Bromine-Functionalized Covalent Organic Frameworks for Efficient Triboelectric Nanogenerator

Covalent organic frameworks (COFs) enable precise integration of various organic building blocks into porous skeletons through topology predesign. Here, we report the first example of COFs by integrating electron withdrawing bromine group onto the skeletons for triboelectric nanogenerators (TENG). The resulting framework exhibits high surface area and good crystallinity. Thus, the bromine functionalized COF has more regular aligned π columns and arrays over the skeleton than bare COFs, which in turn significantly enhances charge transport ability. As a result, bromine functionalized COFs showed higher electrical output performance at 5 Hz with a peak value of short circuit current density of 43.6 μA and output voltage of 416 V, which is 2 and 1.3 times higher than those of bare COFs (21.6 μA and 318 V), respectively. These results demonstrated that this strategy for engineering electron withdrawing groups on the skeleton could open a new aspect of COFs for developing TENG devices.     

Generation and characterization of air micro-bubbles in highly hydrophobic capillaries

The generation of air microbubbles in microfluidic systems or in capillaries could be of great interest for transportation (single cell analysis, organite transportation) or for liquid compartmentation. The physicochemical characterization of air bubbles and a better understanding of the process leading to bubble generation during electrophoresis is also interesting in a theoretical point of view. In this work, the generation of microbubbles on hydrophobic Glaco™ coated capillaries has been studied in water-based electrolyte. Air bubbles were generated at the detection window and the required experimental parameters for microbubbles generation have been identified. Generated bubbles migrated against the electroosmotic flow, as would do strongly negatively charged solutes, under constant electric field. They have been characterized in terms of dimensions, electrophoretic mobility, and apparent charge.     

Surface charging behaviors of electrocatalytic interfaces with partially charged chemisorbates

The surface charge is a key concept in electrochemistry. Mathematically, the surface charge is obtained from a spatial integration of the volume charge along a particular direction. Ambiguities thus arise in choosing the starting and ending points of the integration. As for electrocatalytic interfaces, the presence of chemisorbates further complicates the situation. In this minireview, I adopt a definition of the surface charge within a continuum picture of the electric double layer. I will introduce surface charging behaviors of firstly ordinary electrochemical interfaces and then electrocatalytic interfaces featuring partially charged chemisorbates. Particularly, the origin of nonmonotonic surface charging behaviors of electrocatalytic interfaces is explained using a primitive model. Finally, a brief account of previous studies on the nonmonotonic surface charging behavior is presented, as a subline of the spectacular history of electric double layer.     

Modular synthesis of photodegradable polymers with different sensitive wavelengths as UV/NIR responsive nanocarriers

We report the modular and facile synthesis of three novel polymers able to photodegrade by UV and visible light via the Passerini multicomponent polymerizations of 1,6‐hexanedioic acid and 1,6‐diisocyanohexane with 5‐methoxy‐2‐nitrobenzaldehyde ( M2 ), 4,5‐dimethoxy‐2‐nitrobenzaldehyde ( M3 ) or 7‐(N,N‐diethylamino)‐4‐formylcoumarin ( M4 ) respectively. This synthetic strategy takes the advantage of the in situ formation of a photolabile chromophore via the Passerini reaction of an aromatic aldehyde with an acid and an isocyanide, thus it is a versatile approach to regulating the photochemical property of the photolabile chromophores by just changing the aldehyde structure. Importantly, two polymers ( P3 and P4 ) even exhibit NIR degradability due to the two‐photon absorption, and their nanoparticles formulated by the single emulsion method have been used as the NIR‐responsive nanocarriers for hydrophobic dyes. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 334–341     

Unraveling the Mechanisms of the Excited-State Intermolecular Proton Transfer (ESPT) for a D-π-A Molecular Architecture

Precise revealing the mechanisms of excited-state intermolecular proton transfer (ESPT) and the corresponding geometrical relaxation upon photoexcitation and photoionization remains a formidable challenge. In this work, the compound (E)-4-(((4H-1,2,4-triazol-4-yl)imino)methyl)-2,6-dimethoxyphenol (TIMDP) adopting a D-π-A molecular architecture featuring a significant intramolecular charge transfer (ICT) effect has been designed. With the presence of perchloric acid (35 %), TIMDP can be dissolved through the formation of a HClO₄–H₂O–OH(TIMDP)–N(TIMDP) hydrogen-bonding bridge. At the ground state, the ICT effect is dominant, giving birth to crystals of TIMDP. Upon external stimuli (e.g., UV light irradiation, electro field), the excited state is achieved, which weakens the ICT effect, and significantly promotes the ESPT effect along the hydrogen-bonding bridge, resulting in crystals of [HTIMDP]⁺ ⋅ [H₂O] ⋅ [ClO₄]⁻. As a consequence, the mechanisms of the ESPT can be investigated, which distorted the D-π-A molecular architecture, tuned the emission color with the largest Stokes shift of 242 nm, and finally, high photoluminescence quantum yields (12 %) and long fluorescence lifetimes (8.6 μs) have achieved. These results not only provide new insight into ESPT mechanisms, but also open a new avenue for the design of efficient ESPT emitters.     

Experimental techniques and the underlying device physics

This review, which has a very deep tutorial nature to it, aims to collect a range of experimental techniques that are relevant to charge transport and place them all under one device‐physics framework. The types of semiconductors in mind are low mobility ones with an emphasis toward organic semiconductors. As this contribution needs to have a finite length, there are many important methods or techniques not covered in this review. My hope is that by covering methods that are very different in nature, it would make it easier to extend the understanding or intuition collected through this review to methods/techniques not mentioned. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1119–1152     

Light/Electricity Energy Conversion and Storage for a Hierarchical Porous In2S3@CNT/SS Cathode towards a Flexible Li-CO2 Battery

A photoinduced flexible Li-CO₂ battery with well-designed, hierarchical porous, and free-standing In₂S₃@CNT/SS (ICS) as a bifunctional photoelectrode to accelerate both the CO₂ reduction and evolution reactions (CDRR and CDER) is presented. The photoinduced Li-CO₂ battery achieved a record-high discharge voltage of 3.14 V, surpassing the thermodynamic limit of 2.80 V, and an ultra-low charge voltage of 3.20 V, achieving a round trip efficiency of 98.1 %, which is the highest value ever reported (<80 %) so far. These excellent properties can be ascribed to the hierarchical porous and free-standing structure of ICS, as well as the key role of photogenerated electrons and holes during discharging and charging processes. A mechanism is proposed for pre-activating CO₂ by reducing In³⁺ to In⁺ under light illumination. The mechanism of the bifunctional light-assisted process provides insight into photoinduced Li-CO₂ batteries and contributes to resolving the major setbacks of the system.     

Acceptor-Doping Accelerated Charge Separation in Cu2O Photocathode for Photoelectrochemical Water Splitting: Theoretical and Experimental Studies

Cu₂O is a typical photoelectrocatalyst for sustainable hydrogen production, while the fast charge recombination hinders its further development. Herein, Ni²⁺ cations have been doped into a Cu₂O lattice (named as Ni-Cu₂O) by a simple hydrothermal method and act as electron traps. Theoretical results predict that the Ni dopants produce an acceptor impurity level and lower the energy barrier of hydrogen evolution. Photoelectrochemical (PEC) measurements demonstrate that Ni-Cu₂O exhibits a photocurrent density of 0.83 mA cm⁻², which is 1.34 times higher than that of Cu₂O. And the photostability has been enhanced by 7.81 times. Moreover, characterizations confirm the enhanced light-harvesting, facilitated charge separation and transfer, prolonged charge lifetime, and increased carrier concentration of Ni-Cu₂O. This work provides deep insight into how acceptor-doping modifies the electronic structure and optimizes the PEC process.     

Synthesis and optoelectronic properties of conjugated polymers based on a dithienobenzimidazole unit in the main chain

Three conjugated polymers with the dithienobenzimidazole (DTBIm) unit ( P1 , P3 , and P4 ) and one conjugated polymer with the dithienobenzoxazole unit ( P2 ) were synthesized by the cross‐coupling polymerization. The absorption maxima showed a red‐shift in the order of P3 (406 nm), P2 (426 nm), P1 (438 nm), and P4 (450 nm), which was studied in detail using the frontier molecular orbital calculation of the model compounds. The energy levels of the highest occupied molecular orbital and the lowest unoccupied molecular orbital of the DTBIm unit‐containing conjugated polymers were estimated by the cyclic voltammetry. The transformation from DTBIm ( P4 ) to dithienobenzimidazolium ( P4' ) was also carried out to shift the absorption maxima of P4' (454 nm) by promoting the intramolecular charge transfer between the DTBIm and thiophene units. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 401–409