Variation of pH and Composite Dosage on the Photocatalytic Activity for ZnO/epoxy Nanocomposites

In this research, Zinc oxide (ZnO)/epoxy nanocomposite was synthesized by simple casting method with 2wt. % ZnO concentration. The aim of this work was to study the effect of pH and composite dosage on the photocatalytic activity of ZnO/ epoxy nanocomposite. Scanning electron microscopy (SEM) technique images proof the homogeneous distribution of ZnO nanoparticles in epoxy. A synthesized nanocomposite samples were characterized by Fourier Transform Infrared spectrometer (FTIR) measurements. Two spectra for epoxy and 2wt.% ZnO/epoxy nanocomposites were similar and there are no new bonds formed from the incorporation of ZnO nanoparticles. Using HCl and NaOH were added to Methylene blue (MB) dye (5ppm) to gat pH values 3 and 8. The degradation of the dye was 90.816% were pH =8 after 180 min. under sun-light. The degradation was 6.131% were pH=3 after 240 min. under sun-light irradiation. It is found that the base solution help in accelerating the photocatalytic process, pH with high value provides greater concentration of hydroxyl ions which interact with h+ to form hydroxyl radicals OH- that give an enhancement degradation rate of dyes. The dose of ZnO was increased from 3g to 6g with Methylene blue MB (5ppm) the degradation was 94.3755% after 240 min. under sun-light irradiation. This means that increasing the dose of ZnO, the photocatalytic activity will be increased.

PENENTUAN SIFAT LARUTAN ASAM, BASA, DAN GARAM DENGAN INDIKATOR EKSTRAK DAUN TANAMAN HIAS

Learning Natural Sciences (IPA) is not only taught by means of lectures or memorization, but by experimental or demonstration methods, so that it is more active for students. In the experiment of acid-base solutions in science class VII SMP/MTs, natural indicators were used as a test solution to replace synthetic indicators. In addition to making students active, it also minimizes practicum costs. This experiment used leaf extracts of ornamental plants such as miana, butterfly and red purslane which were made together with students and teachers. After comparing the test results between synthetic indicators (litmus paper and phenolphthalein) with homemade natural indicators, it can be concluded that the extract can be used as an alternative to the solution test. Because there are different changes when dropped into an acid and alkaline solution. When tested the pH of the solution using the extract indicator, there was a change in the pH range in an acid solution of 3.2 and a base solution of 10.8. By observing the color change, it can be concluded that ornamental plant extracts can be used as an alternative to acid-base indicators to replace synthetic indicators. For miana the color changes from orange (acidic) – brownish yellow – light green (alkaline), red purslane from pink (acidic) – dark red to dark brown (alkaline) and butterfly from red (acid) – purple - to green (base). ABSTRAKPembelajaran Ilmu Pengetahuan Alam (IPA) tidak hanya diajarkan dengan cara ceramah atau menghafal saja melainkan dengan metode eksperimen atau demonstrasi, sehingga lebih mengaktifkan siswa. Pada percobaan larutan asam-basa dalam IPA kelas VII SMP/MTs digunakan indikator alamiah sebagai uji larutan menggantikan indikator sintetis. Selain membuat siswa aktif juga meminimalisir biaya praktiku=m. Percobaan ini digunakan ekstrak daun tanaman hias seperti miana, kupu-kupu dan krokot merah yang dibuat bersama-sama siswa dengan guru. Setelah membandingkan hasil uji antara indikator sintetis (kertas lakmus dan fenolftalein) dengan indikator alamiah buatan sendiri dapat disimpulkan bahwa ekstrak tersebut dapat digunakan sebagai alternatif untuk uji larutan. Karena terdapat perubahan yang berbeda saat diteteskan ke dalam larutan asam dan basa. Saat diuji pH larutan dengan menggunakan indikator ekstrak tersebut terdapat perubahan rentang pH dalam larutan asam 3,2 dan larutan basa 10,8. Dengan mengamati perubahan warna dapat diambil kesimpulan bahwa ekstrak tanaman hias dapat digunakan sebagai alternatif indikator asam basa menggantikan indikator sintetis. Untuk miana perubahan warna dari oranye (asam) – kuning kecoklatan – hijau muda (basa), krokot merah dari merah muda (asam) – merah tua menjadi coklat tua (basa) dan kupu-kupu dari merah (asam) – ungu - menjadi hijau (basa).

The Effectiveness of Contextual Research-Based Teaching Materials on Students’ Learning Independence and Concept Mastery

Innovation in teaching materials used in online learning is very urgent based on students’ needs. This study aims to measure the effectiveness of contextual research-based teaching materials to improve students’ learning independence and concept mastery of acid-base solution properties. The research method is Research and Development, referring to Borg and Gall. The research subjects were 60 students and 7 science teachers who have used teaching materials based on contextual research findings. The data collection technique in this study is a test that aims to determine the concept mastery and a questionnaire to measure students’ learning independence. Based on the results of the study, it is known that the average percentage of student learning independence is 78% (Good category). Besides, an average value of 73.83 is obtained with an N-Gain of 64% (Medium category). The use of contextual research-based teaching materials can increase learning independence in terms of information search and concept mastery of acid-base solution properties.

Titanate Nanotubes as Futuristic Catalyst Support Material

Titanate Nanotubes (TNT) were synthesized by aging commercial titanium dioxide (TiO2 - Degussa P25) with an alkali (KOH) solution at different time intervals. The prepared materials were investigated for their surface composition and textural behaviour by X-ray powder diffraction (XRD), Raman spectroscopy, Gas (N2 and CO2) adsorption measurements, and Transmission electron microscopy (TEM). The X-ray diffraction spectra revealed the decrease in the crystalline nature of the materials decreased by exposing them for a longer duration in the base solution. Raman spectra results showed that ageing time affected the structural properties. The specific surface area and the pore size of the newly synthesised materials were affected by the ageing process. The TEM images showed the influence of ageing during the formation of titanate nanotubes. HRTEM revealed that Pd particle sizes of <1 nm was present inside the tubes.

Titanate Nanotubes as Futuristic Catalyst Support Material

Titanate Nanotubes (TNT) were synthesized by aging commercial titanium dioxide (TiO2 - Degussa P25) with an alkali (KOH) solution at different time intervals. The prepared materials were investigated for their surface composition and textural behaviour by X-ray powder diffraction (XRD), Raman spectroscopy, Gas (N2 and CO2) adsorption measurements, and Transmission electron microscopy (TEM). The X-ray diffraction spectra revealed the decrease in the crystalline nature of the materials decreased by exposing them for a longer duration in the base solution. Raman spectra results showed that ageing time affected the structural properties. The specific surface area and the pore size of the newly synthesised materials were affected by the ageing process. The TEM images showed the influence of ageing during the formation of titanate nanotubes. HRTEM revealed that Pd particle sizes of <1 nm was present inside the tubes.

The Multiplicative Base Solution to the Differential Equations in Analog Circuits

This work focuses to solve any order of scalar differential equation involved in analog circuit representation. These types of mathematical representations have many applications in analysis and processing such as noise, filter, audio, RLC distributed interconnection (nodes) and transmission lines. Such systems are represented with scalar type differential equations and use numerical method to find a solution. One of the most successful methods is the fourth-order Runge–Kutta. This study introduced a multiplicative version of Runge–Kutta (MRK4) method. The performance analysis of the MRK4 is examined based on the error analysis method. The MRK4 method is applied to solve equations representing the linear and the nonlinear type systems. Results indicate the MRK4 to be superior with respect to the RK4 method.

Production of trans-cinnamic acid by whole-cell bioconversion from l-phenylalanine in engineered Corynebacterium glutamicum

Background trans-cinnamic acid (t-CA) is a phenylpropanoid with a broad spectrum of biological activities including antioxidant and antibacterial activities, and it also has high potential in food and cosmetic applications. Although significant progress has been made in the production of t-CA using microorganisms, its relatively low product titers still need to be improved. In this study, we engineered Corynebacterium glutamicum as a whole-cell catalyst for the bioconversion of l-phenylalanine (l-Phe) into t-CA and developed a repeated bioconversion process. Results An expression module based on a phenylalanine ammonia lyase-encoding gene from Streptomyces maritimus (SmPAL), which mediates the conversion of l-Phe into t-CA, was constructed in C. glutamicum. Using the strong promoter PH36 and ribosome binding site (RBS) (in front of gene 10 of the T7 phage), and a high-copy number plasmid, SmPAL could be expressed to levels as high as 39.1% of the total proteins in C. glutamicum. Next, to improve t-CA production at an industrial scale, reaction conditions including temperature and pH were optimized; t-CA production reached up to 6.7 mM/h in a bioreactor under optimal conditions (50 °C and pH 8.5, using NaOH as base solution). Finally, a recycling system was developed by coupling membrane filtration with the bioreactor, and the engineered C. glutamicum successfully produced 13.7 mM of t-CA (24.3 g) from 18.2 mM of l-Phe (36 g) and thus with a yield of 75% (0.75 mol/mol) through repetitive supplementation. Conclusions We developed a highly efficient bioconversion process using C. glutamicum as a biocatalyst and a micromembrane-based cell recycling system. To the best of our knowledge, this is the first report on t-CA production in C. glutamicum, and this robust platform will contribute to the development of an industrially relevant platform for the production of t-CA using microorganisms.