Synthesis of carboxylated chlorophyll derivatives and their activities in dye-sensitized solar cells

Chlorophyll-a derivatives possessing a carboxy group in the substituent at the 3-position were prepared by chemical modification of methyl pyropheophorbide-d bearing the 3-formyl group via a Wittig, Barbier-type, or Knoevenagel reaction. The synthetic carboxylated chlorophyll pigments were employed as dye sensitizers for solar cells and their performances were compared in a conventional device based on a mesoporous titanium dioxide electrode and a liquid electrolyte. The solar power conversion efficiency was suppressed with an increase in the length of the oligomethylene moiety between the chlorin π-system and the carboxy group, while a corresponding π-linked ethenylene spacer enhanced the efficiency.     

Curcumin as a photosensitizer: From molecular structure to recent advances in antimicrobial photodynamic therapy

Nowadays multi-drug resistant microorganisms is a serious public health problem worldwide. To overcome it, new antimicrobial strategies have been developed. Among them, antimicrobial photodynamic therapy is an efficient tool against various micro-organisms in different medical and healthcare fields. The antimicrobial photodynamic protocol is based on the interaction of a photosensitizer, molecular oxygen, and an appropriate light source. Herein, we described the main physical and chemical proprieties of curcumin, an useful natural photosensitizer, including its degradation pathways, analytical methods for quantification, extraction method, synthetic methodologies, and pharmaceutical formulations used. Moreover, a comprehensive review of the past 10 years (2010−2019) concerning the application of curcumin as photosensitizer against microorganisms is described and discussed.     

Polyoxometalate-based high-nuclear cobalt-vanadium-oxo cluster as efficient catalyst for visible light-driven CO2 reduction

A high-nuclear {Co₁₆-V₄} cluster was firstly isolated by pure inorganic lacunary POM units, which exhibits excellent photocatalytic activity for CO₂-to-CO conversion under visible light irradiation.     

Fullerene C60 derivatives as antimicrobial photodynamic agents

Functionalized fullerenes have shown interesting biomedical applications as potential phototherapeutic agents. The hydrophobic carbon sphere of fullerene C₆₀ can be substituted by cationic groups to obtain amphiphilic structures. These compounds absorb mainly UV light, but absorption in the visible region can be enhanced by anchoring light-harvesting antennas to the C₆₀ core. Upon photoexcitation, fullerenes act as spin converters by effective intersystem crossing. From this excited state, they can react with ground state molecular oxygen and other substrates to form reactive oxygen species. This process leads to the formation of singlet molecular oxygen by energy transfer or superoxide anion radical by electron transfer. Photodynamic inactivation experiments indicate that cationic fullerenes are highly effective photosensitizers with applications as broad-spectrum antimicrobial agents. In these structures, the hydrophobic character of C₆₀ improves membrane penetration, while the presence of positive charges increases the binding of the fullerene derivatives with microbial cells. Herein, we summarize the progress of antimicrobial photodynamic inactivation based on substituted fullerenes specially designed to improve the photodynamic activity.     

Photosensitizing properties of the porphycene immobilized in sol-gel derived silica coating films

Porphycene was covalently immobilized in a sol-gel silica film deposited on a glass plate, and the immobilized porphycene showed a photosensitizing property with recycling for the photo-oxidation of 1,5-dihydroxynaphthalene.     

Synthesis and Photoproperties of Silicon Phthalocyanines and Silicon Naphthalocyanines

Silicon phthalocyanines and silicon naphthalocyanines, which are two derivatives in the family of hematoporphyrin, have been synthesized to assess their potential as photosensitizers for photodynamic therapy. For these complexes the red shift of their Q-band maximum absorption tends to depend on the nature of the axial substituent. The bimolecular rate coefficients for the interacting between photosensitizer, either SiNC or SiPC, and generated singlet molecular oxygen were determined from the time-resolved emission spectrum of singlet oxygen at 1.27 μm. On the basis of these data the electron-transfer quenching mechanism is discussed in relation to the Marcus model.     

Biomimetic synthesis of CuInS2 nanoparticles: Characterization,cytotoxicity, and application in quantum dots sensitized solar cells

CuInS₂ (CIS) nanoparticles have unique chemical, toxicological and optoelectronic properties that favor their technological applications. In the present work we report a novel one step biomimetic method for the aqueous synthesis of CIS nanoparticles, that is also low cost and environmentally friendly. This biomimetic method uses only CuSO₄ and InCl₃ as precursor salts, and the biological molecule glutathione as sulfur donor and stabilizer of the nanoparticles (NPs). The reaction is performed at low temperatures, under aerobic conditions and atmospheric pressure. CIS nanoparticles produced by our biomimetic method exhibit fluorescence emission between 650 and 700 nm when excited at 500 nm. A size between 10 and 15 nm was determined by Dynamic light scattering (DLS) and corroborated by electron transmission microscopy. X-ray diffraction analysis (XRD) confirmed the crystalline structure of the CIS NPs produced. Energy Dispersive X-Ray Spectroscopy (EDX) analyses revealed the presence of Cu, In, and S in a 0.6: 1.4: 2 ratio, which has been reported for other CIS NPs in literature. No cytotoxicity of CIS NPs was observed in human OKT6/TERT2 cells and bacteria. Besides, the potential application of biomimetic CIS NPs as photosensitizers in quantum dots sensitized solar cells (QDSSCs) was confirmed. The biocompatibility, spectroscopic properties, and energy harvesting performance in solar cells of the CIS NPs produced by our biomimetic method make them suitable for their use in different biotechnological applications.     

A Highly Efficient Aggregation-induced Emission Photosensitizer for Photodynamic Combat of Multidrug-resistant Bacteria

With the antibiotic abuse and the resulting increased antibiotic resistance,the bacterial infection has posed a serious threat to human health.Photodynamic therapy is an effective tool for treating localized and superficial infections.It is a promising approach for the treatment of superbugs and with minimal risk of induced antibiotic resistance.Herein,an isoquinolinium-based photosensitizer,LIQ-TPE,with aggregation-induced emission properties is designed and synthesized.It is with high 1O2 generation efficiency and shows efficient antibacterial performance towards both Gram-negative and Gram-positive bacteria,and even methicillin-resistant Staphylococcus aureus(MRSA).LIQ-TPE thus shows great promise as an effective antimicrobial agent to combat the menace of multi-drug resistant bacteria.     

Polydopamine as a Visible-Light Photosensitiser for Photoinitiated Polymerisation

Polydopamine (PDA) is a synthetic model for melanin and has a wide range of opto-electronic properties that underpin its utility in applied and biological settings, from broadband light absorbance to possessing stable free radical species. Here, we show that PDA free radicals are photo-responsive under visible light irradiation, enabling PDA to serve as a photo-redox catalyst. Steady-state and transient electron spin resonance spectroscopy reveals a reversible amplification in semiquinone radical population within PDA under visible light. This photo-response modifies the redox potential of PDA and supports sensitisation of exogenous species via photoinduced electron transfer (PET). We demonstrate the utility of this discovery by employing PDA nanoparticles to photosensitise a common diaryliodonium photoinitiator and initiate free-radical polymerisation (FRP) of vinylic monomers. In situ ¹H nuclear magnetic resonance spectroscopy reveals an interplay between PDA-driven photosensitising and radical quenching during FRP under blue, green, and red light. This work provides crucial insights into the photoactive free radical properties of melanin-like materials and reveals a promising new application for polydopamine as a photosensitiser.     

平面型卟啉类衍生物吸收光谱的密度泛函计算

用于光动力疗法（PDT）中的光敏剂是一类吸收一定波长的光后达到激发三重态,然后将三重态能量转移给生物体内的氧分子使得基态氧激发为单线态氧的一类物质。目前,临床应用的光敏剂大部分是以卟啉为主的平面型分子。平面分子一般具有较大的共轭键,被光激发后系间窜跃小,三重态寿命较长,因此可以获得高产率的单线态氧。然而临床使用的这类光敏剂吸收波长位于紫外区域,照射光会对人体组织造成光损伤,因此改善临床光敏剂光毒性特征,合成具有可见光区域吸收波段的光敏剂是光动力疗法研究的重要内容之一。该研究依据密度泛函(DFT)及其含时理论(TD-DFT),对三类平面型卟啉衍生物[耳坠型卟啉(a), 三磺酸基酞菁(b), 三磺酸基酞菁合Ni(Ⅱ)(c)]的基态和激发态性质进行了严格的密度泛函计算。几何优化计算显示：分子(a)的最稳定构型中,所有原子都处于一个平面,分子直径大约是7 Å, 分子空穴达到5 Å。分子(b)所有的原子也处于同一平面,分子直径达到8 Å,但是分子空穴只有4 Å。分子(c)的最稳定构型与平面结构发生了偏离,这是由于金属Ni的四配位倾向形成变形四面体,分子的空穴变得更小。几何优化结果说明耳坠型卟啉分子大的空穴有助于其捕获更多的基态氧并进行能量传递。前线轨道能量和轨道布局计算显示：耳坠型分子(a)最高占据能量是最高的,即电子更易被激发。三类分子的最高占据轨道与最低空轨道的能级间隔分别为0.072, 0.076和0.075 a.u.,可以看出耳坠型分子(a)有最低的能级间隙。从轨道布局来看,三类分子中所有原子的p轨道参与了共轭大π键的形成,其中分子(c)中金属d轨道也参与了大π键的形成。对三类分子的吸收光谱进行了模拟,三类分子都具有卟啉特有的Soret带和Q带。(a)分子Q带位于450～900 nm,(b)分子和(c)分子的Q带位于400～800 nm, 其中(a)分子的最大吸收波段是939 nm。该研究从分子结构,轨道能量以及吸收光谱对三类卟啉类光敏剂的微观特性进行了理论计算和讨论,研究结果将为发现和开发近红外吸收的卟啉类高效光敏剂提供理论依据。