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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 sp3-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. ispartof: NANOSCALE vol:15 issue:10 pages:4932-4939 ispartof: location:England status: published

Tip-enhanced Raman scattering (TERS) microscopy is an advanced technique for investigation at the nanoscale that provides topographic and chemical information simultaneously. The TERS probe plays a crucial role in the microscopic performance. In the recent past, the development of silver nanowire (AgNW) based TERS probes solved the main tip fabrication issues, such as low mechanical strength and reproducibility. However, this fabrication method still suffers from low control of the protruded length of the AgNW. In this work, a simple water-air interface electrocutting method is proposed to achieve wide controllability of the length. This water cutting method was combined with a succedent Au coating on the AgNW surface, and the probe achieved an up to 100× higher enhancement factor (EF) and a 2× smaller spatial resolution compared to pristine AgNW. Thanks to this excellent EF, the water-cut Au-coated AgNW probes were found to possess high TERS activity even in the nongap mode, enabling broad applications.

We report a facile all-optical method for spatially resolved and reversible chemical modification of a graphene monolayer. A tightly focused laser on graphene under water introduces an sp

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 C60 (Li@C60) 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@C60 has been a bottleneck for applications in the fields of solar cells, electronics and optics. In 2010, highly purified Li@C60 was finally obtained, encouraging further studies. In this study, we demonstrate a facile method to fabricate thin films of Li@C60 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. ispartof: Rsc Advances vol:12 issue:1 pages:389-394 ispartof: location:England status: Published online

Tip-enhanced Raman scattering (TERS) microscopy is an advanced technique for investigation at the nanoscale because of its excellent properties, such as its label-free functionality, non-invasiveness, and ability to simultaneously provide topographic and chemical information. The probe plays a crucial role in TERS technique performance. Widely used AFM-TERS probes fabricated with metal deposition suffer from relatively low reproductivity as well as limited mapping and storage lifetime. To solve the reproducibility issue, silver nanowire (AgNW)-based TERS probes were developed, which, thanks to the high homogeneity of the liquid-phase synthesis of AgNW, can achieve high TERS performance with excellent probe reproductivity, but still present short lifetime due to probe oxidation. In this work, a simple Au coating method is proposed to overcome the limited lifetime and improve the performance of the AgNW-based TERS probe. For the Au-coating, different [Au]/[Ag] molar ratios were investigated. The TERS performance was evaluated in terms of changes in the enhancement factor (EF) and signal-to-noise ratio through multiple mappings and the storage lifetime in air. The Au-coated AgNWs exhibited higher EF than pristine AgNWs and galvanically replaced AgNWs with no remarkable difference between the two molar ratios tested. However, for longer scanning time and multiple mappings, the probes obtained with low Au concentration showed much longer-term stability and maintained a high EF. Furthermore, the Au-coated AgNW probes were found to possess a longer storage lifetime in air, allowing for long and multiple TERS mappings with one single probe.

Metal–organic frameworks (MOFs) are interesting candidates for nonlinear optics (NLO). Here, it will be demonstrated how combining host and guest emission can greatly improve NLO performance of MOFs by accommodating Li@C60 into MOF-177.

Novel metal-organic frameworks containing lanthanide double-layer-based secondary building units (KGF-3) were synthesized by using machine learning (ML). Isolating pure KGF-3 was challenging, and the synthesis was not reproducible because impurity phases were frequently obtained under the same synthetic conditions. Thus, dominant factors for the synthesis of KGF-3 were identified, and its synthetic conditions were optimized by using two ML techniques. Cluster analysis was used to classify the obtained powder X-ray diffractometry patterns of the products and thus automatically determine whether the experiments were successful. Decision-tree analysis was used to visualize the experimental results, after extracting factors that mainly affected the synthetic reproducibility. Water-adsorption isotherms revealed that KGF-3 possesses unique hydrophilic pores. Impedance measurements demonstrated good proton conductivities (σ=5.2×10-4 S cm-1 for KGF-3(Y)) at a high temperature (363 K) and relative humidity of 95 % RH.

Membrane-less organelles (MLOs) are formed by biomolecular liquid-liquid phase separation (LLPS). Proteins with charged low-complexity domains (LCDs) are prone to phase separation and localize to MLOs, but the mechanism underlying the distributions of such proteins to specific MLOs remains poorly understood. Recently, proteins with Arg-enriched mixed-charge domains (R-MCDs), primarily composed of R and Asp (D), were found to accumulate in nuclear speckles via LLPS. However, the process by which R-MCDs selectively incorporate into nuclear speckles is unknown. Here, we demonstrate that the patterning of charged amino acids and net charge determines the targeting of specific MLOs, including nuclear speckles and the nucleolus, by proteins. The redistribution of R and D residues from an alternately sequenced pattern to uneven blocky sequences caused a shift in R-MCD distribution from nuclear speckles to the nucleolus. In addition, the incorporation of basic residues in the R-MCDs promoted their localization to the MLOs and their apparent accumulation in the nucleolus. The R-MCD peptide with alternating amino acids did not undergo LLPS, whereas the blocky R-MCD peptide underwent LLPS with affinity to RNA, acidic poly-Glu, and the acidic nucleolar protein nucleophosmin, suggesting that the clustering of R residues helps avoid their neutralization by D residues and eventually induces R-MCD migration to the nucleolus. Therefore, the distribution of proteins to nuclear speckles requires the proximal positioning of D and R for the mutual neutralization of their charges. ispartof: INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES vol:23 issue:14 ispartof: location:Switzerland status: published

Even without external photon pumping, cavity vacuum fields can be strongly coupled with molecular transitions (electronic excitation and molecular vibration), resulting in the formation of polarito...

Recently, our group introduced the use of silver nanowires (AgNWs) as novel non-invasive endoscopic probes for detecting intracellular Raman signals. This method, although innovative and promising, relies exclusively on the plasmonic waveguiding effect for signal enhancement. It, therefore, requires sophisticated operational tools and protocols, drastically limiting its applicability. Herein, an advanced strategy is offered to significantly enhance the performance of these endoscopic probes, making this approach widely accessible and versatile for cellular studies. By uniformly forming gold structures on the smooth AgNW surface via a galvanic replacement reaction, the density of the light coupling points along the whole probe surface is drastically increased, enabling high surface-enhanced Raman scattering (SERS) efficiency upon solely focusing the excitation light on the gold-etched AgNW. The applicability of these gold-etched AgNW probes for molecular sensing in cells is demonstrated by detecting site-specific and high-resolved SERS spectra of cell compartment-labeling dyes, namely, 4',6-diamidino-2-phenylindole in the nucleus and 3,3'-dioctadecyloxacarbocyanine on the membrane. The remarkable spectral sensitivity achieved provides essential structural information of the analytes, indicating the overall potential of the proposed approach for cellular studies of drug interactions with biomolecular items.

The thermodynamic (PCN-222) and kinetic (PCN-224) products of porphyrinic Zr-metal-organic frameworks (MOFs) were synthesized via an anodic dissolution approach for the first time. To the best of our knowledge, this is the first report of MOF polymorphs being controlled by electrolysis. The selective formation of PCN-222 requires an amorphous component to be present on the electrode during the initial reaction process.

Site-selective chemistry opens new paths for the synthesis of technologically important molecules. When a reactant is placed inside a Fabry-Perot (FP) cavity, energy exchange between molecular vibrations and resonant cavity photons results in vibrational strong coupling (VSC). VSC has recently been implicated in modified chemical reactivity at specific reactive sites. However, as a reaction proceeds inside an FP cavity, the refractive index of the reaction solution changes, detuning the cavity mode away from the vibrational mode and weakening the VSC effect. Here we overcome this issue, developing actuatable FP cavities to allow automated tuning of cavity mode energy to maintain maximized VSC during a reaction. As an example, the site-selective reaction of the aldehyde over the ketone in 4-acetylbenzaldehyde is achieved by automated cavity tuning to maintain optimal VSC of the ketone carbonyl stretch during the reaction. A nearly 50 % improvement in site-selective reactivity is observed compared to an FP cavity with static mirrors, demonstrating the utility of actuatable FP cavities as microreactors for organic chemistry.

Owing to their excellent photoluminescence (PL) properties in a narrow linewidth below 30 nm and high photoluminescence quantum yield (PLQY), organometal halide perovskite nanocrystals (PeNCs) are ...

Despite having great value across a wide variety of scientific fields, two-photon polymerizations currently suffer from two significant problems: the need for photoinitiators, which generate toxic side products, and the irreversibility of the process. Hence, the design of a versatile approach that circumvents these issues represents a major scientific challenge. Herein, we report a two-photon absorption strategy where reversible [2 + 2] cycloaddition of bis-thymines was achieved without the need for any photoinitiator. The cycloaddition and cycloreversion reactions could be induced by simply changing the irradiation wavelength, and repeated writing and erasing cycles were performed. The simplicity, reversibility, and biocompatibility of this strategy open up a whole new toolbox for applications across a wide variety of scientific fields. ispartof: ACS OMEGA vol:5 issue:20 pages:11547-11552 ispartof: location:United States status: published

Light-molecule strong coupling has emerged within the last decade as an entirely new method to control chemical reactions. A few years ago it was discovered that the chemical reactivity could be altered by vibrational strong coupling (VSC). While the potential of VSC in organic chemistry appears enormous, only a limited number of reactions have been investigated under VSC to date, including solvolysis and deprotection reactions. Here we investigate the effect of VSC on a series of aldehydes and ketones undergoing Prins cyclization, an important synthetic step in pharmaceutical chemistry. We observe a decrease of the second-order rate constant with VSC of the reactant carbonyl stretching groups. We measure an increased activation energy due to VSC, but proportional changes in activation enthalpy and entropy suggest 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.

Silver nanowires have attracted considerable attention as subdiffraction limited diameter waveguides in a variety of applications including cell endoscopy and photonic integrated circuitry. Optical signal transport occurs by coupling light into propagating surface plasmons, which scatter back into light further along the wire. However, these interconversions only occur efficiently at wire ends, or at defects along the wire, which are not controlled during synthesis. Here, we overcome this limitation, demonstrating the visible laser light-induced fabrication of gold nanostructures at desired positions on silver nanowires, and their utility as efficient in/out coupling points for light. The gold nanostructures grow via plasmon-induced reduction of Au(III) and are shown to be excellent "hotspots" for surface-enhanced Raman scattering. ispartof: NANO LETTERS vol:20 issue:4 pages:2460-2467 ispartof: location:United States status: published

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

Nonlinear optical (NLO) materials have attracted considerable attention due to their potential applications for wavelength converters and electro-optical modulators. One way to fabricate SHG materials is to align asymmetric organic dyes with high second-order hyperpolarizability constants. Here, we demonstrate one-dimensional alignment of asymmetric organic dyes in pores of metal-organic framework (MOF). MOF with Kagome-type lattice was synthesized to encapsulate the organic dyes in its one-dimensional pores. The organic dyes were oriented along with the onedimensional pores, which was confirmed by fluorescence under linearly-polarized excitation light.

The coupling of (photo)chemical processes to optical cavity vacuum fields is an emerging method for modulating molecular and material properties. Recent reports have shown that strong coupling of the vibrational modes of solvents to cavity vacuum fields can influence the chemical reaction kinetics of dissolved solutes. This suggests that vibrational strong coupling might also effect other important solution-based processes, such as crystallization from solution. Here we test this hitherto unexplored notion, investigating pseudopolymorphism in the crystallization from water of ZIF metal–organic frameworks inside optical microcavities. We find that ZIF-8 crystals are selectively obtained from solution inside optical microcavities, where the OH stretching vibration of water is strongly coupled to cavity vacuum fields, whereas mixtures of ZIF-8 and ZIF-L are obtained otherwise. Moreover, ZIF crystallization is accelerated by solvent vibrational strong coupling. This work suggests that cavity vacuum fields might become a tool for materials synthesis, biasing molecular self-assembly and driving macroscopic material outcomes., Strong coupling of optical cavity vacuum fields and solvent vibrations leads to selective crystallization in a pseudo-polymorphic MOF system.

Bismuth vanadate (BiVO4) microcrystals enclosed with up to 42 low and high index facets were synthesized through truncation of BiVO4 octahedral crystals via a simple and highly reproducible hydrothermal method. The size and shape of the truncated BiVO4 crystals could be tuned by varying the acid concentration, reaction temperature and reaction period. Compared to the BiVO4 octahedral crystals without truncation, the 42-faceted ones showed an enhanced photocatalytic activity in the degradation of rhodamine B molecules due to the enhanced charge separation on the exposed low and high index facets. This was confirmed at sub-particle level by the photo-deposition of gold and manganese oxide nanoparticles selectively on hot electron and hole accumulated facets, respectively. Our results will provide a guideline for the synthesis of more efficient BiVO4 and many other multinary metal oxide-based photocatalysts. Moreover, the synthesized microcrystals are perfect materials for the study of photocatalytic property of BiVO4 at single and sub-particle level.

Most targeting strategies of anticancer drug delivery systems (DDSs) rely on the surface functionalization of nanocarriers with specific ligands, which trigger the internalization in cancer cells via receptor-mediated endocytosis. The endocytosis implies the entrapment of DDSs in acidic vesicles (endosomes and lysosomes) and their eventual ejection by exocytosis. This process, intrinsic to eukaryotic cells, is one of the main drawbacks of DDSs because it reduces the drug bioavailability in the intracellular environment. The escape of DDSs from the acidic vesicles is, therefore, crucial to enhance the therapeutic performance at low drug dose. To this end, we developed a multifunctionalized DDS that combines high specificity towards cancer cells with endosomal escape capabilities. Doxorubicin-loaded mesoporous silica nanoparticles were functionalized with polyethylenimine, a polymer commonly used to induce endosomal rupture, and hyaluronic acid, which binds to CD44 receptors, overexpressed in cancer cells. We show irrefutable proof that the developed DDS can escape the endosomal pathway upon polymeric functionalization. Interestingly, the combination of the two polymers resulted in higher endosomal escape efficiency than the polyethylenimine coating alone. Hyaluronic acid additionally provides the system with cancer targeting capability and enzymatically controlled drug release. Thanks to this multifunctionality, the engineered DDS had cytotoxicity comparable to the pure drug whilst displaying high specificity towards cancer cells. The polymeric engineering here developed enhances the performance of DDS at low drug dose, holding great potential for anticancer therapeutic applications. ispartof: SCIENTIFIC REPORTS vol:9 issue:1 ispartof: location:England status: published

We report a simple method to control the end shape of silver nanowires by adding pure water in the conventional polyol synthesis. The use of 0.2-0.4% (v/v) water in ethylene glycol as a solvent provides pencil-like silver nanowires with sharp ends in a high yield. We have demonstrated remote excitation of SHG on the sharp nanowires, promising a point light source for super resolution microscopy. ispartof: CHEMICAL COMMUNICATIONS vol:55 issue:77 pages:11630-11633 ispartof: location:England status: published

A series of novel metal organic frameworks with lanthanide double-layer-based inorganic subnetworks (KGF-3) was synthesized assisted by machine learning. Pure KGF-3 was difficult to isolate in the initial screening experiments. The synthetic conditions were successfully optimized by extracting the dominant factors for KGF-3 synthesis using two machine-learning techniques. Cluster analysis was used to classify the obtained PXRD patterns of the products and to decide automatically whether the experiments were successful or had failed. Decision tree analysis was used to visualize the experimental results, with the factors that mainly affected the synthetic reproducibility being extracted. The water adsorption isotherm revealed that KGF-3 possesses unique hydrophilic pores, and impedance measurements demonstrated good proton conductivities (σ = 5.2 × 10−4 S cm−1 for KGF-3(Y)) at a high temperature (363 K) and high relative humidity (95%).

The coupling of (photo)chemical processes to optical cavity vacuum fields is an emerging method for modulating molecular and material properties. Recent reports have shown that strong coupling of the vibrational modes of solvents to cavity vacuum fields can influence the chemical reaction kinetics of dissolved solutes. This suggests that vibrational strong coupling might also effect other important solution-based processes, such as crystallization from solution. Here we test this hitherto unexplored notion, investigating pseudopolymorphism in the crystallization from water of ZIF metal-organic frameworks inside optical microcavities. We find that ZIF-8 crystals are selectively obtained from solution inside optical microcavities, where the OH stretching vibration of water is strongly coupled to cavity vacuum fields, whereas mixtures of ZIF-8 and ZIF-L are obtained otherwise. Moreover, ZIF crystallization is accelerated by solvent vibrational strong coupling. This work suggests that cavity vacuum fields might become a tool for materials synthesis, biasing molecular self-assembly and driving macroscopic material outcomes. ispartof: CHEMICAL SCIENCE vol:12 issue:36 pages:11986-11994 ispartof: location:England status: published

Quantum-confined cesium lead tribromide perovskite quantum dots (PeQDs) are attractive photonic sources for versatile optoelectronic devices and thus the synthetic routes have been explored via various techniques. However, the lack of a general method to fabricate the quantum-confined PeQD with remarkable stability at colloidal state has been one of the major obstacles to device applications. Herein, we propose a simple and robust ligand-assisted reprecipitation method associated with didodecyl dimethyl ammonium bromide for quantum-confined PeQDs with remarkable stability at colloidal state. This method will shed a light on the field of colloidal PeQDs synthesis for the next generation of photonic sources.

Defects influence the properties of metal-organic frameworks (MOFs), such as their storage amount and the diffusion kinetics of gas molecules. However, the spatial distribution of defects is still poorly understood due to a lack of visualization methods. Here, we present a new method using nonlinear optics (NLO) that allows the visualization of defects within MOFs. ispartof: CHEMICAL COMMUNICATIONS vol:56 issue:87 pages:13331-13334 ispartof: location:England status: published

The coupling of (photo)chemical processes to optical cavity vacuum fields is an emerging method for modulating molecular and material properties. Recent reports have shown that strong coupling of the vibrational modes of solvents to cavity vacuum fields can influence the chemical reaction kinetics of dissolved solutes. This suggests that vibrational strong coupling might also effect other important solution-based processes, such as crystallization from solution. Here we test this hither-to unexplored notion, investigating pseudopolymorphism in the crystallization from water of ZIF metal-organic frameworks inside optical microcavities. We find that ZIF-8 crystals are selectively obtained from solution inside optical microcavities, where the OH stretching vibration of water is strongly coupled to cavity vacuum fields, whereas mixtures of ZIF-8 and ZIF-L are obtained otherwise. This work suggests that cavity vacuum fields might become a tool for materials synthesis, biasing molecular self-assembly and driving macroscopic material outcomes.

Vibrational polaritonic chemistry is emerging as an exciting new sub-field of chemistry, one in which strong interactions with optical cavity vacuum fields are another degree of freedom alongside temperature, solvent, catalyst, and so on to modify thermochemical reactivity. The field stands at a fascinating juncture with experimental works on a variety of organic reactions continuing to blossom, just as many theoretical works appear which diverge significantly in their predictions compared to experiments. The outlook for the field is no doubt an exciting one as it seeks to unify the observed novel optical cavity-induced chemical phenomena with satisfying accompanying physical theory. In this minireview we highlight experimental works on vibrational polaritonic chemistry that have appeared most recently, focusing on the chemistry of the rate-limiting steps to provide mechanistic insight. We hope this review will encourage synthetic chemists to enter the field and we discuss the opportunities and challenges that lie ahead as polaritonic chemistry grows into the future. ispartof: CHEMPLUSCHEM vol:85 issue:9 pages:1981-1988 ispartof: location:Germany status: published

Intracellular pH affects many biological processes such as apoptosis, proliferation, endocytosis, and multidrug resistance. In view of this, highly sensitive pH sensing in live cells is essential f...

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.

Graphene, a single atomic layer of sp2 hybridized carbon, is a promising material for future devices due to its excellent optical and electrical properties. Nevertheless, for practical applications, it is essential to deposit patterned metals on graphene in the micro and nano-meter scale in order to inject electrodes or modify the 2D film electrical properties. However, conventional methods for depositing patterned metals such as lift-off or etching leave behind contamination. This contamination has been demonstrated to deteriorate the interesting properties of graphene such as its carrier mobility. Therefore, to fully exploit the unique properties of graphene, the controlled and nano-patterned deposition of metals on graphene films without the use of a sacrificial resist is of significant importance for graphene film functionalization and contact deposition. In this work, we demonstrate a practical and low-cost optical technique of direct deposition of metal nano-patterned structures without the need for a sacrificial lift-off resist. The technique relies on the laser induced reduction of metal ions on a graphene film. We demonstrate that this deposition is optically driven, and the resolution is limited only by the diffraction limit of the light source being used. Patterned metal features as small as 270 nm in diameter are deposited using light with a wavelength of 532 nm and a numerical aperture of 1.25. Deposition of different metals such as Au, Ag, Pd, Pb and Pt is shown. Additionally, change in the Fermi level of the graphene film through the nano-patterned metal is demonstrated through the electrical characterization of four probe field effect transistors. ispartof: NANOSCALE vol:12 issue:20 pages:11063-11069 ispartof: location:England status: published

Cell membranes contain lateral systems that consist of various lipid compositions and actin cytoskeleton, providing two-dimensional (2D) platforms for chemical reactions. However, such complex 2D environments have not yet been used as a synthetic platform for artificial 2D nanomaterials. Herein, we demonstrate the direct synthesis of 2D coordination polymers (CPs) at the liquid-cell interface of the plasma membrane of living cells. The coordination-driven self-assembly of networking metal complex lipids produces cyanide-bridged CP layers with metal ions, enabling "pseudo-membrane jackets" that produce long-lived micro-domains with a size of 1-5 μm. The resultant artificial and visible phase separation systems remain stable even in the absence of actin skeletons in cells. Moreover, we show the cell application of the jackets by demonstrating the enhancement of cellular calcium response to ATP.

The covalent functionalization of carbon-based materials through aryldiazonium chemistry has emerged as a powerful tool for physicochemical property modification. However, the characterization tech...

In this chapter, we introduce multiphoton photochromic reversible reaction in a diarylethene derivative at nanometer scale much beyond the diffraction limit. For this, we have utilized nonlinear plasmonics along a plasmonic waveguide, particularly on the chemically synthesized silver nanowire. Propagating near-field surface plasmons excited by near-infrared femtosecond laser pulses successfully excite diarylethene derivatives surrounding a silver nanowire. Three-photon cyclization and two-photon cycloreversion reaction induced through the propagating surface plasmon polaritons were visualized by means of fluorescence imaging. We demonstrated one-color near-infrared laser reversible control by tuning the laser power.