The donor (D)-π spacer-acceptor (A) framework with electronic push–pull effects provides suitable molecular architectures for molecular design used as efficient light-harvesting sensitizers in dye-sensitized solar cells (DSSCs). Efficiencies of light harvesting and electron injection to the semiconductor of sensitizers play critical roles in DSSC performance. Here, we employed density functional theory to systematically and comparatively investigate the effects of π-spacers of D-π spacer-A types of dyes in solution and adsorbed on a (TiO2)38 anatase cluster on various photophysical properties. The absorption spectra, electron transfer probability, and related photophysical properties of D-π spacer-A types of dyes were investigated as functions of different types (thiophene (Th)- and phenyl (Ph)-based), lengths, and planarity (bridging two neighboring rings; dithieno-thiophene (DTT) and fluorene (FL)-based) of π-spacers, while the D (diphenylamine) and A (cyano-acrylic acid) moieties remained the same. Spacers could significantly influence the λmax values and electron transfer probability. The spacer length has a red-shifted effect in λmax for the Th-, DTT-, and FL-based sensitizers due to their planar conjugated structures; nevertheless, the λmax values are saturated by ring number three. In contrast, the Ph-based spacers induce a blue-shift in λmax with spacer length due to their nonplanar structures. Interestingly, the Th- and DTT-based spacers with lower LUMO energy levels trap more electron density and thus reduce the probability of electron density transfer to TiO2 φET(λmax, TiO2) upon photoexcitation; moreover, the φET(λmax, TiO2) values decrease significantly with ring number. On the other hand, the φET(λmax, TiO2) values for the Ph- and FL-based sensitizers are less sensitive to the spacer length. Interestingly, the orders of theoretical maximum short-circuit current density of four studied families of molecules are correlated with their λmax values. Our study shows the Th–Th motif used as a π-spacer balances the spectral match with solar radiation and φET(λmax, TiO2) suitable for DSSC applications. Our results based on molecular and electronic structures could be used for rational sensitizer design of organic dyes for DSSC applications.

In this study, the optimization of microwave-assisted alkaline (MAA) pretreatment is performed to attain the optimal operating parameters for the delignification of cocoa pod husk (CPH). The MAA performance was examined by heating the CPH solid with different particle sizes (60–120 mesh) and NaOH solution with a different sample to a solvent (SS) ratio (0.02–0.05 g/L), for short irradiation time (1–4 min). Box-Behnken Design (BBD) was utilized to optimize the percentage of lignocellulose composition changes. The results show that by enlarging particle size, the content of lignin and cellulose decreased while hemicellulose increased. By prolong irradiation time, the content of lignin and hemicellulose decreased while cellulose elevated. On the other hand, increasing the SS ratio was not significant for hemicellulose content changes. From FTIR and SEM characterization, the MAA drove the removal of lignin and hemicellulose of CPH and increased cellulose slightly. Supported by kinetic study which conducted in this work, it was exhibited that MAA pretreatment technology is an effective delignification method of CPH which can tackle the bottleneck of its commercial biofuel production. 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).

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Melinjo (Genus Gnetii gnemonii Folium) merupakan spesies tanaman yang berasal dari semenanjung Malaysia dan Indonesia, diketahui memiliki senyawa bioaktif yang dapat dimanfaatkan dibidang kesehatan. Tujuan penelitian ini ini adalah untuk menganalisis profil senyawa bioaktif daun melinjo (Gnetii gnemonii Folium) yang memiliki fungsi sebagai antimikroba dengan menghambat pertumbuhan bakteri Staphylococcus aureus serta memformulasi gel dari ekstrak daun melinjo. Ekstrak daun melinjo dibuat dengan metode maserasi menggunakan pelarut etanol 70%, 3 hari. Analisis profil senyawa bioaktif daun melinjo menggunakan skrining fitokimia dan pengujian aktivitas antibakteri dilakukan menggunakan metode difusi cakram Kirby-Bauer terhadap Staphylococcus aureus. Konsentrasi ekstrak etanol daun melinjo yang digunakan interval konsentrasi 50%-80%. Ekstrak dengan konsentrasi optimum diformulasikan dalam bentuk gel dan dilakukan evaluasi mutu fisik sediaan gel meliputi organoleptis, uji homogenitas, uji pH, uji daya lekat dan uji daya sebar selama 28 hari. Hasil analisis menunjukkan senyawa bioaktif daun melinjo meliputi Tanin, Saponin, Alkaloid, Flavonoid, dan Triterpenoid. Ekstrak 80% daun melinjo memberikan efek antibakteri dengan zona hambat terbesar 13,08mm. Gel dari ekstrak daun melinjo 80% memberikan efek antibakteri dengan kategori kuat terhadap bakteri Staphylococcus aureus dengan diameter zona hambat sebesar 16,91mm.

Molecular modeling using Quantitative Structure and Activity Relationship (QSAR) has been performed on caffeic acid derivatives which is previously studied as an effective antioxidant agent. This research focuses on a set of experimentally IC50 value data of 4 caffeic acid derivatives. The mathematical method (i.e., multilinear regression calculation) was used to build the QSAR model. QSAR analysis was employed on fitting subset using log (1/IC50) as a dependent variable and atomic net charges aromatic carbons, dipole moment and partition coefficient in n-octanol/water as independent variables. The PM3 method was used to calculate the quantum chemical descriptors, chosen to represent the electronic descriptors of molecular structures. The relationship between log (1/IC50) and the descriptors was described by resulted in the QSAR model. The resulted QSAR model for caffeic acid derivatives as an antioxidant is presented below: -7.858+1.149dipol+0.485logP-61.68C5 R=1; R2=0.999; SE=0.008; F=342 QSAR model for caffeic acid derivatives showed the enhancement of antioxidant activity due to the decrease of electronic properties (derived from the dipole moment value and C5 atomic charge), Log P representing hydrophobicity did not show a significant effect on antioxidant activity while increasing the chain length of antioxidant molecules indicate an increase in steric hindrance causes a decrease in antioxidant activity. The calculated PRESS (Predicted Residual Error Sum of Square) value was 6.69E-05, which indicates the calculated log (1/IC50) using QSAR Hansch Model of caffeic acid derivatives is similar with experimental data.

Indonesia merupakan negara yang memiliki berbagai macam tanaman herbal berkhasiat obat. Salah satu jenis tanaman obat yang sering digunakan untuk pengobatan adalah rimpang kunyit. Rimpang kunyit mengandung senyawa alkaloid, tanin dan flavonoid yang telah terbukti sebagai antibakteri. Penelitian ini dilakukan secara in vitro untuk mengetahui kandungan senyawa dan aktivitas ekstrak rimpang kunyit yang dilanjutkan dengan pengujian menggunakan metode Kadar Hambat Minimum (KHM) terhadap bakteri Staphylococcus aureus. Penyarian ekstrak rimpang kunyit dilakukan dengan cara sokhletasi menggunakan pelarut etanol 96%. Pengujian aktivitas antibakteri dilakukan dengan metode difusi dengan variasi konsentrasi 45%, 55%, 65% dan 75%. Hasil penelitian ini menunjukkan bahwa ekstrak rimpang kunyit 45% merupakan konsentrasi minimum yang memiliki aktivitas antibakteri terhadap S.aureus sebesar 12,5 mm

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