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We present a hidden Markov model analysis for fluorescent time series of quantum dots. A fundamental quantity to measure optical performance of the quantum dots is a distribution function for the light-emission duration. So far, to estimate it, a threshold value for the fluorescent intensity was introduced, and the light-emission state was evaluated as a state above the threshold. With this definition, the light-emission duration was estimated, and its distribution function was derived as a blinking plot. Due to the noise in the fluorescent data, however, this treatment generates a large number of artificially short-lived emission states, thus leading to an erroneous blinking plot. In the present paper, we propose a hidden Markov model to eliminate these artifacts. The hidden Markov model introduces a hidden variable specifying the light-emission and quenching states behind the observed fluorescence. We found that it is possible to avoid the above artifacts by identifying the state from the hidden-variable time series. We found that, from the analysis of experimental and theoretical benchmark data, the accuracy of our hidden Markov model is beyond human cognitive ability., Comment: 16pages, 11figures, 4tables

We report the results of our investigation of agarose gel electrophoresis and hybridization of mercaptopropionic-acid-capped quantum dots (MPA-capped QDs) conjugated with short single-stranded DNA, as part of a study of closely spaced linear QD chains. The electrophoresis results suggest that migration speed and separation resolution depend on the amount of MPA on the QD surface. The QDs separated by electrophoresis according to DNA valence, i.e., the amount of DNA per particle, were used as building blocks for the synthesis of linear QD oligomers.

We report our recent trials examining the single-molecule three-dimensional (3D) detection of protein conformational dynamics at room temperature. Using molecular chaperones as model proteins and cadmium selenide (CdSe) semiconductor quantum dots (QDs) as nanometer-scale probes, we monitored the temporal evolution of ATP-induced conformation changes with a total internal reflection fluorescence (TIRF) microscopy imaging technique in buffer solutions. The two-dimensional (2D) degenerate nature of the emission dipoles of the QDs, due to the uniaxial wurtzite crystal structure, made it possible to capture the 3D orientation using a polarization modulation technique in real time. The temporal resolution was half the period of analyzer rotation. Although still insufficient, the obtained signals suggest possible 3D detection of specific motions, which supports the two-step conformational changes triggered by ATP attachment., 18th International Conference on Dynamical Processes in Excited States of Solids (DPC2013), August 4-9，2013, Fuzhou, China

In this paper, we describe the synthesis and characterization of quantum dot (QD) chains. We used small QD-DNA conjugates, i.e., short-ligand-capped QDs conjugated with short (15-mers) single-stranded DNA, as the building blocks. The small conjugates were separated based on the valence of the DNA, i.e., the amount of DNA per particle, using agarose gel electrophoresis. The conjugates formed self-assemblies composed of closely spaced (inter-particle spacing of 0.6–2 nm) QDs. We report the results of our investigation of the electrophoresis and hybridization of the conjugation.

The results of room-temperature fluorescence lifetime measurements are reported for the excitation of J aggregates (Js) of pseudoisocyanine chloride (PIC-Cl) prepared in potassium polyvinyl sulfate (PVS) polymer thin films, their aqueous solutions, and NaCl aqueous solutions. Variations of the microscopic morphologies of the aggregates were investigated. The results show that fluorescence decay features correlated to the morphology change. The observed fluorescence lifetime and quantum efficiency of PIC J aggregates (PIC-Js) in a NaCl aqueous solution were 310 ps and 28%, respectively. The lifetime of the fibril-shaped macroaggregates prepared in PVS thin films was below the instrumental time resolution of 5 ps, and the efficiency decreased to below 3%. The results indicate that PIC-Js prepared with PVS polymers have an increased nonradiative contribution to the excitation deactivation process. In particular, macro-Js with isolated fibril-shaped structures revealed nonradiative pathway(s) that are closely associated to the specific packaging morphology of the constituent meso-Js. The possibility of a destructive effect on the formation of cavity-polaritons is also discussed.

Versatile novel implementations in microspectroscopy are developed, which can provide angle-resolved optical spectroscopy at local sample areas almost in diffraction limit. By selecting focus position of light flux incident within the back focal plane of the objective lens radially from the position of the optical axis of the microscope with employing off-centered pinhole, we can obtain parallel beam with oblique incidence and its angle tuning at the sample surface. In this paper, we describe our specific optical setup and its practical working principle in detail. We report, as a demonstration of its performance, our latest studies on optical properties of cavity polariton states in the so-called quantum microcavity structures, which contain molecular J-aggregates of pseudoisocyanine (PIC) dye as active working materials. By using the microscope technique, we obtain a fair amount of improvement in the linewidth observation of cavity polariton spectra.

We report single molecule spectroscopic evidence of FRET in CdSe quantum dot (QD) conjugated with Cy5-labeled molecular chaperone systems in buffer solutions. Donor QDs are core-shell type nanocrystals covered with organic surfactants on their outermost surfaces, i.e. CdSe/ZnS/TOPO’s. As prototype molecular chaperones, we adopt prefoldins (PFDs), on which Cy5’s are labeled as acceptors. Donor QDs possess two-fold degenerate emission dipoles perpendicular to the c-axis, due to their Wurtzite crystal structures, while acceptor Cy5’s possess linear absorption and emission dipoles. Thus, their combination provides novel features to those in conventional FRET systems. PFDs are jellyfish-shaped hexameric co-chaperones of group II chaperonins, which recognize hydrophobic portions of denatured proteins and encapsulate them within their central cavities. Hence, PFDs will also capture the CdSe/ZnS/TOPO QDs due to its surface similarity to the denatured proteins. By introducing simple microscope setup for single QD-PFD-Cy5 spectroscopy, we have successfully captured the emission spectra in FRET regime. We also have observed peculiar features in time evolution profiles of single QD emissions conjugated with Cy5-labeled PFDs under polarization modulation measurements. Notable point of our hybrid conjugates is that they are biochemically in living action. We describe our present results in relation to possible protein reactions.

擬イソシアニン(PIC)分子による J 会合体を分散させたポリマー薄膜を活性層とする平行平板型微小共振器を作製し，J 会合体の励起子と共振器光子の強結合状態としての「共振器ポラリトン」を形成した．独自に工夫した光学系を用いて反射および発光スペクトルの角度依存性を計測し，偏光依存性，共振器ミラー依存性，活性層の J 会合体濃度依存性などとあわせ，室温でも安定で明瞭なポラリトン状態の生成を確認し，その特徴を精査した．加えて，顕微計測を応用した局所角度分解分光法を考案し，その動作を確認するとともに，J 会合体の高濃度極限の一形態とも考えられる「フィブリル構造」J 会合体のポラリトン状態の検証に向けて，その手法の適用を開始した．室温で安定な共振器ポラリトンの形成は，無機半導体の量子微小共振器では十分に達成し得ていない優れた特徴であり，J 会合体の有機半導体光ナノ材料としての優位性を示す好例である．無機半導体 QW による共振器ポラリトンとの比較の上で，その実体と将来性についても議論する．

We have investigated reflection properties of light-matter strong coupling in a planar metal-mirror microcavity with highly concentrated PIC J-aggregates. Large vacuum Rabi-splitting ranging from 100 to 250 meV is obtained depending on the concentration of the J-aggregates. The factors for providing these large Rabi-splitting will be discussed based on its concentration dependence. We also present our recent study focused on microscopic reflection properties of the microcavity. We have improved microscope optics which enables us to measure local reflection spectra within 0.3- μ m-diameter area. Observation of incident-light-angle dependence becomes possible. We found existence of micrometer-scale inhomogeneity in the Rabi-splitting (e.g. ± 10 % in a 17 μ m × 17 μ m region), which will be interpreted mainly by the spatial distribution of J’s in the active layer.

Resonant energy transfer in hybrid CdSe quantum dot (QD) conjugated with Cy5-labelled molecular chaperone systems is observed with single molecule imaging technique. Photonic QDs are the core-shell type nanocrystals covered with organic surfactants on the outermost surfaces, i.e. CdSe/ZnS/TOPO's, and prefoldin (PFD) is used as prototype molecular chaperons. PFD is a jellyfish-shaped hexameric co-chaperone of group II chaperonins, which recognize hydrophobic portion of denatured proteins and encapsulate them within its central cavity. So the CdSe/ZnS/TOPO QDs can also be captured be cause of its surface similarity to the denatured proteins. We have found one possible reaction pathway to get such artificial complex in aqueous solutions with keeping bioactivities of the proteins. Performance of the complex is evaluated by TIRF imaging microscopy. As the proteins are transparent in visible wavelength region, labeling dyes, Cy5, which also work as acceptors, are connected to detect their behaviors microscopically. Forster type energy transfer is observed from the QD donors to Cy5-labeled PFD acceptors in single molecule level, which can be a distinct evidence for the complex formation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present a study of strong exciton-photon coupling and its dependence on incident light polarization in a metal-metal mirror microcavity containing PIC J-aggregates. Rabi-splitting energies between upper and lower polariton branches are estimated as 94 meV and 69 meV for s- and p-polarized incident light, respectively. These large values are due to large oscillator strength of Frenkel excitons in the PIC J-aggregates and strong confinement of light attributed to the metallic microcavity as well. As for the effective thickness of the active layer for s-polarized light, a good agreement is obtained between Lfiteff = 201 nm deduced from the experimental data and Lcalceff = 207 nm calculated from the summation of the measured thickness of active layer with the estimated penetration depths into silver mirrors. We also discuss the difference in the polarization dependences of Rabi-splitting energy, quantitatively. It is concluded that the polarization dependence is mainly due to an alignment of the J-aggregates in the active layer and is not affected so much by anisotropy of the penetration depths into the silver mirrors. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We describe our improved synthesis and optical properties of high quality type II CdTe/CdSe nanocrystals (NCs). Specifically, clear shell-thickness dependences have been observed in the absorption and photoluminescence (PL) spectra and PL decay profiles as well. The magnitude of the lowest absorption band decreases drastically with large redshift as the shell thickness increases. The origin will be discussed on the bases of the model where the spatial configuration of the lowest electron-hole pair in the NCs changes from that of type I to type II as the shell thickness increases. As for the PL lifetime of the lowest electron-hole excitations, substantial increase is observed with increasing shell thickness. This can also be understood by considering the spatial configuration; spatial overlap between electron and hole wavefunctions decreases with increasing shell thickness, thus the lifetime increases. As for the NCs with extremely thin shell (∼1 ML; 1 ML = 0.35 nm), the PL lifetime seems much longer than expected. This suggests that the thin shells seem imperfect and work rather a kind of trap sites than layers. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present our recent study of microscopic single-molecule imaging on the artificial complex of tetramethylrhodamine linked with a propyl chain onto silica glass surface, i.e. an asymmetric fluorescence resonance energy transfer (FRET) structure with non-radiative acceptor. In the synthesis of the complex, we used a mixture of two kinds of isomers to introduce rather small photodynamic difference among them. This isomeric structure change will provide more or less a distinctive photophysical change in e.g. non-radiative relaxation rate. Our recent observation at room temperatures, so far, shows that such contributions can be discriminated in the histograms of the fluorescent spot intensities; broad but distinctive multi-components appear. To identify the isomeric difference as a cause of structures, some configurational assumptions are necessary. One such basic prerequisite is that the transition dipoles of the chromophores should be oriented almost parallel to the glass surface. In order to make clear the modeling, we also provide preliminary experiments on the polarization dependence of the imaging under rotating polarization in epi-illumination.

We report here the distinctive modifications of photoluminescence (PL) behaviors in single CdSe/ZnS/TOPO nanocrystals depending on their environments. Long-time traces of PL intensity from single nanocrystals have been obtained in both vacuum and a wet nitrogen atmosphere. While all of the nanocrystals in both environments exhibit PL blinking behaviors, i.e. on–off intermittency of PL intensity, as usual, some of the nanocrystals in the wet nitrogen atmosphere show significant increase in duration time of on-events. As for the duration time of blinking off-events, it is for the moment associated with the occasional events of carrier capturing at trap sites on or near the nanocrystal surfaces. We propose a model in which adsorbed water molecules at the trap sites on the nanocrystal surfaces transform them under light irradiation, which eventually decreases the occurrence of the trapping events due to their inactivation. It in turn increases the PL on-times. In addition to the drastic modification of the blinking profile, we also found that in the PL time traces some kinds of undulated behaviors, i.e. continuous and rather low frequency fluctuation of PL intensity, appear during each on-event in vacuum while they disappear totally in the wet nitrogen atmosphere. These results are also described on the basis of the inactivation model of the trap sites introduced above.

Feasibilities to stabilize CdSe/ZnS/trioctylphosphineoxide (TOPO) nanocrystals (quantum dots, QDs) in aqueous solutions with prefoldin macromolecules in their bioactive states are reported. Prefoldin is a jellyfish-shaped hexameric co-chaperone of the group II chaperonins. As a protein folding intermediate is captured within its central cavity, so CdSe/ZnS/TOPO QDs would also be included within this cavity. It is also found the QDs can be much more dispersed in aqueous solutions and suspended for certain period of time by adding trace amount of t-butanol in the buffer prior to the mixing of the QDs mother solution. While biochemical procedures are evaluated with ordinary fluorescence measurements, possible complex formations are also evaluated with TIRFM single-molecule detection techniques.

We have investigated photobrightening effects of photoluminescence (PL) from CdSe/ZnS/TOPO nanocrystals (NCs) in ambient nitrogen gas saturated with water molecules (H 2 O/N 2 ). The PL intensities from NC ensemble samples increase more than twice after 1200-s irradiation of cw light. These increases mostly recover to their previous values under continuous light irradiation when we evacuate the H 2 O/N 2 atmosphere. These results indicate that the adsorption of H 2 O molecules onto NC surfaces provides some functions as to restore almost reversibly the PL-quenching defects or trap sites on or near the NC surfaces. To elucidate the mechanism of this restoring function microscopically, we have also measured time evolution of PL intensity profiles from single NCs both in H 2 O/N 2 and in vacuum. While blinking behaviors of the PL intensity being observed in both environments, we have found significant increase of PL on-times in case of single NC observations in the H 2 O/N 2 compared with those in vacuum. As for the blinking off-times, it is for the moment associated with the occasional events of carrier captures at the trap sites on or near the NC surfaces. Thus, we propose the photo-adsorption of H 2 O molecules inactivates these trap sites and decreases the occurrence of the capturing events, which in turn increase PL on-times and eventually provide the photobrightenings.

We present our recent study of single fluorescent molecules with specific structure, i.e. tetramethylrhodamine derivative linked with a propyl chain onto silica glass surface. For fluorescent reagent in its synthesis, we used a mixture of two kinds of isomers, which provides a sample with single molecules photophysically different each other even if chemically the same. The isomeric structural difference so introduced in the molecules will provide rather small but probably distinctive photophysical difference, for example, in non-radiative relaxation rates, which we try to detect out with our improved single-molecule microscope imaging technique. To make clear the detectability of such weak inter- or intra-molecular interactions microscopically is significant for versatile applications of single-molecule detections in life science. Our present observation at room temperatures shows so far that such decoupled contributions can be discriminated in the histograms of the intensities of the observed fluorescent spots as broader but separated multi-component structures in the distribution under specific experimental configurations. We will discuss some of the prerequisite for such detections; suitable spatio-temporal resolutions with sufficient S/N ratio, algorithms for data analysis, etc. but also precise sample operations are inevitable.

We have investigated photoluminescence (PL) properties of CdSe/ZnS/TOPO nanocrystals (NCs) in various kinds of gases at one atmospheric pressure. Increase of PL intensity with spectral shift is observed under 488 nm cw light irradiation in all cases. Especially, the PL intensity increases more than twice after 1200 s irradiation in nitrogen gases saturated with vapor of polar molecules, such as H2O and NH3. The increased PL intensity with the spectral shift mostly recovers to its previous values when the sample is evacuated under continuous light irradiation. These results indicate that photo-adsorption of the polar molecules onto NC surfaces provides some reversible restoring functions to the PL quenching defects or trap sites on or near the surfaces. The existence of the trap sites on NC surfaces is already widely introduced for describing e.g., blinking phenomena. Assuming part of these traps being charged, we propose the photo-induced effects can be understood as charge-compensated inactivation of the trap sites due to the adsorption of the polar molecules consistently.

Results on microscopic fluorescence imaging and spectroscopy of fibril-shaped J-aggregates of pseudoisocyanine dyes prepared in thin film matrices of polyvinyl sulfate (PVS) are reported compared with simultaneous observation of the reflection micro-spectroscopy. While the shape of the local reflectance spectra show huge broadening and sometimes dip structures at higher local reflectance levels, we have found that local fluorescence spectra are rather simple and narrow single peak appears at 572 nm or bit longer which is almost coincide with that of ordinary J-band. The result is not inconsistent with the exciton–polariton onset scheme, based on which initial reflectance properties are interpreted. Anomalous local polarization dependences are also observed in fluorescent transition dipoles as in the local reflectance observation, indicating the anomaly is inherent to the fibril formation.

To optimize far-field detection optics as well as to extend fundamental skills related to molecular manipulation, samples for single molecule fluorescence detection are fabricated by chemically immobilizing rhodamine-6G derivative molecules on a silica glass surface. While the dye molecules are bleached out within several 10s to 100s of seconds in air as usual, the sample as well as far-field detection system works efficiently. The histogram of the integrated counts of the individual fluorescent spots in the observed images indicates that most of the spots observed involve single chromophores for each spot. The histogram also indicates that there exist two kinds of distinctive molecular sites in the immobilized samples, whereas only single site is detected in the rhodamine-6G spin-coated samples. We consider so far that the existence of the two sites may correspond to the local molecular configurations caused by the mixture of two types of isomers in the cross-linked chromophores. Observation of blinking profiles is also described.

有機分子の配位結合によって結晶表面を封止したCdSeナノ結晶の合成法, および, ナノ結晶表面におけるZnS積層膜作製法の最適化を行い, 吸収・発光測定と高分解電子顕微鏡撮影 (HRTEM) より試料の評価を行った. その先鋭な吸収・発光バンドは, サイズ分散の狭さと結晶性の良さを示しており, HRTEM像からもこの事実が確認できる. また, 最適化により, 常に発光量子効率が室温で50%を超えるナノ結晶の作製が可能となった. この試料を用いて, 自作走査型レーザー顕微鏡で単一ナノ結晶の発光強度時間変化を観測したところ, 突然の激しい発光強度の乱高下や, 光照射に伴う発光明滅周期の増加などを示すこれまでの報告にないナノ結晶が多数観測された. その原因を究明するため, メゾスコッピックな系といえる1000個程度のナノ結晶の集団からの積分発光強度を測定し, その光照射効果を測定したところ, 通常のナノ結晶とは逆の光照射に伴う発光強度の増大が確認され, その増大はナノ結晶周辺の気体雰囲気の種類に依存することが明らかになった. 以上の単一とメゾスコピック系におけるナノ結晶の異常な発光の振舞いは, 気体分子の光吸着がナノ結晶表面の無輻射緩和中心に対して封止効果をもたらすことに起因すると考えられる.

Results on microscopic reflection imaging and spectroscopy of fibril-shaped J-aggregates of pseudoisocyanyne dyes prepared in thin film matrices of polyvinyle alcohol (PVA) are reported. We have found that formation of fibril-shaped structures with sub-micron widths is also possible in PVA. Despite the aggregation mechanism should be different from those in polyvinyl sulfate, reflection images and local spectroscopy show that the exciton–polariton characters are basically similar in the two matrices. Anomalous polarization dependence is also observed in PVA and seems rather strengthened.

We report our recent observations on anomalous reflection properties of organic microcavity containing PIC J-aggregates in fibril-shaped structures as one of their highest-density limiting case. Even in ordinary low density PIC-Js dispersed in polymer matrices, they easily go into the exciton-photon strong coupling regime and new quantum states, i.e. exciton-polaritons, are formed. Vacuum Rabi-splitting, an indicator of the coupling strength, can be controlled by the density of PIC-Js in the microcavities in low density regime. Fibril-shaped PIC-J aggregates are bundle-like, self-assembled higher-order structure of Js and are considered as a high-density limiting case. Angular dependence of the local reflection spectra are observed by our improved microscopy. While in the low density cases, clear anti-crossing behaviours of the two branches appear, which is the evidence of the polariton formations, the highest-density limiting cases show one or two anomalous reflection dip structures with almost no angular dependence. The result is inconsistent with neither ordinary polariton reflection property nor bare exciton nor cavity photon properties. We tentatively consider that the anomaly is inherent to the fibril formation and is caused by possible breakdown of polariton coherence due to the inter-fiber energy transfer. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report a recent study on photoluminescence (PL) properties of CdSe/ZnS/TOPO nanocrystals (NCs) in a planar full microcavity composed of top and bottom two metal (Ag) mirrors, and also in a similar structure but without top mirror, i.e. half-microcavity, respectively. Angular-dependencies of PL spectra and PL decay curves have been measured to investigate PL modifications due to light-matter coupling in the microcavities. Obtained results indicate that PL dynamics are drastically changed depending on the microcavity structures. In the full-microcavity, PL emission is directed at particular angles and its decay-time is shortened, both of which can be described in terms of so-called Purcell effect, i.e. the interaction between photon-modes and confined excitons in the NCs. As for the half-microcavity, anomalous PL band appears at low energy side of a main PL band associated with the confined excitons. The origin of the anomalous PL will be interpreted as due to the interaction between specific photon-modes in the half-microcavity structure and excitons associated with surface states. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

係結については多くの研究がなされているが,違例,破格とされる例の全体像は明らかではない。しかし,係結の本質に迫るためにも,係結の違例の詳細な調査,整理が必要である。本稿は,係結の違例のうち,一つの結びに二つ(以上の)係助詞が係る現象(「二重の係り」と呼ぶ)についてとりあげ,(1)用例は極めて少ないがそれでも中古和文中に異文のない例(またはそれに準ずるもの)も存在すること,(2)「二重の係り」となるのは「-ぞーぞー連体形」「-なむーなむー連体形」「-こそーこそー已然形」のように同じ係助詞どうしに限られること,(3)「二重の係り」の句型は三つのタイプに限られること,などを指摘する。

Fibril-shaped J-aggregates of pseudoisocyanine dyes are prepared in thin-film matrices of polyvinyl sulfate and their microscopic fluorescence and reflectance imaging are investigated at room temperatures. Improved experiment, both in sample preparations and in microscope optics, allows us to resolve the higher-energy bands in the spectrum and to determine the directions of local absorption and fluorescence transition dipoles more precisely. Based on the anisotropies of the local transition dipoles, we have assigned the 540 nm middle band to be the upper exciton, Davidov split, transition and the higher 495 nm to its vibronic sub-band, while the J-band at 572 nm to be the lower Frenkel exciton transition. Assuming linear chain directions of individual J's to be parallel in average to the long axis of the fibril, the result also implies that a zigzag-type molecular conformation is most suitable for the model of PIC-J aggregates.

本稿は,従来実態が調査されていない「係結の流れ」について正面から取り上げ,「成立しない係結び」という裏側から係結についての考察を試みたものである。源氏物語の「係結びの流れ」の調査から,次の諸点が指摘される。(1)流れは「なむ」が最も多い,(2)接続句内の流れは「こそ」は逆接で「なむ」は順接で流れることが多い,(3)「なむ」は流れた後で再度「なむ」の係結によって結ばれる文が多いのに対し,「ぞ」は一文中に一度しか使われないことが多い。これらの実態は,各係助詞の特徴を色濃く反映していると考えられ,この点から,「ぞ」は卓立,「こそ」は対比的強調,「なむ」は文全体の基調に関係するという傾向が指摘される。

In the Japanese language, a noun is usually followed by a particle in a sentence. And the particle marks the case. As for the classical Japanese, it is known that a noun is often used without having a particle when the noun is interpreted as either the nominative or the accusative. (I call this type of noun "the noun phrase without a particl" in this paper.) In The Tale of Genji, however, noun phrases without a particle are found which are interpreted as neither the nominative nor the accusative. This paper deals with the various usages of the noun phrases without a particle found in The Tale of Genji and shows that they are classified into the following three types : I, the ones which are taken as the nominative, the accusative, the dative, and other cases, ii. The ones which can function as the conjunctive, and iii. The ones indicating the theme of the sentence.

Photobrightening and photobluing effects of photoluminescence (PL) from CdSe/ZnS/TOPO nanocrystal ensembles, i.e. ca. 1000 nanocrystals, have been investigated in several environments. The PL intensity increases more than twice with blue shift under continuous light irradiation in a wet nitrogen (H(2)O/N(2)) atmosphere, while in a pure nitrogen atmosphere and vacuum their behaviors are nothing particular. In addition, increasing rates of both the brightening and bluing effects in the H(2)O/N(2) atmosphere depend on irradiation intensities. These results suggest that both effects should be associated with photo-adsorption of water molecules onto nanocrystal surfaces. As for the brightening effect, we propose that the photo-adsorption of water molecules provides some restoring functions to PL-quenching defects or trap-sites on or near nanocrystal surfaces. On the other hand, the origin of the bluing effect is not clear from the results of the ensemble measurements. To get further insight into the bluing effect, PL spectra from single nanocrystals are measured under continuous light irradiation in cyclic environments in which the H(2)O/N(2) atmosphere and vacuum are alternating. As a result, blue-shifted PL induced by the light irradiation in the H(2)O/N(2) atmosphere recovers almost to its initial one reversibly under evacuation. The mechanism of the photobluing effect will be discussed also on the bases of the photobrightening model introduced above.

A magneto-optical (MO) microscope that uses the polarization modulation method has been developed for quantitative MO imaging. In this technique, images of MO rotation and ellipticity are reconstructed from three images for different polarization states; i.e., linear, right-circular, and left-circular polarization states. The three polarization states are generated either by rotating a quarter-wave plate or by changing the voltage applied to a liquid crystal modulator (LCM). Measurements are performed using a patterned thin film of Bi,Ga-substituted yttrium iron garnet prepared on a glass substrate. The values of MO rotation and ellipticity obtained from the images for several wavelengths between 450 and 650 nm are found to agree quantitatively with those obtained by an MO spectrometer. Hysteresis loops at any point of the image can be displayed by simply placing a pointer at the position. A real-time MO imaging with a rate of 1 frame/s is also achieved by using the LCM and a high-speed charge-coupled device camera.

We present our recent study of polarization modulating fluorescence imaging microscopy on single CdSe colloidal quantum dots (QDs) and quantum rods (QRs) adsorbed on silica glass substrates at room temperatures. Simple optical setup is introduced to provide detection of emission profiles projected on to the sample plane as well as detection of rotating excitation polarization effect. While most studies so far in structural changes in biological or amorphous systems rely on extrinsic fluorophores with linear transition dipoles, those with twofold degenerate dipoles are noteworthy due to the intrinsic advantage for 3D orientation information. Performance of modulations is also evaluated in combination with tetramethylrodamine moieties as typical linear emitters. CdSe QDs with aspect ratio of 1.3 actually reveal plane-polarized emission at room temperature and, based on maximum-likelihood analysis, are exceptionally highly oriented on silica glass substrates.