We recently found that polyvinylpyrrolidone (PVP)-protected metal nanoparticles dispersed in water/butanol mixture spontaneously float to the air/water interface and form two-dimensional assemblies due to classical surface excess theory and Rayleigh-Bénard-Marangoni convection induced by butanol evaporation. In this study, we found that by leveraging this principle, a unique structure is formed where hetero gold nanospheres (AuNPs)/gold nanostars (AuNSs) complexes are dispersed within AuNP two-dimensional assemblies, obtained from a mixture of polyvinylpyrrolidone-protected AuNPs and AuNSs that interact electrostatically with the AuNPs. These structures were believed to form as a result of AuNPs/AuNSs complexes formed in the water/butanol mixture floating to the air/water interface and being incorporated into the growth of AuNP two-dimensional assemblies.
View Article and Find Full Text PDFWe designed an external stimulus-responsive anti-Stokes emission switching using dual-annihilator-based triplet-triplet annihilation upconversion systems. This system, which was constructed by incorporating a palladium porphyrin derivative as a sensitizer and 9,10-diphenylanthracene (DPA) and 9,10-bis(triisopropylsilyl)ethynylanthracene (TIPS) as annihilators into polymer thin films, produced TIPS- and DPA-based anti-Stokes emission under low and high excitation powers, respectively. The mechanism involves the following: under low excitation power, triplet energy transfer from triplet-excited PdOEP to DPA is induced, followed by relay to TIPS.
View Article and Find Full Text PDFWhile the distance dependence of metal-enhanced fluorescence has been extensively studied for composite systems comprising fluorophores and metal nanoparticles, the corresponding distance dependence of triplet-triplet annihilation upconversion (TTA-UC) systems remains unexplored. Herein, we investigated the influence of the spatial distance between Ag nanoprisms (AgPRs) and TTA-UC thin films consisting of a palladium octaethylporphyrin (PdOEP) sensitizer and a 9,10-diphenylanthracene (DPA) emitter, aiming at enhancing the upconverted (UC) emission as efficiently as possible. Results indicated that the optimal distance for the examined system was significantly longer (12.
View Article and Find Full Text PDFIn this study, a photothermal therapy agent that works efficiently in the second biological transparency window was developed based on the localized surface plasmon (LSP) resonance of symmetry-broken open-shell nanostructures of low-cost Cu (CuOSNs). The strong LSP resonance and superior photothermal conversion ability in the second biological transparency window were achieved by generating the dipolar bonding mode due to the plasmon hybridization between the nanoshell dipole and the nanohole dipole at the opening edge in CuOSNs derived from the symmetry breaking of a Cu nanoshell. Oxidative dissolution of CuOSNs in water was significantly suppressed by successive coating with the self-assembled monolayer of 16-mercaptohexadecanoic acid and a thin silica layer.
View Article and Find Full Text PDFImproving the performance of upconversion systems based on triplet-triplet annihilation (TTA-UC) can have far-reaching implications for various fields, including solar devices, nano-bioimaging, and nanotherapy. This review focuses on the use of localized surface plasmon (LSP) resonance of metal nanostructures to enhance the performance of TTA-UC systems and explores their potential applications. After introducing the basic driving mechanism of TTA-UC and typical sensitizers used in these systems, we discuss recent studies that have utilized new sensitizers with distinct characteristics.
View Article and Find Full Text PDFAlthough plasmonic palladium (Pd) nanospheres are thermodynamically stable and have high photothermal conversion due to the free and bound electron coupling associated with the intrinsic high interband transition, they have not attracted attention as a photothermal conversion material for next-generation photothermal cancer therapy. This is because the Pd nanospheres generate the localized surface plasmon resonance (LSPR) intrinsically in the ultraviolet region, which is far away from the biological transparent window (750-900 nm). In this study, we controlled the LSP wavelength of Pd nanospheres by coating with high refractive index TiO shells taking advantage of the Pd LSPR which is highly sensitive to changes in the local refractive index around the nanospheres.
View Article and Find Full Text PDFThe performance improvement of solid-state triplet-triplet annihilation-based photon upconversion (TTA-UC) systems is required for the application to various solar devices. The performance can be improved by making use of the local strong electric field generated through the excitation of localized surface plasmon (LSP) resonance of metal nanostructures. However, since the improvement is effective only within the limited nanospace around nanoparticles (, the near-field effect), a methodology for improving the performance over a wider spatial region is desirable.
View Article and Find Full Text PDFSelf-assembly of porphyrins is a fascinating topic, not only for mimicking chlorophyll assemblies in photosynthetic organisms, but also for the potential of creating molecular-level devices. Herein, zinc porphyrin derivatives bearing a meta-pyridyl group at the meso position were prepared and their assemblies studied in chloroform. Among the porphyrins studied, one with a carbamoylpyridyl moiety gave a distinct H NMR spectrum in CDCl , which allowed the supramolecular structure in solution to be probed in detail.
View Article and Find Full Text PDFAbsorption enhancement based on interaction between the localized surface plasmon (LSP) and molecular exciton is one of the most important phenomena for the development of high-performance solar devices. In this study, hybrids of plasmonic metal nanoparticles and dye molecules have been developed, which exhibit enhanced absorption at precisely tuned wavelengths in a visible region. The hybrids consist of a porphyrin derivative, which has four absorption peaks (Q-bands) in a range of 500-700 nm, and triangular silver nanoprisms (AgPRs), which are developed by us to exhibit precisely tuned LSP resonance wavelengths.
View Article and Find Full Text PDFWe have succeeded in significantly enhancing fluorescence from intrinsically phosphorescent palladium octaethylporphyrin (Pd-porphyrin) that has an intersystem crossing efficiency of ∼1 by using silver nanoprisms (AgPRs). This was achieved by controlling the wavelength of the localized surface plasmon (LSP) resonance of AgPRs and the distance between the Pd-porphyrin molecules and the AgPR surfaces. In addition to enhancing phosphorescence by spectrally overlapping the phosphorescence band with the LSP resonance band, tuning the LSP wavelength to approximately 520 nm led to the appearance of a new emission band around the wavelength corresponding to the fluorescent radiation.
View Article and Find Full Text PDFIn recent years, monodispersed magnetic nanoparticles with a core/shell structure are expected for their wide applications including magnetic fluid, recoverable catalysts, and biological analysis. However, their synthesis method needs numerous processes such as solvent substitution, exchange of protective agents, and centrifugation. A simple and rapid method for the synthesis of monodispersed core-shell nanoparticles makes it possible to accelerate their further applications.
View Article and Find Full Text PDFWe describe efficient visible- and near-infrared (vis/NIR) light-driven photocatalytic properties of hybrids of CuO and plasmonic Cu arrays. The CuO/Cu arrays were prepared simply by allowing a Cu half-shell array to stand in an oxygen atmosphere for 3 h, which was prepared by depositing Cu on two-dimensional colloidal crystals with a diameter of 543 or 224 nm. The localized surface plasmon resonances (LSPRs) of the arrays were strongly excited at 866 and 626 nm, respectively, at which the imaginary part of the dielectric function of Cu is small.
View Article and Find Full Text PDFA novel organic small molecule bis-triphenylamine with spiro(fluorene-9,9'-xanthene) as the conjugated system, named BTPA-4, is successfully synthesized and employed as the hole-selective layer (HSL) in colloidal quantum dots solar cells (CQDSCs). The introduction of BTPA-4 layer can significantly prolong effective carrier lifetime (τ), increase charge recombination resistance (R), and thus diminish the interfacial charge recombination at the PbS-QDs/Au electrode interface. The effect of BTPA-4 as HSL in the device performance is especially significant for the open-circuit voltage (V) and power conversion efficiency (PCE), with a ∼ 10% and 15% enhancement respectively, comparing with those of device without the HSL.
View Article and Find Full Text PDFUpon mixing acetylacetonedioxime and copper(ii) nitrate in water, the acetylacetonedioxime is spontaneously nitrosated at the central α-carbon and four of the nitrosated ligand molecules and five Cu ions self-assemble into a pentanuclear metallacrown complex, whose structure has been revealed by single crystal X-ray analysis and magnetic interactions between the Cu ions in the complex have been probed. The lability of the core Cu ion in the complex is suggested.
View Article and Find Full Text PDFWe demonstrated the usefulness of Cu light-harvesting plasmonic nanoantennae for the development of inexpensive and efficient artificial organic photoelectric conversion systems. The systems consisted of the stacked structures of layers of porphyrin as a dye molecule, oxidation-suppressing layers, and plasmonic Cu arrayed electrodes. To accurately evaluate the effect of Cu nanoantenna on the porphyrin photocurrent, the production of CuO by the spontaneous oxidation of the electrode surfaces, which can act as a photoexcited species under visible light irradiation, was effectively suppressed by inserting the ultrathin linking layers consisting of 16-mercaptohexadecanoic acid, titanium oxide, and poly(vinyl alcohol) between the electrode surface and porphyrin molecules.
View Article and Find Full Text PDFPyrrole-imidazole polyamides are versatile DNA minor groove binders and attractive therapeutic options against oncological targets, especially upon functionalization with an alkylating agent such as seco-CBI. These molecules also provide an alternative for oncogenes deemed "undruggable" at the protein level, where the absence of solvent-accessible pockets or structural crevices prevent the formation of protein-inhibitor ligands; nevertheless, the genome-wide effect of pyrrole-imidazole polyamide binding remain largely unclear to-date. Here we propose a next-generation sequencing-based workflow combined with whole genome expression arrays to address such issue using a candidate anti-cancer alkylating agent, KR12, against codon 12 mutant KRAS.
View Article and Find Full Text PDFWe demonstrate up to ∼630-fold enhancement of the photocurrent from a porphyrin monolayer on a plasmonic Ag-array electrode showing plasmon absorption in the Q-band region relative to that on a planar Ag electrode. The photocurrent obtained by the Q-band excitation in the plasmonic electrodes even exceeded that obtained by the Soret-band excitation in a normal, nonplasmonic electrode.
View Article and Find Full Text PDFA coupled light-harvesting antenna-charge-separation system, consisting of self-assembled zinc chlorophyll derivatives that incorporate an electron-accepting unit, is reported. The cyclic tetramers that incorporated an electron acceptor were constructed by the co-assembly of a pyridine-appended zinc chlorophyll derivative, ZnPy, and a zinc chlorophyll derivative further decorated with a fullerene unit, ZnPyC60 . Comprehensive steady-state and time-resolved spectroscopic studies were conducted for the individual tetramers of ZnPy and ZnPyC60 as well as their co-tetramers.
View Article and Find Full Text PDFWe developed a new hybrid consisting of Ag nanoprisms, poly(N-isopropylacrylamide) (PNIPAm), and fluorophores via layer-by-layer assembly. The fluorescence intensity below the lower critical solution temperature (LCST) of PNIPAm was 6.4 times stronger than that above the LCST, meaning that the hybrids can function as nanosized highly thermoresponsive fluorescent sensors.
View Article and Find Full Text PDFWe demonstrate that Pd nanospheres exhibit much higher susceptibility of the localized surface plasmon resonance (LSPR) peak to medium refractive index changes than commonly used plasmonic sensing materials such as Au and Ag. The susceptibility of spherical Au nanoparticle-core/Pd-shell nanospheres (Au/PdNSs, ca. 73 nm in diameter) was found to be 4.
View Article and Find Full Text PDFWe investigated the dependence of the surface-enhanced Raman scattering (SERS) activity of densely arranged two-dimensional assemblies of spherical Au(core)-Ag(shell) nanoparticles (Au/AgNSs) on the nanoparticle diameter. The size-controlled Au/AgNSs were synthesized using the Au nanosphere seed-mediated growth method without any bulky stabilizers. The diameters of the Au/AgNSs were 38, 53, and 90 nm and the ratio of the total diameter to the Au core diameter was adjusted to ca.
View Article and Find Full Text PDFThe development of robust dyes is a highly important theme for any applications of dyes. Here we present photophysical and electrochemical characterization of a set of robust dyes based on the thienylnaphthalimide unit. The set is comprised of the thienylnaphthalimide derivatives with phenyl- (Ph-), 4-nitrophenyl- (NO2Ph-), and 4-(diphenylamino)phenyl (Ph2NPh-) substituents as exemplars covering electron-withdrawing to electron-donating groups.
View Article and Find Full Text PDFOrdered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles.
View Article and Find Full Text PDFSelf-assembled structures formed from a pyridine-appended zinc chlorophyll derivative are reported. While the zinc complex forms cyclic oligomers in chloroform solution, as indicated by (1)H NMR studies (including diffusion-ordered spectroscopy), vapor pressure osmometry, and cold-spray ionization mass spectrometry, it forms double-stranded helical coordination polymers in the solid state, as revealed by single-crystal X-ray analysis.
View Article and Find Full Text PDFWe have prepared a novel sandwich-type double-decker porphyrin complex with cerium, in which one of the porphyrins has long alkyl chains and the other has a pendant free-base porphyrin unit. The preparation of the complex was achieved with a Sonogashira coupling reaction between a preformed double-decker complex bearing an ethynyl moiety and an iodophenyl porphyrin. This complex forms moderately ordered self-assembled monolayers at the interface of 1-phenyloctane and highly oriented pyrolytic graphite.
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