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Herein, we report significant fluorescence quenching induced by intramolecular photoinduced electron transfer (PET) in electron donor–acceptor-type π-conjugated organic molecules with methoxy-containing donor moieties. The fluorescence quenching of the diketopyrrolopyrrole (DPP, a well-known highly emissive luminophore) derivatives seemed to be affected by the methoxy moieties. Steady-state optical properties of the synthesized materials were analyzed in the solution, aggregate (N-methyl-2-pyrrolidone/H2O), and solid states in order to understand the influence of the surrounding environment. The mechanistic aspect of the intramolecular PET process in methoxy-containing DPP derivatives was revealed by singlet oxygen generation measurements and ultrafast femtosecond transient absorption spectroscopy. These results could provide crucial insights toward designing emissive π-conjugated organic molecules.

The purpose of this study is to fabricate porous polyurethane membranes that maintain oil absorption performance even when the surface is contaminated. The segmented polyurethane (SPU) films were prepared by the solvent casting method and the porous SPU membranes were prepared by electrospinning. A superhydrophobic methylsilicone network was formed both on the hydroxylated SPU (SPU−OH) film and membrane surfaces by condensation with methyltrichlorosilane. The morphological changes to the methylsilicone-network-coated SPU (SPU−OH−Si) were observed by field emission scanning electron microscopy. The changes in the chemical components on the surface by the introduction of the methylsilicone network were confirmed by attenuated total reflection Fourier transform infrared spectroscopy, and the type of wettability of the surface was confirmed to be superhydrophobicity and superoleophilicity on the SPU−OH−Si film or membrane by contact angle measurements. The self-cleaning performances of the prepared surfaces were confirmed using methylene blue, Oil Red O, and SiC adsorption tests. As a result, the SPU−OH−Si surface displayed excellent self-cleaning properties, as well as oil removal performance, in contaminated water. Furthermore, the oil absorption property was preserved even when the membrane was pre-contaminated with SiC particles.

Weakly coordinating anions (WCAs) offer two succinct advantages when they are introduced as counter anions in a dye. First, replacing strong electrostatic attraction between a cationic dye and its counter anion with the relatively weak electrostatic attraction from a WCA can improve photo-stability of the dye due to charge distribution. Second, the steric hindrance due to the WCAs forms a spatial obstacle between the unstable charged site of the cationic dye and an external element that may degrade the dye. In this study, WCAs are introduced as counter anions in basic dyes to improve their photostability. Basic Yellow 1, Rhodamine 6G, and Rhodamine B were selected as dyes due to their particularly low photostabilities among cationic dyes. Three WCAs were investigated, where two were composed of anions surrounded by fluorine moieties (hexafluorophosphate and bis(trifluoromethane)sulfonimide), and one is surrounded by oxygen moieties (bis(oxalate)borate) Upon dissolving these dyes in three different organic solvents (Chloroform, Methylene Chloride, and Dimethylformamide), the photostabilities of almost all the WCA-substituted dyes were comparatively improved. The photo-stability of each WCA-substituted dye was especially improved in low polarity solvents and the bis(trifluoromethane)sulfonamide-basic dye pairs showed the highest photo-stabilities among four anion-dye pairs including the unsubstituted dyes.

Edge-functionalized graphene nanoplatelets (GnPs) were synthesized by a simple ball-milling process of graphite in the presence of halogen (F, I), metalloids (Se, Te and Sb) and subsequently applied to dye-sensitized solar cells (DSSCs) as counter electrodes (CEs). In our previous works, a series of edge-functionalized GnPs were thoroughly studied and successfully utilized as CEs in DSSCs , with the aim of finding possible alternatives to the noble and expensive Pt metal as CE. However, in each study, the GnP-CEs were not only fabricated with different dyes and electrolytes but were also evaluated on different occasions, and thus, it was difficult to identify which type of edge-functionalized GnPs was the best. Herein, DSSCs with different edge-functionalized GnP-CEs were fabricated under the same environmental conditions, photovoltaic performances were then evaluated employing both I −/I3− and Co(bpy)32+/3+ (bpy = 2,2′-bipyridine) redox couples with three different sensitizers to assess the electrocatalytic activity of the different GnP-CEs. Photovoltaic performances of edge-halogenated GnP-CEs with N719 dye employing the I−/I3− redox couple were lower than those of the metalloid-doped GnP-CEs and were even inferior to Pt-CE, which was consistent with the Rct values. Conversely, among the metalloid-doped GnP-CEs, SbGnP-CE exhibited a higher Rct value and lower power conversion efficiency (PCE) value of 8.70% and 6.60% with N719 and SGT-130 dyes, respectively. However, when the devices were fabricated with the Co(bpy)32+/3+ redox couple, the opposite occurred and SbGnPs displayed the highest PCE of 10.42% with SGT-130 dye and 12.08% with SGT-021 dye. Furthermore, SeGnP-CE and TeGnP-CE showed superior compared to the Pt-CE with both I−/I3− and Co(bpy)32+/3+ electrolyte solutions.

Achieving a long triplet lifetime and a high triplet quantum yield for efficient triplet sensitizers are crucial for commercializing triplet–triplet annihilation–upconversion (TTA-UC). Although many donor-acceptor (D-A) or heavy atom-based triplet sensitizers have been extensively studied, each strategy suffers from major drawbacks, such as low triplet quantum yield of D-A and short triplet lifetime of heavy atoms. Herein, we propose the integration of a donor-acceptor with a heavy atom, which improves both triplet lifetime and quantum yield because of the simultaneous utilization of photoinduced electron transfer and the heavy atom effect. To prove this, we synthesized Triphenylamine(D)-BODIPY(A)-bromine(H) (AM6, AM7, and AM8), which were compared with standards such as Triphenylamine(D)-BODIPY(A) (AM2) and BODIPY-Bromine (AM9). The donor-acceptor-heavy atom (D-A-H) compounds (AM6, AM7, AM8) exhibited excellent TTA-UC emission efficiency (3.9–6.5 %), which were high compared to AM2 (1.5 %) and AM9 (1.7 %). Moreover, threshold intensity (Ith) of AM6, AM7 and AM8 were lower (176–465 mW/cm2) than AM9 (1,916 mW/cm2), even though they had heavy atom. This demonstrates that D-A-H is an effective molecular design for triplet sensitizers with a synergistic effect.

The near-infrared (NIR) absorbing film is a film to block unnecessary near-infrared light. The NIR absorbing film is one of the main components to improve the image quality of digital cameras. In this work, we studied the stability of NIR absorbing films made of NIR absorbing dyes by varying the kind of transparent polymeric binders, which have different thermal stability. We analyzed the optical properties, thermal stability, and microscopic morphology of the NIR absorbing films and investigated the change of these properties by the heat. The NIR absorbing films using dithiolene dye showed good thermal stability. The diimmonium dyes showed discoloration and decomposition in the films using binders with low thermal stability because of the change of molecular arising from the dissociation of counter anions arrangement. Consequently, we could improve the stability of diimmonium dye-based NIR absorbing films by applying thermally stable binders to the NIR absorbing films.

Near-infrared (NIR) absorbing film is one of the principal components of CMOS (complementary metal oxide semiconductor) image sensors to make the images photographed by a camera the same as the images perceived by the human eye. In this study, we have developed a series of diimmonium dyes that broadly and strongly absorb the near-infrared region. The diimmonium dyes were synthesized by introducing bis(fluorosulfonyl)imide counter anions. The synthesized diimmonium dyes showed solvatochromism depending on the polarity of solvents. The absorptivity and the maximum absorption wavelength of diimmonium dye were changed by the solvent polarity. The thermal stability of diimmonium dye was affected by the stability of the counter anion. Diimmonium dyes have been applied to the NIR absorbing films. The absorption spectra of NIR absorbing films made of different dyes showed similar positions of the absorption band. The absorbance of NIR absorbing films prepared with MC showed much higher absorbance than the films processed with MEK. Consequently, it is demonstrated that modification of counter anions of diimmonium dye affects the absorptivity and thermal stability of diimmonium dyes.

One feasible alternative to Pt catalyst in dye-sensitized solar cells (DSSCs) is metalloid tellurium (Te)-doped graphene nanoplatelets (TeGnPs). These were prepared by ball-milling graphite in the presence of Te crystals. Introduction of Te at the edges of TeGnPs was confirmed with various analytical techniques including time of flight secondary ion mass spectrometry (TOF-SIMS). The resultant TeGnPs are herein evaluated as counter electrode (CE) materials for the cobalt reduction reaction (CRR) in DSSCs. TeGnP-CE exhibits much lower charge transfer resistance ( R ct =0.15 Ω cm 2 ) than that ( R ct =1.77 Ω cm 2 ) of Pt-CE. More importantly, TeGnP-CE displays an extreme electrochemical stability for the Co(bpy) 3 2+/3+ (bpy=2,2'-bipyridine) redox couple even after 1000 potential cycles. The SM315-based DSSC fabricated with TeGnP-CE shows a better power conversion efficiency (PCE=11.58%) than that with Pt-CE (11.03%), suggesting that TeGnP-CE could be one of the best alternatives to Pt-CE in DSSCs.

Donor–acceptor (D–A) triplet photosensitizers have gained considerable attention in the field of photodynamic therapy. While numerous studies have been conducted on these photosensitizers, their energy transfer mechanism has not been completely elucidated. Herein, we prepared BODIPY-based D–A complexes (AM2–4) to investigate their photophysical and solvatochromic properties. In addition, the hypothesis that a decrease in the singlet and triplet energy gap (ΔEST) can increase the intersystem crossing rate and singlet oxygen quantum yield (SOQY) was investigated. Moreover, by designing the experiments under more controlled conditions than those reported in previous studies, we obtained more accurate data. AM2–4 materials with the charge-transfer (CT) character exhibited higher SOQY (0.32–0.44) than AM1 without the CT character. Besides, as the electron-accepting power of the photosensitizers increased, ΔEST between the first singlet excited state and triplet excited state decreased, resulting in an increased SOQY. This study elucidates the molecular mechanism of D–A triplet photosensitizers and contributes to the development of efficient photosensitizers for photodynamic therapy.

Covalent organic framework (COF) is an emerging class of porous materials constructed by covalently linked building blocks including reactive organic functional groups. COFs are characterized by their ordered structures, high stability, and structural diversity. Covalent triazine framework (CTF) is a subclass of COFs, which consists of triazine building units. CTFs have attracted broad interests because of the large conjugated system with high nitrogen contents. Perylene derivative is one of the superior building units for practical applications of CTFs. Thus, in this work, we explored which synthetic strategy is appropriate for constructing the high-performance perylene based CTF by comparing two synthetic methods. The perylene-based triazine polyimides were synthesized by two different methods. The i-PTPI was synthesized by the imidization reaction which is one of the polycondensation reactions. The t-PTPI was synthesized by the acid-catalyzed trimerization reaction. The resultants showed significant differences in properties such as chemical composition, thermal stability, crystallinity and porosity even they consisted of the same building units because of these different synthesis routes. Consequently, this study proved that imidization method was more suitable to construct highly crystalline, porous and stable perylene-based CTF than the acid-catalyzed trimerization method.

The color filter is an integral part of the white-OLED display, LCD, and CMOS image sensor. This study aimed to improve the color property and thermal stability of a dye-based color filter. For this purpose, the dispersed-dye-based color filter was developed using dye dispersions. Six metal (Cu, Zn) phthalocyanine dyes bearing bulky benzoic acid groups and chlorine were synthesized and their optimized molecular structures, electrostatic potential surfaces, optical properties, thermal stability, and dispersion properties were determined using computational modeling, UV–Vis spectrometry, TGA, and DLS. The synthesized dyes showed suitable spectral properties and thermal stability for green color filters. Among the dyes, polychloro zinc phthalocyanine had superior dispersion properties owing to its distorted geometric structure. A dispersant containing both amine and ammonium groups as anchors was effective in dispersing the dyes. The color filters with the dye dispersions were prepared by spin-coating. As the bulkiness of the dye increased, their dispersibility was enhanced but their thermal stability decreased. On the other hand, it was observed that the higher the dispersibility of the dye, the superior the color properties and the smaller the thickness of the films. All color filters showed better stability than the traditional soluble-dye-based color filter. This study confirmed that the dispersed-dye-based color filter with fine dye particles exhibits superior stability compared with the dye-based color filter, without compromising color properties.

A dye-sensitized solar cell (DSSC), one of the present photovoltaic technologies, has always been associated with some problems that make them unsatisfactory for practical use. Among them, developing low-cost, durable, and highly active electrocatalysts such as platinum (Pt) alternatives is one of the urgent issues for practical and/or large-scale commercial applications. In this study, as one of the feasible Pt alternatives, edge-selectively antimony-doped graphene nanoplatelets (SbGnPs) were prepared by a simple eco-friendly mechanochemical reaction between pristine graphite and Sb powder for the use of a counter electrode (CE) in dye-sensitized solar cells, for the first time. The selective doping of metalloid Sb at the edges of graphene nanoplatelets (GnPs) and their structure were confirmed by various analytical techniques including atomic-resolution transmission electron microscopy (AR-TEM). The resultant SbGnPs exhibited a much lower charge-transfer resistance (Rct) compared to that of Pt as electrocatalysts toward a Co(bpy)32+/3+ (bpy = 2,2′-bipyridine) redox couple, displaying ‘zero loss stability’ of electrocatalytic activity for the Co(bpy)33+ reduction reaction even after 1000 potential cycles. DSSCs employing Co(bpy)32+/3+ were systematically evaluated in a comparison with the N-doped graphene nanoplatelet (NGnP) CE as a reference. The SbGnP-CE-based DSSC employing an SGT-021 sensitizer based on a D–π–A structured zinc(II)-porphyrin showed better power conversion efficiency (12.08%) than the Pt (11.26%) or the NGnPs (11.53%). The outstanding electrocatalytic activity of the SbGnPs with an unusual electrochemical stability suggests that they could be a possible candidate as the best alternative to a Pt-CE for DSSCs in conjunction with cobalt electrolytes.

In this study, we developed a series of highly stable UV absorbers for polymers which require lengthy high temperature processes, such as polyimide (PI). Three types of linear dimeric hydroxyphenyl benzotriazole derivatives were synthesized by linking monomers with different linker moieties (phenyl, disulfide, biphenyl). The arrangement between the monomers was affected by the type of linker moiety introduced in the dimeric hydroxyphenyl benzotriazole derivatives. As a result, the intermolecular interactions changed resulting in changes in thermal stability and solubility. These results revealed that dimeric hydroxyphenyl benzotriazole derivatives had remarkable stability compared to the monomer. Especially, a novel dimeric UV absorber with phenyl linker (PBT) exhibited excellent stability suitable for high temperature processes.

Edge-selectively halogenated graphene nanoplatelets (XGnPs, X=Cl, Br, and I) were prepared by the mechanochemically driven reaction between graphite and diatomic halogen molecules (Cl2, Br2 or I2). The contents of halogens (Cl, Br, and I) in XGnPs were 3.18, 1.77, and 0.66 at%, respectively, by X-ray photoelectron spectroscopy. The XGnPs as counter electrodes (CEs) showed remarkably enhanced electrocatalytic activities toward Co ( bpy ) 3 3 + reduction reaction in dye-sensitized solar cells (DSSCs) with an excellent electrochemical stability. Amongst XGnPs, IGnP-CE demonstrated the lowest charge-transfer resistance (Rct) of 0.46 Ω cm2 at the CE/electrolyte interface. This value is much lower than that of Pt-CE (0.81 Ω cm2). In addition, the DSSC with IGnP-CE had the highest fill factor (71.3%) and cell efficiency (10.31%), whereas those of DSSCs with Pt-CE were only 70.6% and 9.92%, respectively.

Edge-selectively fl uorinated graphene nanoplatelets (FGnPs) are prepared by mechanochemically driven reaction between fl uorine gas (20 vol% in argon) and activated carbon species from graphitic C‐C bonds unzipped by high-speed stainless steel balls with a high kinetic energy. The fl uorination at edges of the unzipped graphene nanoplatelets (GnPs) is confi rmed by various analytical techniques while the content of flin FGnPs is determined to be 3.0 and 3.4 at% by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy, respectively. Because of the large difference in electronegativity between carbon ( χ = 2.55) and fl uorine ( χ = 3.98) and the strong C‐F bond, the edge-fl uorination of GnPs can provide the maximized charge polarization with an enhanced chemical stability. Thus, electrodes based on the resultant FGnPs demonstrate superb electrochemical performance with excellent stability/cycle life in dye-sensitized solar cells (FF: 71.5%; J sc : 14.44 mA cm −2 ; V oc : 970 mV; PCE: 10.01%) and lithium ion batteries (650.3 mA h g −1 at 0.5 C, charge retention of 76.6% after 500 cycles).

The I3− reduction mechanism on carbon-based materials is clarified by electrochemical kinetics and DFT-NEGF calculations., Metal-free carbon-based electrocatalysts for dye-sensitized solar cells (DSSCs) are sufficiently active in Co(II)/Co(III) electrolytes but are not satisfactory in the most commonly used iodide/triiodide (I−/I3−) electrolytes. Thus, developing active and stable metal-free electrocatalysts in both electrolytes is one of the most important issues in DSSC research. We report the synthesis of edge-selenated graphene nanoplatelets (SeGnPs) prepared by a simple mechanochemical reaction between graphite and selenium (Se) powders, and their application to the counter electrode (CE) for DSSCs in both I−/I3− and Co(II)/Co(III) electrolytes. The edge-selective doping and the preservation of the pristine graphene basal plane in the SeGnPs were confirmed by various analytical techniques, including atomic-resolution transmission electron microscopy. Tested as the DSSC CE in both Co(bpy)32+/3+ (bpy = 2,2′-bipyridine) and I−/I3− electrolytes, the SeGnP-CEs exhibited outstanding electrocatalytic performance with ultimately high stability. The SeGnP-CE–based DSSCs displayed a higher photovoltaic performance than did the Pt-CE–based DSSCs in both SM315 sensitizer with Co(bpy)32+/3+ and N719 sensitizer with I−/I3− electrolytes. Furthermore, the I3− reduction mechanism, which has not been fully understood in carbon-based CE materials to date, was clarified by an electrochemical kinetics study combined with density functional theory and nonequilibrium Green’s function calculations.

Dye-sensitized solar cells (DSSCs) have aroused intense interest and been regarded as one of the most prospective solar cells, due to low-cost, flexibility, simple device fabrication and high conversion efficiency under weak light, in comparison to the conventional photovoltaic devices. Very recently, G2E in Swiss and G24i in UK including Korean and Japan companies have demonstrated commercial and prototyped components based on DSSC technology with liquid electrolytes. However, the unit costs, long-term device stability and power conversion efficiency must be further improved for real-life applications. For this purpose, considerable efforts have been devoted to the search for low cost Pt-free catalysts that exhibit high electrochemical activity and fast electron transfer kinetics, while a platinum (Pt) catalyst is still the most efficient and widely used counter electrode (CE) in DSSCs, but it has some problems that make it unsatisfactory, such as its high manufacturing cost, due to scarcity, and poor long-term stability for the iodide/triiodide redox couple in a DSSC. As a result, significant efforts have been devoted to finding possible alternatives to Pt, including carbon blacks, carbon nanotubes, functionalized graphene, and heteroatom-doped GnPs as efficient metal-free electrocatalysts. One of the most promising candidates as CE materials is non-metallic heteroatom-doped graphene nanoplatelets (GnPs). Heteroatom-doped GnPs gave high power conversion efficiency (PCE) of DSSCs employing cobalt electrolytes. However, they are not sufficiently active in iodidde electrolytes, which are more common and desirable electrolytes. Thus, the better elcetrocatalytical ability and electrochemical stability of carbon-basedmaterials toward the redox couples still need to be significantly improved for the practical applicationof DSSCs. Very recently, a series of edge-fuctionalized heteroatom-doped and metalliod-doped graphene nanoplatelets (GnPs) have been prepared through a simple mechanochemical ball-milling process. In this presentation, comparative study of edge-functionalized heteroatom-doped and metalloid-doped graphene nanoplatelets as metal-free counter electrodes for highly efficient dye-sensitized solar cells employong bothe redox shuttles will be described to understand and establish the structure-property relationship between sort of fuctionalization and cell performance with regard to the present GnPs through the same fabrication process under the same experimental condition. References: Hwan Kyu Kim, and Jong-Beom Baek, et. al., Science Adv., 2(6), 1(2016). Jong-Beom Baek and Hwan Kyu Kim, et. al., Nano Energy, 30, 867 (2016). Jong-Beom Baek and Hwan Kyu Kim, et. al., J. Mater. Chem. A, 4, 9029 (2016) Jong-Beom Baek and Hwan Kyu Kim, et. al., Nano Energy, 13, 336 (2014). Jong-Beom Baek and Hwan Kyu Kim, et. al., Adv. Mater, 26, 3055 (2014). Jong-Beom Baek and Hwan Kyu Kim, et. al., ACS Nano, 7, 5243 (2013).

Three novel carbazole-based molecules have been synthesized and successfully applied as hole-transporting materials (HTMs) of CH3NH3PbI3-based perovskite solar cells. In particular, the perovskite cell with SGT-405, having a three-arm-type structure, exhibited a remarkable photovoltaic conversion efficiency (PCE) of 14.79%.

The cloning and characterization of genes expressed in plant disease resistance could be an initial step toward understanding the molecular mechanisms of disease resistance. A metallothionein-like gene that is inducible by tobacco mosaic virus and by wounding was cloned in the process of subtractive cloning of disease resistance-response genes in Nicotiana glutinosa. One 530-bp cDNA clone (KC9–10) containing an open reading frame of 81 amino acids was characterized. Genomic Southern blot hybridization with the cDNA probe revealed that tobacco metallothionein-like genes are present in few or in one copy per diploid genome. Northern blot hybridization detected strong induction of a 0.5-kb mRNA by wounding and tobacco mosaic virus infection, but only mild induction was detected when copper was tested as an inducer. Methyl jasmonate, salicylic acid, and ethylene were also tested as possible inducers of this gene, but they had no effect on its expression. The possible role of this gene in wounded and pathogen-stressed plants is discussed.