Theoretical insights on type I/II photoreactions of potential Zn(II) polypyridyl photosensitizers for two-photon photodynamic therapy.

Large two-photon absorption cross-sections are vital to photosensitizers (PSs) in TP-PDT, which can be used to develop in-depth treatment for diseased cells and minimize the harm to surrounding cells. Here, we conduct a study about photophysical properties of one Ru(II) polypyridyl complex and two designed Zn(II) polypyridyl complexes by means of DFT and TD-DFT methods. The main results are as follows: firstly, the two-photon absorption spectrum of two designed complexes Zn-OMe and Zn-OCOOCH3 are all within the phototherapeutic window (550-900 nm). Secondly, large SOC values and small energy gaps ΔES-T of these complexes guarantee the efficiency of ISC process. Thirdly, their T1 energy is greater than that required for generating 1O2 (0.98 eV) via Type II photoreaction. In addition, the calculated results of vertical electron affinities (VEA) and vertical ionization potentials (VIP) show that these complexes are able to form superoxide ions O2(-) via Type I photoreaction. Specifically, both of two designed Zn-centric complexes have larger TPA cross-sections than that of Ru-centric complex. In a word, we are pleased to report two potential photosensitizers with excellent performance and reasonable price for Type I/II photoreactions. We expect our study will offer some theoretical guidance and help in TP-PDT.

Theoretical insight into the photophysical properties of long-lifetime Ir(iii) and Rh(iii) complexes for two-photon photodynamic therapy.

Two-photon photodynamic therapy (TP-PDT) plays crucial roles in curing tumors because it involves deep penetration of drugs into the tissue and has minimal damage to the surrounding cells. Our theoretical study was aimed at providing fresh insights into photosensitizers, such as [Ir(N^C)2(N^N)]+ (N^C = 2-phenylpyridine, N^N = bis-benzimidazole) and [Rh(N^C)2(N^N)]+, to treat cancer via the TP-PDT route. To better understand the properties of the complexes [Ir(N^C)2(N^N)]+ and [Rh(N^C)2(N^N)]+, the one-photon and two-photon absorption electronic spectra, energy gap (ΔES-T), strength of two-photon absorption cross-section (δ), spin-orbit matrix element (S1|HSO|Tj), and phosphorescence lifetimes (τ) were calculated by DFT and TD-DFT. The calculation results suggested that both complexes met the criteria (i.e. an efficient ISC process, enough energy to produce 1O2 and phototherapeutic window of the absorption wavelength) of photosensitizers; importantly, the designed complex [Rh(N^C)2(N^N)]+ had better performance than [Ir(N^C)2(N^N)]+, especially in the long-lived triplet excited state. It is expected that our research can make quite a few contributions to the development of photosensitizers and establish some guidelines for experiments based on TP-PDT.

Theoretical study on photophysical properties of three high water solubility polypyridyl complexes for two-photon photodynamic therapy.

Two-photon photodynamic therapy (TP-PDT) is a very promising treatment that has drawn much attention in recent years due to its ability to penetrate deeper into tissues and minimize the damage to normal cells. Here, the properties of three highly water soluble Ru(ii) and Zn(ii) polypyridyl complexes as photosensitizers (PSs) were examined, including the one-photon and two-photon absorption (OPA and TPA) spectra, singlet-triplet energy gap (ΔH-L), TPA cross-section and spin-orbit coupling constant via Density Function Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT). Their potential therapeutic use as photosensitizers in TP-PDT is proposed, where the reasoning is as follows: first, they possess strong absorption in the therapeutic window; second, the vertical excitation energy is greater than 0.98 eV, which can generate a singlet oxygen species and the remarkable coupling between the S1 and T1 states. Moreover, the spin-orbit matrix elements are greater than 0.24 cm-1 for Ru-bpy and Zn-tpy, indicating that the intersystem spin crossing processes are efficient. It is expected that these complexes will be applied to PSs in TP-PDT, and we hope this research can serve as a guideline for the development of efficient two-photon PSs.

Volatile Organic Compound Gas-Sensing Properties of Bimodal Porous α-Fe2O3 with Ultrahigh Sensitivity and Fast Response.

Porous solid with multimodal pore size distribution provides plenty of advantages including large specific surface area and superior mass transportation to achieve high gas-sensing performances. In this study, α-Fe2O3 nanoparticles with bimodal porous structures were prepared successfully through a nanocasting pathway, adopting the bicontinuous 3D cubic symmetry mesoporous silica KIT-6 as the hard template. Its structure and morphology were characterized by X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, and so on. Furthermore, the gas sensor fabricated from this material exhibited excellent gas-sensing performance to several volatile organic compounds (acetone, ethyl acetate, isopropyl alcohol, n-butanol, ethanol, and methanol), such as ultrahigh sensitivity, rapid response speed (less than 10 s) and recovery time, good reproducibility, as well as stability. These would be associated with the desirable pore structure of the material, facilitating the molecules diffusion toward the entire sensing surface, and providing more active sensing sites for analytical gas.

Ordered Large-Pore Mesoporous Cr2O3 with Ultrathin Framework for Formaldehyde Sensing.

A series of ordered mesoporous chromium oxides (Cr2O3) were synthesized by first replicating bicontinuous cubic Ia3d mesoporous silica (KIT-6), then a controlled mesostructural transformation from Ia3d to I4132 symmetry during the replication from KIT-6 to Cr2O3 was achieved by reducing the pore size and interconnectivities of KIT-6, accompanied with an increase in pore size from 3 to 12 nm and a decrease in framework thickness from 8.6 to 5 nm of the resultant Cr2O3 replicas. The gas-sensing behavior of the Cr2O3 replicas toward formaldehyde (HCHO) was systematically investigated. Ordered mesoporous Cr2O3 with both large accessible pores (12 nm) and an ultrathin framework (5 nm) exhibits the best sensing performance, with a response (Rgas/Rair = 119) toward 9 ppm of HCHO 4.4 times higher than that (Rgas/Rair = 27) of its counterpart with small pores and a thick framework. Moreover, it possesses excellent selectivity for detecting HCHO over other interference gases such as CO, benzene, toluene, p-xylene, NH3, H2S, and moisture. The significantly enhanced sensing performance of ordered large-pore mesoporous Cr2O3 with ultrathin framework suggests its great potential for the selective detection of HCHO.

Ordered mesoporous NiO with thin pore walls and its enhanced sensing performance for formaldehyde.

A class of formaldehyde (HCHO) gas sensors with a high response were developed based on ordered mesoporous NiO, which were synthesized via the nanocasting route by directly using mesoporous silica as the hard template. A series of mesoporous NiO with different textural parameters such as specific surface area, pore size, pore wall thickness were achieved by selecting mesoporous silica with different pore sizes as templates. The gas sensing properties for formaldehyde (HCHO) of the NiO specimens were examined. The results show that this mesoporous NiO possesses a much higher response to HCHO even at low concentration levels than the bulk NiO, and a larger specific surface area and pore size as well as thinner pore walls would be beneficial for enhancing the sensing properties of NiO.

Synthesis and characterization of hollow cadmium oxide sphere with carbon microsphere as template.

Cadmium Oxide (CdO) hollow spheres have been synthesized by using carbon microsphere as sacrificial template. The products were characterized by X-ray powder diffraction (XRD), scanning electronic microscopy (SEM) and transmission electron microscopy (TEM). The average diameter and shell thickness of as-prepared hollow spheres are about 600 nm and 50 nm, respectively. The formation of hollow spheres was investigated and it was found that the shell formed when the heating temperature reached about 673 K and the sequential heat treatment could remove the carbon template. Moreover, the influence of other experimental parameters including concentration (0.1-5 M) and type of cadmium salts (cadmium chloride, cadmium acetate and cadmium nitrate, etc.) as well as type of solvents (water, ethanol and dimethylfomamide) were also investigated.

Facile one-step solvothermal synthesis of iron oxide/polypyrrole nanocomposites and their magnetic properties.

Iron oxide/polypyrrole (PPy) nanocomposites (NCs) were prepared by a facile one-step solvothermal process using FeCl3 x 6H2O and pyrrole as starting materials. The resultant products were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and superconducting quantum interference device magnetometer (SQUID). TEM image suggested the mesoporosity of the iron oxide/polypyrrole nanocomposites and pyrrole is found to play an important role in controlling the final morphology and porosity of the products. Magnetic hysteresis measurement reveals that nanocomposite shows a superparamagnetic behavior, and possesses a larger saturation magnetization strength (M(s)) of about 15.06 emu/g at room temperature, which allows its application in adsorption or separation as magnetically recyclable materials.