Mechanically Robust, Thermally Stable, Broadband Antireflective, and Superhydrophobic Thin Films on Glass Substrates

In this study, we developed a simple and versatile strategy to fabricate hierarchically structured lotus-leaf-like superhydrophobic thin films. The thin films are broadband antireflective, and the average transmittance of coated glass substrates reached greater than 95% in the wavelength range of 530–1340 nm, in contrast to 92.0% for bare glass substrate. The thin film surface shows a static water contact angle of 162° and a sliding angle less than 4°. Moreover, the thin film is thermally stable up to 300 °C, and shows remarkable stability against strong acid, strong alkali, water drop impact, and sand impact abrasion, while retaining its superhydrophobicity. Further, the thin film can pass the 3H pencil hardness test. The current approach may open a new avenue to a variety of practical applications, including windshields, eyeglasses, windows of high rise buildings and solar cells, etc

Interface Band Engineering Charge Transfer for 3D MoS₂ Photoanode to Boost Photoelectrochemical Water Splitting

In photoelectrochemical (PEC) cells, it is a crucial issue to steer the charge flow in the electrode, including the internal movement of charge in the catalyst and the charge transfer across the catalyst–substrate interface toward the external circuit. Here, we fabricated vertically aligned MoS₂ nanosheets (NSs) on carbon fiber cloth (CFC) substrates decorated without and with a Au layer as two photoanodes for PEC water splitting, whereby the interface electron transfer mediated by the embedded Au was demonstrated to contribute to photoelectrode performance. The photoexcited Au plasmon switches the interface barrier from n-type Schottky to a p-type one, making the built-in potential act in accordance with external positive potential to together drive electron transfer and charge separation at the interface. The enhanced electron-transfer dynamic at the Au-embedded interface is determined in terms of the output current, impedance, and incident photon-to-current conversion measurements, being responsible for the significantly increased PEC activity in the MoS₂/Au@CFC photoelectrode. This work gains insight into the importance of engineering charge transfer across the catalyst–substrate interface in PEC electrodes

Selective Fluorination of 4‑Substituted 2‑Aminopyridines and Pyridin-2(1<i>H</i>)‑ones in Aqueous Solution

Fluorination of 2-aminopyridines and pyridin-2­(1<i>H</i>)-ones in the presence of Selectfluor, water, and chloroform under mild conditions has been realized. This method gives fluorinated pyridines in good to high yields with high regioselectivities. The electron-deficient pyridine system is activated by an amino or hydroxyl group at C2. The regioselectivity of the fluorination reaction is strongly dependent upon the substituent pattern in the 2-aminopyridine or pyridin-2­(1<i>H</i>)-one. The transformation of the 3-fluoro-substituted pyridine derivative into fluorinated zolimidine was achieved as well

NiS₂/Reduced Graphene Oxide Nanocomposites for Efficient Dye-Sensitized Solar Cells

NiS₂ nanoparticles and nanocomposites of NiS₂ with reduced graphene oxide (NiS₂@RGO) have been successfully prepared via a facile hydrothermal reaction of nickel ions and sulfur source in the absence or presence of graphene oxide. NiS₂@RGO nanocomposites exhibit excellent electrocatalytic performance for reduction of triiodide, owing to the improved conductivity and positive synergetic effect between NiS₂ and RGO. As a consequence, the dye-sensitized solar cell with the NiS₂@RGO counter electrode (CE) produces a power conversion efficiency of 8.55%, which is higher than that (7.02%) for the DSSC with the NiS₂ CE, higher than that (3.14%) for the DSSC with the RGO CE, and also higher than that (8.15%) for the DSSC with the reference Pt CE under the same conditions

Charge Transfer Switching in Donor–Acceptor Systems Based on BN-Fused Naphthalimides

Six-membered azaborine rings have been straightforwardly fused on naphthalimide-based donor–acceptor systems, and a series of BN-containing heteroaromatic compounds <b>BN1</b>–<b>BN3</b> were constructed. Electron-donating triphenylamines were functionalized in the extended direction of the 3- or/and 4-position of the naphthalimide unit. For comparison, reference <b>BN0</b> without triphenylamine was also prepared. The intramolecular charge transfer (ICT) interactions in the resulting BN-fused naphthalimides (<b>BN0</b>–<b>BN3</b>) together with their precursors (<b>N0</b>–<b>N3</b>) and fluoride-coordinated analogues (<b>FBN0</b>–<b>FBN3</b>) have been systematically investigated by photophysical, electrochemical, and theoretical approaches. It is found that the fusion of the azaborine ring has a great effect on the ICT properties of the D–A systems based on BN-fused naphthalimides. For the precursors without boron, the extension of an electron donor from the 3-position of naphthalimide is superior in enhancing the D–A interactions. On the contrary, upon fusion of the azaborine ring on naphthalimide, the dominant orientation of the ICT interactions conversely converts to the extended direction of the 4-position of naphthalimide in the D–A molecules based on BN-fused naphthalimides. Most interestingly, upon coordinating the boron by a fluoride ion, the ICT interactions are dramatically enlarged and the substitution position of the triphenylamino group has a negligible effect on the ICT properties of the fluoride-coordinated analogues

Reduced Graphene Oxide–TaON Composite As a High-Performance Counter Electrode for Co(bpy)₃^3+/2+-Mediated Dye-Sensitized Solar Cells

We report herein the investigation of TaON nanoparticles incorporating a reduced graphene oxide (RGO) nanocomposite as a counter electrode for application in Co­(bpy)₃^3+/2+ (bpy = 2,2′-bipyridine)-mediated dye-sensitized solar cells (DSSCs). The RGO–TaON nanocomposite has been prepared by mixing graphene oxide (GO) and presynthesized TaON nanoparticles in ethanol/water followed by the facile hydrazine hydrate reduction of GO to RGO. Compared with RGO or TaON alone, the RGO–TaON nanocomposite shows a much higher electrocatalytic activity for the reduction of Co­(bpy)₃³⁺ species owing to synergistic effects, resulting in significantly improved solar-cell performance when it is applied as the counter electrode in DSSCs. An efficiency of 7.65% for the DSSC with the RGO–TaON counter electrode is obtained, competing with the efficiency produced by the Pt counter electrode; additionally, the former exhibits a much better electrochemical stability than the latter in a Co­(bpy)₃^3+/2+ acetonitrile solution

Charge Transfer Switching in Donor–Acceptor Systems Based on BN-Fused Naphthalimides

Six-membered azaborine rings have been straightforwardly fused on naphthalimide-based donor–acceptor systems, and a series of BN-containing heteroaromatic compounds <b>BN1</b>–<b>BN3</b> were constructed. Electron-donating triphenylamines were functionalized in the extended direction of the 3- or/and 4-position of the naphthalimide unit. For comparison, reference <b>BN0</b> without triphenylamine was also prepared. The intramolecular charge transfer (ICT) interactions in the resulting BN-fused naphthalimides (<b>BN0</b>–<b>BN3</b>) together with their precursors (<b>N0</b>–<b>N3</b>) and fluoride-coordinated analogues (<b>FBN0</b>–<b>FBN3</b>) have been systematically investigated by photophysical, electrochemical, and theoretical approaches. It is found that the fusion of the azaborine ring has a great effect on the ICT properties of the D–A systems based on BN-fused naphthalimides. For the precursors without boron, the extension of an electron donor from the 3-position of naphthalimide is superior in enhancing the D–A interactions. On the contrary, upon fusion of the azaborine ring on naphthalimide, the dominant orientation of the ICT interactions conversely converts to the extended direction of the 4-position of naphthalimide in the D–A molecules based on BN-fused naphthalimides. Most interestingly, upon coordinating the boron by a fluoride ion, the ICT interactions are dramatically enlarged and the substitution position of the triphenylamino group has a negligible effect on the ICT properties of the fluoride-coordinated analogues

Ionic Conductor with High Conductivity as Single-Component Electrolyte for Efficient Solid-State Dye-Sensitized Solar Cells

Imidazolium iodide is an often used component in iodine-based dye-sensitized solar cells (DSSCs), but it cannot operate an efficient DSSC in the absence of iodine due to its low conductivity. For this study, lamellar solid iodide salts of imidazolium or piperidinium with an N-substituted propargyl group have been prepared and applied in solid-state DSSCs. Owing to the high conductivity arising from the lamellar structure, these solid-state ionic conductors can be used as single-component solid electrolytes to operate solid-state DSSCs efficiently without any additives in the electrolyte and post-treatments on the dye-loaded TiO₂ films. With a propargyl group attached to the imidazolium ring, the conductivity is enhanced by about 4 × 10⁴-fold as compared to the alkyl-substituted imidazolium iodide. Solid-state DSSC with the 1-propargyl-3-methylimidazolium iodide as the single-component solid-state electrolyte has achieved a light-to-electricity power conversion efficiency of 6.3% under illumination of simulated AM1.5G solar light (100 mW cm^–2), which also exhibits good long-term stability under continuous 1 sun soaking for 1500 h. This finding paves the way for development of high-conductivity single-component solid electrolytes for use in efficient solid-state DSSCs

In Situ Growth of Co_0.85Se and Ni_0.85Se on Conductive Substrates as High-Performance Counter Electrodes for Dye-Sensitized Solar Cells

We present herein a facile one-step low-temperature hydrothermal approach for in situ growth of metal selenides (Co_0.85Se and Ni_0.85Se) on conductive glass substrates. The as-prepared metal selenides on conductive substrates can be used directly as transparent counter electrodes for dye-sensitized solar cells (DSSCs) without any post-treatments. It is found that graphene-like Co_0.85Se exhibits higher electrocatalytic activity than Pt for the reduction of triiodide. As a consequence, the DSSC with Co_0.85Se generates higher short-circuit photocurrent and power conversion efficiency (9.40%) than that with Pt

Molecular Engineering of Quinoxaline-Based Organic Sensitizers for Highly Efficient and Stable Dye-Sensitized Solar Cells

A series of quinoxaline based metal-free organic sensitizers has been designed and synthesized for dye-sensitized solar cells (DSSCs). The absorption, electrochemical, and photovoltaic properties for all sensitizers have been systematically investigated. It is found that the incorporation of quinoxaline unit instead of thienopyrazine unit results in a negative shift of the lowest unoccupied molecular orbital levels for <b>FNE44</b>, <b>FNE45</b>, <b>FNE46</b>, and <b>FNE47</b>, in comparison to <b>FNE32</b>, which induces a remarkable enhancement of the electron injection driving force from the excited organic sensitizers to the TiO₂ semiconductor. Moreover, when the alkyl substituents are removed from the spacer part in <b>FNE44</b> to the donor part in <b>FNE45</b> and <b>FNE46</b>, a more conjugated system and a bathochromically shifted maximum absorption band can be realized, which consequently results in an increased light harvesting efficiency and photogenerated current. In addition, the length of the alkyl substituents on the donor part has a certain influence on the DSSC performance. Combining the three contributions, <b>FNE46</b>-based DSSC with liquid electrolyte displays the highest power conversion efficiency (η) of 8.27%. Most importantly, a η of 7.14% has been achieved for <b>FNE46</b> based quasi-solid-state DSSC and remained at 100% of the initial value after continuous light soaking for 1000 h, which indicates that <b>FNE46</b> is appropriate for promising commercial application. Our findings will facilitate the understanding of the crucial importance of molecular engineering and pave a new path to design novel metal-free organic dyes for highly efficient and stable DSSCs