. The NLO emission of the host and guests can be combined instead of using only either one of the two. The interaction between the host and guest can be a source for further improvement by changing the symmetry, dipole moment, bond lengths, charge distribution, etc. Additionally, unstable NLO molecules can potentially be stabilized by accommodation in the MOF. Here, we demonstrate a new strategy for MOFs by combining MOF-177 as a host and Li@C-60 as a guest for NLO, meaning that both the MOF itself as well as the guest molecules are emitting NLO signals, as well as further increasing the emission using their interaction elongating bonds within the MOF, thus fully using the MOF's potential for second harmonic generation. Using this approach, the overall emission can be boosted by 40% compared to MOF-177 alone. Furthermore, the accommodation into MOF-177 stabilizes Li@C-60 that is normally unstable under ambient conditions without a counterion.

Metal-organic frameworks (MOFs) are interesting candidates for applications in nonlinear optics (NLO). However, current design strategies for MOFs in NLO are typically limited to either engineering the MOF itself or using the MOF to align NLO-active molecules within its pores. But more design factors can be considered when engineering MOFs and choosing guest molecules. The NLO emission of the host and guests can be combined instead of using only either one of the two. The interaction between the host and guest can be a source for further improvement by changing the symmetry, dipole moment, bond lengths, charge distribution, etc. Additionally, unstable NLO molecules can potentially be stabilized by accommodation in the MOF. Here, we demonstrate a new strategy for MOFs by combining MOF-177 as a host and Li@C-60 as a guest for NLO, meaning that both the MOF itself as well as the guest molecules are emitting NLO signals, as well as further increasing the emission using their interaction elongating bonds within the MOF, thus fully using the MOF's potential for second harmonic generation. Using this approach, the overall emission can be boosted by 40% compared to MOF-177 alone. Furthermore, the accommodation into MOF-177 stabilizes Li@C-60 that is normally unstable under ambient conditions without a counterion.

We developed adaptive optical (AO) two-photon excitation microscopy by introducing a spatial light modulator (SLM) in a commercially available microscopy system. For correcting optical aberrations caused by refractive index (RI) interfaces at a specimen's surface, spatial phase distributions of the incident excitation laser light were calculated using 3D coordination of the RI interface with a 3D ray-tracing method. Based on the calculation, we applied a 2D phase-shift distribution to a SLM and achieved the proper point spread function. AO two-photon microscopy improved the fluorescence image contrast in optical phantom mimicking biological specimens. Furthermore, it enhanced the fluorescence intensity from tubulin-labeling dyes in living multicellular tumor spheroids and allowed successful visualization of dendritic spines in the cortical layer V of living mouse brains in the secondary motor region with a curved surface. The AO approach is useful for observing dynamic physiological activities in deep regions of various living biological specimens with curved surfaces.

Light-molecule strong coupling has emerged within the last decade as a new method to control chemical reactions. A few years ago it was discovered that chemical reactivity could be altered by vibrational strong coupling (VSC). Only a limited number of reactions have been investigated under VSC to date, including solvolysis and deprotection reactions. Here the effect of VSC on a series of aldehydes and ketones undergoing Prins cyclization, an important synthetic step in pharmaceutical chemistry, is investigated. A decrease of the second-order rate constant with VSC of the reactant carbonyl stretching groups is observed. We also observe an increased activation energy due to VSC, but proportional changes in activation enthalpy and entropy, suggesting no substantive change in reaction pathway. The addition of common cycloaddition reactions to the stable of VSC-modified chemical reactions is another step towards establishing VSC as a genuine tool for synthetic chemistry.

A fluorophore encapsulated in a metal-organic framework showed photochromic multicolour fluorescence. Irradiation with an ultraviolet laser induced the relocation of the fluorophore from a polar to a nonpolar environment, altering the emission from red to blue. This change in emission color can be repeatably recovered by heating the fluorophore-MOF composite.