Investigation of Chlorophyl-a Derived Compounds as Photosensitizer for Photodynamic Inactivation

Chlorophyll has unique physicochemical properties which makes them good as photosensitizer of Photodynamic Inactivation (PDI). The physicochemical properties of chlorophyll as photosensitizer can be optimized through several routes.  One of the possible route is by replacing the metal ion center of chlorophyll with other ions. In this research, the effect of coordinated metal ion in the natural chlorophyll-a was studied for bacterial growth (S. aureus) inhibition. The replacement of metal in the center of chlorophyll hopefully can improve the intensity of Intersystem Crossing Mechanism (ISC) lead to the formation of singlet oxygen species. The chlorophyll a and b were isolated from spinach via precipitation technique using 1,4 dioxane and water. The chlorophyll a and b were separated using sucrose column chromatography. The thin layer chromatography result showed that chlorophyll a (Rf: 0.57) had been well separated with chlorophyll b (Rf: 0.408). The absorption spectra of chlorophyll a and b showed that the Soret band was observed at 411 and 425 nm, while the Q band appeared at 663 and 659 nm. Replacement of metal ion center shifted the Soret band of chlorophyll- a derivatives to lower energy region, while Q-band was slightly shifted to the higher energy region. The absorption and the fluorescence intensity were  also observed decreasing after ion replacement. The Inhibition activity investigation over S. aureus showed the highest inhibition activity was exhibited by Zn-pheophytin-a (66.8%) followed by chlorophyll a (30.1 %) and Cu-pheophytin-a (0%). The inhibition activity is correlated with decreasing fluorescence intensity. The formation of singlet oxygen by ISC mechanism is hypothesized to deactivate the excitation state of Cu-pheophytin-a. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Pengaruh Variasi Dopan Asam Terhadap Kinerja Baterai Sekunder Polianilina|Zn

Studi tentang baterai sekunder polianilina(PAni)|Zn telah banyak dikembangkan, tetapi sejauh ini masih belum ada penjelasan mengenai pengaruh asam terhadap kinerja baterai tersebut. PAni disitensis menggunakan metoda elektrodeposisi dengan tegangan 0,7 V selama 30 menit. PAni hasil sintesis dikarakterisasi menggunakan Voltammetri dan Spektroskopi Inframerah. Baterai PAni|Zn didesain dalam bentuk sandwich, kemudian pengukuran kinerja digunakan impedansi serta pengisian-pengosongan. Baterai dengan elektroda PAni-Cl dan PAni-Br mempunyai kinerja yang lebih baik dengan specific capacity saat ke-60 yaitu 55,4 dan 37,4 mAh g-1. Pengukuran impedansi pada baterai dengan elektroda PAni-Cl, PAni-Br, dan PAni HClO4, menunjukan resistance solution (Rs) secara berurutan yaitu 1,38; 2,56; dan 3,03 W dan resistance charge transfer (Rct) 2,24; 2,97; dan 7,71 W. Oleh sebab itu, baterai PAni|Zn dengan dopan HCl menunjukkan kinerja terbaik dibanding dengan asam yang lain

Hydroxymethyl PEDOT microstructure-based electrodes for high-performance supercapacitors

The development of conducting polymer-based supercapacitors offers remarkable advantages, such as good ionic and electronic conductivity, ease of synthesis, low processing cost, and mechanical flexibility. 3,4-ethylenedioxythiophene (PEDOT) is a conducting polymer with robust chemical and environmental stability during storage and operation in an aqueous environment. Yet, improving its electrochemical capacitance and cycle life remains a challenge for high-performance supercapacitors exceeding the current state-of-the-art. The fabrication of PEDOT composites with carbon nanomaterials and metal oxides is the commonly used approach to enhance capacitance and stability. This work discusses a comparative study to fabricate highly stable PEDOT derivative electrodes with remarkable specific capacitance via a straightforward electrochemical polymerization technique. The hydroxymethyl PEDOT (PEDOTOH) doped with perchlorate in a dichloromethane (DCM) solvent (197 F g−1) exhibits superior performance compared to the polymer formed in an aqueous solution (124 F g−1). Furthermore, the electropolymerized PEDOTOH on flexible Au/Kapton substrates was assembled into a free-standing symmetrical supercapacitor in an agarose additive-free gel. The use of agarose gel electrolytes can offer easy handling, no leakage, moderate ionic conductivity, and flexibility for miniaturization and integration. The supercapacitor reached a specific capacitance of 36.96 F g−1 at a current density of 13.7 A g−1, an energy density of 14.96 Wh kg−1, and a power density of 22.2 kW kg−1 among the highest values reported for PEDOT-based supercapacitors. The self-standing supercapacitor achieves an industry-par capacitance retention of ∼98% after 10000 charge/discharge cycles at 10 A g−1. This study provides insights into the effect of solvents and electropolymerization modes on the polymer structure and its electrochemical properties toward high-performance supercapacitor devices

Analysis of ethylene biosynthesis gene expression profile during titanium dioxide (TiO2) treatment to develop a new banana postharvest technology

Banana is an important crop that demands proper methods in postharvest handling. As a climacteric fruit, thebanana fruit ripening process is affected by ethylene. Several methods have been developed to extend the shelf life of a banana, such as using ethylene scrubbers. In this study, ttanium dioxide (TiO2), a photocatalyst, was used as an alternatve method to delay the fruit ripening process. The effect of TiO2 on the ripening‐related gene MaACS1 was investgated. Banana fruits were placed in a TiO2‐coated glass chamber and observed for ten days. Fruit ripening in the treated chamber was delayed for eight days compared to the control. Total RNA was extracted from control and TiO2‐treated fruit pulp and synthesized into cDNA. Reverse transcripton PCR was performed to investgate the gene expression, which showed that MaACS1 expression was relatvely lower than treated control. The fnding of these studies suggested that the TiO2 chamber has the potental to extend the shelf life of banana by delaying its ripening process and decreasing the expression of MaACS1. To the best of our knowledge, no previous study has investgated the effect of TiO2 on the expression of genes related to banana fruit ripening

The effect of the A-Site cation on the structural transformations in ABi4Ti4O15 (A¼ Ba, Sr): Raman scattering studies

The effect of the type of A-site cation on the structural transformations of ABi4Ti4O15 (A¼ Ba, Sr) was studied by a comparative analysis of the Raman scattering of BaBi4Ti4O15 and SrBi4Ti4O15 in the temperature range 120–850 K. The results are also compared with those previously reported on PbBi4Ti4O15. Similar to PbBi4Ti4O15, BaBi4- Ti4O15, and SrBi4Ti4O15 exhibit an additional structural transformation at Ta < Tc and Ta decreases with the increase in the ionic radius of the A-site cation. This structural alteration consists of rearrangements of the A-site cations, which for A¼ Ba is accompanied by readjustment of the octahedral tilting and a change in the BO6 geometry. The results presented here confirm that the development of spontaneous polarization in four-layer Aurivillius-type ferroelectrics is triggered by the rigid-layer phonon mode, i.e., vibrations of the Bi2O2 planes relative to the perovskite-like blocks, rather than by cationic vibrations only within the perovskites blocks

Synthesis of Spherical Nanostructured g-Al2O3 Particles using Cetyltrimethylammonium Bromide (CTAB) Reverse Micelle Templating

We demonstrated the synthesis of spherical nanostructured g-Al2O3 using reverse micelle templating to enhance the surface area and reactant accessibility. Three different surfactants were used in this study: benzalkonium chloride (BZK), sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). We obtained spherical nanostructured particles only using CTAB that form a reverse micelle emulsion. The particles have wide size distribution with an average size of 2.54 mm. The spherical particles consist of nanoplate crystallites with size 20-40 nm randomly arranged forming intercrystallite spaces. The crystalline phase of as-synthesized and calcined particles was boehmite and g-Al2O3, respectively as determined by XRD analysis. Here, the preserved particle morphology during boehmite to g-Al2O3 transformation opens a facile route to synthesize g-Al2O3 particles with complex morphology. The specific surface area of synthesized particles is 201 m2/g, which is around five times higher than the conventional g-Al2O3 (Aldrich 544833). Spherical nanostructured g-Al2O3 provides wide potential applications in catalysis due to its high density closed packed structure, large surface area, and high accessibility.