254-nm Radiation Research Articles

Reversible photochromic effect and excellent mechanical properties of Nd3+-doped Zr6Nb2O17 purple ceramics

The development of colored ceramics is limited because it can only display a single color. Therefore, colored ceramics that can achieve reversible switching between two different colors can make up for this deficiency. In this study, we report a novel rare-earth doped colored ceramic, Zr6Nb2O17: xNd3+ (abbreviated as ZNO: xNd), which has been successfully obtained with good mechanical and photochromic properties of purple ceramics by component adjustment. The doping of rare earth Nd3+ ions changed the color of the ceramic matrix from light curry to light purple, and more importantly, enhanced its mechanical properties, with optimal Vickers hardness and fracture toughness values of 16.53 GPa and 5.2 MPa·m1/2, respectively. Alternating 365 nm irradiation and 350°C thermal stimulation, the ceramic samples exhibited good photochromic properties, with the highest photochromic contrast of 21.1 %, and good reversibility and cyclic stability. Finally, it is important to clarify that the photochromic mechanism is mainly caused by the formation of color centers resulting from electrons or holes being trapped by intrinsic or extrinsic defects. These results indicate that ZNO: xNd purple ceramics can be applied in the field of colored ceramics and provide a new path for the development of rare earth-colored ceramics.

Intrahippocampal Supramolecular Assemblies Directed Bioorthogonal Liberation of Neurotransmitters to Suppress Seizures in Freely Moving Mice.

The precise delivery of anti-seizure medications (ASM) to epileptic loci remains the major challenge to treat epilepsy without causing adverse drug reactions. The unprovoked nature of epileptic seizures raises the additional need to release ASMs in a spatiotemporal controlled manner. Targeting the oxidative stress in epileptic lesions, here the reactive oxygen species (ROS) induced in situ supramolecular assemblies that synergized bioorthogonal reactions to deliver inhibitory neurotransmitter (GABA) on-demand, are developed. Tetrazine-bearing assembly precursors undergo oxidation and selectively self-assemble under pathological conditions inside primary neurons and mice brains. Assemblies induce local accumulation of tetrazine in the hippocampus CA3 region, which allows the subsequent bioorthogonal release of inhibitory neurotransmitters. For induced acute seizures, the sustained release of GABA extends the suppression than the direct supply of GABA. In the model of permanent damage of CA3, bioorthogonal ligation on assemblies provides a reservoir of GABA that behaves prompt release upon 365nm irradiation. Incorporated with the state-of-the-art microelectrode arrays, it is elucidated that the bioorthogonal release of GABA shifts the neuron spike waveforms to suppress seizures at the single-neuron precision. The strategy of in situ supramolecular assemblies-directed bioorthogonal prodrug activation shall be promising for the effective delivery of ASMs to treat epilepsy.

Discerning the catalytic treatment of cationic dye wastewater in photoreactor comprising ternary (Co3+/Co2+)-embedded SnO2/ZnFe2O4 composite sensitive toward ultra-violet illumination.

Herein, magnetic (Co3+/Co2+)-integrated SnO2, SnO2/ZnFe2O4, and ZnFe2O4 composites have been prepared from triply distilled water and 30% of isopropanol in the water medium. The phase evolution, microstructure, and magnetism were investigated successfully and tested for cationic dye wastewater degradation containing Rhodamine 6G and Methylene Blue under ultra-violet irradiation. Composite spheres are attributed to efficient heterojunction interfaces between ZnFe2O4 and SnO2 semiconductors with the support of (Co3+/Co2+) nanoparticles. The results provide a simple, low-cost, environmentally friendly, and scalable method of ternary composites to degrade mixed dyes. Co3+/Co2+-implanted SnO2/ZnFe2O4 offered narrowed bandgap energy, more light absorption, diminishing electron-hole recombination, and more charge carriers toward cationic dye wastewater than the binary components. The rate constant of Rhodamine 6G degradation was observed at 0.0237min-1, and Methylene Blue degradation was observed at 0.0187min-1 at 90min under UV (λ = 365nm) irradiation. Capturing studies of various organic reactive species and mechanisms of composites was also proposed in detail.

Colourful cholesteric liquid crystal polymer network gratings prepared through nanoimprinting

ABSTRACT Both the colourful cholesteric liquid crystal polymer network (CLCN) patterns and the gratings have attracted much attention for their applications as optical materials. Herein, the photochromic cholesteric liquid crystal (CLC) mixtures were prepared using a photoisomerizable chiral dopant. The structural colour of the CLC mixtures was tunable by changing the chiral dopant concentration and the intensity of the 365-nm irradiation light. The CLCN gratings with a structural colour were prepared using the UV nanoimprinting lithography method. The structural colours of the CLCN gratings originate from both the cholesteric and the grating structures. Moreover, a patterned CLCN grating was prepared using a photochromic CLC mixture, which could be applied for decoration and anti-counterfeiting.

Ion valence-gated photochromism of an aza-crowned diarylethene.

A non-photochromic diarylethene 2o with an N-phenylaza-15-crown-5 was synthesized. When the nitrogen atom in the aza-crown ring was protonated, it became photochromic due to the prevention of a twisted intramolecular charge transfer (TICT). Although addition of a monovalent metal cation (Li+, Na+, K+, Rb+, Cs+, Cu+, Ag+) in acetonitrile could not stop the TICT so that it was not photochromic, the addition of a multivalent metal cation (Mg2+, Ca2+, Sr2+, Ba2+, Fe2+, Ni2+, Al3+, Sb5+) changed 2o to be photochromic due to the strong attraction of the lone pair on the nitrogen atom. In the presence of excess Cu2+, 2o was oxidized to be EPR-detectable 2o·+, which was thermally unstable as well as inert towards visible-light irradiation. However, 2o·+ was further oxidized to be fairly stable 2o2+ by the irradiation of 365-nm light in the presence of Cu2+. ESI-MS measurements strongly suggested the generation of 2o·+ by mixing 2o with Cu(ClO4)2 in acetonitrile, and the transformation of 2o·+ to 2o2+ by successive 365-nm light irradiation. Fe3+ similarly worked as the oxidant, but the two-step oxidation of 2o to 2o2+ occurred more easily.

Effects of ZnO/trimethylsilyl cellulose nano-composite coating on anti-UV and anti-fungal properties of papers

Trimethylsilyl cellulose (TMSC) was employed as the coating matrix for the application of zinc oxide nanoparticles (ZnO) onto paper surfaces and the protections of ZnO/TMSC coating against UV-induced damages and fungal spoilage were evaluated. Filter papers were immersed in 2% w/v TMSC solution loaded with ZnO and air-dried. Three ZnO/TMSC suspensions were prepared with 0.1, 0.5, and 1% w/v ZnO NPs. The presences of ZnO/TMSC protective layers were confirmed with ATR-IR spectroscopy. The coated papers exhibited high surface hydrophobicities. After the coated papers were subject to 365-nm UV irradiation at 400 W for 3 h, the contact angles dramatically dropped. The trimethylsilyl (TMS) groups exposed on the surface formed a moisture barrier and were partially removed on UV exposure. ATR-IR revealed that more TMS groups were removed in the protective layer with no ZnO. UV-irradiated papers turned yellow and papers protected with 1% ZnO/TMSC exhibited significantly lower color changes than that of the uncoated one. Compared to the TMSC-coated paper, the addition of ZnO resulted in a significant reduction in tensile strength at maximum. However, after UV irradiation, significant increases in both the strain at break and strength at maximum were only observed in 1% ZnO/TMSC-protected papers. Regarding their anti-fungal properties, the 1% ZnO/TMSC films were effective in growth inhibitions of Aspergillus sp. and Penicillium sp. on the nonirradiated papers. Despite being hydrophilic after UV-irradiation, growths of the molds were severely suppressed on the UV-irradiated paper.

Pseudomorphic Synthesis of Monodisperse Afterglow Carbon Dot-Doped SiO2 Microparticles for Photonic Crystals.

Synthesizing monodisperse afterglow microparticles (MPs) is crucial for creating photonic crystal (PC) platforms with multiple optical states for optoelectronics. However, achieving high uniformity in both size and morphology is challenging for inorganic afterglow MPs using conventional methods. In this contribution, a novel approach for the synthesis of carbon dot (CD)-doped SiO2 MPs with tunable afterglow properties and size distributions is reported. These mechanism studies suggest that the pseudomorphic transformation of SiO2 MPs enables CD doping, providing a hydrogen bond-enriched environment for triplet state stabilization, which generates green afterglow while retaining the uniformity in size and morphology of the parent SiO2 MPs. Furthermore, the utility of CD-doped SiO2 MPs in the fabrication of rationally designed PC patterns is shown using a combined consecutive dip-coating and laser-assisted etching strategy. The pattern displays multiple optical responses under different lighting conditions, including angle-dependent structural colors and blue luminescence under daylight and upon 365-nm irradiation, respectively, as well as time-dependent green afterglow after ceasing UV excitation. The findings pave the way for further controlling the dynamics of spontaneous emissions by PCs to enable complicated optical states for advanced photonics.

Effects of various light-emitting diode wavelengths on periodontopathic bacteria and gingival fibroblasts: An in vitro study

BackgroundIn recent years, light has been used for bacterial control of periodontal diseases. This in vitro study evaluated the effects of light-emitting diode (LED) irradiation at different wavelengths on both Porphyromonas gingivalis and human gingival fibroblasts (HGF-1). MethodsP. gingivalis suspension was irradiated with LEDs of 365, 405, 450, 470, 565, and 625 nm at 50, 100, 150, and 200 mW/cm2 for 3 min (radiant exposure: 9, 18, 27, 36 J/cm2, respectively). Treated samples were anaerobically cultured on agar plates, and the number of colony-forming units (CFUs) was determined. Reactive oxygen species (ROS) levels were measured after LED irradiation. The viability and damage of HGF-1 were measured through WST-8 and lactate dehydrogenase assays, respectively. Gene expression in P. gingivalis was evaluated through quantitative polymerase chain reaction. ResultsThe greatest reduction in P. gingivalis CFUs was observed on irradiation at 365 nm with 150 mW/cm2 for 3 min (27 J/cm2), followed by 450 and 470 nm under the same conditions. While 365-nm irradiation significantly decreased the viability of HGF-1 cells, the cytotoxic effects of 450- and 470-nm irradiation were comparatively low and not significant. Further, 450-nm irradiation indicated increased ROS production and downregulated the genes related to gingipain and fimbriae. The 565- and 625-nm wavelength groups exhibited no antibacterial effects; rather, they significantly activated HGF-1 proliferation. ConclusionsThe 450- and 470-nm blue LEDs showed high antibacterial activity with low cytotoxicity to host cells, suggesting promising bacterial control in periodontal therapy. Additionally, blue LEDs may attenuate the pathogenesis of P. gingivalis.

A PSCLC Pattern Prepared Based on Handedness Inversion for Anti-counterfeiting.

Handedness inversion has been widely studied in supramolecular chemistry and material sciences. Herein, a photoisomerizable chiral dopant was synthesized, which could induce the formation of a cholesteric phase with right-handedness. The Bragg reflection band of the cholesteric liquid crystal (CLC) mixture shifted to the long wavelength with extending 365 nm UV light irradiation time. Based on this photochromic property, a colourful polymer-stabilized CLC (PSCLC) film was prepared using a grayscale mask. A handedness reversible CLC mixture was prepared using a mixture of this chiral dopant and S5011. With extending the UV light irradiation time, the handedness of the CLC mixture changed from right- to left-handedness. A patterned PSCLC film was prepared using this CLC mixture. Complementary images were observed under right- and left-handedness circularly polarized lights. The results shown here not only give us a better understanding the competition between photopolymerization and photoisomerization, but also lay the foundations for decoration and anti-counterfeiting.

Ultrafast inactivation of SARS-CoV-2 by 254-nm UV-C irradiation on porous and non-porous media of medical interest using an omnidirectional chamber

Covid-19 has spurred a renewed interest in decontamination techniques for air, objects and surfaces. Beginning in 2020, urgent effort was done to permit the reuse of UV-C for inactivating SARS-CoV-2. However, those studies diverged widely on the dose necessary to reach this goal; until today, the real value of the sensitivity of the virus to a 254-nm illumination is not known precisely. In this study, decontamination was performed in an original UV-C large decontamination chamber (UVCab, ON-LIGHT, France) delivering an omnidirectional irradiation with an average dose of 50 mJ/cm2 in 60 s. Viral inactivation was checked by both cell culture and PCR test. SARS-CoV-2 was inactivated by UV-C light within 3 s on both porous (disposable gown) and non-porous (stainless steel and apron) surfaces. For the porous surface, an irradiation of 5 min was needed to achieve a completely negative PCR signal. The Z value estimating the sensitivity of SARS-CoV-2 to UV-C in the experimental conditions of our cabinet was shown to be > 0.5820 m2/J. These results illustrate the ability of this apparatus to inactivate rapidly and definitively high loads of SARS-CoV-2 deposited on porous or non-porous supports and opens new perspectives on material decontamination using UV-C.

Colourful patterns prepared using a cholesteric liquid crystal mixture with both thermochromic and photochromic properties

ABSTRACT Colourful polymer-stabilised cholesteric liquid crystal (PSCLC) film attracted much attention for their applications in decoration and anti-counterfeiting. Herein, a chiral dopant was synthesised using trans-p-hexoxycinnamic acid. With the addition of this chiral dopant in a reactive LC mixture, both thermochromic and photochromic phenomena were found. The Bragg reflection band of the CLC mixture shifted to long wavelength with extending 365-nm UV light irradiation time or increasing temperature. The structural colour can cover the visible range. The photochromic property of the CLC mixture was driven by the photoisomerisation of the chiral dopant. Colourful PSCLC patterns were prepared based on the thermochromic and/or photochromic properties and using masks. The results shown here not only give us a better understanding the competition between photopolymerisation and photoisomerisation, but also lay a foundation for the preparation of the decorations.

Study on the preparation of molecularly imprinted ZrO2-TiO2 photocatalyst and the degradation performance of hydroquinone.

In this paper, molecularly imprinted Zr-doped TiO2 photocatalysts (MIP-ZrO2-TiO2) were prepared by the molecularly imprinted sol-gel method for the photocatalytic degradation study of hydroquinone (HQ) as the target pollutant. For the effectiveness of the MIP-ZrO2-TiO2 catalyst in degrading HQ, the effects of Zr doping ratio, imprinted molecule dosage, calcination conditions, and pollutant concentration on its photocatalytic activity were investigated. XRD, TEM, XPS, and other techniques were used to evaluate the materials, and the findings revealed that MIP-ZrO2-TiO2 films with imprinted HQ were successfully produced on the ZrO2-TiO2 surface. The optimal preparation conditions were n(Ti):n(Zr) = 100:8, m(HQ) = 1.5g, 550°C for the calcination temperature, and 2h for the calcination duration. The optimum reaction conditions were 10mg/L HQ concentration, 1g/L catalyst dose, and a pH of 6.91. According to the findings of photocatalytic tests, during 30min of UV lamp (365nm) irradiation, the degradation rates of MIP-ZrO2-TiO2, ZrO2-TiO2, and TiO2 for HQ were 90.58%, 83.94%, and 58.30%, respectively. The findings revealed that the doping of Zr metal and the addition of imprinted molecules improved the photocatalytic activity of TiO2, which can be used for the efficient treatment of low concentrations of hard-to-degrade hydroquinone.

Liquid-Metal-Assisted Synthesis of Patterned GaN Thin Films for High-Performance UV Photodetectors Array.

GaN's outstanding physical characteristics allow for a wide range of applications in numerous industries. Although individual GaN-based ultraviolet (UV) photodetectors are the subject of in-depth research in recent decades, the demand for photodetectors array is rising as a result of advances in optoelectronic integration technology. However, as a prerequisite for constructing GaN-based photodetectors array, large-area, patterned synthesis of GaN thin films remains a certain challenge. This work presents a facile technique for pattern growing high-quality GaN thin films for the assembly of an array of high-performance UV photodetectors. This technique uses UV lithography, which is not only very compatible with common semiconductor manufacturing techniques, but also enables precise patterning modification. A typical detector has impressive photo-response performance under 365nm irradiation, with an extremely low dark current of 40 pA, a high Ilight /Idark ratio over 105 , a high responsivity of 4.23 AW-1 , and a decent specific detectivity of 1.76 × 1012 Jones. Additional optoelectronic studies demonstrate the strong homogeneity and repeatability of the photodetectors array, enabling it to serve as a reliable UV image sensor with enough spatial resolution. These outcomes highlight the proposed patterning technique's enormous potential.

Different biological effects of exposure to far-UVC (222nm) and near-UVC (254nm) irradiation.

Ultraviolet C (UVC) light has long been used as a sterilizing agent, primarily through devices that emit at 254nm. Depending on the dose and duration of exposure, UV 254nm can cause erythema and photokeratitis and potentially cause skin cancer since it directly modifies nitrogenated nucleic acid bases. Filtered KrCl excimer lamps (emitting mainly at 222nm) have emerged as safer germicidal tools and have even been proposed as devices to sterilize surgical wounds. All the studies that showed the safety of 222nm analyzed cell number and viability, erythema generation, epidermal thickening, the formation of genetic lesions such as cyclobutane pyrimidine dimers (CPDs) and pyrimidine-(6-4)-pyrimidone photoproducts (6-4PPs) and cancer-inducing potential. Although nucleic acids can absorb and be modified by both UV 254nm and UV 222nm equally, compared to UV 254nm, UV 222nm is more intensely absorbed by proteins (especially aromatic side chains), causing photooxidation and cross-linking. Here, in addition to analyzing DNA lesion formation, for the first time, we evaluated changes in the proteome and cellular pathways, reactive oxygen species formation, and metalloproteinase (MMP) levels and activity in full-thickness in vitro reconstructed human skin (RHS) exposed to UV 222nm. We also performed the longest (40days) in vivo study of UV 222nm exposure in the HRS/J mouse model at the occupational threshold limit value (TLV) for indirect exposure (25mJ/cm2) and evaluated overall skin morphology, cellular pathological alterations, CPD and 6-4PP formation and MMP-9 activity. Our study showed that processes related to reactive oxygen species and inflammatory responses were more altered by UV 254nm than by UV 222nm. Our chronic in vivo exposure assay using the TLV confirmed that UV 222nm causes minor damage to the skin. However, alterations in pathways related to skin regeneration raise concerns about direct exposure to UV 222nm.

The individual and combined effect of ozone and UV-C on mass loss, respiration, texture and colour changes of fresh-cut lettuce

The aim of this study was to investigate the effect of UV-C and ozonation as individual and combined treatments on the quality characteristics (mass loss, colour, texture and respiration rate) of fresh-cut lettuce, employing three different UV-C fluences and one O3 concentration that have been reported in the literature to have a positive effect on disinfection of fresh-cut lettuce. Fresh-cut ‘Romaine’ lettuce (Lactuca sativa L. var. longifolia) was exposed to three fluences 0.20, 0.40 and 0.80 kJ/m2 of ultraviolet-C (254 nm) radiation, to gaseous O3 concentration of 5 mg/L for 5 min, and their combination. The produce was stored unpackaged for 5 days at 5.7oC and 91.95%. The applications of O3, UV-C and their combinations (UV-C+O3) gave good results in terms of quality characteristics preservation. Individual or combined treatments prevented mass loss throughout the cold storage compared to control samples. The combined treatment of UVC with O3 achieved more than 25% less mass loss (maximum values) compared to the other tested treatments and control samples. The respiration rate was increased in individual and combined treatments, especially in the UV-C treatment. The UV-C fluence < 0.80 kJ/m2 and O3 concentration 5 mg/L for 5 mins applications achieved improved texture quality in terms of positive peaks (crispness). The crispness of the treated samples was increased by 35% compared to control samples, especially for the UV-C+O3 combination. Limited colour degradation was noted since the UV-C fluence and O3 concentration and dosage were kept below the limits of UV-C fluence < 5 kJ/m2 and O3 concentration < 5 mg/L for which quality degradation has been reported in the literature.

Photocatalytic H2-production and benzyl-alcohol-oxidation mechanism over CdS using Co2+ as hole cocatalyst

The sluggish oxygen evolution reaction (OER) is often the bottleneck of photocatalytic overall water splitting, greatly suppressing the hydrogen-production activity. Herein, the slow OER was replaced by selective benzyl alcohol (BA) oxidation to benzaldehyde (BD) to promote H2 production. The photocatalytic reaction was conducted over CdS quantum dots, which were modified with Co2+ hole cocatalysts to further accelerate the rate-limiting BA oxidation. The photocatalytic system exhibits an ultra-high H2-production rate of 257.8 mmol g−1 h−1 with a remarkable apparent quantum yield of 69.3% under 365-nm light irradiation. The high performance is attributed to the Co2+ hole cocatalysts on CdS surfaces, which not only enhance light absorption but also facilitate photogenerated carrier transfer. More importantly, both photogenerated electrons and holes are fully utilized in meaningful reactions. This work exemplifies a bifunctional photocatalytic system for simultaneous production of self-separated hydrogen and benzaldehyde, both of which are important industrial products.

Two-Photon Laser Lithography of Functional Microstructures of Integrated Photonics: Waveguides, Microcavities, and Prism Input/Output Adapters of Optical Radiation

The development and optimization of methods for creating functional elements of micron and sub-micron sizes for photonic integrated circuits is one of the main tasks of nanophotonics. Two-photon laser lithography is actively developing now to form three-dimensional structures with subwave resolution. Results of this development are reported and it is shown that the use of optimized lithography schemes, the spatial filtering of laser beam used, and the introduction of laser dyes into polymer lead to the formation of optically homogeneous high-quality bulk microstructures with characteristic features down to 300 nm with necessary functional properties. The capabilities of optimized two-photon laser lithography are demonstrated by examples of ring microcavities and optical waveguides with prism input/output adapters located above a substrate. Optical losses upon the coupling of 405-nm radiation into a waveguide using a printed prism adapter was no more than 1.25 dB.

Ultrathin In2 O3 Nanosheets toward High Responsivity and Rejection Ratio Visible-Blind UV Photodetection.

Photoelectrochemical-type visible-blind ultraviolet photodetectors (PEC VBUV PDs) have gained ever-growing attention due to their simple fabrication processes, uncomplicated packaging technology, and high sensitivity. However, it is still challenging to achieve high-performance PEC VBUV PDs based on a single material with good spectral selectivity. Here, it is demonstrated that individual ultrathin indium oxide (In2 O3 ) nanosheets (NSs) are suitable for designing high-performance PEC VBUV PDs with high responsivity and UV/visible rejection ratio for the first time. In2 O3 NSs PEC PDs show excellent UV photodetection capability with an ultrahigh photoresponsivity of 172.36mA W-1 and a high specific detectivity of 4.43 × 1011 Jones under 254nm irradiation, which originates from the smaller charge transfer resistance (Rct ) at the In2 O3 NSs/electrolyte interface. The light absorption of In2 O3 NSs takes a blueshift due to the quantum confinement effect, granting good spectral selectivity for visible-blind detection. The UV/visible rejection ratio of In2 O3 NSs PEC PDs is 1567, which is 30 times higher than that of In2 O3 nanoparticles (NPs) and exceeds all recently reported PEC VBUV PDs. Moreover, In2 O3 NSs PEC PDs show good stability and good underwater imaging capability. The results verify that ultrathin In2 O3 NSs have potential in underwater optoelectronic devices.

Photobiochemical mechanisms of biomolecules relevant to germicidal ultraviolet irradiation at 222 and 254 nm

To inactivate viruses and microorganisms, ultraviolet light in the short wavelength region is a promising candidate for mitigating the infection of disease. Germicidal mercury lamps emitting at 254 nm and KrCl excimer lamps emitting at 222 nm have sterilisation properties. In this work, wavelength dependence of the photobiochemical mechanisms was investigated with 222- and 254-nm irradiation to analyze the underlying damage mechanisms of DNA/RNA and proteins, using Escherichia coli, a protease, an oligopeptide, amino acids, plasmid DNA and nucleosides. The photorepair of damaged DNA and the “dark” reversion of the hydrates of uracil phosphoramidite coupling blocks were also investigated.

Photo-cleaving and photo-bleaching quantum yields of coumarin-caged luciferin

We applied quantitative bioluminescence experiments to evaluate the photo-cleaving quantum yields and cross sections of coumarin-caged luciferin quantitatively. We synthesized 112 mg of 6’-[(7-diethylaminocoumarin-4-yl)methoxy]-D-luciferin and determined its purity as 94%. It was found that the photo-cleaving quantum yield of coumarin-caged luciferin for 325-nm irradiation is 5.41×10−4 and for 405-nm irradiation is 6.27×10−5, and that the photo-bleaching quantum yield of coumarin-caged luciferin for 325-nm irradiation is 3.87×10−3 and for 405-nm irradiation is 5.83×10−4. Both photo-cleaving and photo-bleaching quantum yields of coumarin-caged luciferin with 325-nm irradiation are 10 times larger than those with 405-nm irradiation. These 10-fold differences were unexpectedly large, and indicate that the photo-cleavage and photo-bleaching occur not after the relaxation process from the second and third excited state to the first excited state but during the relaxation, which corresponds to the non-equilibrium situation.