Topological, morphological and optical properties of Gamma irradiated Ni (II) tetraphenyl porphyrin thin films

Photofixation of N2 to ammonia utilizing Ni@TPP-HPA nanocomposite under visible-light illumination

The production of ammonia as an important raw material in the chemical, agricultural, and food industries has been always a significant concern. However, conventional ammonia production methods require high energy consumption and costs. The photocatalytic rotes use green light sources and cost-effective photocatalysts to obtain ammonia from water under aerobic conditions and preventing production of greenhouse gases in the environment. To produce an effective heterogeneous catalyst, a new tetraphenylporphyrin-heteropolyacid (TPP-HPA) nanohybrid material is synthesized and loaded onto Ni nanoparticles in this work. Then, FE-SEM, EDS, XRD, and FT-IR analyses were applied to characterize the prepared nanohybrid material Ni@TPP-HPA. After that, the new inorganic-organic nanohybrid photocatalyst was introduced as an effective, environmental friendly, and recyclable mediator for N2 photofixation. The results showed that Ni@TPP-HPA is a good photocatalyst for the N2 fixation reaction and can be easily recycled without losing its activity for at least five runs. The Ni@TPP-HPA nanocomposite demonstrated the maximum ammonia generation by 2760 μmol L-1 g-1 under mild conditions when using methanol as a hole scavenger. Additionally, effects of solvent type, temperature, reaction time, irradiation source, solution pH, and other electron scavengers on the rate of NH4+ production were investigated and discussed.

Influence of gamma irradiation on linear and nonlinear optical properties of nanocrystalline manganese(III) chloride tetraphenylporphine thin films

90 nm thickness of MnTPPCl thin films were deposited by thermal evaporation technique on glass and quartz substrates under vacuum. The examined thin films were irradiated by ⁶⁰Co γ-rays with 150 kGy. XRD and FTIR techniques are used to comprehend the structure of MnTPPCl thin films. The results confirmed that the structure of pristine thin films is nanocrystallites dispersed in the amorphous matrix and the irradiated films have an amorphous structure. Refractive index, oscillator's parameters (dispersion energy, E_d, oscillator energy, E_o), the absorption coefficient, optical energy gap, and Urbach energy were estimated before and after exposure to γ-irradiation by using spectrophotometric measurements. All mentioned parameters were influenced by the γ-irradiation process. The type of electronic transition was classified as a direct allowed transition. The gamma irradiation process was caused an increase in the fundamental band gap energy from 2.48 to 2.52 eV (blue shift) which is good for solar cells window. Third-order nonlinear optical susceptibility χ⁽³⁾ and the nonlinear refractive index n₂ of MnTPPCl thin films were studied before and after γ-irradiation. An increase in χ⁽³⁾ and n₂ with γ-irradiation is observed, so it is recommended to be used as optical switching applications.

Structures and properties of porphyrin-based film materials part I. The films obtained via vapor-assisted methods

This review is devoted to porphyrin-based film materials. Various technological and scientific applications of ones are close to surface and interface related phenomena. In the part I of review the following topics are discussed the recent progress in field of submonolayers, monolayers and multilayers films on the vapor-solid interfaces, including results on (i) conformational behavior of adsorbed molecules, (ii) aggregation and surface phases formation, (iii) on-surface coordination networks, and (iv) on-surface chemical reactions. The examples of combined approaches to developing materials and porphyrin-based film materials application are also presented.

Ultrafast dynamics of hemin aggregates

The effects of solvents on the conformation of hemin and their implications on the dynamics of the complex have been studied using the time-resolved optical Kerr effect (OKE) with 35 fs laser pulses (at a central wavelength of 800 nm). The OKE enabled estimation to be made of the third-order nonlinear electronic susceptibility (χ⁽³⁾) of hemin solutions: it was found to be significantly smaller than that in hemin thin films. The real and imaginary components of χ⁽³⁾ were negative in both the solvents, suggesting that one-photon as well as two-photon absorption processes contribute to the nonlinear electronic susceptibility of hemin. Our study of the ultrafast heme dynamics not only unveils the instantaneous electronic response related to electronic susceptibility but also brings to the fore a novel libration process that has hitherto remained undetected. The hindered rotation in the femtosecond domain that may be responsible for this libration process possibly stems from π-π hemin oligomers formed in aqueous solution. The present results provide new insights into the conformational dynamics in the self-assembly of heme oligomers that may also be significant in certain pathogenic conditions where free heme is formed in biological systems.

Influence of gamma ray irradiation and annealing temperature on the optical constants and spectral dispersion parameters of metal-free and zinc tetraphenylporphyrin thin films: A comparative study

In this work, we report on the effect of γ-ray irradiation and annealing temperature on the optical properties of metal-free tetraphenylporphyrin, H2TPP, and zinc tetraphenylporphyrin, ZnTPP, thin films. Thin films of H2TPP and ZnTPP were successfully prepared by the thermal evaporation technique. The optical properties of H2TPP and ZnTPP films were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500 nm. The absorption spectra of H2TPP showed four absorption bands, namely the Q, B, N and M bands. The effect of inserting Zn atom into the cavity of porphyrin macrocycle in ZnTPP molecule distorted the Q and B bands, reduced the width of absorption region and influenced the optical constants and dispersion parameters. In all conditions, the type of electron transition is indirect allowed transition. Anomalous dispersion is observed in the absorption region but normal dispersion occurs in the transparent region of spectra. We adopted multi-oscillator model and the single oscillator model to interpret the anomalous and normal dispersion, respectively. We have found that the annealing temperature has mostly the opposite effect of γ-ray irradiation on absorption and dispersion characteristics of these films.

Successive ion layer adsorption and reaction (SILAR) technique synthesis of Al(III)-8-hydroxy-5-nitrosoquinolate nano-sized thin films: characterization and factors optimization

Nano Al(III)-8-hydroxy-5-nitrosoquinolate [Al(III)-(HNOQ)(3)] thin films were synthesized by the rapid, direct, simple and efficient successive ion layer adsorption and reaction (SILAR) technique. Thin film formation optimized factors were evaluated. Stoichiometry and structure were confirmed by elemental analysis and FT-IR. The particle size (27-71 nm) was determined using scanning electron microscope (SEM). Thermal stability and thermal parameters were determined by thermal gravimetric analysis (TGA). Optical properties were investigated using spectrophotometric measurements of transmittance and reflectance at normal incidence. Refractive index, n, and absorption index, k, were determined. Spectral behavior of the absorption coefficient in the intrinsic absorption region revealed a direct allowed transition with 2.45 eV band gap. The current-voltage (I-V) characteristics of [Al(III)-(HNOQ)(3)]/p-Si heterojunction was measured at room temperature. The forward and reverse I-V characteristics were analyzed. The calculated zero-bias barrier height (Φ(b)) and ideality factor (n) showed strong bias dependence. Energy distribution of interface states (N(ss)) was obtained.