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Quantum diamond magnetometers using lock-in detection have successfully detected weak bio-magnetic fields from neurons, a live mammalian muscle, and a live mouse heart. This opens up the possibility of quantum diamond magnetometers visualizing microscopic distributions of the bio-magnetic fields. Here, we demonstrate a lock-in-based wide-field quantum diamond microscopy, achieving a mean volume-normalized per pixel sensitivity of 43.9 $\mathrm{nTμm^{1.5}/Hz^{0.5}}$. We optimize the sensitivity by implementing a double resonance with hyperfine driving and magnetic field alignment along the $$ orientation of the diamond. Additionally, we show that sub-ms temporal resolution ($\sim$ 0.4 ms) can be achieved while keeping the per-pixel sensitivity at a few tens of nanotesla per second using quantum diamond microscopy. This lock-in-based diamond quantum microscopy could be a step forward in mapping functional activity in neuronal networks in micrometer spatial resolution.

Precise measurement of the size and size distribution of colloidal nanoparticles are an important component of evaluating nanoparticle safety. However, size measurements become increasingly difficult to perform as particle size decreases. The sizes and size distributions of nanoparticles can be determined using a variety of techniques. In this study, we used an electrospray scanning mobility particle sizer (ES-SMPS) to investigate the effect of nanoparticle concentration on the size and size distribution measurements of 20 nm and 50 nm silica nanoparticles. To calculate the size of the water droplets in the electrospray, the droplet size distribution in sucrose solutions was determined at various sucrose concentrations. The average water droplet diameter was ~ 697.5 nm, regardless of sucrose concentration. Based on these results, we estimated the appropriate nanoparticle concentration ranges for the ES-SMPS size determination of 20-nm and 50-nm silica nanoparticles. Reliable measurements of the 20- and 50-nm silica nanoparticles could be performed at concentrations of

Size and shape distributions of gold nanorod samples are critical to their physico-chemical properties, especially their longitudinal surface plasmon resonance. This interlaboratory comparison study developed methods for measuring and evaluating size and shape distributions for gold nanorod samples using transmission electron microscopy (TEM) images. The objective was to determine whether two different samples, which had different performance attributes in their application, were different with respect to their size and/or shape descriptor distributions. Touching particles in the captured images were identified using a ruggedness shape descriptor. Nanorods could be distinguished from nanocubes using an elongational shape descriptor. A non-parametric statistical test showed that cumulative distributions of an elongational shape descriptor, that is, the aspect ratio, were statistically different between the two samples for all laboratories. While the scale parameters of size and shape distributions were similar for both samples, the width parameters of size and shape distributions were statistically different. This protocol fulfills an important need for a standardized approach to measure gold nanorod size and shape distributions for applications in which quantitative measurements and comparisons are important. Furthermore, the validated protocol workflow can be automated, thus providing consistent and rapid measurements of nanorod size and shape distributions for researchers, regulatory agencies, and industry.

The primary crystallite size of titania powder relates to its properties in a number of applications. Transmission electron microscopy was used in this interlaboratory comparison (ILC) to measure primary crystallite size and shape distributions for a commercial aggregated titania powder. Data of four size descriptors and two shape descriptors were evaluated across nine laboratories. Data repeatability and reproducibility was evaluated by analysis of variance. One-third of the laboratory pairs had similar size descriptor data, but 83% of the pairs had similar aspect ratio data. Scale descriptor distributions were generally unimodal and were well-described by lognormal reference models. Shape descriptor distributions were multi-modal but data visualization plots demonstrated that the Weibull distribution was preferred to the normal distribution. For the equivalent circular diameter size descriptor, measurement uncertainties of the lognormal distribution scale and width parameters were 9.5% and 22%, respectively. For the aspect ratio shape descriptor, the measurement uncertainties of the Weibull distribution scale and width parameters were 7.0% and 26%, respectively. Both measurement uncertainty estimates and data visualizations should be used to analyze size and shape distributions of particles on the nanoscale.

The size of nanoparticles is considered to influence their toxicity, as smaller-sized nanoparticles should more easily penetrate the cell and exert toxic effects. However, conflicting results and unstandardized methodology have resulted in controversy of these size-dependent effects. Here, we introduce a unique approach to study such size-dependent effects of nanoparticles and present evidence that reliably supports this general assumption along with elucidation of the underlying cytotoxic mechanism.We prepared and physically characterized size-controlled (20-50 nm) monodispersed silica nanoparticles (SNPs) in aqueous suspensions. Then, a variety of biochemical assessments are used for evaluating the cytotoxic mechanisms.SNP treatment in three cell lines decreased cell viability and migration ability, while ROS production increased in dose- and size-dependent manners, with SNPs30 nm showing the greatest effects. 30- and 40-nm SNPs were observed similar to these biological activities of 20- and 50-nm, respectively. Under the conventionally used serum-free conditions, both 20-nm and 50-nm SNPs at the ICOur results highlight the need to revise safety guidelines to account for this demonstrated size-dependent cytotoxicity under serum-free conditions, which may be similar to the microenvironment after tissue penetration.

Despite the rapid expansion of the biomedical applications of graphene oxide (GO), safety issues related to GO, particularly with regard to its effects on vascular endothelial cells (ECs), have been poorly evaluated. To explore possible GO-mediated vasculature cytotoxicity and determine lateral GO size relevance, we constructed four types of GO: micrometer-sized GO (MGO; 1089.9 ± 135.3 nm), submicrometer-sized GO (SGO; 390.2 ± 51.4 nm), nanometer-sized GO (NGO; 65.5 ± 16.3 nm), and graphene quantum dots (GQDs). All types but GQD showed a significant decrease in cellular viability in a dose-dependent manner. Notably, SGO or NGO, but not MGO, potently induced apoptosis while causing no detectable necrosis. Subsequently, SGO or NGO markedly induced autophagy through a process dependent on the c-Jun N-terminal kinase (JNK)-mediated phosphorylation of B-cell lymphoma 2 (Bcl-2), leading to the dissociation of Beclin-1 from the Beclin-1–Bcl-2 complex. Autophagy suppression attenuated the SGO- or NGO-induced apoptotic cell death of ECs, suggesting that SGO- or NGO-induced cytotoxicity is associated with autophagy. Moreover, SGO or NGO significantly induced increased intracellular calcium ion (Ca2+) levels. Intracellular Ca2+ chelation with BAPTA-AM significantly attenuated microtubule-associated protein 1A/1B-light chain 3-II accumulation and JNK phosphorylation, resulting in reduced autophagy. Furthermore, we found that SGO or NGO induced Ca2+ release from the endoplasmic reticulum through the PLC β3/IP3/IP3R signaling axis. These results elucidate the mechanism underlying the size-dependent cytotoxicity of GOs in the vasculature and may facilitate the development of a safer biomedical application of GOs. Statement of Significance Graphene oxide (GO) have received considerable attention with respect to their utilization in biomedical applications. However, GO-related safety issues concerning human vasculature are very limited. In this manuscript, we report for the first time the differential size-related biological effects of GOs on endothelial cells (ECs). Notably, Subnanometer- and nanometersized GOs induce apoptotic death in ECs via autophagy activation. We propose a molecular mechanism for the GO-induced autophagic cell death through the PLCβ3/IP3/Ca2+/JNK signaling axis. Our findings could be provide a better understanding of the GO sizedependent cytotoxicity in vasculature and facilitate the future development of safer biomedical applications of GOs.

The electromechanical properties of ternary InAsP nanowires (NWs) were investigated by applying a uniaxial tensile strain in a transmission electron microscope (TEM). The electromechanical properties in our examined InAsP NWs were governed by the piezoresistive effect. We found that the electronic transport of the InAsP NWs is dominated by space-charge-limited transport, with a I ∞ V2 relation. Upon increasing the tensile strain, the electrical current in the NWs increases linearly, and the piezoresistance gradually decreases nonlinearly. By analyzing the space-charge-limited I–V curves, we show that the electromechanical response is due to a mobility that increases with strain. Finally, we use dynamical measurements to establish an upper limit on the time scale for the electromechanical response.

Background Silica nanoparticles (SiNPs) are widely used for biosensing and diagnostics, and for the targeted delivery of therapeutic agents. Safety concerns about the biomedical and clinical applications of SiNPs have been raised, necessitating analysis of the effects of their intrinsic properties, such as sizes, shapes, and surface physicochemical characteristics, on human health to minimize risk in biomedical applications. In particular, SiNP size-associated toxicological effects, and the underlying molecular mechanisms in the vascular endothelium remain unclear. This study aimed to elucidate the detailed mechanisms underlying the cellular response to exposure to trace amounts of SiNPs and to determine applicable size criteria for biomedical application. Methods To clarify whether these SiNP-mediated cytotoxicity due to induction of apoptosis or necrosis, human ECs were treated with SiNPs of four different non-overlapping sizes under low serum-containing condition, stained with annexin V and propidium iodide (PI), and subjected to flow cytometric analysis (FACS). Two types of cell death mechanisms were assessed in terms of production of reactive oxygen species (ROS), endoplasmic reticulum (ER) stress induction, and autophagy activity. Results Spherical SiNPs had a diameter of 21.8 nm; this was further increased to 31.4, 42.9, and 56.7 nm. Hence, we investigated these effects in human endothelial cells (ECs) treated with these nanoparticles under overlap- or agglomerate-free conditions. The 20-nm SiNPs, but not SiNPs of other sizes, significantly induced apoptosis and necrosis. Surprisingly, the two types of cell death occurred independently and through different mechanisms. Apoptotic cell death resulted from ROS-mediated ER stress. Furthermore, autophagy-mediated necrotic cell death was induced through the PI3K/AKT/eNOS signaling axis. Together, the present results indicate that SiNPs within a diameter of

We present a single-molecule diffusional-mobility-shift assay (smDIMSA) for analyzing the interactions between membrane and water-soluble proteins in the crowded membrane of living cells. We found that ligand-receptor interactions decreased the diffusional mobility of ErbB receptors and β-adrenergic receptors, as determined by single-particle tracking with super-resolution microscopy. The shift in diffusional mobility was sensitive to the size of the water-soluble binders that ranged from a few tens of kilodaltons to several hundred kilodaltons. This technique was used to quantitatively analyze the dissociation constant and the cooperativity of antibody interactions with the epidermal growth factor receptor and its mutants. smDIMSA enables the quantitative investigation of previously undetected ligand-receptor interactions in the intact membrane of living cells on the basis of the diffusivity of single-molecule membrane proteins without ligand labeling.

Local application requires fewer nanoparticles than systemic delivery to achieve effective concentration. In this study, we investigated the potential toxicity and efficacy of bare titanium dioxide (TiO 2 ) nanoparticles by local administration into the eye. Mono-disperse, 20 nm-size TiO 2 nanoparticles did not affect the viability of retinal constituent cells within certain range of concentrations (~ 1.30 μg/mL). Furthermore, local delivery of TiO 2 nanoparticles did not induce any significant toxicity at the level of gene expression and histologic integrity in the retina of C57BL/6 mice. Interestingly, at the low concentration (130 ng/mL) without definite toxicity, these nanoparticles suppressed in vitro angiogenesis processes and in vivo retinal neovascularization in oxygen-induced retinopathy mice when they are administered intravitreally. Taken together, our results demonstrate that even TiO 2 nanoparticles can be safely utilized for the treatment of retinal diseases at the adequate concentration levels, especially through local administration. From the Clinical Editor In this paper the local application of titanium dioxide is described as a local treatment for retinal diseases associated with neovascularization. While these nanoparticles have known systemic toxicity, this work demonstrates that when applied locally in a mouse model, they can be used without observable toxicity even in their native forms.

Gold nanoparticles are known to be distributed to many tissues following their oral, inhalation, or intravenous exposure. Information on the biodistribution and clearance of gold nanoparticles from these tissues is, therefore, important to understand their behavior in vivo. To study the effect of size on the biodistribution of gold nanoparticles, Sprague-Dawley rats were exposed by inhalation to small gold nanoparticles (13 nm in diameter on average) at an exposure concentration of 12.8 ± 2.42 µg/m(3), and to large gold nanoparticles (105 nm in diameter on average) at an exposure concentration of 13.7 ± 1.32 µg/m(3). The experimental animals were exposed to the gold nanoparticles and the control animals to fresh air for 5 days (6 h/day), followed by a recovery period of 1, 3, and 28 days in fresh air. None of the exposed animals exhibited any toxic response to the gold nanoparticles. Despite the difference in size, both small and large gold nanoparticles deposited mainly in rat lungs. Their biodistribution from the lungs to secondary target organs was significantly higher with the small compared to the large gold nanoparticles. While the large gold nanoparticles were only found in the blood, the small gold nanoparticles were detected in the liver, spleen, brain, testes, and blood. In addition, the elimination half-life of the small gold nanoparticles from the lungs was significantly shorter than that of the large gold nanoparticles. The present data may, therefore, suggest that the smaller gold nanoparticles are able to translocate from the lungs, the primary exposure organ to extrapulmonary organs at a faster rate than the larger gold nanoparticles and thus confirming previous observations reported in the literature.

We report a gold substrate manipulation from very-flat to highly-curved surfaces with a thermal treatment as a function of annealing temperature, which greatly affects the quality of SAM with respect to density and ordering. Annealing of gold film greatly removes nanometer-scale protrusions, leading to a very-flat surface with a large grain size as comparable with gold coating on mica. The quality of alkanethiol SAM are evaluated using Fourier transform infrared and time of flight secondary ion mass spectroscopy. Our proposed method delivers good ordering between molecules in the SAMs to promote a high density on extremely small areas for a cost-effective and miniaturized biochip.

Gold nanorod-attached PEGylated graphene-oxide (AuNR-PEG-GO) nanocomposites were tested for a photothermal platform both in vitro and in vivo. Cytotoxicity of AuNR was reduced after encapsulation with PEG-GO along with the removal of cetyltrimethylammonium bromide (CTAB) from AuNR by HCl treatment. Cellular internalization of the CTAB-eliminated AuNR-PEG-GO nanocomposites was examined using dark-field microscopy (DFM), confocal Raman microscopy and transmission electron microscopy (TEM). To determine the photothermal effect of the AuNR-PEG-GO nanocomposites, A431 epidermoid carcinoma cells were irradiated with Xe-lamp light (60 W cm(-2)) for 5 min after treatment with the AuNR-PEG-GO nanocomposites for 24 h. Cell viability significantly decreased by ~40% when the AuNR-PEG-GO-encapsulated nanocomposites were irradiated with light as compared with the cells treated with only the AuNR-PEG-GO nanocomposites without any illumination. In vivo tumor experiments also indicated that HCl-treated AuNR-PEG-GO nanocomposites might efficiently reduce tumor volumes via photothermal processes. Our graphene and AuNR nanocomposites will be useful for an effective photothermal therapy.

To prepare stabilized TiO2 nanoparticles (TiO2 NPs) in aqueous media as a suspension of the primary particles, we attempted to optimize the conditions for dispersing stable, aggregated TiO2 NPs (A-TiO2 NPs) in aqueous HCl/NaOH solutions or 5 mM pH buffered aqueous solutions. The A-TiO2 NPs with a hydrodynamic diameter (or DLS size) of 150 +/- 20 nm could be dispersed at high concentration (63.5 +/- 0.5 mg/ml) in a 5 mM phosphate buffer (PB) solution of pH 8, and a primary TiO2 (P-TiO2) NP suspension (1.2 +/- 0.3 mg/ml) with DLS size of 30 +/- 5 nm could be separated from the highly concentrated A-TiO2 NP suspension by sonication and subsequent centrifugation. It was observed by comparing the UV-Vis absorption spectra of the A-TiO2 and P-TiO2 NP suspensions that the extinction coefficient of the TiO2 NPs in the aqueous suspension depended on the degree of aggregation. The stabilized P-TiO2 NP suspension in aqueous solution can be used to study nanotoxicity as well as to characterize the physicochemical properties of TiO2 NPs.

Gold nanoparticles (AuNPs) and poly(ethylene glycol) (PEG) are known to be safe, biocompatible materials. In this study, AuNPs were conjugated with PEG ligands, and the suspensions of AuNPs with and without free PEG ligands were characterized using UV-visible spectroscopy, hydrodynamic size measurement, and time-of-flight SIMS (ToF-SIMS) imaging analysis. The two AuNPs solutions were each dropped onto a hydrophilic surface (bare Si wafer) and a hydrophobic surface (a plasma-polymerized cyclohexane-coated Si wafer), then dried to produce self-aggregated micropatterns, from which ToF-SIMS images were obtained. From these ToF-SIMS images, we calculated the Pearson product–moment correlation coefficient (PMCC) of the AuNPs and PEG intensities to quantitatively measure the coexistence of both materials in the solution. Good coexistence between AuNPs and PEG ligands was obtained only from the sample film prepared by dropping the suspension of PEG-conjugated AuNPs without free ligands onto a hydrophobic surface. The degrees of coexistence (i.e. PMCC value) seem to correlate with the amount of free PEG ligands in suspension to affect the stability of organic conjugated nanoparticles in solution. In addition, it was found that minimal interaction between the conjugated ligands and the substrate used for the sample film preparation led to an optimum PMCC statistical analysis. Our results lead us to believe that this new approach could simplify the method by which to quantitatively study the degrees of coexistence between nanoparticles and ligands, the amount of free ligands, and the stability of ligand-conjugated nanoparticles in suspension. Copyright © 2012 John Wiley & Sons, Ltd.

A variety of fluorescent nanoparticles have been developed for demanding applications such as optical biosensing and fluorescence imaging in live cells. Silica-based fluorescent nanoparticles offer diverse advantages for biological applications. For example, they can be used as labeling probes due to their low toxicity, high sensitivity, resolution, and stability. In this research, a new class of highly fluorescent, efficient nanoparticles composed of a newly synthesized poly[di(2-methoxy-5-(2-ethylhexyloxy))-2,7-(9,9-dioctyl-9 H -fluorene)] (PDDF) core and a silica shell (designated as PDDF@SiO 2 ) were prepared using a simple reverse micelle method, and their fluorescent properties were evaluated using methods such as single-dot photoluminescence measurements. The enhanced photostability of the particles and their potential applications for bioanalysis are discussed in this article. The morphology, size, and fluorescent properties for prepared PDDF@SiO 2 nanoparticles were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and photoluminescence spectroscopy. The prepared particles size, which was approximately 60 nm, resulted in an excellent colloidal stability in a physiological environment. The photobleaching dynamics, total numbers of emitted photons (TNEP) and statistical measurements of individual nanoparticles were observed using laser scanning fluorescence microscopy to assess the structure and photostability of PDDF@SiO 2 nanoparticles. Additionally, PDDF@SiO 2 nanoparticles were used in cell toxicity and permeation tests for biological analyses, demonstrating a great potential for use as powerful, novel materials within the emerging fields of biosensing and biomedical engineering.

A multiplexed assay technique to measure the photocatalytic activity (PCA) of nanoparticles (NPs) in aqueous suspension was developed based on the observation of TiO(2) NPs-photocatalytic oxidation rate of NADH by monitoring the fluorescence intensities. 96 sample solutions of a small volume (150 μL) could be assayed in a single run without separation of NPs within 15 min. PCA values can be measured with high sensitivity and low experimental uncertainties through the observation at various concentrations of photocatalyst, substrate, aqueous protons and pH buffer ions in a short measurement time.

Dimeric intercellular adhesion molecule-1 (ICAM-1) has been known to more efficiently mediate cell adhesion than monomeric ICAM-1. Here, we found that truncation of the intracellular domain of ICAM-1 significantly enhances surface dimerization based on the two criteria: 1) the binding degree of monomer-specific antibody CA-7 and 2) the ratio of dimer/monomer when a mutation (L42→C42) was introduced in the interface of domain 1. Mutation analysis revealed that the positively charged amino acids, including very membrane-proximal ⁵⁰⁵R, are essential for maintaining the structural transition between the monomer and dimer. Despite a strong dimer presentation, the ICAM-1 mutants lacking an intracellular domain (IC1ΔCTD) or containing R to A substitution in position 505 (⁵⁰⁵R/A) supported a lower degree of cell adhesion than did wild-type ICAM-1. Collectively, these results demonstrate that the native structure of surface ICAM-1 is not a dimer, but is an intermediate monomer-dimer equilibrium structure by which the effectiveness of ICAM-1 can be fully achieved.

Gold nanoparticles (AuNPs) and poly(ethylene glycol) (PEG) are known safe materials to be used in vivo, and so, are becoming increasingly important in biomedical applications. Here, the stability of PEG-conjugated AuNPs in an aqueous solution was monitored as a function of time using several techniques, namely dynamic light scattering (DLS)-size analysis, UV-visible absorption spectrometry and ToF-SIMS. Roughly 15-nm-sized AuNPs were synthesized and pegylated with mPEG (MW = 5 kDa). Four different samples were synthesized, depending on whether or not a dialysis procedure was performed right after synthesis of the AuNPs or pegylation of the AuNPs. The DLS results show that size of mPEG-conjugated AuNPs and standard deviation increased in cases where a dialysis procedure was performed after pegylation of the AuNPs, indicating aggregation of the AuNPs due to the detachment of mPEG ligands from the surface of the AuNPs. Also, results from UV-visible absorption spectra and ToF-SIMS images point to the likelihood that free mPEG ligands in solution help prevent aggregation by maintaining a dynamic equilibrium between the conjugated ligands on the surface of the AuNPs and the free ligands in the aqueous solution. Conversely, once free, mPEG ligands were eliminated from the solution by dialysis and conjugated mPEG ligands detached from the surface of AuNPs into the solution, suspension stability lowered and the AuNPs showed signs of aggregation. We believe that the ToF-SIMS imaging analysis with DLS and UV-visible absorption analyses would be useful to study the stability of PEG-conjugated AuNPs in different environmental conditions.

Various techniques are used to measure the mean particle size (PS) and the particle size distribution (PSD) and relevant uncertainties of the measured mean PS and PSD can be obtained by using statistical treatments. Among those techniques, microscopic analysis methods provide the possibility to observe individual particles, allowing detailed information about the PS. However, there is no existing method to estimate the uncertainty of the PSD from a finite number of data obtained by microscopic measurement. We found that it is possible to adopt the method of deducing the standard deviation of the sample standard deviation to estimate the PSD uncertainty from the result of a microscopic analysis when the sample data follow a normal or log-normal distribution. The recommended minimum number of data for the application of developed statistical methods was deduced by simulation with population data sets of pseudorandom numbers. It was found that the PS of gold nanoparticles (NPs) synthesized by the conventional reduction method in aqueous solution followed a log-normal distribution, indicating that this method is applicable to estimate the PSD uncertainty of synthetic Au NPs from the measured PS data obtained by microscopic methods.

The functionalization of fullerene nanowhiskers was accomplished by non-covalent π–π interaction using pyrenebutanoic acid, succinimidyl ester to immobilize target molecules on the nanowhiskers. Fourier-transform infrared spectroscopy and fluorescence microscopy proved that the fullerene nanowhiskers were functionalized without damaging the nanostructure.

The photodegradation mechanism of recombinant human interferon-alpha2a (IFNalpha2a) has been investigated using absorption, fluorescence, and circular dichroism (CD) spectroscopies, and fluorescence photobleaching kinetics measurements under various conditions. After photobleaching, the absorption profile of aromatic amino acid residues in IFNalpha2a was almost absent, and an absorption profile showing a monotonic increase toward short wavelengths was observed. According to the CD spectrum analysis, partial unfolding of IFNalpha2a was accompanied by a complete loss of fluorescence. This unfolding was attributed to tryptophan-mediated photoinduced disulfide bond cleavage. Photooxygenation and photoionization of tryptophan (Trp) residues followed by subsequent radical reactions were the main photodegradation pathways of IFNalpha2a. Photobleaching kinetics was faster in acidic solution (pH 2.5) than in neutral solution (pH 7.4). The variation of photobleaching kinetics seemed to be caused by the structural differences in IFNalpha2a according to the solution pH. The relationship between the protein conformation and photobleaching rate could be explained based on the competition between excited state energy transfer and the photoionization process in Trp residues.

The energy transfer process upon photoexcitation in binary polymer blends with different donor/acceptor pairs were investigated with the aid of the steady-state and time-resolved photoluminescence methods. The observed differences in the energy transfer effi- ciency are not fully explained by the Forster radius, deduced from the spectral overlap calculation. The order of energy transfer efficiencies for different donor/acceptor pairs does not follow the sequence of Forster radius, particularly for the acceptors having relatively long PL lifetimes. Hence, an alternative simple model is proposed to account for the order of energy transfer efficiency, which is to include the effect of the acceptor PL lifetime, specifically in the presence of excess donor. Such is the case with usual polymer LED devices.

By using the single molecule detection (SMD) technique based on laser scanning fluorescence microscopy, we have developed a method to count the number of labeled fluorophores in a single biomolecul...

Recently published near field scanning optical measurements (NSOM) on the conjugated polymer MEH-PPV exhibited a strong dependence of the photoluminescence intensity on the applied electric fields at the NSOM tip. The observed effect is apparently due to exciton quenching by hole polarons. In the present paper, a model "single carrier" electro-modulated-photoluminescence device is used to further explore the exciton quenching effect of hole polarons in MEH-PPV. Hole polarons, created by charge injection from an ITO electrode, are observed to dramatically quench the photoluminescence intensity of MEH-PPV. The Stern-Volmer quenching efficiency of a hole polaron in conjugated polymer thin films was measured to be 390 nm 3 . This value, and other data presented herein, are consistent with the published NSOM photoluminescence modulation measurements and offer further evidence that hole polarons are efficient photoluminescence quenchers in MEH-PPV.

Divinylenediethylhexyloxyphenyl and either triphenyltriazine (PTPV) or diphenoxyphenyltriazine (POTPV) were alternately connected to inhibit the dimer emission of the divinylenediethylhexyloxyphenyl unit and to enhance the electron mobility of light-emitting polymers. A photoluminescence (PL) spectrum of a PTPV film showed characteristics of excimer emissions, whereas POTPV generated a singlet exciton PL emission. A blend of POTPV with poly(vinyl carbazole) (PVK) enhanced the PL intensity of POTPV upon the photoexcitation of PVK, and this indicated efficient energy transfer between the two polymers. Contrary to expectations based on the good overlap of spectra for the PL emission of the donor and the light absorption of the acceptor, the energy transfer from PVK to PTPV was incomplete upon the photoexcitation of the blend at the ultraviolet-visible absorption maximum of PVK. However, the excimer PL emission of PTPV was completely suppressed. The lifetime ratio of the excitations of the donor and the acceptor was proven to be one of the critical factors in the energy transfer, in addition to the Forster energy-transfer principle. The excimer emission was suppressed by the photoexcitation of the chromophores below a certain critical energy level.

Graphene has recently been attracting increasing attention due to its unique electronic and chemical properties and many potential applications in such fields as semiconductors, energy storage, flexible electronics, biosensors and medical imaging. However, the toxicity of graphene in the case of human exposure has not yet been clarified. Thus, a 5-day repeated inhalation toxicity study of graphene was conducted using a nose-only inhalation system for male Sprague-Dawley rats. A total of three groups (20 rats per group) were compared: (1) control (ambient air), (2) low concentration (0.68 ± 0.14 mg/m3 graphene) and (3) high concentration (3.86 ± 0.94 mg/m3 graphene). The rats were exposed to graphene for 6 h/day for 5 days, followed by recovery for 1, 3, 7 or 28 days. The bioaccumulation and macrophage ingestion of the graphene were evaluated in the rat lungs. The exposure to graphene did not change the body weights or organ weights of the rats after the 5-day exposure and during the recovery period. No statistically significant difference was observed in the levels of lactate dehydrogenase, protein and albumin between the exposed and control groups. However, graphene ingestion by alveolar macrophages was observed in the exposed groups. Therefore, these results suggest that the 5-day repeated exposure to graphene only had a minimal toxic effect at the concentrations and time points used in this study.

Graphene is receiving increased attention due to its potential widespread applications in future. However, the health effects of graphene have not yet been well studied. Therefore, this study examined the pulmonary effects of graphene oxide using male Sprague-Dawley rats and a single 6-hour nose-only inhalation technique. Following the exposure, the rats were allowed to recover for 1 day, 7 days, or 14 days. A total of three groups were compared: control (fresh air), low concentration (0.46±0.06 mg/m3), and high concentration (3.76±0.24 mg/m3). The exposure to graphene oxide did not induce significant changes in the body weights, organ weights, and food consumption during the 14 days of recovery time. The microalbumin and lactate dehydrogenase levels in the bronchoalveolar lavage (BAL) fluid were not significantly changed due to the exposure. Similarly, total cell count, macrophages, polymorphonuclear leukocytes, and lymphocytes were not significantly altered in the BAL fluid. Plus, the histopathological examination of the rat lungs only showed an uptake of graphene oxide in the alveolar macrophages of the high-concentration group. Therefore, these results demonstrate that the single inhalation exposure to graphene oxide induce minimal toxic responses in rat lungs at the concentrations and time points used in the present study.

The fluorescence decay profiles of zinc(II) 5,15-di-(3,5-di-tert-butylphenyl) porphyrin monomer (Z1) and its meso, meso-linked dimer (Z2), trimer (Z3) and tetramer (Z4) were investigated by using the fluorescence upconversion technique. Fluorescence from the S2 state in Z1 was observed to decay with the time constant of 1.2 ps at 460 nm. Corresponding fluorescence rise due to the internal conversion from S2 to S1 states in Z1 was also observed at 635 nm with the time constant of 1.5 ps. The S2 state lifetime of Z2 was largely reduced (90 fs) due to the participation of exciton-split Soret band as a ladder type deactivation channel. Fluorescence decay profile and time-resolved spectra in 530 – 600 nm region revealed that the intramolecular vibrational relaxation (IVR) rate is retarded as the excess vibrational energy decreases in the porphyrin arrays as well as in Z1. The IVR rate was increased from Z1 to Z2 probably due to the additional normal modes related with the inter-unit bond as an efficient intern...

A molecular photodiode with the hetero-Langmuir–Blodgett (LB) film consisting of an electron donor (D), sensitizer (S), relay (R), and acceptor (A) was fabricated. Ferrocene octadecyl amine (Ferrocene), 7,8-dimethyl-10-dodecyl isoalloxazine (flavin), N-Allyl-N′-[3-propylamido-N″,N″-di(n-octadecyl)]-4,4′-bipyridium dibromide (viologen) and N-docosilquinolinium tetracyanodimethan (TCNQ) were used as the D, S, R, and A units, respectively. By aligning the hetero-LB film of the D/S/R/A units on indium tin oxide (ITO) coated glass with an aluminum thin film, a molecular photodiode with a Metal/Insulator/Metal (MIM) structure was constructed. The decay of the transient photocurrent of MIM device was measured using a 355 nm Nd:YAG pulse laser as the light source and the charge transfer rate was obtained. The charge transfer rate was faster in the D/S/R/A heterojunction than in S/R and S/R/A heterojunction devices due to less recombination from the A to S and less back electron transport due to the existence of D molecules. Various effects such as the LB film thickness, interface structure, and Schottky barrier on the charge transfer rate were investigated. The results showed that the charge transport efficiency of the molecular photodiode became higher when the LB film thickness increased and the head/head interfaced structure of the S/R hetero LB films was adopted. Furthermore, improvement of the molecular device efficiency occurred when spacer molecules were adopted between the electrode and the LB film.

The energy relaxation dynamics of the lowest excited singlet and triplet states of the Zn(II)porphyrin monomer and its directly linked arrays were comparatively investigated with increasing the number of porphyrin moieties. While the fluorescence decay rates and quantum yields of the porphyrin arrays increased with the increase of porphyrin units, their triplet-triplet (T-T) absorption spectra and decay times remained almost the same. The difference in the trends of energy relaxation dynamics between the excited singlet and triplet states has been discussed in view of the electronic orbital configurations.

A variety of porphyrin arrays connected together with different linkage were devised for possible applications to molecular optoelectronic devices such as wires, logic gates, and artificial light-harvesting arrays, etc. It has been relatively well established that the light signal transmission in these molecular assemblies is based on exciton migration process, which possibly gives rise to the structural changes during the exciton delocalization process. Zinc(II) 5,15-di(3,5-di-tert-butylphenyl)porphyrin (Z1), its directly meso,meso-linked porphyrin dimer (Z2), trimer (Z3), and tetramer (Z4) were synthesized with the goal to elucidate the relationship between exciton migration and structural change upon photoexcitation. One of the most important factors in structural changes for these porphyrin arrays is mainly determined by the dihedral angle between adjacent porphyrin moieties. For a systematic approach toward the investigation of the exciton coupling dynamics influenced by the relative orientation betw...

Time-resolved fluorescence was measured with hetero Langmuir-Blodgett (LB) films consisting of ferrocene/flavin/viologen/TCNQ on quartz substrate. Ferrocene, flavin, viologen and TCNQ were used as a electron donor (D), sensitizer (S), relay (R) and acceptor (A) units, respectively. Power dependence on charge separation rate was investigated to examine the local heating problem or the excited state annihilation. Based on the decay of fluorescence, charge separation from excited S to R (or A) was calculated. Result showed that long-range electron transfer from S to A occurred in the D/S/R/A hetero LB film in addition to the electron transfer from S to R.

A molecular photodiode was fabricated with the hetero-Langmuir-Blodgett (LB) film consisting of an electron donor (D). sensitizer (S), relay (R) and acceptor (A). Ferrocene, flavin, viologen and TCNQ were used as D, S, R and A units, respectively. By aligning hetero-LB film of D/S/R/A units on ITO glass with an aluminum thin film, a molecular photodiode with the structure of Metal/Insulator/Metal (MIM) was constructed. Due to excitation by irradiation with a 460 nm monochromatic light source, the photoswitching function was observed. And action spectrum of MIM device was measured. To investigate the photoswitching time and charge transport rate, transient photocurrent of MIM device was measured. Result shows that efficient charge transport from D to A in the heterojunction was occurred due to the existence of R and less recombination.

The dynamic equilibrium unfolding pathway of human tumor necrosis factor-alpha (TNF-alpha) during denaturation at different guanidine hydrochloride (GdnHCl) concentrations (0-4.2 M) was investigated by steady-state fluorescence spectroscopy, potassium iodide (KI) fluorescence quenching, far-UV circular dichroism (CD), picosecond time-resolved fluorescence lifetime, and anisotropy decay measurements. We utilized the intrinsic fluorescence of Trp-28 and Trp-114 to characterize the conformational changes involved in the equilibrium unfolding pathway. The detailed unfolding pathway under equilibrium conditions was discussed with respect to motional dynamics and partially folded structures. At 0-0.9 M [GdnHCl], the rotational correlation times of 22-25 ns were obtained from fluorescence anisotropy decay measurements and assigned to those of trimeric states by hydrodynamic calculation. In this range, the solvent accessibility of Trp residues increased with increasing [GdnHCl], suggesting the slight expansion of the trimeric structure. At 1.2-2.1 M [GdnHCl], the enhanced solvent accessibility and the rotational degree of freedom of Trp residues were observed, implying the loosening of the internal structure. In this [GdnHCl] region, TNF-alpha was thought to be in soluble aggregates having distinct conformational characteristics from a native (N) or fully unfolded state (U). At 4.2 M [GdnHCl], TNF-alpha unfolded to a U-state. From these results, the equilibrium unfolding pathway of TNF-alpha, trimeric and all beta-sheet protein, could not be viewed from the simple two state model (N--U).

The first evaluation of the β for 2-[2-(p-diethylaminophenyl)vinyl]furan derivatives is reported in comparison with the corresponding thiophene derivative.

A subnanometer gap-separated linear chain gold nanoparticle (AuNP) silica nanotube peapod (SNTP) was fabricated by self-assembly. The geometrical configurations of the AuNPs inside the SNTPs were managed in order to pose either a single-line or a double-line nanostructure by controlling the diameters of the AuNPs and the orifice in the silica nanotubes (SNTs). The AuNPs were internalized and self-assembled linearly inside the SNTs by capillary force using a repeated wet-dry process on a rocking plate. Transmission electron microscopy (TEM) images clearly indicated that numerous nanogap junctions with sub-1-nm distances were formed among AuNPs inside SNTs. Finite-dimension time domain (FDTD) calculations were performed to estimate the electric field enhancements. Polarization-dependent surface-enhanced Raman scattering (SERS) spectra of bifunctional aromatic linker p-mercaptobenzoic acid (p-MBA)-coated AuNP-embedded SNTs supported the linearly aligned nanogaps. We could demonstrate a silica wall-protected nanopeapod sensor with single nanotube sensitivity. SNTPs have potential application to intracellular pH sensors after endocytosis in mammalian cells for practical purposes. The TEM images indicated that the nanogaps were preserved inside the cellular constituents. SNTPs exhibited superior quality SERS spectra in vivo due to well-sustained nanogap junctions inside the SNTs, when compared to simply using AuNPs without any silica encapsulation. By using these SNTPs, a robust intracellular optical pH sensor could be developed with the advantage of the sustained nanogaps, due to silica wall-protection.

The photocyclization reactions of 2-halopyridinium salt tethered to arene have been studied. The photocyclization of 2-halophenethylpyridinium salts produced a six-membered heterocyclic product, pyrido[2,1-a]-3H,4H-isoquinolinium salt. The 2-halopyridinium salts tethered to phenyl group with methylene linkage (1 and 2a) are more reactive than the 2-halopyridinium salts with an ethylene group (3 and 4a). As expected, the 2-bromopyridinium salt linked to the phenyl group with ethylene linkage (4a) is more reactive than the 2-chloropyridinium salt with the ethylene group (3), which is different from the 2-halopyridinium salt with the methylene linkage. The transient intermediates such as pyridinium salt σ, 2,3-dihydrocyclohexadienyl radicals, and a dibromide radical anion are detected with laser flash photolysis facility. The maximum absorption wavelengths of the pyridinium salt σ, 2,3-dihydrocyclohexadienyl radicals, and dibromide radical anion are 250, 310, and 360 nm, respectively. The lifetimes of the py...

The twisted intramolecular charge transfer (TICT) in the excited state of p -N,N-dimethylaminobenzoic acid (DMABA) has been investigated in the presence of SiO 2 colloids in acetonitrile by using steady-state and time-resolved fluorescence techniques. The SiO 2 -dependent intensity ratio of the TICT emission to the normal emission clearly demonstrates a distinct phenomenon as a function of SiO 2 concentration: an enhancement of the TICT emission occurs upon the addition of 0.3 μM SiO 2 whereas a reduction occurs in the presence of excess SiO 2 colloids. These results suggest that the formation of the excited TICT state is enhanced by the hydrogen bonding between the carboxylic acid of DMABA and SiO 2 colloidal surface.

To prepare stabilized TiO2 nanoparticles (TiO2 NPs) in aqueous media as a suspension of the primary particles, we attempted to optimize the conditions for dispersing stable, aggregated TiO2 NPs (A-TiO2 NPs) in aqueous HCl/NaOH solutions or 5 mM pH buffered aqueous solutions. The A-TiO2 NPs with a hydrodynamic diameter (or DLS size) of 150 +/- 20 nm could be dispersed at high concentration (63.5 +/- 0.5 mg/ml) in a 5 mM phosphate buffer (PB) solution of pH 8, and a primary TiO2 (P-TiO2) NP suspension (1.2 +/- 0.3 mg/ml) with DLS size of 30 +/- 5 nm could be separated from the highly concentrated A-TiO2 NP suspension by sonication and subsequent centrifugation. It was observed by comparing the UV-Vis absorption spectra of the A-TiO2 and P-TiO2 NP suspensions that the extinction coefficient of the TiO2 NPs in the aqueous suspension depended on the degree of aggregation. The stabilized P-TiO2 NP suspension in aqueous solution can be used to study nanotoxicity as well as to characterize the physicochemical properties of TiO2 NPs.

The size and size distribution of nanomaterials are important factors for understanding their characteristics. A scanning electron microscopy (SEM) provides an easily accessible method to characterize nanostructures. We have developed a standard operating protocol (SOP) for the calibration of SEM by using CRMs (certified reference materials) of 1 dimensional (1D) gratings with 80 and 180 nm spacing, respectively, which have been certified by using a metrological AFM. To get consistent analysis results using a fast Fourier transform (FFT) method, the numbers of lateral and longitudinal pixels in the SEM images were determined for line profiling. We could also observed that the pitch values of 1D grating CRM could be obtained as the reference ones within the uncertainty under the following imaging conditions; the exposure time of the sample to the electron beam for an image scanning should be shorter than 120 s and the working distance from 5 to 8.9 mm can be used.

We provide an improved method for measuring the first order hyperpolarizability of organic nonlinear optical materials in solution by the hyper-Rayleigh scattering technique. The method is free from the overestimation which is encountered in the conventional method due to the fluorescence induced by two-photon absorption.

A thorough investigation of the transient species from the laser flash photolysis of haloarene tethered arenes has been performed. Some transient species in the laser photolysis of N-benzyl-2-halopyridinium and N-(2-halobenzyl)pyridinium bromides have been investigated as an effort to understand the photocyclized reaction mechanism as well as to know the properties of the transients themselves. Pyridinium σ, 2,3-dihydrocyclohexadienyl π, and halogen anion radicals are detected in the photolysis of a N-benzyl-2-halopyridinium salt (1 or 2) in water: the absorption maxima are 250, 310, and 355 (Br−Cl•-) nm, respectively. The lifetimes of 2-pyridinium σ radical, 2,3-dihydrocyclohexadienyl π, and bromine chloride (in the case of 1) anion radicals are 0.72 ms, 1.2 ms, and 9.3 μs, respectively. Phenyl σ, 2,3-dihydropyridinium π, and halogen anion radicals are also detected in the laser photolysis of an aqueous solution of a N-(2-halobenzyl)pyridinium salt (3 or 4): the absorption maxima are 250, 310, and 360 ...