The photoreduction of CO2 to hydrocarbon products has attracted much attention because it provides an avenue to directly synthesize value‐added carbon‐based fuels and feedstocks using solar energy. Among various photocatalysts, graphitic carbon nitride (g‐C3N4) has emerged as an attractive metal‐free visible‐light photocatalyst due to its advantages of earth‐abundance, nontoxicity, and stability. Unfortunately, its photocatalytic efficiency is seriously limited by charge carriers′ ready recombination and their low reaction dynamics. Modifying the local electronic structure of g‐C3N4 is predicted to be an efficient way to improve the charge transfer and reaction efficiency. Here, boron (B) is doped into the large cavity between adjacent tri‐s‐triazine units via coordination with two‐coordinated N atoms. Theoretical calculations prove that the new electron excitation from N (2px, 2py) to B (2px, 2py) with the same orbital direction in B‐doped g‐C3N4 is much easier than N (2px, 2py) to C 2pz in pure g‐C3N4, and improves the charge transfer and localization, and thus the reaction dynamics. Moreover, B atoms doping changes the adsorption of CO (intermediate), and can act as active sites for CH4 production. As a result, the optimal sample of 1%B/g‐C3N4 exhibits better selectivity for CH4 with ≈32 times higher yield than that of pure g‐C3N4.
Based on the clinical needs, the criteria for ideal PTA are shown as follows: 1) good biodegradability, 2) good photostability, 3) strong absorption in the NIR region for tissue penetration, 4) high photothermal conversion efficiency (PCE). [2] Preclinical studies and early phase trials of PTT have demonstrated promising therapeutic efficacy for superficial tumors (e.g., skin, head, and neck cancer); [3] its use for deep tumors (e.g., lung cancer and ovarian cancer), however, is hampered by several key factors, such as effective delivery of PTAs to tumor sites, the biocompatibility of PTAs, adsorption, and conversion of photoenergy through deep tissues. [4] Generally, light with a wavelength in the near-infrared-II window (NIR-II, 1000-1700 nm) could provide a deeper tissue-penetration length (≈ 5 mm) with less scattering and tissue absorption, [5] compared with light in the near-infrared-I window (NIR-I, 650-950 nm) with a tissue penetration depth of less than 1 mm. [6] Developing PTAs with high biocompatibility, adsorption in the NIR-II window, and photoenergy-conversion efficiency, in this context, is essential toward PTT for deep tumors.Current NIR-II PTAs are mainly based on inorganic particles (e.g., gold nanoparticles, copper sulfide, and black phosphorus), [7] which are generally non-degradable under physiological conditions. Despite that some studies have claimed biodegradability for such materials, the degradation mechanisms are unclear, and balancing the degradability and photothermal performance of such materials remains difficult. [8] Organic dyes have also been explored, [9] whereas their poor photostability could limit their use as effective NIR-II PTAs. [10] Conjugated polymer, which affords strong absorption in the NIR-II window and excellent photostability, [6a,11,12] is highly promising PTAs; however, such materials are inherently nondegradable under physiological conditions. [13] Most research in polymeric PTAs has been focused on photothermal performance; little attention was paid to their biodegradability. [14] Herein, we report a novel class of biodegradable polymeric PTAs through incorporating a flexible unit containing disulfide bonds into the conjugated backbones. To distinguish it with traditional conjugated polymer, we name this new type of polymer as "pseudo-conjugated polymers". Disulfide bonds are cleavable by glutathione (GSH), the most abundant thiol in animal cells, of which the concentration in tumor cells is generally 100-1000 times higher than that in normal cells. [15] As illustrated Photothermal therapy holds great promise for cancer treatment due to its effective tumor ablation and minimal invasiveness. Herein a new class of biodegradable photothermal agents with effective adsorption in both nearinfrared-I (NIR-I) and NIR-II windows is reported for deep tumor therapy. As demonstrated in a deep-seated ovarian cancer model, photothermal therapy using 1064 nm irradiation effectively inhibits tumor progression and prolongs survival spans. This work provides a new design ...
In this work, four donor (D)-acceptor (A) copolymers based on benzodithiophene (BDT) and benzothiadiazole (BT) with different alkylthiolated and/or fluorinated side chains are developed for efficient fullerene and nonfullerene polymer solar cells (PSCs). The synergistic effect of sulfuration and fluorination on the optical absorption, energy level, crystallinity, carrier mobility, blend morphology, and photovoltaic performance is investigated systematically. By incorporating sulfur atoms onto the side chains, a little blueshifted but significantly increased absorption can be obtained for PBDTS-FBT compared to PBDT-FBT. On the other side, a little more blueshifted but much stronger absorption and much lower-lying highest occupied molecular orbital (HOMO) level can be realized for PBDTF-FBT when introducing fluorine atoms instead of sulfur atoms. With the combination of both fluorination and sulfuration strategies, PBDTS-FBT exhibits the best absorption ability, lowest HOMO energy level, and highest crystallinity, which make PBDTSF-FBT devices show the highest power conversion efficiency (PCE) of 10.69% in fullerene PSCs and 11.66% in nonfullerene PSCs. The PCE of 11.66% is the best value for PSCs based on BT-containing copolymer donors reported so far. The results indicate that fluorination and sulfuration have a synergistically positive effect on the performance of D-A photovoltaic copolymers and their solar cell devices.
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