Stevia rebaudiana leaf contains stevioside and rebaudioside A as main diterpene glycosides. These compounds are used as natural sweetener and potentially as drug candidate of diabetes type 2. Rapid and nondestructive method for S. rebaudiana leaves (n = 23) classification based on geographical area and main diterpene glycosides content was carried out using near infrared spectroscopy combined with multivariate data analysis. Linear discriminant analysis (LDA) was applied to discriminate S. rebaudiana leaves based on geographical area. Principal component analysis (PCA) was established to classify S. rebaudiana leaves based on main diterpene glycosides content. HPLC analysis was used as reference data to divide PCA result into groups. LDA model correctly classified 95% of the S. rebaudiana leaves based on geographical area. PCA model correctly classified 95% and 90% of S. rebaudiana leaves based on rebaudioside A and stevioside content, respectively. The classification method using near infrared spectroscopy combined with multivariate data analysis demonstrate potential use of the classification method established as quality control technique of S. rebaudiana leaves.
IntisariKol merah adalah salah satu bahan organik yang mengandung antosiani. Antosianin ini dapat dimanfaatkan sebagai dye dalam pembuatan prototipe Dye Sensitized Solar Cell (DSSC) sebagai donor elektron. Pada artikel ini dilaporkan bahwa sel surya direndam dalam larutan ekstrak kol merah (Brassica Oleracea Var.) dengan variasi pH larutan yang berbeda-beda yaitu pada pH 1,5; 2,5; dan 3,5. Hasil pengukuran menunjukkan bahwa sel surya dengan perendaman larutan antosianin kol merah pH 3,5 memiliki hasil keluaran paling baik yaitu pada rangkaian terbuka diperoleh arus pendek (Isc) sebesar 56 µA, pada tegangan terbuka (Voc) diperoleh sebesar 250 mV dan besar rapat arus sebesar 24,89 µA/cm 2 pada luasan 15 mm × 15 mm. Nilai efisiensi konversi sel surya mencapai 2,55 ×10 −3 %. ABSTRACTRed cabbage is one of the organic materials containing anthocyanin. Anthocyanin can be used as the dye in Dye sensitized Solar Cell (DSSC) prototype manufacture as the electron donor. In this study, the solar cell was immersed in the extract solution of red cabbage (Brassica oleracea Var) with pH varying at pH 1.5, pH 2.5, and pH 3.5. Krisis EnergiBio sel surya Dye Sensitized Solar Cell (DSSC) merupakan sumber energi alternatif sebagai pengkonversi energi matahari menjadi energi listrik dengan memanfaatkan zat alam sebagai fotosensitizer. Mengingat matahari merupakan sumber energi yang sangat besar, terkait dengan letak Indonesia yang berada pada garis katulistiwa, dalam sehari wilayah indonesia disinari matahari selama 10-12 jam, total intensitas penyinaran rata-rata 4,5 kWh permeter persegi perhari. Lama ratarata matahari bersinar berkisar 2000 jam per tahun sehingga tergolong kaya sumber energi matahari [1]. Berkaitan dengan pemanfaatkan sumber energi matahari, Michael Grätzel adalah peneliti yang pertama kali berhasil mengembangkan sistem sel surya tersintesa pewarna [2,3]. Penelitianya me- * E-MAIL: ferrirusady marsa@ymail.com † E-MAIL: adita@staff.uksw.edu nunjukan bahwa kelebihan dari bio sel surya harganya murah dan tidak menggunakan peralatan canggih sehingga mudah dibuat [3][4][5]. Bio sel DSSC ini perlu dikembangkan mengingat kebutuhan akan energi listrik pada waktu lama akan semakin meningkat yang dikarenakan oleh pemakaian listrik yang tidak terkontrol, akibat pertumbuhan ekonomi dan penduduk yang pesat. Ini akan menimbulkan permasalahan yaitu krisis energi listrik. Target pertumbuhan ekonomi selama 5 tahun kedepan telah dipatok pada angka 7% yang berarti harus ada persiapan penyediaan listrik dengan laju pertumbuhan sekitar 10,5% per tahun. Jika mengacu dari pertumbuhan tersebut maka tahun 2020 perlu penambahaan 30.000 mW untuk wilayah Jawa, Madura, dan Bali [6].Di sisi lain masih perlu banyak pengembangan lebih lanjut guna meningkatkan nilai efisiensi DSSC ini. Dalam penelitian awal Penulis pada paper [7] tentang kinerja dari sel surya (DSSC) terhadap pengaruh jumlah antosianin yang terkandung dalam ekstrak kol merah dari tegangan terhadap waktu yang dihasilkan. Dalam penelitian tersebut diketahui bahwa semakin banyak jum...
Research on bacteriochlorophyll (BChl) a and its derivatives had been conducted to determine the coordination state and the aggregation process in acetone-water and methanol-water. The results showed that there were mainly two absorption peaks in BChl a and its derivatives, namely: Qx and Qy that were very sensitive to coordination state and aggregation process. The coordination state of pigment could be determined based on Qx absorption peak that was influenced by solvents. In addition, the donor number (DN) and taft parameters (β and π*) from each sovents could also be used to determine the coordination state. One or two of axial coordination toward center metal of BChl a and its derivatives have to be filled by donor electron as a foreign nucleophile. Mg-BChl was exist as five-coordinate complexes in acetone but as six-coordinate complexes in methanol. Five-coordinate complexes of Zn-BChl was occurred either in acetone or methanol. Cu-BChl was exist as four-coordinate complexes in acetone but altered to five-coordinate complexes in methanol. The agregation process was influenced by the existence of water added in pigment solution. The order of Mg-BChl a and its derivatives abilities to form new aggregate in acetone-water and methanol-water, in regard of water-addition percentage was as follow: Cu-BChl > Zn-BChl > Mg-BChl. Methanol was the solvent that could form aggregate of Mg-BChl and its derivatives at lower water-addition percentage compared to acetone. Keywords: aggregation, bacteriochlorophyll & its derivatives, coordination state.
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