Temperature- and pH-responsive photosensitization activity of polymeric sensitizers based on poly-N-isopropylacrylamide

We previously reported that a copolymer consisting of N-isopropylacrylamide (NIPAM) and benzophenone (BP) units, behaves as a photosensitizer showing temperature-controlled oxygenation activity in water (J. Am. Chem. Soc.2006, 128, 8751). This polymer shows a heat-induced oxygenation enhancement at low temperature region (5-20 °C), while showing a heat-induced oxygenation suppression at high temperature region (20-60 °C), resulting in an off-on-off activity profile against the temperature window. This is driven by a heat-induced phase transition of the polymer from coil to micelle and then to globule states. In the present work, effects of adding an amine component (N-[3-(dimethylamino)propyl]acrylamide: DMAPAM) to the polymer on the sensitization activity were studied, where the relationship between the phase transition behavior and the activity was clarified by several spectroscopic analyses. The polymers, poly(NIPAM_x-co-BP_y-co-DMAPAM_z), show activity controlled by temperature and pH. The off-on-off activity profile shifts to higher temperature with a pH decrease. This is because protonation of the DMAPAM units leads to an increase in the polymer polarity and, hence, the polymer aggregates at higher temperature. In addition, increase in the DMAPAM content of the polymer leads to further shift of the activity profile. In contrast, at pH < 8, no activity enhancement is observed because complete protonation of the DMAPAM units suppresses polymer aggregation.     

MOFs in photoelectrochemical water splitting: New horizons and challenges

Growing energy consumption with the augmentation in universal population to more than nine billion by 2050 and exhausting fossil fuel reserves necessitates a harsh revolution from non-renewable energy reservoirs to renewable energy reservoirs with zero carbon emission. In the present scenario, solar energy prompted photoelectrochemical (PEC) water splitting or “Artificial Photosynthesis” via light gripping semiconductor material, originates out as the most promising methodology in accomplishing the global energy crisis. Recent studies have amply demonstrated the potential of metal-organic frameworks (MOF) towards PEC applications. They are porous crystalline coordination polymers assembled through an appropriate choice of metal ions and multidentate organic ligands. Owing to their structural regularity and synthetic tunability, MOFs integration with PEC is considered in terms of enhancing and broadening light absorption, providing active sites and directing charge transfer dynamics. Here, we have explored MOFs role in PEC and classified them into different categories such as photosensitizers, co-catalysts, counter electrode, template and also for imparting additional stability to the electrode system. MOFs mediated PEC water splitting is promising but is still rare and in its infancy. Therefore, it is pertinent and timely to take stock of the advancements made and develop insight on the use of MOFs, as an emerging solution for the problems encountered in PEC. This review covers the basics of MOF & mainly describes various case studies done during last 10 years and providing adequate impetus to researchers for critically assessing the recent advances and challenges that are faced by scientists and researchers at large.     

Novel zinc porphyrin with phenylenevinylene meso-substituents: Synthesis and application in dye-sensitized solar cells

A novel zinc porphyrin, P, with phenylenevinylene segments at two opposite meso-positions and carboxyphenyl at the other two meso-positions of the porphyrin ring, was synthesized and characterized. The phenylenevinylene substituents were terminated with electron-accepting 4-nitro-α-cyanostilbene units. Elongation of the π-conjugation enhanced the solubility of P as well as broadened and strengthened the absorption spectrum. We have investigated the application of P in quasi solid state dye-sensitized solar cells (DSSCs). Under illumination intensity of 100 mW cm⁻², a power conversion efficiency of 2.90% was obtained for the DSSC based on P as sensitizer, which was significantly improved to 4.22% upon addition of deoxycholic acid (DCA) into the P solution for TiO₂ sensitization. Coadsorption of DCA decreased the dye adsorption, but significantly improved both short circuit current (J_sc) and open circuit voltage (V_oc). The breakup of π stacked aggregates might improve the electron injection yield and thus J_sc. The electrochemical impedance data indicate that the electron lifetime was improved by the coadsorption of DCA, which was attributed to the improvement in both V_oc and J_sc. The increase in J_sc has also been attributed to the reduction of the back reaction i.e., the recombination of electrons with tri-iodide ions.     

Role of Conducting Polymers in Enhancing TiO2-based Photocatalytic Dye Degradation: A Short Review

Research in the field of TiO₂-based photocatalysis has gained wide attention to address important energy and environmental problem. Lately, the use of conducting polymers as photosensitizers has proven to immensely enhance photodegradation by exhibiting excellent photocatalytic activity under both ultraviolet light and natural sunlight irradiation which is not possible using semiconductors alone. Considering the unique performance of conducting polymer-based nanocomposites in photocatalysis, the present review provides the recent advances in the development of ultraviolet and visible light-responsive conducting polymer-based TiO₂ nanocomposites for their potential application in environmental remediation. This review ends with a summary focusing on the challenges and new dimensions in this still emerging area of research.     

Precise Molecular Engineering of Photosensitizers with Aggregation‐Induced Emission over 800 nm for Photodynamic Therapy

Owing to efficient singlet oxygen (¹O₂) generation in aggregate state, photosensitizers (PSs) with aggregation‐induced emission (AIE) have attracted much research interests in photodynamic therapy (PDT). In addition to high ¹O₂ generation efficiency, strong molar absorption in long‐wavelength range and near‐infrared (NIR) emission are also highly desirable, but difficult to achieve for AIE PSs since the twisted structures in AIE moieties usually lead to absorption and emission in short‐wavelength range. In this contribution, through acceptor engineering, a new AIE PS of TBT is designed to show aggregation‐induced NIR emission centered at 810 nm, broad absorption in the range between 300 and 700 nm with a large molar absorption coefficient and a high ¹O₂ generation efficiency under white light irradiation. Further, donor engineering by attaching two branched flexible chains to TBT yielded TBTC8 , which circumvented the strong intermolecular interactions of TBT in nanoparticles (NPs), yielding TBTC8 NPs with optimized overall performance in ¹O₂ generation, absorption, and emission. Subsequent PDT results in both in vitro and in vivo studies indicate that TBTC8 NPs are promising candidates in practical application.     

Platinum-based photosensitizer with near-infrared aggregation-induced emission for synergistic photodynamic-chemo theranostics

Photodynamic therapy (PDT) is of great interest as an emerging paradigm towards cancer treatment, owing to its advantages of minimal invasiveness and low toxicity. In this work, we incorporated cisplatin into an AIE-based photosensitizer (BT) and achieved a highly efficient antitumor drug (BT-Pt). Possessing AIE characteristics, BT-Pt exhibited NIR fluorescence with large Stokes shift in cells, which can guide the location of the drug. More importantly, the ROS generation efficiency of BT-Pt has extremely been promoted with the fabrication of cisplatin, compared with BT. As a result, BT-Pt demonstrated favorable therapeutic efficacy with a half maximal inhibitory concentration (IC₅₀) value of 1.54 μM for HeLa cells upon white light irradiation, attributed to its synergetic PDT and chemotherapy. The design strategy of such platinated photosensitizer showed great potential in developing multifunctional anticancer drugs with combinatorial photodynamic–chemotherapy, especially when ablating cisplatin resistant cancer cells and hypoxic tumors.     

可见光条件下光敏剂引发的Aza-Henry反应

合成了3-甲氧基噻吨酮,并通过核磁共振、红外光谱、高分辨质谱对其结构进行表征。3-甲氧基噻吨酮紫外-可见光谱表明,其在可见光范围内的紫色光(380 nm)附近有吸收,是一种可见光光敏剂。将该光敏剂应用于2-苯基-1,2,3,4-四氢异喹啉和硝基甲烷的Aza-Henry反应中,在紫色LED光照射的条件下,摩尔分数为5%的光敏剂使反应在6 h内产物的分离产率为84%。根据实验结果,提出了光催化的Aza-Henry反应机理,光敏剂在光照条件下进行能量转移产生单线态氧,单线态氧促进Aza-Henry反应的进行。     

Boosting photocatalytic hydrogen generation by the combination of tunable cobaloxime and covalent organic framework

Here, we have investigated the photocatalytic activities of substituted Schiff-based COFs as photosensitizes and molecular cobaloximes as non-noble metal co-catalysts for the hydrogen production from water under visible light irradiation. The steric and electronic properties of the functional group at the backbone of COFs, and cobaloximes, have a pronounced effect on the photocatalytic performance of the photocatalytic system. We established that the methyl-substituted COF (COF-AD₁) as a photosensitizer, chloro (p-N,N-dimethylpyridine) cobaloxime (Co-2) as co-catalyst and triethanolamine (TEOA) sacrificial electron donor form a highly active photocatalytic system which exhibited a record hydrogen production rate of 7072 μmolg^?1h^?1 with a quantum efficiency of 51.4%, TOF of 35.6, TON of 462.4 for 20 h in a 4:1 acetonitrile/water mixture.     

Two-dimensional X-shaped organic dyes bearing two anchoring groups to TiO2 photoanode for efficient dye-sensitized solar cells

Novel two-dimensional X-shaped donor–π–acceptor (D–π–A)-type dyes were designed and successfully synthesized for use in a dye-sensitized solar cell (DSSC). Two triphenylamine units in these dyes act as electron donor units, while two cyanoacrylic acid groups act as electron acceptor units and anchoring groups to the TiO₂ photoanode. The photovoltaic properties of the newly synthesized dye-containing DSSCs were investigated to identify the effects of conjugation length between the electron donors and acceptors, and the molecular energy levels of the dyes. Among the three dyes we synthesized, (2E,2′E)-3,3′-(5′,5″-(4,5-bis(4-(bis(4-tert-butylphenyl)amino)styryl)-1,2-phenylene)bis(2,2′-bithiophene-5′,5-diyl))bis(2-cyanoacrylic acid) (11) showed the highest power conversion efficiency of 3.14% (η_max = 4.06% with TiCl₄ treatment) under AM 1.5G illumination (100 mW cm⁻²) in a photoactive area of 0.418 cm² with short circuit current density of 7.27 mA cm⁻², open circuit photovoltage of 612 mV, and a fill factor of 70.6%.     

光敏剂诱导化学镀工艺研究

根据光化学催化原理,在酸性镀液中加入光敏剂,通过光照,实现在室温条件下的化学镀镍-磷合金。在以前所做的实验基础上,着重研究了光敏剂浓度、硫酸镍浓度、次亚磷酸钠浓度、pH值、入射光强度及络合剂柠檬酸三钠和乳酸浓度等一系列因素对沉积速度的影响,并得到一系列的规律和结论;利用循环伏安法和交流阻抗技术对不同镀液体系进行测试,提出了光敏剂诱导化学镀反应的机理。