Dense ceramic membranes acting as oxygen and electron ion-conductors can be used as the catalysts for syngas production. The La1-xSrxCo0.8Fe0.2O3+δ (LSCF) systems were known to have a high ionic and electronic conductivity. In the application, the La1-xSrxCo0.8Fe0.2O3+δ membranes required low thermal expansion, microhardness and high oxygen permeation flux. The changes in the expansion, hardness, and oxygen flux of the La1-xSrxCo0.8Fe0.2O3+δ perovskite membranes with various strontium substitutions were studied. The magnitude of both the thermal expansion and the oxygen content of the La1-xSrxCo0.8Fe0.2O3+δ membranes decreased with up to 20 % strontium substitution and then increased with 30 and 40 % strontium ion substitution. Meanwhile, the hardness and shrinkage improved by various strontium ion substitutions, except with 20 % strontium. The highest oxygen flux over La1-xSrxCo0.8Fe0.2O3+δ (0.0 ≤ x ≤ 0.4) membranes in the surface exchange-controlled processes was found of the membrane with 30 % strontium substitution.
Kemunculan bakteri resisten antibiotik menjadi masalah serius di seluruh dunia. Upaya penanggulangan bakteri resisten antibiotik terus dilakukan, salah satunya dengan penggunaan material berukuran nano. Zink oksida (ZnO) merupakan salah satu partikel yang telah terbukti dapat menghambat pertumbuhan bakteri gram negatif dan gram positif. Dalam mencegah terjadinya aglomerasi pada sintesis ZnO berukuran nanometer dapat ditambahkan capping agent alami berupa senyawa metabolit sekunder pada ekstrak kulit pisang raja nangka. Adapun langkah yang dilakukan adalah: 1) ekstraksi metabolit sekunder kulit pisang raja nangka, 2) uji fitokimia, 3) penentuan kadar total flavonoid dan polifenol, 4) sintesis ZnO dengan capping agent alami ekstrak kulit pisang raja nangka, 5) karakterisasi ZnO, dan 6) uji aktivitas antibakteri ZnO. Hasil analisis kualitatif melalui uji fitokimia serta analisis kuantitatif melalui penentuan kadar total polifenol dan flavonoid menunjukkan bahwa ekstrak kulit pisang raja nangka etanol (96%)-air 2:1 (v/v) memiliki kadar metabolit sekunder yang lebih tinggi dibandingkan ekstrak kulit pisang raja nangka etanol (96%)-air 1:1 (v/v). Partikel ZnO berhasil disintesis menggunakan capping agent alami ekstrak kulit pisang raja nangka. Kadar metabolit sekunder yang berbeda pada masing-masing ekstrak mempengaruhi ukuran, morfologi, dan aktivitas antibakteri ZnO hasil sintesis.
A green chemistry-based ZnO nanoparticle synthesis method based on plant extracts has been developed. Raja nangka banana peel is one of them. The extraction time is one of the elements that influences the amounts of secondary metabolites. The longer the extraction time, the more secondary metabolites are obtained. If the optimal time is exceeded, the secondary metabolite compounds will decrease. The purpose of this research was to determine the optimal time to extract secondary metabolites from the raja nangka banana peel and to know the effect of extraction time on the characteristics of ZnO nanoparticles, which include morphology, size, and antibacterial activity against Staphylococcus epidermidis. The steps of this research: maceration, phytochemical tests and total levels tests, synthesis of ZnO nanoparticles, characterization, and antibacterial activity test against Staphylococcus epidermidis. Maceration for 24 hours is the best time for extracting secondary metabolites from raja nangka banana peels. The SEM test results show that the morphology of the three samples had agglomeration. The ZnO nanoparticles with 24-hour raja nangka banana peel extract had a smaller size of 295.2 nm and were spherical. Inhibition zone diameter from ZnO nanoparticles with 24-hour raja nangka banana peel extract has a larger area of 5.65 mm.
In this era, most technology requires electronic equipment. The performance of electronic equipment may be affected by energy storage components like a supercapacitor, so the development of supercapacitor electrode materials using green chemical methods needs to be pursued. Material with a good specific capacitance is MnO2. Most of the MnO2 synthesis methods are not based on green chemistry, so there is an alternative method. One of them is by utilizing the waste from tangerine peels. This study aimed to synthesize MnO2 through dehydroxylation of tangerine peel essential oil. The steps for conducting this research consisted of isolation of tangerine peel essential oil, analysis of the constituent components of tangerine peel essential oil, synthesis of MnO2 through dehydroxylation of essential oils tangerine peel, and MnO2 characterization. XRD results showed that MnO2 synthesized at pH 11 had the highest percentage of α-MnO2 (97%). This is evidenced by the presence of α-MnO2 diffractogram according to the ICSD No.20227. The SEM results showed that MnO2 had a spherical morphology with a particle diameter of 39.51 nm. α-MnO2 has a larger tunnel structure compared to β- and γ-MnO2, making the charge-discharge process easier so that α-MnO2 has the potential as a supercapacitor electrode material.
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