The successful development of highly sensitive, water‐compatible, nontoxic nanoprobes has allowed nanomaterials to be widely employed in various applications. The applicability of highly bright quantum dot (QD)‐based probes consisting of QDs on 120 nm silica nanoparticles (NPs) with silica shells is investigated. Their substantial merits, such as their brightness and biocompatibility, for effective bioimaging are demonstrated. Silica‐coated, QD‐embedded silica NPs (Si@QDs@Si NPs) containing QDs composed of CdSe@ZnS (core‐shell) are prepared to compare their structure‐based advantages over single QDs that have a similar quantum yield (QY). These Si@QDs@Si NPs exhibit approximately 200‐times stronger photoluminescence (PL) than single QDs. Cytotoxicity studies reveal that the Si@QDs@Si NPs are less toxic than equivalent numbers of silica‐free single quantum dots. The excellence of the Si@QDs@Si NPs with regard to in vivo applications is illustrated by significantly enhanced fluorescence signals from Si@QDs@Si‐NP‐tagged cells implanted in mice. Notably, a more advanced version of QD‐based silica NPs (Si@mQDs@Si NPs), containing multishell quantum dots (mQDs) composed of CdSe@CdS@ZnS, are prepared without significant loss of QY during surface modification. In addition, the Si@mQDs@Si NPs display a fivefold higher fluorescence activity than the Si@QDs@Si NPs. As few as 400 units of Si@mQDs@Si‐ NP‐internalized cells can be detected in the cell‐implanted mouse model.
PURPOSEThis study compared the accuracy of an abutment-framework (A-F) taken with open tray impression technique combining cementon crown abutments, a metal framework and resin cement to closed tray and resin-splinted open tray impression techniques for the 3-implant definitive casts. The effect of angulation on the accuracy of these 3 techniques was also evaluated.MATERIAL AND METHODSThree definitive casts, each with 3 linearly positioned implant analogs at relative angulations 0, 30, and 40 degrees, were fabricated with passively fitted corresponding reference frameworks. Ten impressions were made and poured, using each of the 3 techniques on each of the 3 definitive casts. To record the vertical gap between reference frameworks and analogs in duplicate casts, a light microscope with image processing was used. Data were analyzed by two-way analysis of variance and the Tukey test.RESULTSThe open tray techniques showed significantly smaller vertical gaps compare to closed tray technique (P < .05). The closed tray and the resin-splinted open tray technique showed significantly different vertical gaps according to the angulation of implant (P < .05), but the A-F impression technique did not (P > .05).CONCLUSIONThe accuracy of the A-F impression technique was superior to that of conventional techniques, and was not affected by the angulation of the implants.
for the red, green, and blue (RGB) colors but incorporates white light sources, which can be further converted to RGB emission using color filters (CFs). Recent commercialized televisions and computer monitors generally use down-converted displays (DCDs), in which color conversion phosphor films and CFs are laid atop the blue BLU to change its emission to the desired color. Semiconductor nano particles (NPs) such as cadmium (Cd) quantum dots (QDs) and indium phosphide (InP) QDs with narrow spectral bandwidth, high luminous efficiency, and easy tunable wavelength have been recently introduced as more suitable materials for display application than the yttrium aluminum garnet (YAG) phosphors that are widely used at present. QDs have good color purity, but users demand still higher color purity displays that can represent realistic colors. [1-7] Metal-halide perovskites (shortly, perovskite) have simple crystal structures of ABX 3 or A 2 BX 4 (where A is an organic ammonium (e.g., methylammonium (MA; CH 3 NH 3 +) and formamidinium (FA; CH(NH 2) 2 +)) or an alkali metal cation (e.g., Cs +), B is a transition metal cation (e.g., Pb 2+), and X is a halide anion (I − , Br − , and Cl −) [8] (Figure 1a). Perovskite emitters have higher color purity (color gamut ≥ 140% in National Television Standards Committee (NTSC) TV color standard and ≥95% in International Telecommunication Union (ITU) Recommendation Rec. 2020 standard) than inorganic QDs emitters (full width at half maximum (FWHM) ≈ 30 nm; color gamut ≈ 110-115% in NTSC standard and <90% in Rec. 2020 standard). However, perovskite have low exciton binding energy (≈30-50 meV in MAPbI 3 and ≈76 meV in MAPbBr 3), so most of electron-hole pairs are dissociated into free charge carriers, reducing radiative recombination and photoluminescence quantum yield (PLQY) at room temperature. Perovskite nanoparticles (PeNPs) are highly bright [8] and have unique optical and physical properties such as facile emission wavelength tunability, narrow FWHM, and high PLQY (≥95%) compared to inorganic QDs and organic emitters (Figure 1b) [8] and high absorption coefficient compared to inorganic QDs. Therefore, many researchers have tried to use them as light emitters. However, perovskite emitters have limitations when applied to DCDs. First, polar organic solvents or water cause structural changes in perovskites and consequent loss of optical properties. Second, environmental factors such as moisture, heat, light, and oxygen degrade perovskite emitters. Methods to overcome the instability of perovskites to moisture, light, and heat in down-converted displays (DCDs), in which films of perovskite emitters are placed on top of the backlight unit and convert its light to a desired color, are reviewed here. First, the photophysical properties of perovskite emitters as light converters in DCDs are discussed. Second, five strategies to improve stability of perovskite emitting materials (PeMs) mostly in a form of perovskite nanoparticles (PeNPs) are summarized: i) encapsulation in inorganics, ii)...
Aluminum-air battery is a chemical cell that provides high theoretical energy density. However, the anodic dissolution rate of aluminum in 4 M NaOH solution is limited by the film formed on aluminum surface. Electrochemical measurements and scanning electron microscope (SEM) images after potentiostatic polarization were used to analyze the surface structure, ionic reactions, and anodic dissolution of aluminum in 4 M NaOH with chloride solution. The anodic dissolution is mainly affected by aluminum oxide layer. Chloride suppresses slightly the anodic dissolution below the breakdown potential. However, above the breakdown potential, chloride breaks down the oxide layer.
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