Judul: Base-Mediated Synthesis of Carbon Dots From Humic Acids and It’s Optical Properties
Abstrak: Karbon-dots (CDs) merupakan nanomaterial berfluoresens yang sifat optiknya dipengaruhi oleh prekursor karbon dan metode sintesisnya. Penelitian ini bertujuan menyintesis CDs dengan metode hidrotermal termediasi basa dari asam humat (AH) dan mempelajari sifat optiknya dengan variasi jenis dan konsentrasi basa, serta penambahan agen pasivasi. Spektrum UV-Vis CDs-AH hasil sintesis memiliki puncak panjang gelombang pada 200–300 nm (π‒π*) yang berasal dari C=C pada inti CDs dan 300–400 nm (n‒π*) dari C=O di permukaan CDs. Basa NaOH dan NH4OH berpengaruh pada panjang gelombang puncak (λem) dan intensitas emisi CDs-AH. CDs-AH-NaOH memiliki λem 469 nm, sedangkan λem CDs-AH-NH4OH mengalami pergeseran biru menjadi 462 nm disertai penurunan intensitas emisi dengan rasio 1,85. Hasil ini disebabkan gugus fungsi oksigen di permukaan CDs-AH lebih banyak terdeprotonasi dalam NaOH membentuk level energi baru yang lebih rendah dengan efisiensi pendaran yang lebih baik. Peningkatan konsentrasi NaOH 0,1 ke 1 M pada CDs-AH dapat meningkatkan intensitas emisi dengan rasio 2,37. Hal ini diakibatkan oleh dekomposisi AH yang meningkat seiring peningkatan konsentrasi NaOH sehingga jumlah fluorofor AH bertambah. Peningkatan konsentrasi NaOH 0,1 ke 1 M menggeser λem ke arah biru dari 476 menjadi 469 nm. Penambahan urea pada CDs-AH-NaOH 1 M tidak berpengaruh pada λem dan intensitas emisi., Carbon dots (CDs) are fluorescent nanomaterials whose optical properties can be influenced by the carbon precursor and its synthesis method. This research aims to synthesize CDs from humic acid (HA) using base-mediated hydrothermal and study its optical properties by varying the type and concentration of base, as well as adding a passivation agent. The UV-Vis spectrum of CDs-HA has a peak wavelength of 200–300 nm (π–π*), originating from C=C in the CDs core and 300–400 nm (n–π*) from C=O on surface CDs. CDs-HA-NaOH experienced a blue shift (469 to 462 nm) in NH4OH, accompanied by a decreased emission intensity (ratio of 1.85). This result is caused by the oxygen functional groups on the surface of CDs-HA being strongly deprotonated in NaOH, forming a new lower energy level with better luminescence efficiency. Increasing the NaOH concentration (0.1 to 1 M) can increase the emission intensity (ratio of 2.37) and shift the λem towards blue (476 to 469 nm). This is because the more significant concentration of NaOH can break down the HA structure more strongly and increase the number of HA fluorophores. Adding urea to CDs-AH-NaOH 1 M did not affect the λem and emission intensity.
Keyword: ammonium hidroksida, asam humat, karbon-dot, natrium hidroksida, sifat optik, ammonium hydroxide, carbon-dots, humic acid, optical properties, sodium hydroxide

Judul: Synthesis of fluorescent carbon nanoparticle
Abstrak: Nanopartikel karbon (C-dot) merupakan material yang termasuk ke dalam kelas nanopartikel 0 dimensi. C-dot dapat disintesis dari beberapa jenis asam organik yang berperan sebagai sumber karbon dan urea sebagai agen pasivasi permukaan C-dot. C-dot disintesis menggunakan metode oven mikrogelombang. Tujuan penelitian ini ialah menyintesis dan mencirikan C-dot dari beragam asam organik, yaitu asam askorbat, asam sitrat, dan asam oksalat dan beragam kadar urea yang ditambahkan. Kadar urea yang ditambahkan masing-masing 0, 10, 25, 50, dan 75% (b/b). Hasil yang diperoleh menunjukkan pendaran C-dot di bawah lampu ultraviolet 366 nm semakin meningkat dengan meningkatnya kadar urea. Emisi yang dihasilkan dari C-dot ini berada pada panjang gelombang 500 nm. Spektrum inframerah kadar urea yang beragam tidak menunjukkan perbedaan gugus fungsi yang nyata. Ukuran diameter rata-rata C-dot yang diperoleh sebesar ±18 nm. Uji kemampuan sensor C-dot yang dipreparasi dari asam askorbat dan urea 75% menunjukkan selektif terhadap ion logam Cr6+., Carbon nanoparticle (C-dot) is a material which belongs to the class of 0- dimensional nanoparticle. C-dot can be synthesized from several types of organic acid as a carbon source and urea as a passivation agent on the C-dot surface. C-dot was synthesized using microwave method. The purpose of this study was to synthesize and to characterize the C-dot from various organic acids, namely ascorbic acid, citric acid, and oxalic acid and various levels of added urea. The levels of aded urea were 0, 10, 25, 50, and 75% (w/w). The results showed the Cdot luminescence under ultraviolet light 366 nm increased with the increasing levels of urea. An emission resulting from the C-dot is located at a wavelength of 500 nm. Infrared spectra measurements of urea levels showed there was no significant differences in functional groups. The average diameter size of the Cdot was ±18 nm. The ability test toward heavy metal ion of the C-dot prepared using ascorbic acid and urea 75% showed selective toward Cr6+ ion. Key words: ascorbic acid, citric acid, carbon nanoparticle, fluorescence
Keyword: asam askorbat, asam sitrat, C-dot, fluoresens

Judul: Posisi Filogenetik Kura-Kura Carettochelys Insculpta  (Reptillia: Testudinata)
Abstrak: Carettochelys insculpta is an endemic freshwater turtle of southern Papua and northern Australia. Phylogenetic position of this turtle is remain unresolved until now. Most of the research conducted show close relationships of C. insculpta and members of Trionychidae family. However, some of the research show distance between C. insculpta and members of Trionychidae family. This research is conducted to analyze phylogenetic relationship between C. insculpta and other members of Testudinata using 12S rRNA, 16S rRNA, and both gene as markers. DNA samples were obtained from three different organisms of C. insculpta. Two species used as outgroups were Alligator mississippiensis and Iguana iguana. Phylogenetic analysis was carried out using Neighbor-Joining method with Felsenstein 1981 (F81) modeltest. A polytomy tree of Testudinata was produced by using 12S rRNA gene. However, analysis using 16S rRNA and both genes as markers confirmed that C. insculpta was located between the Chelonidae and the Trionychidae family.
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