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In this study, we studied the effect of starting ligands such as 1,4-benzenetdicarboxylic (H2BDC), 1,3,5-benzenetricarboxylic (H3BTC), and 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic (H3TATB) acids on the photocatalytic activity of three bismuth-based MOFs (Bi-MOF) obtained via a microwave-assisted solvothermal process. Different shapes and sizes of ligands displayed different structure properties from the corresponding Bi-MOF. Specifically, Bi-MOF composed of Bi3+ and H3TATB (Bi-TATB) exhibits the largest specific surface area of 355 m2/g, highest surface-oxygen vacancy amount, a more vigorous light absorption intensity with a broader range of visible light absorption and red-shifted absorption edge than that of Bi-MOF composed of Bi3+ and H2BDC (Bi-BDC) and Bi-MOF composed of Bi3+ and H3BTC (Bi-BTC), suggesting the extension in the photocatalytic activity for Bi-TATB. The reason is attributed to the difference in their structural features. Compared with H2BDC and H3BTC ligands in Bi-BDC and Bi-BTC, H3TATB ligands in the structure of Bi-TATB contained more delocalized π electrons. This outcome may facilitate the ligand-to-metal charge transfer (LMCT) and decrease the electronic bandgap of the Bi-TATB, thus contributing to the enhanced photocatalytic rate. The enhanced photocatalytic activity of Bi-TATB was further confirmed by the photodegradation of rhodamine B (RhB) under LED light irradiation, which is 99.1% of RhB removal after 180 min of light irradiation. The as-synthesized Bi-TATB showed promising photocatalytic activity for the degradation of organic dye with an excellent recyclable catalytic efficiency. With the above understanding, Bi-MOF was finally used for the photocatalytic O2 evolution from water under LED light irradiation. The Bi-TATB had a maximum photocatalytic O2 evolution rate of 691 μmol h−1. To the best of the author’s knowledge, there has been no research on both the photocatalytic degradation of organic model dye pollutants and photocatalytic O2 evolution studies using Bi-MOFs with different organic linkers. The results should open an alternative approach of ligand selection that could increase the applicability of Bi-MOF in the field of catalysis.

The binary g-C3N4/UU–200 heterojunction photocatalysts displaying superior photocatalytic activity for organic pollutant elimination under white LED light irradiation were fabricated via an in situ solvothermal method.

A 2 × 2 3-dB coupler is one of the essential photonic components, as a building block of Mach-Zehnder interferometers, to realize large-scale photonic integrated circuits. Unlike typical 2 × 2 3-dB couplers based on direction couplers or multimode interference couplers, adiabatic couplers offer various advantages such as broadband operation and superior fabrication tolerance thanks to their unique operating mechanism of adiabatic mode evolution. However, an adiabatic coupler typically requires a long device length for ideal adiabatic operation without the excitations of unwanted modes. Here, we report on a compact 2 × 2 3-dB adiabatic coupler designed using the shortest mode transformer method. By optimizing the profile of the waveguide widths and the gap spacing, the compact 3-dB coupler was designed with a short coupling length of 23.2 μm. The fabricated device exhibits a 3-dB splitting ratio with less than ± 0.3 dB power oscillation and a low excess loss of 0.23 dB over a broad wavelength range of 1485–1620 nm. To the best of our knowledge, our coupler has the shortest length among the adiabatic couplers with a minimum feature size of 200 nm, reported to date.

In this study, BiVO4 was successfully synthesized via the solvothermal process using a solvent mixture of ethylene glycol and water under different synthesis conditions of temperature and pH. Physicochemical properties such as crystal phase, morphology, and optical absorption of the as-synthesized BiVO4 samples were characterized by X-ray diffraction (XRD), Raman spectra, field emission scanning electron microscopy (FE-SEM), and ultraviolet–visible diffraction reflection spectroscopy (UV–vis DRS). The XRD analysis showed that different synthesis conditions of temperature and pH significantly affected the growth of monoclinic BiVO4 crystals oriented along (0 4 0) facets. Form SEM results, the synthesis conditions, including pH and temperature, have a great effect on the morphology of monoclinic structured BiVO4. As the pH value increases in the range of 0–9 and temperature increases from 80 °C to 180 °C, the morphology of BiVO4 changed from peanut-, rod-, and leaf-like shapes. The photocatalytic activities of as-synthesized BiVO4 photocatalysts were evaluated by the photodegradation of methylene blue (MB) dye under irradiation of white LED light. We have found that by using appropriate synthesis conditions (the synthesis temperature of 140 °C and the synthesis pH of 7) the BiVO4 exhibited high photocatalytic efficiency for MB degradation (about 82.30% after 180 min of irradiation). This result is due to the development of the BiVO4 crystals oriented along (0 4 0) facets with an increase in the intensity ratio of I(0 4 0)/I(1 2 1). The growth of BiVO4 crystals oriented along (0 4 0) facets may be beneficial to enhance the photocatalytic activity of monoclinic scheelite BiVO4.

The present study utilized chemically modified porous carbon (CMPC) as a robust adsorbent for MB treatment. The characteristic findings revealed the existence of many functional groups (C–O/C = O, ...

Bismuth vanadate, BiVO4, is a visible-light response semiconductor for photocatalysis applications such as organic pollutants degradation, oxygen production and carbon dioxide reduction. However, as a single-phase photocatalyst, BiVO4 efficiency is limited by the unpreferable recombination of the photoexcited electron (e−) and hole (h+). Thus, strategies have been designed to enhance the photocatalytic efficiency by promoting the separation of electrons and holes. This can be done by controling the morphology and crystallographic facets of BiVO4, and by building p–n junction photocatalytic systems with a combination of n-type semiconductors (BiVO4) and p-type semiconductors or a monoclinic–tetragonal heterostructure of BiVO4. In particular, a direct p–n junction photocatalytic system with tetragonal zircon-structured BiVO4 (t-z) and monoclinic scheelite-structured BiVO4 (m-s) combination has recently attracted attention. Here we review the synthesis of the monoclinic–tetragonal heterostructured BiVO4 photocatalyst (m–t BiVO4) by calcination, hydrothermal, microwave-assisted hydrothermal and solvothermal methods. m–t BiVO4 formation and the transmission phase between t-z and m-s are controlled by the calcining temperature, precursor pH, metal doping content, type of solvent, implementation of precursors and reaction conditions. We discuss m–t BiVO4 crystal structure, optical characteristics and photocatalytic principles. Successful formation of BiVO4 crystals with a m-s/t-z heterostructure is based on data from X-ray diffraction (XRD), Raman and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). In the m–t BiVO4 heterostructure, a direct p–n junction photocatalytic system is established. When this system is exposed to visible light, the electrons in the conduction band of m-s BiVO4, a n-type semiconductor, migrate easily to the conduction band of t-z BiVO4, while the holes on valence band of t-z BiVO4, a p-type semiconductor, move to the valence band of m-s BiVO4 through an internal electric field. As a result, the e−/h+ charge carriers are spatially separated.

This study aims to synthesize and evaluate the photocatalytic activity of bismuth terephthalate material (Bi-BDC) synthesized by solvothermal (ST) and microwave-assisted solvothermal (MW) methods. Differences in the crystal structure and crystal shape were assessed by analytical methods such as X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrum, X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption, Raman spectrum, and thermal gravimetric analysis (TGA). From XRD, IR, Raman, and XPS results, the fully crystallized Bi-BDC materials were achieved regardless of the preparation router. Bi-BDC-MW exhibited spherical-like morphologies, producing between stacked lamellar, while Bi-BDC-ST method exhibited a heterogeneous structure. The TGA data indicated that Bi-BDC is thermally stable up to 300 °C, suggesting the excellent thermal stability of Bi-BDC. The surface area and pore volume of Bi-BDC-MW (18 m2/g and 85 × 10−3 cm3/g) are higher than those of Bi-BDC-ST (16 m2/g and 52 × 10−3 cm3/g), which is due to its well-defined lamellar microstructure and homogeneity of the crystals. Compared to Bi-BDC-ST, Bi-BDC-MW has a higher value in the content of oxygen vacancy. Moreover, the photocatalytic efficiency of Bi-BDC-MW was significantly higher than that of Bi-BDC-ST, in which 99.44% rhodamine B (RhB) is removed after 360 min of irradiation. The improved photocatalytic efficiency of Bi-BDC-MW is ascribed to the morphology, specific surface area, and oxygen defects, which exhibited the good separation of electrons and holes, as confirmed by the photoluminescence (PL). The results should open a new approach to enhancing the photocatalytic activity of bismuth terephthalate materials.

This research has introduced the intelligent ANFIS-Online controller of STATCOM for improving the dynamic voltage on the power network under a 3-phase short circuit fault. The ANFIS-Online is made using an artificial neural network identifier. And based on the identifier, the premise and consequent parameters of ANFIS are adjusted timely. To demonstrate the performance of the suggested controller, the transient waves are shown to describe the effectiveness of the intelligent ANFIS-Online controller to enhance the transient response of the research system under a 3-phase short circuit fault. It's shown that the suggested intelligent ANFIS-Online controller has provided waves better than the other controllers such as ANFIS controller, ANFIS-PSO controller, ANFIS-GA controller for STATCOM equipment to enhance transient voltage stability.

Sigle phase scheelite-monoclinic BiVO4 materials with different morphologies were successfully fabricated via a facile hydrothermal process by controlling pH of the precursor. The photocatalytic pr...

The development of composite photocatalyst is a promising direction for improving photocatalytic performance of decomposition of organic dyes. This study aimed to fabricate two composite photocatalysts using either Fe3O4 or NiFe2O4 with MIL-53(Fe) as heterogeneous catalysts for the degradation of rhodamine B (RhB) under visible light irradiation by a 40 W compact fluorescent lamp. The physicochemical, the surface, the magnetic and the energy band gap of the photocatalyst were characterized by XRD, FT-IR, Raman, FE-SEM, UV–vis DRS, Brunauer–Emmett–Teller (BET), and VSM. From the photocatalytic activities test results, the NiFe2O4-doped MIL-53(Fe) sample expressed a higher photocatalytic degradation capacity of RhB than that of Fe3O4/MIL-53(Fe) sample, significantly better than that of the bare of Fe3O4, NiFe2O4, and MIL-53(Fe).

A bimetallic metal&ndash, organic framework material, which was generated by bridging iron (III) cations and nickel (II) cations with 1,4-Benzenedicarboxylic anions (Fe2Ni-BDC), was synthesized by a solvothermal approach using nickel (II) nitrate hexahydrate and iron (III) chloride hexahydrate as the mixed metal source and 1,4-Benzenedicarboxylic acid (H2BDC) as the organic ligand source. The structure of samples was determined by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and nitrogen physisorption measurements. The catalytic activity and recyclability of the Fe2Ni-BDC catalyst for the Michael addition amidation reaction of 2-aminopyridine and nitroolefins were estimated. The results illustrated that the Fe2Ni-BDC catalyst demonstrated good efficiency in the reaction under optimal conditions. Based on these results, a reaction mechanism was proposed. When the molar ratio of 2-aminopyridine and trans-&beta, nitrostyrene was 1:1, and the solvent was dichloromethane, the isolated yield of pyridyl benzamide reached 82%, at 80 &deg, C over 24 h. The catalyst can be reused without a substantial reduction in catalytic activity with 77% yield after six times of reuse.

In this study, we investigated sulfate-modified BiVO4 with the high photocatalytic activity synthesized by a sol-gel method in the presence of thiourea, followed by the annealing process at different temperatures. Its structure was characterized by thermal gravimetric analysis (TGA), powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The BiVO4 synthesized in the presence of thiourea and calcined at 600 &deg, C (T-BVO-600) exhibited the highest photocatalytic degradation efficiency of methylene blue (MB) in water, 98.53% MB removal was achieved within 240 min. The reaction mechanisms that affect MB photocatalytic degradation on the T-BVO-600 were investigated via an indirect chemical probe method, using chemical agents to capture the active species produced during the early stages of photocatalysis, including 1,4-benzoquinone (scavenger for O2&minus, ), ethylenediaminetetraacetic acid disodium salt (scavenger for h+), and tert-butanol (scavenger for HO&bull, ). The results show that holes (h+) and hydroxyl radicals (HO&bull, ) are the dominant species of MB decomposition. Photoluminescence (PL) measurement results of terephthalic acid solutions in the presence of BiVO4 samples and BiVO4 powders confirm the involvement of hydroxyl radicals and the separation efficiency of electron-hole pairs in MB photocatalytic degradation. Besides, the T-BVO-600 exhibits good recyclability for MB removal, achieving a removal rate of above 83% after five cycles. The T-BVO-600 has the features of high efficiency and good recyclability for MB photocatalytic degradation. These results provide new insight into the purpose of improving the photocatalytic activity of BiVO4 catalyst.

We synthesized metal-organic framework materials based on bismuth and trimesic acid (Bi-BTC) by the solvothermal method using a mixed solvent of N,N-dimethylformamide (DMF) and methanol (MeOH) at different volume ratios. The results have shown that the presence of MeOH ensured the effective Bi-BTC formation in the DMF environment, meaning that the pure DMF environment was inactive for Bi-BTC formation. The properties of Bi-BTC, such as size and porosity, varied in response to the change of synthetic solvent, resulting in a difference in the photocatalytic properties of the material. The change in the material structure under the influence of different solvents leads to a change in light absorption properties and thus affects their photocatalytic mechanism. Our study contributes a new insight to improve the photocatalytic activity of Bi-BTC.

Mode-division multiplexing (MDM) is an attractive solution for future on-chip networks to enhance the optical transmission capacity with a single laser source. A mode-division reconfigurable optical add/drop multiplexer (ROADM) is one of the key components to construct flexible and complex on-chip optical networks for MDM systems. In this paper, we report on a novel scheme of mode-division ROADM with mode-selective silicon photonic MEMS (micro-electromechanical system) switches. With this ROADM device, data carried by any mode-channels can be rerouted or switched at an MDM network node, i.e., any mode could be added/dropped to/from the multimode bus waveguide flexibly and selectively. Particularly, the design and simulation of adiabatic vertical couplers for three quasi-TE modes (TE0, TE1, and TE2 modes) based on effective index analysis and mode overlap calculation method are reported. The calculated insertion losses are less than 0.08 dB, 0.19 dB, and 0.03 dB for the TE0 mode, TE1 mode, and TE2 mode couplers, respectively, over a wavelength range of 75 nm (1515–1590 nm). The crosstalks are below −20 dB over the bandwidth. The proposed device is promising for future on-chip optical networks with flexible functionality and large-scale integration.

Here, the importance of hydrogen bonding from amino (NH2) functional group on NH2−MIL-88B in oxytetracycline (OTC) adsorption mechanism has been reported. To clarify this finding, two materials including MIL-88B and NH2−MIL-88B derived from two different ligands of 1,4-benzene-dicarboxylic acid (H2BDC) and 2-aminobenzene-1,4-dicarboxylic acid (NH2-BDC) were synthesized and characterized. The X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT–IR) were adopted, and proving the existence of NH2 functional group in the material structure. Comparing the adsorption efficiency among adsorbents with/without NH2 groups was evaluated through several fundamental investigations including the effect of solution pH (3.2–10.8), Na+ ionic strength (25–800 mmol/L), contact time (0–120 min) and initial concentration (20–100 mg/L). The investigations indicated that the best adsorption condition was found at pH 5.7. The OTC sorption process reached out the equilibrium nature rapidly, at 60 min. It was also demonstrated the negligible effect of Na+ ions on OTC adsorption over both MIL-88B and NH2-MIL-88B Some statistical error functions (R2, MRE, χ2, HYBRID, and MPSD) were also selected for better evaluating several nonlinearised kinetic and isothermal models. The principal outcomes revealed that the maximum adsorption capacity (94.9 mg/g) obtained from Langmuir equation by NH2−MIL-88B was above 4-fold higher than that by MIL-88B. Based on these vital evidences, the role of hydrogen bonding and plausible mechanisms in accelerating OTC adsorption has been suggested.

A silicon photonic 3-dB power splitter is one of the essential components to demonstrate large-scale silicon photonic integrated circuits (PICs), and can be utilized to implement modulators, 1 &times, 2 switches, and 1 &times, N power splitters for various PIC applications. In this paper, we reported the design and experimental demonstration of low-loss and broadband silicon photonic 3-dB power splitters. The power splitter was realized by adiabatically tapered rib waveguides with 60-nm shallow etches. The shallow-etched rib waveguides offered strong coupling and relaxed critical dimensions (a taper tip width of 200 nm and gap spacing of 300 nm). The fabricated device exhibited an excess loss as low as 0.06 dB at a 1550-nm wavelength and a broad operating wavelength range from 1470 nm to 1570 nm. The relaxed critical dimensions (200 nm) make the power splitter compatible with standard fabrication processes of existing silicon photonics foundries.

The presence of phenolic compounds in aquatic environment, derived from industrial, domestic or agricultural processes adversely affects the human and animals. This study in aimed at the new and effectiveness of an adsorbent, magnetic porous carbon (MPC), for the removal of phenolic compounds including phenol and 4-nitrophenol from aquatic environment. MPC was synthesized from the metal-organic framework MIL-53 (Fe) via the direct pyrolysis at 600 °C. The MPC structure was characterized by several physical techniques and used for the adsorption experiments. To find the best conditions for the removal of phenol and 4-nitrophenol, we empirically investigated the effects of three variables (initial concentration, dosage and pH) on the removal efficiency using the response surface methodology (RSM). Under the RSM-based optimized conditions, up to 83% phenol was removed at the concentration of 16 mg/L, dosage of 0.7, and pH of 6.6, while the figure for 4-nitrophenol was 97%, at concentration of 26.0 mg/L, dosage of 0.75 g/L, and pH of 5.6. In addition, the nonlinear adsorption kinetics and isotherms were employed to interpret the mechanism and calculate the constants of adsorption rate. The uptake results suggested that the adsorption process was controlled by the chemisorption and the monolayer adsorption. The MPC exhibited the remarkable maximum adsorption capacities, which is 4 times (for phenol) and 5 times (for 4-nitrophenol) higher than those exhibited by origin MIL-53 (Fe). Plausible adsorption mechanisms were explained through dipole-dipole H-bonding, π–π interaction and electrostatic attraction. Because of high capacity, effortless performance and good reusability, the MIL-53 (Fe) derived porous carbon can be a promising material for phenolic species remediation in water.

In this study, we have successfully synthesized BiVO4 materials by hydrothermal method. The degradation of methylene blue (MB) under LED visible light mediated by S2O8/BiVO4/Vis system. The obtained BiVO4 catalyst was characterized by X-ray diffraction (XRD), Raman, scanning electron microscope (SEM), and UV-visible diffuse reflectance spectrum (UV-vis DRS). We investigated the effect of S2O8 concentrate, pH value and initial concentration on the removal rate of MB. The results of XRD spectra showed that the BiVO4 fragment has a crystalline structure in moneblinite monoclinic phase alone. The degradation of MB concentration under visible light mediated S2O8/BiVO4/Vis was 78% after 100 minutes of irradiation. The band gap (Eg) of BiVO4 was estimated to be 2.39 eV. Therein, the presence of Na2SO4 anions decrease concentration of MB with compared to the original using S2O8/BiVO4 system alone.

We report the facial synthesis of Eu-doped MIL-53(Fe) elongated hexagonal dipyramid by solvothermal reaction of Fe(NO₃)₃, Eu(NO₃)₃ and terephthalic acid (TPA) in the presence of N,N-dimethylformamide (DMF). The as-synthesized samples were characterized by XRD, Raman, FT-IR, PL, and SEM. From XRD and Raman results, metal replacement (Eu) with the metal ion (Fe) in the crystal lattice may change the high crystallinity of the MIL-53(Fe) structure, and all the metal ions were incorporated into the structures of MIL-53(Fe) as well as replaced Fe ion or located at interstitial site. From PL result, Eu-doped MIL-53(Fe) showed unique Eu fluorescence properties with high emission intensity, thus enabling it to be a promising functional probe for fluorescent imaging.

Mixed Ni/Fe-base metal-organic framework (Ni/Fe-MOF) with different molar ratios of Ni2+/Fe3+ have been successfully produced using an appropriate solvothermal router. Physicochemical properties of all samples were characterized using X-ray diffraction (XRD), Raman, field emission scanning electron microscopes (FE-SEM), fourier-transform infrared spectroscopy (FT-IR), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence spectra (PL). The photocatalytic degradation performances of the photocatalysts were evaluated in the decomposition of rhodamine B (RhB) under a compact fluorescent daylight lamp. From XRD, IR, XPS, and Raman results, with the presence of mixed ion Fe3+ and Ni2+, MIL-88B (MIL standing for Materials of Institut Lavoisier) crystals based on the mixed metal Fe2NiO cluster were formed, while MIL-53(Fe) was formed with the presence of single ion Fe3+. From UV-Vis DRS results, Ni/Fe-MOF samples exhibited the absorption spectrum up to the visible region, and then they showed the high photocatalytic activity under visible light irradiation. A Ni/Fe-MOF sample with a Ni2+/Fe3+ molar ratio of 0.3 showed the highest photocatalytic degradation capacity of RhB, superior to that of the MIL-53(Fe) sample. The obtained result could be explained as a consequence of the large surface area with large pore volumes and pore size by the Ni2+ incorporating into the MOF&rsquo, s structure. In addition, a mixed metal Fe/Ni-based framework consisted of mixed-metal cluster Fe2NiO with an electron transfer effect and may enhance the photocatalytic performance.

Recently, BiVO4 photocatalysts has been received much attention in field of catalysts. Because it can be used to degrade harmful organic catalysts in visible light, irradiation produces CO2, H2O and less harmful organic matter. In this study, we have successfully synthesized a BiVO4 photocatalysts via co-precipitation method in the presence of urea and different calcined temperatures. The survey calcined temperatures as 300°C; 350°C; 400°C and 450°C. The obtained materials were characterized by Scanning electron microscope (SEM) and X-ray diffraction (XRD). The photocatalytic activity was evaluated by the photocatalytic degradation of rhodamine B (RhB) degradation under visible compact Philip lamp (40W) light irradiation. The result indicates that all samples calcined are monoclinic scheelite structure of BiVO4. The BiVO4-350°C sample performed the best in the photodegradation of RhB.

Herein, we described a tunable method for synthesis of novel hollow mesoporous carbon (MPC) via direct pyrolysis (800 o C) of MIL-53 (Fe) as a self-sacrificed template. The structural characterization revealed a hollow, amorphous, defective and mesoporous MPC along with high surface area (approx. 200 m 2 g −1 ). For the experiments of ibuprofen adsorption onto MPC, effects of contact time, MPC dosage, ionic strength, concentration and temperature were systematically investigated. The optimal conditions consisted of pH = 3, concentration 10 mg l −1 and dose of 0.1 g l −1 for the highest ibuprofen removal efficiency up to 88.3% after 4 h. Moreover, adsorption behaviour, whereby chemisorption and monolayer controlled the uptake of ibuprofen over MPC, were assumed. Adsorption mechanisms including H-bonding, π–π interaction, metal–oxygen, electrostatic attraction were rigorously proposed. In comparison to several studies, the MPC nanocomposite in this work obtained the outstanding maximum adsorption capacity (206.5 mg g −1 ) and good reusability (5 cycles); thus, it can be used as a feasible alternative for decontamination of ibuprofen anti-inflammatory drug from water.

In this study, we investigated the synthesis of BiVO4 nanoparticles via the hydrothermal method and their photocatalytic activity for the degradation of methylene blue (MB) under LED visible light mediated by H2O2. The obtained BiVO4 catalyst was characterized by XRD, Raman, SEM, and UV-vis DRS. The effect of H2O2 concentrate, pH, and MB initial concentration on the removal rate of MB was carefully studied. The results showed that MB was decolorized entirely after 30 min in the BiVO4/H2O2/Vis process whereas the decomposition rate of BiVO4 with the absence of H2O2 is 78% after 60 min. The accelerated degradation of MB by in the BiVO4/H2O2/Vis process is due to H2O2 acts as the external electron acceptor, which could promote the separation of photo-induced electrons and holes.

Amount of energy deposited by a single, tightly focused nanosecond laser pulse in different transparent materials was measured vs. either the incident intensity or energy fluence. An integrating sphere enabled quantification of the energy scattered during the long-lived breakdown process. It was shown that absorptance dependence on the photon flux can be analytically described by the sigmoidal Hill function. We suggest using this analytical description to quantify empirical laser-induced breakdown threshold (LIBT). The structured changes in the breakdown area were analysed by the means of different kinds of microscopy, especially by the high-resolution-transmission- electron-microscopy (HRTEM). The analysis revealed nanocrystallisation in the densified material surrounding the void.

We present characterization of structural modification triggered by tightly focused single pulses of a nanosecond laser inside single-crystal sapphire. Structural changes induced in the shock compressed region were investigated using high resolution transmission electron microscopy (HRTEM). Analysis of the zone around cavity in the bulk of sapphire reveals loss of crystalline order and formation of a mixture of amorphous/poly-crystalline structure. The properties of the laser-affected solid and possible routes of material transformation to the final state long after the pulse end is discussed. The results suggest that transformations to amorphous/poly-crystalline state occur as a result of sufficient heating of the shell region. This creates a localized molten zone which solidifies so rapidly that crystallization is by-passed.