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Previous studies have reported that the reduced scattering coefficient (μs′) in the vastus lateralis changes during ramp-incremental exercise due to blood volume changes or accumulation of metabolic by-products. We aimed to clarify the influences of deoxygenation and blood volume changes during exercise on μs′ dynamics in subjects with various aerobic capacities. Twenty-three healthy young men participated in this study. All subjects performed a ramp-incremental cycling exercise until exhaustion and were divided into two groups: lower (Low: n = 12; peak pulmonary oxygen uptake per kg of fat-free mass (VO2peak), 54.2 ± 5.3 mL/kg/min) and higher aerobic capacity group (High: n = 11; VO2peak, 69.7 ± 5.2 mL/kg/min) by median of VO2peak. Deoxygenated hemoglobin and myoglobin concentrations (deoxy[Hb + Mb]) and total [Hb + Mb] (total[Hb + Mb]) in the vastus lateralis were monitored during the exercise by three-wavelength (760, 800, and 830 nm) time-resolved NIRS. Similarly, μs′ at each wavelength was continuously monitored. With increasing exercise intensity, deoxy[Hb + Mb] and total[Hb + Mb] significantly increased in both groups, and the average values of the peak amplitudes of deoxy[Hb + Mb] and total[Hb + Mb] during exercise showed a 106.4% increase and a 17.9% increase from the start of the exercise, respectively. Furthermore, the peak amplitude of total[Hb + Mb] was significantly greater in High. Conversely, there were no changes in μs′ at any wavelength during exercise and no differences between two groups, suggesting that the great deoxygenation and blood volume changes during incremental exercise have little effect on μs′ dynamics.

The aim of this study was to compare muscle O2 dynamics during exercise among elderly (n = 10, age: 73 ± 3 years), middle-aged (n = 9, age: 50 ± 6 years), and young (n = 10, age: 25 ± 3 years) adults. The subjects performed ramp bicycle exercise until exhaustion. Muscle O2 saturation (SmO2) and relative changes from rest in oxygenated hemoglobin/myoglobin (∆oxy-Hb/Mb), deoxygenated hemoglobin/myoglobin (∆deoxy-Hb/Mb), and total hemoglobin concentration (∆total-Hb) were monitored continuously at the vastus lateralis muscle by near-infrared spatial resolved spectroscopy. At given absolute workloads, SmO2 and ∆oxy-Hb/Mb were significantly lower in elderly than the other groups, while ∆deoxy-Hb/Mb, ∆total-Hb, and pulmonary O2 uptake (VO2) were similar among the three groups. In contrast, there were no significant differences in muscle O2 dynamics during submaximal exercise between middle-aged and young subjects. Muscle O2 dynamics may be relatively preserved in early stages of aging, although muscle deoxygenation is enhanced in late stages of aging, probably due to reduced convective O2 supply. Moreover, change in SmO2 was significantly positively correlated with peak VO2 in the elderly, while a significant negative relationship was observed in middle-aged and young subjects. In late stages of aging, diminished peak VO2 may be caused by attenuated convective O2 transport, while reduced peak VO2 can be explained by lowered muscle O2 extraction in early stages of aging.

PURPOSE Near-infrared spectroscopy (NIRS), performed with a commonly available noninvasive tissue oxygenation monitoring device, is based on the modified Beer-Lambert law (MBLL). Although NIRS based on MBLL (NIRSMBLL) assumes that the optical path length (PL) is constant, the effects of changes in PL during exercise on muscle oxygenation calculated by MBLL are still incompletely understood. Thus, the purposes of this study were to examine the changes in optical properties during ramp incremental exercise and to compare muscle oxygen dynamics measured by time-resolved NIRS with those calculated based on MBLL. METHODS Twenty-two healthy young men performed ramp incremental cycling exercise until exhaustion. Optical properties (reduced scattering coefficient and PL) and absolute oxygenated, deoxygenated, and total hemoglobin and myoglobin concentrations (oxy[Hb + Mb], deoxy[Hb + Mb], and total[Hb + Mb], respectively) at the vastus lateralis were continuously monitored by a three-wavelength (763, 801, and 836) time-resolved NIRS device. The values of oxy-, deoxy-, and total[Hb + Mb] were then recalculated by assuming constant PL. RESULTS PL at all wavelengths statistically significantly shortened during exercise. In particular, PL at 763 nm was greatly shortened, and the average changes during exercise were a 9.8% ± 3.1% reduction. In addition, significant differences in the kinetics of oxy-, deoxy-, and total[Hb + Mb] between directly measuring PL and assuming constant PL were found. The average changes in measured PL and assuming constant PL-deoxy[Hb + Mb] were increases of 28.8 ± 16.0 μM and increases of 16.4 ± 9.3 μM, respectively. CONCLUSION Assuming constant PL in NIRSMBLL significantly underestimated actual muscle oxy/deoxygenation as compared with measurements obtained by real-time PL determination. The percent degree of the underestimated oxy/deoxygenation was greater than the percent degree of the changes in PL.

Near-infrared time-resolved spectroscopy (NIRTRS) can quantitatively evaluate mean optical path length (MPL). Since an increase in optical absorbers in the NIR region (e.g. an increase in deoxygenated hemoglobin during exercise) would shorten the MPL, the NIRS measurement area may vary depending on physical and physiological characteristics of the measurement region and/or the exercise intensity. The aim of this study was to examine the changes in MPL measured by NIRTRS during ramp cycling exercise between fat layer thickness-matched subjects with different aerobic capacities. Healthy control (CON, n = 8) and endurance-trained males (TR, n = 8) performed ramp cycling exercise until exhaustion. Deoxygenated hemoglobin concentration (Deoxy-Hb), total hemoglobin concentration (Total-Hb) and oxygenated hemoglobin concentration (Oxy-Hb) were evaluated by a three-wavelength NIRTRS system. MPL in each wavelength (MPL760, MPL800 and MPL830) was monitored continuously. With increasing exercise intensity, Total- and Deoxy-Hb significantly increased and Oxy-Hb decreased in both groups. Total- and Oxy-Hb during exercise were significantly higher in TR than CON (P < 0.05, P < 0.01, respectively). Furthermore, Deoxy-Hb also tended to be higher in TR than CON (P = 0.07). In addition, MPL at all wavelengths significantly shortened with an increase in exercise intensity, with no differences between CON and TR. In particular, MPL760 at peak exercise shortened more than 10% compared to the start of exercise in both groups, even though MPL830 decreased only a few per cent. These findings suggest that the NIRS measurement area may be reduced during ramp cycling exercise due to shortened MPL. Additionally, the changes in MPL may be especially greater at 760 nm than at the other wavelengths due to greater changes in Deoxy-Hb during exercise. Furthermore, this study indicates that the measurements of muscle deoxygenation using continuous-wave NIRS can be less accurate since they are significantly affected by changes in the optical path length.

InP-based quantum dots (QDs) have been proposed as an alternative to CdSe-based QDs for both bioimaging and device displays. In this work, we incorporate hydrophilic InP/ZnS QDs into silica nanocapsules. The morphology, number of incorporated QDs, and photoluminescence (PL) properties of the capsules depend on the alkoxide hydrolysis conditions. By selecting a method of QD surface silanization, multiple QDs (typically 3) are incorporated into the nanocapsules (∼40 nm in size) without causing significant deterioration of the initial PL efficiency (up to 36%). Degradation analysis in different buffer solutions indicates that silica nanocapsules have higher stabilities than pristine QDs. The surface of the nanocapsules was modified with carboxyl groups without any change in morphology. Bright PL images with high resolution were obtained after introducing the nanocapsules into rat hippocampal neurons, when compared with commercial Q-trackers (polymer coated CdSe/ZnS QDs).

The cytotoxicity of cadmium-containing quantum dots (QDs) is reportedly caused by released Cd2+ as well as other factors such as ligand, size, and surface modification. The tolerated concentration of QDs therefore deviates from ~ 1 to 1000 nM. However, the concentration of Cd2+ released from QDs has seldom been correctly and systematically measured. We prepared highly emitting silica capsules with incorporated multiple CdSe/ZnS QDs through a sol-gel-derived wet method. The concentration of released Cd2+ in buffer solution was measured as a function of the preparation conditions of the capsules. When the shell thickness of the capsule was 15 nm, the release was effectively suppressed compared with a capsule shell thickness of 10 nm. Heat treatment at 40 °C further suppressed the leakage. When the silicon alkoxide hydrolysis time was increased from 3 to 15 h, and the surface was modified with COOH groups, the leakage reached a minimum of ~ 0.01 ppb for a QD concentration of 10 nM after 15 h of dispersion. This was two orders of magnitude less than polymer-coated analogues with the same surface functional groups. These silica capsules did not show any toxicity to culture cells, whereas the polymer-coated ones showed high toxicity with the same QD concentration. Silica capsules are therefore not only the expected ideal, but show significantly superior performance when correctly prepared for biomedical application with CdSe/ZnS QDs, owing to their strong suppression of Cd2+ leakage into solution.

Animal cells are generally cryopreserved in cryovials in a cell suspension state containing 5%-10% v/v dimethyl sulfoxide (DMSO) used as a cryoprotective agent. However, cryopreservation of cells in an attached state has not been intensively studied, and the effective freezing solution remains unknown. Here we determined the suitable DMSO concentration for the cryopreservation of human hepatoma HepG2 cells attached to glass and polydimethylsiloxane (PDMS) matrices coated with poly-l-lysine. With the use of the glass matrix, the rate of cell adhesion increased with the DMSO concentration up to 30% v/v in the freezing solution. In contrast, the cell-adhesion rate remained constant in the case of the PDMS matrix irrespective of the DMSO concentration between 10% v/v and 30% v/v. The viability of post-thawed cells attached to glass or PDMS matrix was also investigated. The viability was highest at the DMSO concentration of 20% v/v in the freezing solution. The DMSO concentration of 30% v/v, however, had a cytotoxic effect on the cell viability. Thus, the 20% v/v DMSO concentration was found to be most suitable for the cryopreservation of HepG2 cells in the attached state. This dose is high compared to the DMSO concentration used for the cryopreservation of cells in the suspended state.

The incorporation of emitting quantum dots (QDs) into silica and their sustained photostability have been the subject of research over the last two decades. This report focuses on the synthesis of luminescent silica beads by directly coating silica on the hydrophobic CdSe-based QDs by exchanging the original ligand (oleic acid) through partially hydrolyzed tetra-alkoxysilane, using a surface silanization approach. It was found that the ratio of QD/alkoxide upon silanization must be optimized to get uniform coating of silica. The thickness of silica layer was controlled judiciously by a subsequent reverse micelle method. The photostability of silica beads in water thus prepared was evaluated systematically by a newly developed, and facile method using high irradiation intensity (ca. 45 W/cm2). When the thickness of the silica layer attained a value of 5 nm, the photostability of QDs improved drastically, probably due to a change in the glass structure. We have found that the addition of small amount of water increased the degree of surface silanization, resulting in ca. 46 % enhancement of the photoluminescence (PL) degradation time of QDs. We also discuss the advantages of this direct coating method with tetra-alkoxysilanes in comparison with other organo-alkoxysilanes as primers.

Fat layer thickness (FLT) affects near infrared spectroscopy (NIRS) measurement. The aim of this study was to determine an indicator of muscle function with less influence of FLT, even without normalization, by comparing muscle O2 dynamics during exercise in subjects with similar physical characteristics except for FLT. Healthy male subjects with thick FLT (n = 5, FLT: 5.3 ± 0.4 mm) and those with thin FLT (n = 6, FLT: 3.5 ± 0.5 mm) participated in this study. All subjects performed constant work cycling exercise (CWE) at moderate intensity for 6 min. Oxygenated hemoglobin concentration, deoxygenated hemoglobin concentration and total hemoglobin concentration were monitored by using time resolved NIRS (NIRTRS). VO2peak was not significantly different between THICK and THIN (THICK: 54.0 ± 1.8, THIN: 50.0 ± 6.2 mL/kg/min). Changes in all NIRTRS variables at the onset of CWE were significantly larger in THIN than THICK, and the changes in each variable were significantly correlated to FLT. In contrast, there were no relationships between changes in NIRTRS variables during CWE and FLT. These results suggest that muscle deoxygenation at the onset of exercise, which is used as muscle O2 extraction, can be strongly influenced by FLT. In contrast, muscle oxygenation during CWE, which is used as exercise-induced functional hyperemia, may not be influenced by FLT.

The aim of this study was to compare the muscle oxygen dynamics between early post-myocardial infarction (n = 12; MI) and age-matched elderly subjects without MI (n = 12; CON) in several leg muscles during ramp cycling exercise. Muscle oxygen saturation (SmO2), deoxygenated-hemoglobin concentration (∆deoxy-Hb), and total-hemoglobin concentration (∆total-Hb) were monitored continuously at the distal site of vastus lateralis (VLd), proximal site of the vastus lateralis (VLp), rectus femoris (RF), vastus medialis (VM), gastrocnemius medialis (GM), and tibialis anterior (TA) muscles by near infrared spatial resolved spectroscopy. At given absolute workloads, higher SmO2 was observed at VLd, VLp, RF, and VM in MI, compared to CON. Simultaneously, in MI, deoxy-Hb was lower at VLd, VLp, and VM than CON. In contrast to the thigh muscles, muscle oxygen dynamics were similar between groups in GM and TA. In total-Hb, no significant differences were found at any measurement sites. These results demonstrated that the absence of muscle deoxygenation was observed in MI muscles, especially in the thigh muscles, but not in the lower leg muscles.

Muscle unloading causes muscle function deterioration, but the extent to which training frequency or volume can be reduced while preserving muscle function during muscle unloading is unknown. We examined the effects of low-volume muscle endurance and strength training on forearm muscle oxidative capacity, endurance, and strength during a 3-week immobilization. Twenty-seven, healthy, male volunteers were divided into four groups: immobilization only (IMM); immobilization with endurance and strength training, once-weekly (IMM + EST1) or twice-weekly (IMM + EST2); and control, without immobilization or training (CNT). Endurance training involved dynamic handgrip exercise, at 30 % of maximal voluntary contraction (MVC), until exhaustion (~60 s). Strength training involved intermittent isometric handgrip exercise at 70 % MVC (40 s). Muscle oxidative capacity was evaluated after exercise using the phosphocreatine recovery time constant using 31phosphorus magnetic resonance spectroscopy. Endurance performance was evaluated according to the total work during dynamic handgrip exercise at 30 % MVC at 1 Hz until exhaustion. Muscle oxidative capacity and total work deterioration was restricted to the IMM (P

Near-infrared-emitting quantum dots (QDs) were fabricated via organic synthesis strategies through constructing CdTe/CdSe/ZnSe/ZnS multishell heterostructure. An effective shell-coating route was developed for multishell growth on CdTe cores. Core/shell growth was monitored by absorption and photoluminescence (PL) spectroscopy and transmission electron microscopy observation. Yellow emitting CdTe cores were coated with a CdSe shell to generate type II structure. This yields core/shell QDs with red photoluminescence. The passivation by the ZnSe shell having a substantially wide bandgap confines the excitons within the CdTe/CdSe interface and isolates them from the solution environment and consequently improves the stability of the heterostructure. An additional ZnS shell was deposited around the outer layer of CdTe/CdSe/ZnSe QDs to form a heterostructure through the reaction between zinc oleate and trioctylphosphine sulfur in the crude CdTe/CdSe/ZnSe solution. By varying CdTe core size and each shell thickness, the PL wavelength of the obtained heterostructure can span from 580 to 770 nm. The PL efficiency is quenched in CdTe QDs in diluted solution but increases substantially up to 24% for CdTe/CdSe core/shell QDs. The PL efficiency of CdTe/CdSe/ZnSe/ZnS QDs with average diameter of 5.4 nm and a PL peak wavelength of 770 nm is 20%.

Suppression of energy-wasting nonradiative carrier relaxation in photoactivated semiconductor quantum dots (QDs) is an essential requirement for applications such as QD-sensitized solar cell (QDSSC). Here we report that in situ surface passivation of CdSe/ZnS QDs using dithiothreitol (DTT) results in the 4-fold enhancement of photoluminescence (PL) quantum efficiency of QDs. By the analyses of PL intensities and blinking statistics of single QDs, the PL enhancement is assigned to a combination of processes such as unexpected appearance of bright QDs, gradual increase in the PL intensity of QDs, and substantial suppression of blinking. These processes not only suggest the suppression of nonradiative carrier recombination in QDs passivated with DTT molecules but also enable us to classify the nonradiative carrier recombination centers in QDs into low-density defects in which the rates of nonradiative recombination largely exceed the rates of radiative relaxation and high-density defects in which the rates o...

Nanomaterials with well-defined size, shape, composition, and surface functionalities offer multimodal and multifunctional platforms for various bioanalytical, bioimaging, and therapeutic applications. In this review, we focus on the different theranostic formulations of nanomaterials based on gold, silver, silica, semiconductor quantum dots, upconversion lanthanides, oxide magnets, polymers, liposomes, carbon nanotubes, graphene and carbon nanohorns, and their applications in photothermal and photodynamic therapy of cancer.

We find the spontaneous binding of single DNA molecules to uncoated silver nanoparticles (AgNPs) in aqueous solution with Mn(2+) (3 mM). From dark-field optical microscopic imaging of AgNPs bound to DNA molecules, we demonstrate analysis of the Brownian motion of single DNA molecules via plasmon resonance elastic light scattering. Our results provide that the plasmonic imaging technique is free from photobleaching and blinking and thus is useful in long-time observations of single-molecule DNA dynamics.

A two-step approach including the assembly of QDs and subsequent Stober synthesis has been developed to encapsulate hydrophobic CdSe/Cd(x)Zn(1-x)S core/shell QDs into SiO2 beads. TEM observation shows that the core/shell QDs have high concentration in the SiO2 bead. The fabrication mechanism was proposed for these SiO2 bead. First, partially hydrolyzed tetraethyl orthosilicate (TEOS) replaces the initial ligands of the QDs and assembles the QDs into seeds by condensation reaction. 3-mercaptopropyltrimethoxysilane (MPS) was applied to control the assembly process and inhibit a heavy aggregation. Second, the mixed silane TEOS/carboxyethylsilanetriol sodium (CES) was used for Stober process. The carboxyl group of CES can react with the sulfhydryl of the MPS facilitating the deposition of the SiC2 on the QDs seeds. Sonication was required for the formation of well-dispersed and well-coated SiO2 beads. The combined application of MPS and CES, the decent silane concentration, and the sonication during the Stober process were crucial for the synthesis of SiO2 beads with high concentrated QDs.

The water sorption and drying behavior of crosslinked dextran gels was investigated in relation to the dependency on the density of the crosslinks. Sorption isotherms indicate that the amount of sorption was more for the gels with a lower crosslink density. Almost all the isotherms show sorption and desorption hysteresis, the extent of this hysteresis being more marked with the gels with lower crosslink density. The rate of drying was also dependent on the crosslink density. These results can be explained by considering that the polymer network in a gel with a low crosslink density is more flexible to easy change during water sorption and drying than in one with a higher crosslink density.

CdTe nanocrystals (NCs) were fabricated through an organic synthesis. The growth and properties of CdTe NCs depended strongly on the preparation conditions. In a reaction system of octadecene and tetradecylphosphonic acid (TDPA), the growth was slow. CdTe NCs with cubic-like morphology were created in trioctylamine (TOA) using octadecylphosphonic acid (ODPA)-CdO or TDPA-CdO as precursors. The TOA and ODPA system gives rise to NCs with high photoluminescence (PL) efficiencies (12%). A CdxZn1-xS shell coating on the CdTe core, gave rise to tunable dark red PL (630–670 nm). The morphology and PL properties of the CdTe cores were drastically affected by shell coating and this determined the properties of CdTe/CdxZn1-xS NCs. Small CdTe NCs were easily coated with CdxZn1-xS shells. The resulting core/shell NCs revealed a spherical morphology. However, shell growth became slow when large CdTe cores were used. This is ascribed to the cores with a cubic-like morphology. CdS interlayer plays an important role for the formation of the CdTe/CdxZn1-xS NCs because the experimental result indicated it is difficult to coat CdTe NCs with a ZnS shell. The core/shell NCs benefited from a CdxZn1-xS composite shell because CdTe/CdS NCs created via a similar procedure revealed a low PL efficiency. Copyright © 2012 John Wiley & Sons, Ltd.

We demonstrate an organic synthesis to fabricate hydrophobic core/shell CdSe/Cd1−x Zn x S quantum dots (QDs) with tunable photoluminescence (PL) between green and red at relatively low temperature using trioctylphosphine S reacted directly with cadmium and zinc acetate. A seeded growth strategy was used for preparing large CdSe cores. Large CdSe cores revealed a rod-like morphology while small one exhibited a spherical shape. Being coated with a Cd1−x Zn x S shell on spherical CdSe cores with an average size of 3.9 nm in diameter, core/shell QDs exhibited a cubic morphology (a length of 5 nm). In contrast, the core/shell QDs created using a small core (3.3 nm in diameter) show a spherical morphology. Namely, the anisotropic aggregation behavior of CdS monomers on CdSe cores occurs when the rod-like core is coated with a Cd1−x Zn x S shell. CdS interlayer plays an important role for such morphology evolution because all CdSe cores with a pure ZnS shell exhibited a spherical morphology. The PL properties of CdSe/Cd1−x Zn x S core/shell QDs depended strongly on the size and morphology of the cores. The QDs revealed a narrow and tunable PL spectrum. It is believed that this facile strategy can be extended to synthesize other core–shell QDs at low temperature.

Hydrophobic oleic acid-capped CdSe/Cd x Zn 1− x S core/shell quantum dots (QDs) with high photoluminescence (PL) efficiency of 62% and a PL peak wavelength of 602 nm were assembled in SiO 2 particles through a novel silanization technique. Ligand exchange (3-mercaptopropyltrimethoxysilane (MPS) instead of oleic acid) occurred via the connection of mercapto groups and QDs when MPS was added in the toluene solution of the QDs. After being silanized using MPS, partially hydrolyzed tetraethyl orthosilicate (TEOS) was attached to the surface of the silanized QDs. The hydrophobic CdSe/Cd x Zn 1− x S QDs were then transferred from toluene phase to water phase by the hydrolysis of TEOS through the addition of ethanol, ammonia, and water. Further hydrolysis and condensation of the TEOS and MPS causes them to form assemblies in the water phase. MPS is crucial for proper assembly of the QDs in SiO 2 particles and for controlling the size of resulting SiO 2 particles. The resulting SiO 2 particles exhibited tunable diameters from several tens to 100 nm. After being encapsulated in SiO 2 particles, the QDs revealed a PL efficiency of 25%. Because of the resulting SiO 2 particles encapsulating multiple hydrophobic CdSe/Cd x Zn 1− x S QDs and having a functional surface (mercapto group), they are applicable to bio-probes.

A method has been developed to incorporate multiple hydrophobic CdSe/CdxZn1−xS QDs into SiO2 beads by a two-step microemulsion process and retain the high photoluminescence (PL) efficiencies of the QDs. In step 1, the QDs were silanized by using partially hydrolyzed tetraethyl orthosilicate (TEOS) via replacing oleic acid (OA) on the surface of QDs. In step 2, these silanized QDs were transferred into aqueous phase in the reverse micelle solution by adding a small amount of water and stirring for a few hours. Then these silanized QDs assembled and subsequently encapsulated in a SiO2 shell by a reverse micelle synthesis. The initial silanization plays an important role for the QDs to be coated within a homogeneous SiO2 shell and retain a high PL efficiency in water. Single QDs were coated into silica beads by this two-step microemulsion process without water addition before ammonia and TEOS addition and pre-stirring for a certain time. The number of QDs incorporated into the silica beads can be controlled by adjusting the stirring time. More QDs can be incorporated into silica spheres by partially hydrolyzed 3-mercaptopropyl trimethoxysiliane (MPS) or 3-aminopropyltrimethoxysilane (APS) functionalization at step 1. An improvement in the PL efficiency (up to 35%) of silica spheres was obtained after APS functionalization of QDs. The silica coating shows a bit blueshift for the PL peak wavelength of the QDs. The full width at half maximum (FWHM) of PL spectra was decreased 4 nm after silica coating of the QDs.

要 旨：健常成人女性8名を対象に，随意最大筋力の30%強度，運動頻度1 Hzで疲労困憊に至るまで継続する掌握運動を1日1セット，週に5回，6週間のトレーニングを実施した。そのトレーニング前後に，漸増負荷掌握運動時における尺側前腕屈筋群の筋酸素消費量を近赤外連続光分光法を用いて評価した。その結果，最高筋酸素消費量はトレーニング前後で有意差は認められなかったが，最大運動強度はトレーニング後で有意に増加した。

Highly luminescent CdSe/Cd x Zn 1 − x S core/shell quantum dots (QDs) have been fabricated by a facile environmentally friendly organic route. The spherical cores and core/shell QDs were created by using Cd(AC) 2 ·2H 2 O, Zn(AC) 2 , oleic acid, trioctylphosphine (TOP), Se, S, and trioctylamine. The preparative condition such as reaction time (2–6 min), temperature (from 290 to 310 °C), and feed rate of TOPSe (0.3–2 mL/min) creates various sizes of the cores with photoluminescence (PL) wavelengths between 570 and 618 nm. Spherical CdSe cores were coated with a Cd x Zn 1 − x S shell via a single coating step by using different growth kinetics of CdS and ZnS at 300 °C. The CdSe/Cd x Zn 1 − x S core/shell QDs exhibited a significant red shift of PL peaks (up to 646 nm) from the initial PL of CdSe cores with much improved PL efficiency above 40% when the shell growth. By changing the size of the core and the thickness of the shell, the emission colors of the obtained core/shell QDs can be tuned between green and red.

Photoluminescence properties from water soluble CdSe/ZnS QDs encapsulated with hybrid trioctylphosphine-poly(acrylamide-co-acrylic acid)-ethanolamine (TOPO-PSMA-EA) shell have been investigated. It was found that PL efficiency of CdSe/ZnS QDs in water was increased 5–30% after introducing PSMA-EA polymers to encapsulate CdSe/ZnS-TOPO QDs. Higher PSMA concentrations were found to enhance the PL efficiency of QDs up to 1.8 folds, which is ascribed to a better packing and passivation of the TOPO-PSMA-EA shell over the QDs. Time-resolved photoluminescence suggested that the mean lifetime of photoexcited carriers in the water-soluble CdSe/ZnS-TOPO-PSMA-EA QDs elongated 2–17 ns compared with that of uncoated samples, indicating that PL quenching defects were effectively removed for CdSe/ZnS QDs with hybrid TOPO-PSMA-EA shell.

We demonstrate the formation of one-, two-, and three-dimensional nanocomposites through the self-assembly of silanized CdSe/ZnS quantum dots (QDs) by using a controlled sol–gel process. The self-assembly behavior of the QDs was created when partially hydrolyzed silicon alkoxide monomers replaced hydrophobic ligands on the QDs. We examined systematically self-assembly conditions such as solvent components and QD sizes in order to elucidate the formation mechanism of various QD nanocomposites. The QD nanocomposites were assembled in water phase or on the interface of water and oil phase in emulsions. The partially hydrolyzed silicon alkoxides act as intermolecules to assemble the QDs. The QD nanocomposites with well-defined solid or hollow spherical, fiber-like, sheet-like, and pearl-like morphologies were prepared by adjusting the experimental conditions. The high photoluminescence efficiency of the prepared QD nanocomposites suggests partially hydrolyzed silicon alkoxides reduced the surface deterioration of QDs during self-assembly. These techniques are applicable to other hydrophobic QDs for fabricating complex QD nanocomposites.

Aqueous CdTe and organic CdSe/ZnS quantum dots (QDs) were encapsulated into SiO2beads using various controlled sol-gel processes. Ligand exchange is a key to adjust the QD number in each bead and get a high photoluminescence (PL). Namely, partial ligand exchange from thioglycolic acid to 3-mercaptopropyotrimethoxysilane (MPS) on the CdTe QDs enables retention of the initial PL efficiency of the QDs in water, while the simultaneous addition of a poor solvent (ethanol) resulted in regulated assembly of the QDs through condensation of hydrolyzed MPS. SiO2beads thus prepared had, for example, a diameter of 17 nm and contained 3 QDs each. The PL efficiency of these beads was 30%, while the initial PL efficiency was 38% in a colloidal solution. In addition, a method including surface silanization, phase transfer and self-assembly, and SiO2shell growth has been developed to incorporate multiple hydrophobic CdSe/ZnS QDs into SiO2beads where they are well suited for bio-application due to their high brightness, less-cytotoxic, and non-blinking nature. To investigate the potential use for labeling in bio-applications, SiO2beads with multiple QDs were conjugated with IgG using streptavidin-maleimide as linkers. This preparation method is an important step towards fabricating intensely emitting biocompatible SiO2beads impregnated with semiconductor QDs.

We exploit the synthesis of CdSe core and CdSe/CdxZn1–xS core–shell quantum dots (QDs) with spherical and rod morphologies through a controlled core formation and single coating step by using different growth kinetics of CdS and ZnS. The size and morphology of CdSe cores depended strongly on the injection speed of trioctylphosphine selenium (TOPSe), reaction temperature, and time. The cores with spherical morphology exhibited tunable photoluminescence (PL) wavelength from 544 to 623 nm. CdSe cores with rod morphology and a PL peak wavelength of 623 nm were prepared when TOPSe was injected slowly. The molar ratio of Cd/Zn upon preparation was adjusted for investigating the effect of the CdxZn1–xS shell on the properties of the resulting core–shell QDs. The coated QDs exhibited a controlled red shift from the initial PL of CdSe cores with much improved PL efficiency (a maximum value of 89%). CdSe/CdxZn1–xS core–shell QDs prepared by using those rod cores exhibited a PL peak wavelength of 652 nm and a PL eff...

SiO 2 beads with quantum dots (QDs) including hydrophilic CdTe or hydrophobic CdSe/ZnS were prepared through sol–gel procedures. These beads contained single or multiple QDs by controlling the ligand exchange and the QD assembly during incorporation. Namely, SiO 2 beads with CdTe QDs retained high photoluminescence (PL) efficiencies up to 40% when thioglycolic acid was partially replaced by 3-mercaptopropyltrimethoxysilane. Multiple CdSe/ZnS QDs were assembled into a SiO 2 bead (∼7 QDs in each bead) through surface silanization using tetraethyl orthosilicate instead of organic ammine. The stability of CdTe QDs and luminescent SiO 2 beads was investigated by measuring the degradation of PL intensity against the concentration of phosphate-buffered saline (PBS) buffer solutions. The Stern–Volmer quenching constant K sv of QDs depended strongly on the properties of the QDs and the thickness and porous type of SiO 2 shell. Red- and green-emitting CdTe QDs exhibited K sv of 2.02 × 10 −2 and 8.93 × 10 −2 mM −1 , respectively. The II-type pores (cylindrical pores) in the SiO 2 shell resulted in quick degradation while the IV-type pores (ink-bottle-shaped pores) led the QDs a high stability. Because both two kinds of QDs in SiO 2 beads revealed high PL efficiency and stability in buffer solution, these luminescent beads should be utilizable for bioapplications.

Lipophilic quantum dots (QDs, CdSe/ZnS) were encapsulated into size-controlled SiO2 beads by reflux. Slow silanization of QDs by adjusting the amount of tri-n-octylphosphine oxide (TOPO) and tetraethyl orthosilicate (TEOS) in toluene solution is the key to maintaining the initial photoluminescence efficiency. The silanized QDs formed assemblies when transferred into the aqueous phase by a condensation reaction. Beads were created after further deposition of SiO2 monomers on the assemblies. The speed of the transfer into the aqueous phase was controlled by adjusting the amount of TOPO on the surface of the QDs. Reflux was used to accelerate this transfer speed so as to prevent linear-type assemblies and degradation of the photoluminescence properties. Under optimal preparation conditions, SiO2 beads containing multiple QDs (20 ± 2.5 per bead) were formed with a narrow size distribution (44 ± 4 nm in diameter). Their photoluminescence efficiency was 29%, whereas the initial value in toluene was 30%. This me...

Highly luminescent SiO2 beads with concentrated CdTe quantum-dots (QDs) stabilized by thioglycolic acid (TGA) have been prepared by using a two-step synthesis including coating the surface of the QDs with SiO2 and subjecting them to a subsequent inverse micelle process. Two types of bead structures were formed together with a solid structure, depending on the preparation procedures and conditions. The first contains a composite consisting of Cd2+, TGA, SiO2, and QDs (with egg-yolk structure). This composite was created when highly alkaline water (pH ≥10) was added to the solution of surface-coated QDs before a sol–gel reaction occurred in the water droplets though the migration of the content inside the droplets before they solidified. The second contains a void inside of them (hollow structure). This void was formed when highly alkaline water was added after the water droplets had formed. The beads thus prepared demonstrated high photoluminescence efficiency (70%, almost same as the initial colloidal solution) that was maintained for more than a week in water. The lifetime measurement indicates the reduction of non-radiative rate and increment of radiation lifetime of QDs by the SiO2 coating. The mean concentration of QDs in typical beads was about 0.002 M, where ca. 140 QDs were dispersed in all SiO2 beads 60 nm in diameter.

Judicious selection of the amount of surfactant during synthesis enables a drastic increase in the photoluminescence efficiency of aqueous CdTe nanocrystals (NCs) stabilized by thioglycolic acid (TGA). Elemental determination of the NCs was undertaken to identify the origin of this effect. The molar ratio of (Te + S) to Cd approached unity when the optimum amount of TGA was used during synthesis, whereas the number of S atoms originating from TGA molecules in one NC (2.6 nm of diameter) remained unchanged at 90 ± 3. This indicates that the core lattice composition at the beginning of synthesis, rather than the surface conditions, affects the photoluminescence efficiency of the NCs even after prolonged refluxing.

ZnSe-based nanocrystals (ca. 4-5 nm in diameter) emitting in blue region (ca. 445 nm) were incorporated in spherical small silica particles (20–40 nm in diameter) by a reverse micelle method. During the preparation, alkaline solution was used to deposit the hydrolyzed alkoxide on the surface of nanocrystals. It was crucially important for this solution to includeZn2+ions and surfactant molecules (thioglycolic acid) to preserve the spectral properties of the final silica particles. This is because these substances in the solution prevent the surface of nanocrystals from deterioration by dissolution during processing. The resultant silica particles have an emission efficiency of 16% with maintaining the photoluminescent spectral width and peak wavelength of the initial colloidal solution.

CdSe quantum dots (QDs) are potential fluorescent reagents, but leakage of Cd and Se often induces cytotoxicity. Here we prepared CdSe-based QDs with glass to reduce their leakage and examined their cytotoxicity using keratinocyte cells. The cytotoxicity of the QDs with glass was obviously lower than that of the commercial QDs with polymer, suggesting their safety for biological applications.

CdTe nanocrystals (NCs, green- and red-emitting) prepared by an aqueous method were embedded into transparent glass films (15-20 microm thick) using a sol-gel method. Photodegradation of the NCs in the films due to UV irradiation (365 nm) was investigated quantitatively by measuring the PL efficiency as a function of the irradiation time for various irradiation intensities at several temperatures. Since CdTe NCs prepared by an aqueous method incorporate sulfur atoms from the surfactant (thioglycolic acid) during prolonged reflux in an alkaline region, the surface of red-emitting NCs (3.9 nm phi) is much more sulfur rich than that of green-emitting ones (2.6 nm phi), as previously reported. Due to this composition difference, the degradation behaviors of the two types of NCs differ significantly. The photodegradation of green-emitting glass films depended linearly on the irradiation intensity, whereas that of red-emitting ones showed a quadratic dependence. The activation energies of the photodegradation for both types of films were similar, 304 +/- 9 and 288 +/- 7 meV/particle, respectively. The NCs in the film were more than 2 orders of magnitude more robust than those in colloidal solutions. Comparison of the degradation of the glass films in air and in an Ar atmosphere revealed that the main mechanism of the photodegradation of the green-emitting NCs was oxidization from the first electronically excited state. The mechanism of the red-emitting NCs was not oxidization but a surface change probably related to a surfactant reaction.

This paper describes the formation of cuprous oxide (Cu2O) particles ∼10 nm in diameter and their reduction by hydrogen gas in porous glasses. Nanoparticles of Cu2O coated with metallic copper are expected to show high third-order optical nonlinear susceptibilities (χ(3)). The porous glass is a medium in which nanoparticles can be partially reduced without forming agglomerations. Images obtained using transmission electron microscopy showed that particles with the desired core-shell structure were actually formed, even though some particles were not reduced uniformly from the surface. The χ(3)/α (α: absorbance) values in relevant conditions (10−13 esu·cm) were similar to that of copper because of the formation of a byproduct of copper nanoparticles on reduction.

Water-dispersible ZnSe nanocrystals (2–3 nm in diameter) producing photoluminescence (PL) in a blue region were prepared using several thiol-stabilizers. Thioglycerol (TG) gives the most intense PL having a shoulder at 387 nm and a maximum at 475 nm. The former was assigned to the excitonic emission, whereas the latter was assigned to a defect emission. Reflux increases the PL intensity, but did not change its peak wavelength significantly. TG plays an essential role in stabilizing the ZnSe colloidal solution, but it also creates defect emission. Therefore, the less the amount of surfactant, the more the PL intensity becomes in a range where the solution is not precipitated. The attachment and removal of TG on the surface of nanocrystals only occur at refluxing temperature (100 °C). On the other hand, removal of hydroxyl ions from the surface occurs at room temperature when pH is reduced. The ζ-potential and PL intensity are correlated strongly with the pH of the colloidal solution. This indicates hydroxyl ions passivate the surface significantly. Under optimized conditions of TG ratio and reflux time, the ZnSe nanocrystals in water produced whitish-blue emissions with an efficiency of 10% relative to rhodamine 6G. The nanocrystals in water are stable for months in a refrigerator.

We describe a facile sol–gel process using a silane coupling agent to encapsulate photoluminescent CdTe nanocrystals. An amino-containing matrix and CdTe NCs stabilized by thioglycolic acid were found to be the best combination to prepare the glass because of the interaction between amino and carboxyl groups. The process of synthesis was optimized to prevent nanocrystals from agglomerating. The optical absorption and luminescent spectra of CdTe nanocrystals remained unchanged after being embedded into the glass matrix. Multi-color nanocrystals embedded in glass had the photoluminescence efficiencies up to 41%, which were similar to those of starting nanocrystals in solution. The nanoparticles embedded in glass had excellent stability over time and with heat treatment.

The mechanism of room temperature persistent spectral hole burning was investigated using Eu-doped sodium borate glass (35Na2O–65B2O3). The concentrations dependence of defect centers on the extent of hole burning was investigated for several Eu concentrations because the mechanism proposed so far are of two types: electron transfer to Eu3+ from Eu2+ and from defect centers in the glass. When the defect concentration increased due to X-ray irradiation, a high-temperature hole burning was observed at a Eu concentration (0.3 mol %) ; where the phenomenon is not observed in a normal sample without X-ray irradiation. When the Eu concentration was very low (0.1 mol %) , a spectral hole was observed only at low temperatures even when the concentration of defect centers became saturated due to X-ray irradiation. Furthermore, a concentration quenching of fluorescence from Eu3+ became obvious at Eu concentrations of more than ca. 1 mol % . Hole burning became obvious at the same concentration. These findings indicate that the mechanism is an energy transfer from selectively excited Eu3+ to adjacent Eu2+ and subsequent electron transfer from Eu2+ to Eu3+. Defect centers in the glass reduce the barrier height of this electron transfer.

The forearm muscles of five healthy males were monitored for changes in microvessel hemoglobin saturation (SO2-TRS) by near infrared time-resolved spectroscopy (NIRTRS) and changes in phosphorus metabolites by magnetic resonance spectroscopy (31P-MRS) during 12 min of resting arterial occlusion. Muscle oxygenation and phosphorus metabolites were also measured during grip exercises at varying intensities. Upon the initiation of occlusion, SO2-TRS fell progressively until it reached a plateau in the latter half of the occlusion. Phosphocreatine (PCr) began to decrease around 6 min after the initiation of arterial occlusion. The resting O2 store and O2 consumption were 295 μM and 0.95 μM/sec, respectively-values which reasonably agree with the reported results. A significant correlation was observed between the changes in SO2-TRS and PCr during exercise (r2 = 0.80, p < 0.001). These results indicate that NIRTRS is able to provide reliable information about resting metabolism and oxidative rate during exercise. NIRTRS and MRS are useful to monitor oxygenation and energetics noninvasively in the human muscle.

CdTe nanocrystals (3–6 nm) prepared by an aqueous method have been embedded in glass matrices through the sol–gel method by using two coupling agents, mercaptopropyl silane (MPS) and aminopropyl silane (APS). The nanocrystals are stabilized by thioglycolic acid (TGA). In the case of MPS, the nanocrystals are dispersed homogeneously because of a thiol group both in TGA and the CdTe surface. However, it takes a month to get a condensed polymer-like sample at room temperature. In contrast, an amino group in APS accelerates the sol–gel reaction drastically. Further, the amino group reacts quickly with a carboxyl group in TGA. This reaction prevents the CdTe from agglomeration. Consequently, stable luminescent glass with good transparency has been prepared in three days. The quantum efficiency of photoluminescence of the glass is ∼5%. The neutral-pH region during synthesis degrades the photoluminescence.

The purpose of this study was to quantitatively examine the changes in muscle oxygen consumption (VO2mus) after food intake as measured by near-infrared continuous wave spectroscopy (NIRcws). Six healthy male subjects were given a meal with a calculated total energy content of 10 kcal/kg body. VO2mus was measured from 15 min to 150 min after they finished eating. VO2mus in the finger flexor muscles was estimated by the rate of deoxygenation during arterial occlusion using NIRcws. The absolute value of VO2mus was calculated using each subject's resting metabolic rate measured by 31Phosphorus-magnetic resonance spectroscopy (31P-MRS). Deep tissue temperature (TD) was also monitored in the forearm same area. The control experiment followed the same protocol but without meal. There was a significant increase in VO2mus: pre-meal value was 1.47 ± 0.17 μM O2/s, post-meal peak value (post 120 min) was 2.31 ± 0.38 μM O2/s (p < .05 vs. pre). In contrast, the control experiment did not show any increase. There was n...

Photochemical hole-burning in sodium-borate glass (35Na 2 O–65B 2 O 3 ) was investigated as a function of doped Eu-ion concentration from 0.1 to 5 mol% both at room temperature and 12 K. In our preparation, 50–70% of Eu 3+ was reduced to Eu 2+ . As the concentration of Eu ion exceeded 1 mol%, the fluorescence was quenched, and meanwhile the photochemical hole started burning. The spectral hole was most efficiently burnt at concentrations between 2 and 3 mol% at room temperature. Low temperature experiment showed that there are three kinds of processes for the hole formation. One is a transient process relaxed within 1–2 min. Another is observed only at low temperatures. The third one is observed persistently even at room temperature. The extent of these components depends on Eu-ion concentration. In view of these concentration dependences, the suggested mechanism of room temperature hole-burning is an energy or electron transfer between Eu 3+ and Eu 2+ . Defect centers created by reduction process of the glass may play a role to help this transfer.

ZnSe nanocrystals are prepared in water by a wet chemistry method. By selecting an appropriate pH value and surface-capping agents, a whitish blue fluorescence peaking at 470 nm is observed under ZV irradiation. The intensity of this fluorescence increases dramatically under reflux and saturates after ~ 40 hrs. The final mean size of the ZnSe nanocrystals measured by transmission electron microscopy is aboyt 2 nm in diameter. The quantum efficiency of the fluorescence form the final solution is estimated to be ~1%, although the preparation conditions have not yet been completely optimized. These properties are discussed in comparison with those of similarly prepared CdTe and differently prepared ZnSe nanocrystals.

Photoluminescence (PL), thermostimulated luminescence (TSL) and X-ray induced luminescence (XIL) studies of BaFBr:Eu, BaFBrI:Eu (Fuji) and BaFBr (undoped) reveal that in these phosphors: (i) oxygen impurity and self-trapped exciton (STE) emissions occur at about 480 and 300 nm, respectively; (ii) TSL peaks below RT display O 2− F emission whereas the TSL peak above RT displays 380–400 nm Eu 2+ emission; (iii) in the XIL spectra of oxygen rich BaFBr:Eu, the Eu 2+ emission builds-up with increasing temperature above 100 K at the expense of 300 nm STE emission which indicates an energy transfer from STE to Eu 2+ ; (iv) in BaFBr:Eu 2+ with excess oxygen content, PSL is quenched; (v) in Fuji BaFBrI:Eu 2+ which has a very low oxygen content and high PSL efficiency as revealed in its PL, PSL and TSL spectra, only Eu 2+ emission is seen in the XIL spectra between 100 and 300 K which indicates an efficient energy transfer from STE to Eu 2+ ; and (vi) the presence of STE emission in BaFBr (undoped) and 400 nm Eu 2+ emission in Fuji IP along with O 2− F emission in their low temperature TSL spectra is a proof of the trapping of excitons near the O 2− F sites during X-irradiation and their release during thermostimulaton. Possible implications of these results on the PSL process in BaFBr:Eu are discussed.

A new method for controlling the photoluminescence (PL) wavelength of silica-coated quantum dots (QDs) without changing the sizes of the core QDs is reported. When silica-coated green-emitting CdTe QDs were refluxed in aqueous solution containing Cd 2+ and a sulfur-containing surfactant (thioglycolic acid (TGA)), the PL peak wavelength shifted to red with a significant increase in PL efficiency. This spectral shift was attributed to the reduction of the quantum confinement effect by the formation of small CdS-like clusters very close to the QDs in the silica shells. When the silica-coated QDs were refluxed in a solution of higher pH, the extent of this red shift increased. The larger red shift of the PL with pH is attributed to the hydrolysis speed of TGA increasing with pH. There is faster generation of S 2− and as a consequence the growth rate of CdS-like clusters is enhanced. When a different sulfur-containing surfactant (thioglycerol (TG)) was used for reflux, the PL spectral shift and enhancement of PL efficiency became very small. This was because TG did not hydrolyze significantly enough to release S 2− . These results demonstrate that the reported reflux procedure is a promising method for tuning the PL color of QDs through selection of the solution pH and the surfactant during reflux.

The purpose of this study was to investigate the change in vitamin E level in both serum and red blood cells (RBC) during exercise and to clarify the effect of vitamin E supplementation. Ten young sedentary female subjects received 200 mg D-alpha-tocopherol acetate daily for 1 wk after the initial exercise bout. After 1 wk of vitamin E supplementation, the same subjects repeated the same exercise. Before vitamin E supplementation, the alpha-tocopherol level in the serum (serum-alpha-tocopherol) did not change after exercise, but a significant decrease in the alpha-tocopherol level in RBC (RBC-alpha-tocopherol) was observed after exercise (p0.05). On the other hand, after vitamin E supplementation, the serum-alpha-tocopherol level decreased significantly after exercise (p0.05), while the RBC-alpha-tocopherol level was maintained after exercise. Furthermore, a negative correlation between the changes in serum- and RBC-alpha-tocopherol levels was observed only after vitamin E supplementation (r = 0.667, p0.05). The present results suggest that as RBC suffers oxidative stress, vitamin E in RBC is consumed to protect RBC from oxidative damage during exercise. These results also suggest that when there is a sufficient amount of vitamin E in the serum, vitamin E is shifted from the serum to RBC, resulting in a steady RBC-alpha-tocopherol level and a decrease in the serum-alpha-tocopherol level under oxidative stress such as exercise.

Fluorescence properties have been studied for Mn:ZnS crystallites with average diameter of 4 nm prepared by an aqueous colloidal method under 266 nm light excitation. The intensity ratio of the blue band at ∼430 nm to the orange band at ∼590 nm has decreased after the preparation on a time scale of hours in aqueous solution. On the other hand, hyperfine structures of Mn2+ in the electron paramagnetic resonance spectrum have increased markedly on the same time scale in solution samples. These phenomena are attributed to the redistribution of defect centers in nanocrystals. Such phenomena have not been observed in samples incorporated into poly(vinyl alcohol). The orange emission is mainly due to the 6A1 ← 4T1 transition of Mn2+, while the blue emission is tentatively assigned to the donor−acceptor pair transition in which the acceptor is related to the Zn2+ vacancy. Fluorescence decay times of the blue and orange bands have been found to be ∼10 ns and ∼1 ms, respectively, the latter being the same as in th...

A sol-gel method has been used to prepare particle-dispersed glasses containing superfine (less than 30 nm in diameter) particles of cuprous oxide Cu2O. The X- ray diffraction spectrum of the bulk material and the absorption spectra of thin (less than 1 μm thick) films show that partial reduction induced by an exposure to H2 produces core-shell-structured (Cu2O core and Cu shell) superfine- particle-dispersed glasses. Those glasses are stable in a dry atmosphere.