Evaluation of Phototoxicity of Short-Wavelength Laser Light Utilizing PCNA Accumulation.

In recent years, diseases such as age-related macular degeneration and retinal pigment degeneration caused by excessive exposure to short-wavelength visible light have become significant concerns. With the aim of quantitatively evaluating the toxicity of short-wavelength light, proliferating cell nuclear antigen (PCNA) accumulation at the irradiation site was investigated using live cell imaging techniques to irradiate individual living cells with short-wavelength laser light. By examining the dependency of PCNA accumulation on the irradiation site within the cells and their cell cycle, it was observed that PCNA accumulation occurred only when the cell nucleus of cells in the S phase of the cell cycle was irradiated. We investigated the accumulation of PCNA at the laser irradiation site using laser light at wavelengths of 405 nm and 375 nm, with intensities ranging from 0.5 µW to 9.0 µW. The results confirmed an increase in PCNA accumulation with increasing intensity, and a higher accumulation was observed with laser light irradiation at a wavelength of 375 nm compared to 405 nm. By comparing the PCNA accumulation and 24 h cell viability, we demonstrated the feasibility of quantitatively assessing laser light toxicity through the measurement of PCNA accumulation.

Plasmonic Metamaterial Ag Nanostructures on a Mirror for Colorimetric Sensing.

In this study, we demonstrate the localized surface plasmon resonance (LSPR) in the visible range by using nanostructures on mirrors. The nanohemisphere-on-mirror (NHoM) structure is based on random nanoparticles that were obtained by heat-treating silver thin films and does not require any top-down nanofabrication processes. We were able to successfully tune over a wide wavelength range and obtain full colors using the NHoM structures, which realized full coverage of the Commission Internationale de l'Eclairage (CIE) standard RGB (sRGB) color space. Additionally, we fabricated the periodic nanodisk-on-glass (NDoG) structure using electron beam lithography and compared it with the NHoM structure. Our analysis of dark-field microscopic images observed by a hyperspectral camera showed that the NHoM structure had less variation in the resonant wavelength by observation points compared with the periodic NDoG structure. In other words, the NHoM structure achieved a high color quality that is comparable to the periodic structure. Finally, we proposed colorimetric sensing as an application of the NHoM structure. We confirmed the significant improvement in performance of colorimetric sensing using the NHoM structure and succeeded in colorimetric sensing using protein drops. The ability to fabricate large areas in full color easily and inexpensively with our proposed structures makes them suitable for industrial applications, such as displays, holograms, biosensing, and security applications.

Flame retardance-donated lignocellulose nanofibers (LCNFs) by the Mannich reaction with (amino-1,3,5-triazinyl)phosphoramidates and their properties.

Nitrogen/phosphorus-containing melamines (NPCM), a durable flame-retardant, were prepared by the successive treatment of ArOH (Ar = Br n C6H5-n , n = 0, 1, 2, and 3) with POCl3 and melamine monomer. The prepared flame-retardants were grafted through the CH2 unit to lignocellulose nanofibers (LCNFs) by the Mannich reaction. The resulting three-component products were characterized using FT-IR (ATR) and EA. The thermal behavior of the NPCM-treated LCNF fabric samples was determined using TGA and DSC analyses, and their flammability resistances were evaluated by measuring their Limited Oxygen Index (LOI) and the UL-94V test. A multitude of flame retardant elements in the fabric samples increased the LOI values as much as 45 from 20 of the untreated LCNFs. Moreover, the morphology of both the NPCM-treated LCNFs and their burnt fabrics was studied with a scanning electron microscope (SEM). The heat release lowering effect of the LCNF fabric against the water-based paint was observed with a cone calorimeter. Furthermore, the mechanical properties represented as the tensile strength of the NPCM-treated LCNF fabrics revealed that the increase of the NPCM content in the PP-composites led to an increased bending strength with enhancing the flame-retardance.

Influence of lithium salt-induced phase separation on thermal behaviors of poly(vinylidene fluoride)/ionic liquid gels and pore/void formation by competition with crystallization.

The thermal behavior of poly(vinylidene fluoride)/1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide/lithium bis(trifluoromethylsulfonyl)amide (PVDF/[C2mim][TFSA]/LiTFSA) gels, prepared by cooling from the hot solution, was investigated with various concentrations of LiTFSA (C LiTFSA). The peak melting temperature (T m) of the gels shifted toward higher temperatures with increased C LiTFSA. However, the thickness of lamellar crystal was found to decrease with the increase in C LiTFSA, which meant that the increase in T m was not caused by the thickening of lamellar crystal. Furthermore, we found the appearance of domains above T m in the high C LiTFSA region (≥20 wt%), which was a lithium ion-rich phase caused by the phase separation. Therefore, it is considered on the basis of Nishi-Wang equation that an increase in the interaction parameter with increasing C LiTFSA toward the phase separation increased the T m. The phase-separated domains competed with the subsequent crystallization, which resulted in the formation of micrometer-sized pores and nanometer-sized voids in the spherulites. Spectral measurements revealed that PVDF was not specifically solvated in the solution state above the crystallization temperature, while [TFSA]- anion formed a complex with lithium ion irrespective of the PVDF content. These results led to the consideration that an increase in the interaction parameter might be caused by the strong interaction between lithium ion and [TFSA]- anion to form the complex, which would also lower the interaction between PVDF and [TFSA]- anion.

A study of alcohol-induced gelation of beta-lactoglobulin with small-angle neutron scattering, neutron spin echo, and dynamic light scattering measurements.

Gelation of beta-lactoglobulin (beta-Lg) in various alcohol-water mixtures with 0.1 M (M = mol L(-1)) hydrochloric acid was investigated with small-angle neutron scattering (SANS), neutron spin echo (NSE), and time-resolved dynamic light scattering (TRDLS) measurements. The beta-Lg in alcohol-water solutions undergoes gelation at specific alcohol concentrations where the alcohol-induced alpha-helical structure of beta-Lg is stabilized. The SANS profiles showed that beta-Lg exists as a single molecule at a low alcohol concentration. With increasing alcohol concentration, the profiles indicate a power law behavior of approximately 1.7 when the samples gelate. These behaviors were observed in all alcohol-water mixtures used, but the alcohol concentrations where the SANS profiles change shift to a lower alcohol concentration region with an increase in the size of the hydrophobic group of the alcohols. Apparent diffusion constants, obtained from the intermediate scattering function (ISF) of NSE and the intensity time correlation function (ITCF) of TRDLS, mainly depend on the viscosity of alcohol-water mixtures before gelation. After gelation, on the other hand, the ISFs of gels do not change appreciably in the range of the NSE time scale, indicating the microscopically rigid structure of beta-Lg gel. The ITCF functions obtained from TRDLS follow a double exponential decay type before gelation, but a logarithmic one (exponent alpha = 0.7) after gelation. It is most likely that the alcohol-induced gelation undergoes a similar mechanism to that for the heat-induced one at pH = 7 where beta-Lg aggregates stick together to form a fractal network, although the gelation time is faster in the former than in the latter.

Deformation mechanism of nanocomposite gels studied by contrast variation small-angle neutron scattering.

Contrast-variation small-angle neutron scattering (CV-SANS) was applied to investigate the deformation mechanism of high-performance nanocomposite polymer hydrogels (NC gels) consisting of polymer chains and inorganic clay platelets. Anisotropic SANS functions were obtained at various stretching ratios, lambda 's up to lambda=9 and were decomposed to three partial structure factors, S(ij)(Q parallel,Q perpendicular). Here, the subscripts i and j denote the polymer (P) or clay (C) and Q parallel and Q perpendicular are the magnitude of the scattering vectors along and perpendicular to the stretching directions, respectively. SCC(Q parallel,Q perpendicular) and S_{PP}(Q parallel,Q perpendicular) suggested that the orientation of clay platelets saturated by lambda approximately 3 , while the polymer chain stretching continued by further stretching. On the other hand, SCP(Q parallel,Q perpendicular) , only available by CV-SANS, indicated the presence of a polymer-enriched layer adsorbed to clay surface, which are responsible for large extensibility of NC gels over 1000% strain and large toughness exceeding 780 kPa.

Quasi-elastic neutron scattering study on water and polymer dynamics in thermo/pressure sensitive polymer solutions.

Dynamics of water and poly(N-isopropylacrylamide) (PNIPA) in concentrated aqueous solutions, where the majority of water molecules are attached to polymer chains, has been investigated with use of incoherent quasi-elastic neutron scattering (QENS) and dynamic light scattering (DLS) measurements as functions of temperature, T, and hydrostatic pressure, P. It was observed by QENS that the self-diffusion coefficient, D(water), of water in PNIPA/H(2)O solutions increased by P at temperatures below the lower critical solution temperature (LCST) of PNIPA aqueous solutions. However, above the LCST, D(water) decreased by P, as is often reported in non-hydrogen bonding solutions. In isobaric heating runs, therefore, the jump in D(water) at LCST decreased with increasing pressure. On the other hand, the mean-square displacement, , of the local vibrational motion of PNIPA in PNIPA/D(2)O solutions, where the incoherent scattering signal of PNIPA was predominantly observed, was reduced due to the aggregation behavior of PNIPA by pressurizing, which was also confirmed by using DLS. The jump in at the LCST became gradual by pressurizing, which was consistent with the changes of the dynamics of water obtained in PNIPA/H(2)O solutions.

Microphase separation in nanocomposite gels.

Microphase separation in poly(N-isopropylacrylamide)(PNIPA)-clay nanocomposite hydrogels (NC gels) is investigated by means of contrast-variation small-angle neutron scattering (CV-SANS) and dynamic light scattering (DLS). By using CV-SANS, it is revealed that microphase separation occurs in NC gels above the lower-critical solution temperature (LCST) of PNIPA aqueous solutions. The observed partial scattering functions show that only the spatial distribution of PNIPA chains is highly distorted by microphase separation and PNIPA chains are preferentially adsorbed on the clay surfaces, where the PNIPA-rich phase forms nanoscaled bicontinuous structure mediated by the clay particles. Additional DLS measurements for dilute solutions with PNIPA and/or the clay nanoparticles confirm that aggregation of PNIPA above the LCST is dramatically suppressed by addition of clay particles. Based on these observations, we conclude that strong affinity between the polymer and clay has a significant effect on the phase separation in NC gels and allows one to tune the length scale of the phase separation phenomenon by clay concentration.

Dynamics and microstructure analysis of N-isopropylacrylamide/silica hybrid gels.

The mechanical properties, gelation process, and microstructure of N-isopropylacrylamide (NIPAm)/silica hybrid gels were investigated by using mechanical measurements, dynamic light scattering (DLS), and contrast-variation small-angle neutron scattering (CV-SANS). The three different hybrid gels, containing an equal total volume fraction of silica particles of different sizes (NS_S: small = 20-30 angstroms radius; NS_M: medium = 40-55 angstroms; and NS_L: large = 100-150 angstroms), were employed for comparison. An obvious effect on the compressive properties due to the size of the silica particles was observed, with harder materials produced from particles of smaller size. The gelation process was strongly dependent on the competition between silica aggregation and NIPAm polymerization, as measured by using the DLS methods. In the case of NS_S, the rate of aggregation was larger than NIPAm polymerization, resulting in the formation of an aggregate-dominant microstructure. The aggregation rate for NS_M and NS_L, however, was comparable to the NIPAm polymerization rate, leading to simultaneous aggregation and polymerization. CV-SANS determined that the NIPAm adsorption layer on the silica surface was clearly affected on a microscopic scale by the silica particle sizes.

Structural characterization of ionic gelator studied by dynamic light scattering and small-angle neutron scattering.

Structural characterization of a hydrogel consisting of an oligomeric electrolyte, poly[pyridinium-1,4-diyliminocarbonyl-1,4-phenylenemethylene chloride] (1-Cl) as an ionic gelator was carried out by static and dynamic light scattering (SLS/DLS) and small-angle neutron scattering (SANS) techniques. All the measurements were performed by changing the concentration and temperature. We have successfully obtained the weight average molecular weight and the degree of polymerization of poly(1-Cl) by SLS. The sol-gel transition was clearly observed as large fluctuations in the scattering intensity of the time-intensity correlation function. Time correlation function of the scattering light intensity entailed a power law behavior at the sol-gel transition. 1-Cl hydrogel showed strong hysteresis and its hysteresis loop was observed both by DLS and theological methods. We have estimated the critical concentration of gelation and the gelation temperature by DLS. The enthalpy change for gelation was estimated to be ca. -10 kJ/mol. SANS experiments revealed that the unit structure of the gel network is responsible for the gelation of 1-Cl hydrogel.

In situ small-angle neutron scattering and rheological measurements of shear-induced gelation.

The microscopic structure of shear-induced gels for a mixed solution of 2-hydroxyethyl cellulose and nanometer-size spherical droplets has been investigated by in situ small-angle neutron scattering (SANS) with a Couette geometry as a function of shear rate gamma. With increasing gamma, the viscosity increased rapidly at gamma approximately 4.0 s(-1), followed by a shear thinning. After cessation of shear, the system exhibited an extraordinarily large steady viscosity. This phenomenon was observed as a shear-induced sol-gel transition. Real-time SANS measurements showed an increase in the scattering intensity exclusively at low scattering angle region. However, neither orientation of polymer chains nor droplet deformation was detected and the SANS patterns remained isotropic irrespective of gamma. It took about a few days for the gel to recover its original sol state. A possible mechanism of gelation is proposed from the viewpoint of shear-induced percolation transition.

Pressure-induced reentrant micellization of amphiphilic block copolymers in dilute aqueous solutions.

The pressure-induced structural changes of a block copolymer, poly(2-ethoxyethoxyethyl vinyl ether)-block-poly(2-hydroxyethyl vinyl ether) (pEOEOVE-b-pHOVE) in aqueous solutions, were studied by means of small-angle neutron scattering (SANS) and dynamic light scattering (DLS) from atmospheric pressure up to 400 MPa. pEOEOVE-b-pHOVE formed a spherical micellar structure above 40 degrees C due to poor solubility of pEOEOVE. Micellization phase diagram was determined by DLS, and a covex-upward pressure-temperature (P-T) phase diagram was obtained having a peak around (P,T)=(150 MPa,48 degrees C). The SANS curves at 50 degrees C were analyzed as a function of P. The micellar core size decreased by pressurizing at low P's (P

Pressure-induced phase transitions of hydrophobically solvated block-copolymer solutions.

The structures of poly(2-(2-ethoxy)ethoxyethyl vinyl ether)-block-poly(2-methoxyethyl vinyl ether) in D2O have been investigated with small-angle neutron scattering (SANS) as a function of temperature T and pressure P. At ambient pressure, the solution underwent a two-step transition at 40 and 65 degrees C, both of which were convex-upward functions of P having a maximum around P0 approximately 150 MPa. The first transition was assigned to a microphase separation to form a bcc structure, and the second was to a macrophase separation. Pressurizing at 28 degrees C resulted in a macrophase separation with divergence at 350 MPa. At 45 degrees C, a reentrant microphase separation was observed by increasing P. Differences in the states of hydrophobic solvation in the low (PP0) are discussed based on the SANS structure factors.