2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Semiconductor-based Photocatalytic Hydrogen Generation

Generations Yi Ma,† Xiuli Wang,† Yushuai Jia,† Xiaobo Chen,‡ Hongxian Han,*,† and Can Li*,† †State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, China ‡Department of Chemistry, College of Arts and Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, Missouri 64110, United States

Titanium dioxide-based nanomaterials for photocatalytic fuel generations.

Boron dipyrromethene (Bodipy) is one of the most extensively investigated organic chromophores. Most of the investigations are focused on the singlet excited state of Bodipy, such as fluorescence. In stark contrast, the study of the triplet excited state of Bodipy is limited, but it is an emerging area, since the triplet state of Bodipy is tremendously important for several areas, such as the fundamental photochemistry study, photodynamic therapy (PDT), photocatalysis and triplet–triplet annihilation (TTA) upconversion. The recent developments in the study of the production, modulation and application of the triplet excited state of Bodipy are discussed in this review article. The formation of the triplet state of Bodipy upon photoexcitation, via the well known approach such as the heavy atom effect (including I, Br, Ru, Ir, etc.), and the new methods, such as using a spin converter (e.g. C60), charge recombination, exciton coupling and the doubly substituted excited state, are summarized. All the Bodipy-based triplet photosensitizers show strong absorption of visible or near IR light and the long-lived triplet excited state, which are important for the application of the triplet excited state in PDT or photocatalysis. Moreover, the methods for switching (or modulation) of the triplet excited state of Bodipy were discussed, such as those based on the photo-induced electron transfer (PET), by controlling the competing Forster-resonance-energy-transfer (FRET), or the intermolecular charge transfer (ICT). Controlling the triplet excited state will give functional molecules such as activatable PDT reagents or molecular devices. It is worth noting that switching of the singlet excited state and the triplet state of Bodipy may follow different principles. Application of the triplet excited state of Bodipy in PDT, hydrogen (H2) production, photoredox catalytic organic reactions and TTA upconversion were discussed. The challenges and the opportunities in these areas were briefly discussed.

The triplet excited state of Bodipy: formation, modulation and application

Room-temperature phosphorescent materials that emit light in the visible (red, green, and blue; from 400 to 700 nm) have been a major focus of research and development during the past decades, due to their applications in organic light-emitting diodes (OLEDs), light-emitting electrochemical cells, photovoltaic cells, chemical sensors, and bio-imaging. In recent years, near-infrared (NIR) phosphorescence beyond the visible region (700–2500 nm) has emerged as a new, promising, and challenging research field with potential applications toward NIR OLEDs, telecommunications, night vision-readable displays. Moreover, NIR phosphorescence holds promise for in vivo imaging, because cells and tissues exhibit little absorption and auto-fluorescence in this spectral region. This review describes the overall progress made in the past ten years on NIR phosphorescent transition-metal complexes including Cu(I), Cu(II), Cr(III), Re(I), Re(III), Ru(II), Os(II), Ir(III), Pt(II), Pd(II), Au(I), and Au(III) complexes, with a primary focus on material design complemented with a selection of optical, electronic, sensory, and biologic applications. A critical comparison of various NIR phosphorescent materials reported in the literature and a blueprint for future development in this field are also provided.

Near-infrared phosphorescence: materials and applications

This review article presents the most recent developments in the use of materials based on dipyrromethene (DPM) and azadipyrromethenes (ADPM) for organic photovoltaic (OPV) applications. These chromophores and their corresponding BF2-chelated derivatives BODIPY and aza-BODIPY, respectively, are well known for fluorescence-based applications but are relatively new in the field of photovoltaic research. This review examines the variety of relevant designs, synthetic methodologies and photophysical studies related to materials that incorporate these porphyrinoid-related dyes in their architecture. The main idea is to inspire readers to explore new avenues in the design of next generation small-molecule and bulk-heterojunction solar cell (BHJSC) OPV materials based on DPM chromophores. The main concepts are briefly explained, along with the main challenges that are to be resolved in order to take full advantage of solar energy.

Design, synthesis and photophysical studies of dipyrromethene-based materials: insights into their applications in organic photovoltaic devices.

The dyads 3, 4, and 6, combining the Bodipy chromophore with a Pt(bpy)(bdt) (bpy = 2,2′-bipyridine, bdt = 1,2-benzenedithiolate, 3 and 6) or a Pt(bpy)(mnt) (mnt = maleonitriledithiolate, 4) moiety, have been synthesized and studied by UV−vis steady-state absorption, transient absorption, and emission spectroscopies and cyclic voltammetry. Comparison of the absorption spectra and cyclic voltammograms of dyads 3, 4, and 6 and those of their model compounds 1a, 2, 5, and 7 shows that the spectroscopic and electrochemical properties of the dyads are essentially the sum of their constituent chromophores, indicating negligible interaction of the constituent chromophores in the ground state. However, emission studies on 3 and 6 show a complete absence of both Bodipy-based fluorescence and the characteristic luminescence of the Pt(bpy)(bdt) unit. Dyad 4 shows a weak Pt(mnt)-based emission. Transient absorption studies show that excitation of the dyads into the Bodipy-based 1ππ* excited state is followed by single...

Sensitizing the sensitizer: the synthesis and photophysical study of bodipy-Pt(II)(diimine)(dithiolate) conjugates.

New platinum(II) terpyridyl acetylide complexes having the ability to bind to TiO(2) have been synthesized and assayed in their ability to sensitize platinized titanium dioxide for the photogeneration of H(2) using visible light (lambda > 410 nm). Specifically, the complexes [Pt(tpy-phen-COOH)(C[triple bond]C-C(6)H(5))]Cl (1), where tpy-phen-COOH = 4'-(4-carboxyphenyl)-[2,2';6',2'']terpyridine and C[triple bond]C-C(6)H(5) = phenylacetylide, and [Pt(tpy-COOH)(C[triple bond]C-C(6)H(5))]Cl (2), where tpy-COOH = 4'-carboxy-2,2';6',2''-terpyridine, were prepared to investigate the effectiveness of attachment and proximity to the TiO(2) surface on hydrogen yield. Both complexes 1 and 2 sensitize the photogeneration of hydrogen, but produce fewer turnovers than the unbound chromophore, [Pt(ttpy)(C[triple bond]C-C(6)H(5))]PF(6) (5). On the basis of these observations and electrochemical data, a major limitation to the effectiveness of these chromophores is their instability upon oxidation. To attempt to remedy this problem, two donor-chromophore (D-C) dyads, [Pt(tpy-phen-COOH)(C[triple bond]C-C(6)H(4)CH(2)-PTZ)]PF(6) (3), where C[triple bond]C-C(6)H(4)CH(2)-PTZ = N-(4-ethynylbenzyl)-phenothiazine and [Pt(tpy-COOH)(C[triple bond]C-C(6)H(4)CH(2)-PTZ)]Cl (4) were prepared to function as TiO(2)-attached sensitizers. Transient absorption measurements have shown that the PTZ moiety reductively quenches the Pt center in several picoseconds. While the resultant PTZ(+) radical cation is capable of oxidizing rapidly the triethanolamine sacrificial electron donor, dyads 3 and 4 attached to platinized TiO(2) do not function to generate hydrogen upon irradiation, in contrast with results seen for 1 and 2.

Platinum(II) Terpyridyl Acetylide Complexes on Platinized TiO2: Toward the Photogeneration of H2 in Aqueous Media

A multi-layer barrier coating technology was developed using nano-fibrillated cellulose (NFC) alongside a hydrophobic, paraffin-free biowax for manufacturing an eco-friendly functional packaging paper. Anionic NFC was prepared by isolating hardwood-bleached kraft pulp (Hw-BKP) using a micro-grinder, and cationic NFC was prepared by the quaternization reaction of the anionic NFC. Thereafter, a three-layer barrier-coated paper was manufactured using cationic and anionic NFCs and biowax. The air permeability and water vapor transmission rate (WVTR) of the three-layer barrier-coated paper were measured, and its coverage and coating layer structure were observed by scanning electron microscopy (SEM). The air permeability of the three-layer barrier-coated paper was more than 15,000 s and those WVTR was 67.1 g/m2/day. Its coverage and surface were considerably uniform and smooth. Thick and effective barrier coating layers were formed as indicated by SEM images. Therefore, it was concluded that a multi-layer barrier-coated paper with considerably high barrier properties could be produced using cationic and anionic NFCs with high gas barrier properties and biowax with high moisture barrier properties. Further, the structure could be used as a functional packaging paper with high barrier properties.

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Multi-layer barrier coating technology using nano-fibrillated cellulose and a hydrophobic coating agent

In this study, we attempted to manufacture a pilot scale Taylor-flow nanogrinder (pilot nanogrinder) and evaluated its grinding efficiency by analyzing the characteristics of cellulose nanofiber (CNF). To prepare an enzyme-pretreated CNF (EN-CNF), softwood bleached kraft pulp (SwBKP) was grounded using the pilot nanogrinder after being pretreated with 1.0% of an endo-glucanase. EN-CNF was also prepared with the same pretreated SwBKP using an imported microgrinder as a control. Finally, their particle size, viscosity, and fiber width were determined.BRThe enzyme effectively reduced the fiber length of SwBKP for producing EN-CNF using grinders due to the removal of amorphous regions and microfibrils from SwBKP. As the grinding time of the pilot nanogrinder increased, the particle size and fiber width of EN-CNF decreased and the viscosity of EN-CNF increased. The imported grinder showed the same trends.BRBased on the fiber width of the EN-CNFs, the grinding efficiency of the pilot nanogrinder was 98% that of the imported microgrinder and improved significantly compared to the previous study. However, the pilot nanogrinder required more grinding time than the imported microgrinder for manufacturing the CNFs of similar size. Therefore, although the pilot grinder effectively produced CNF, it was also necessary to develop a technology that could accelerate the grinding process. 

Development of Domestic Taylor-flow Nanogrinder for Manufacturing Cellulose Nanofiber I - Evaluation of the Physical Properties of Enzyme-Pretreated Cellulose Nanofiber for the Performance Evaluation of a Pilot Scale Taylor-flow Nanogrinder -

The applicability of cotton-bleached soda pulp (C-BSP) was investigated as a raw material for manufacturing cationic nano-fibrillated cellulose (NFC) via quaternization of anionic NFC using glycidyl-trimethyl-ammonium chloride (GMA). The anionic NFC was prepared by beating and micro-grinding C-BSP, and quaternization was performed post treatment to induce a charge reversal in anionic NFC. The characteristics of cationic NFC manufactured using C-BSP and hardwood-bleached kraft pulp (Hw-BKP) as a control were analyzed. Relatively higher mechanical energy was required to prepare anionic NFC from C-BSP than that from Hw-BKP. Fourier transform infrared and zeta potential analyses results showed that quaternization by GMA post treatment electrostatically induced charge reversal in anionic NFC. However, GMA did not affect the fiber width and viscosity of the cationic NFCs. It was found that cationic NFC could be manufactured via quaternization of anionic NFC manufactured from C-BSP using less GMA than that for Hw-BKP.

/pdf/manufacture-and-characterization-of-cationic-nano-73m0841h.pdf

Soo-Hyun Lee

Papers

Sensitizing the sensitizer: the synthesis and photophysical study of bodipy-Pt(II)(diimine)(dithiolate) conjugates.

Platinum(II) Terpyridyl Acetylide Complexes on Platinized TiO2: Toward the Photogeneration of H2 in Aqueous Media

Multi-layer barrier coating technology using nano-fibrillated cellulose and a hydrophobic coating agent

Development of Domestic Taylor-flow Nanogrinder for Manufacturing Cellulose Nanofiber I - Evaluation of the Physical Properties of Enzyme-Pretreated Cellulose Nanofiber for the Performance Evaluation of a Pilot Scale Taylor-flow Nanogrinder -

Manufacture and characterization of cationic nano-fibrillated cellulose from cotton pulp