Naoto Shirahata

Luminescence probe has been broadly used for bio-imaging applications. Among them, near-infrared (NIR) quantum dots (QDs) are more attractive due to minimal tissue absorbance and larger penetration depth. Above said reasons allowed whole animal imaging without slice scan or dissection. This review describes <i>in vitro</i> and <i>in vivo</i> imaging of NIR QDs in the regions of 650-900 nm (NIR-I) and 1000-1450 nm (NIR-II). Also, we summarize the recent progress in bio-imaging and discuss the fut

This review describes a series of representative synthesis processes, which have been developed in the last two decades to prepare silicon quantum dots (QDs). The methods include both top-down and bottom-up approaches, and their methodological advantages and disadvantages are presented. Considerable efforts in surface functionalization of QDs have categorized it into (i) a two-step process and (ii) <i>in situ</i> surface derivatization. Photophysical properties of QDs are summarized to highlight

A novel design of white light emitting diodes (WLEDs) emerges to meet the growing global demand for resource sustainability while preserving health and environment. To achieve this goal, a facile method is developed for the chemical synthesis of a luminescent silicon nanocrystal (ncSi) with a large Stokes shift between absorption and emission. The WLED is prepared by a simple spin‐coating method, and contains a hybrid‐bilayer of the ncSi and luminescent polymer in its device active region. Inter

The optical use of colloidal silicon nanocrystals (Si NCs) has gained increasing attention for its possible contributions to building a sustainable society that ideally uses resources and energy with high efficiency without causing damage to the environment or human health. Si wafers (E(g) ≈ 1.1 eV) dominate modern microelectronics as an impressive electronic material, but they exhibit relatively poor optical performance owing to an indirect bandgap structure. Interestingly, however, full contro

Silicon quantum dots that emit light in the wavelength range of 300 to 450 nm are fabricated. Size-tunable UV luminescence is achieved by precise control of the diameter of the nanocrystals and complete surface passivation with alkoxy monolayers.

This article describes a variety of monolayers anchored directly onto silicon surfaces without an oxide interlayer, their formation mechanisms, their technological applications, and our personal views on the future prospects for this field. The chemical modification of non-oxidized silicon surfaces utilizing monolayers was first reported in 1993. The basic finding that a non-oxidized silicon surface could be neutralized with alkyl chains through direct covalent linkage, i.e., silicon-carbon, has

A quick and convenient method was developed to synthesize organically functionalized silicon nanocrystals via a one-step reaction, which is a green chemistry route.

It is revealed that rigorous control of the size and surface of germanium nanoparticles allows fine color tuning of efficient fluorescence emission in the visible region. The spectral line widths of each emission were very narrow (<500 meV). Furthermore, the absolute fluorescence quantum yields of each emission were estimated to be 4-15%, which are high enough to be used as fluorescent labeling tags. In this study, a violet-light-emitting nanoparticle is demonstrated to be a new family of lumine

Abstract We demonstrate a novel lithographic technique utilizing a solvent to fabricate a chemically based semiconductor microdevice from an aqueous solution. According to this technique, SnO 2 thin film could be integrated onto predefined sites on a SiO 2 /Si wafer. A patterned octadecyltrimethoxysilane self‐assembled monolayer (ODS‐SAM) was prepared by vacuum ultraviolet (VUV) irradiation through a photomask to use as a template for the fabrication of a micropatterned SnO 2 thin film on the Si

Functional near-IR (NIR) emitting nanoparticles (NPs) adapted for two-photon excitation fluorescence cell imaging were obtained starting from octadecyl-terminated silicon nanocrystals (ncSi-OD) of narrow photoluminescence (PL) spectra having no long emission tails, continuously tunable over the 700-1000 nm window, PL quantum yields exceeding 30%, and PL lifetimes of 300 μs or longer. These NPs, consisting of a Pluronic F127 shell and a core made up of assembled ncSi-OD kept apart by an octadecyl

This paper presents a novel process for the fabrication of site-selectively deposited tin oxide ultrathin films (<10 nm) by using molecular recognition between the precursors and the surface of the Si substrate. Using this simple technique, the film thickness of micropatterned tin oxide films was easily controlled. Patterned self-assembled monolayers, in which both hydrophilic and hydrophobic areas formed, were used as templates for the site-selective deposition of the films. Two precursors of S

We report a one-pot synthesis of water dispersible fluorescent silica nanoparticles (NPs) functionalized with terminal amine groups, starting from silicon tetrabromide (SiBr₄) and aminopropyltriethoxy silane (APTES). The NPs range from 1 to 2 nm in diameter, and exhibit an intense blue emission with a quantum yield (QY) of around 34% in water. They were characterized using XRD, XPS, TEM and FTIR spectroscopy for structural analysis. A tentative mechanism explaining the origin of the N

Impurity-doping in nanocrystals significantly affects their electronic properties and diversifies their applications. Herein, we report the synthesis of transition metal (Mn, Ni, Co, Cu)-doped oleophilic silicon nanocrystals (SiNCs) through hydrolysis/polymerization of triethoxysilane with acidic aqueous metal salt solutions, followed by thermal disproportionation of the resulting gel into a doped-Si/SiO₂ composite that, upon HF etching and hydrosilylation with 1-n-octadecene, produce

Full control in size distribution and surface chemistry of Si nanocrystals (NCs) allows the high efficiency of visible light emission. The NC synthesis and subsequent surface modification with organic monolayers are performed in a single step by laser chemical method. Interestingly, it is found that the distinct emission in the green and blue range arises from the difference in NC size and molecular coverage of the monolayers.

In the current paper, we provide direct evidence of a controlled structure of silicon nanocrystals (SiNCs). The photoluminescence quantum yields (PLQYs) are considerably enhanced by ligand exchange between the hydrogen atoms and hydrocarbon chains. To systematically study this phenomenon, we prepared SiNCs by thermal disproportionation of amorphous hydrogen silsesquioxane that was derived from triethoxysilane, which was followed by hydrofluoric etching and hydrosilylation of 1-alkenes. The estim