Judul: Green Synthesis Nanopartikel Perak Menggunakan Limbah Jeruk Purut (Citrus hystrix dc) dengan Variasi Konsentrasi AgNO3
Abstrak: Jeruk purut (Citrus hystrix) merupakan tumbuhan perdu yang kaya manfaat. Kandungan dalam kulit jeruk purut berpotensi dijadikan bahan bioreduktor dalam sintesis nanopartikel. Nanopartikel dengan sifat fisis dan kimiawinya yang unik diharapkan mampu meningkatkan nilai jual serta efektivitas pemanfaatannya. Nanopartikel perak sebagai salah satu jenis nanopartikel logam secara alami memiliki kemampuan antibakteri yang baik serta proses sintesisnya sudah banyak dilakukan. Pada penelitian ini, kulit jeruk purut dipilih sebagai bioreduktor dengan meninjau kondisi optimal pengaruh variasi konsentrasi AgNO3 dan waktu penyimpanan terhadap green synthesis nanopartikel perak. Rancangan percobaan dibuat menggunakan Response Surface Methodology dengan bentuk Central Composite Design. Ukuran partikel yang dihasilkan berkisar pada 86-236 nm yang masih dalam ukuran toleransi nanopartikel. Nilai absorbansi maksimum 0,241-0,506 yang tercapai pada panjang gelombang 268-279 nm. Hasil penelitian ini menunjukkan bahwa nanopartikel perak berdiameter kurang dari 100 nm tercapai pada variasi konsentrasi 1 mM dengan waktu simpan 1 dan 29 jam., Kaffir lime (Citrus hystrix) is a herbaceous plant that is rich in benefits. The content in kaffir lime peel has the potential to be used as a bioreductant in the synthesis of nanoparticles. Nanoparticles with unique physical and chemical properties are expected to increase the selling value and effectiveness of their utilization. Silver nanoparticles as a type of metal nanoparticles naturally have good antibacterial abilities and many synthesis processes have been carried out. In this study, kaffir lime peel was chosen as a bioreductant by reviewing the optimal conditions for the effect of variations in AgNO3 concentration and storage time on the green synthesis of silver nanoparticles. The experimental design was made using the Response Surface Methodology in the form of a Central Composite Design. The resulting particle size ranges from 86-236 nm which is still within the tolerance of nanoparticles. The maximum absorbance value of 0.241-0.506 is achieved at a wavelength of 267-279 nm. The results of this study showed that silver nanoparticles with a diameter of less than 100 nm were achieved at a concentration variation of 1 mM with a shelf life of 1 and 29 hours.
Keyword: AgNO3, Kulit jeruk purut, Nanopartikel, RSM, Sintesis hijau

Judul: Aktivitas Antimikroba Nanopartikel Perak yang Disintesis Menggunakan Ekstrak Kulit Jeruk Purut
Abstrak: Jeruk purut telah dikenal luas oleh masyarakat Indonesia. Namun sejauh ini belum banyak masyarakat yang mampu memanfaatkan limbah kulit jeruk purut, khususnya limbah di pasar dan di rumah yang dapat menambah nilai guna dan tentunya nilai jualnya. Jeruk purut kaya manfaat terutama kulit buah dan daunnya sebagai agen antibakteri yang dapat mutakhir membunuh kuman. Berdasarkan hal tersebut penelitian ini menggunakan limbah kulit jeruk purut yang dapat dimanfaatkan sebagai bioreduktor dalam sintesis nanopartikel perak menggunakan metode green synthesis untuk menguji sifat antibakterinya. Di sisi lain, penggunaan reagen kimia dalam proses sintesis nanopartikel perak dapat berdampak terhadap lingkungan serta membutuhkan biaya pengeluaran yang tinggi. Oleh sebab itu dalam penelitian ini dilakukan metode alternatif yang lebih murah dan ramah lingkungan yang tidak berdampak pada lingkungan. Justru membantu mengurangi limbah rumah tangga. Hasil kemampuan antibakteri menunjukan bahwa nanopartikel yang telah disintesis dengan konsentrasi 1 mM dan 1,5 mM ditemukan efektif membunuh pertumbuhan spesies bakteri Stapylococcus aureus., Kaffir lime has been widely known by the people of Indonesia. However, so far not many people have been able to utilize the waste of kaffir lime peels. Kaffir lime is rich in benefits, especially the skin of the fruit and leaves as an antibacterial agent that can kill germs. Based on this, this research uses kaffir lime peel waste which can be used as a bioreductant in the synthesis of silver nanoparticles using the green synthesis method to test its antibacterial properties. On the other hand, the use of chemical reagents in the synthesis of silver nanoparticles can have an impact on the environment and require high costs. Therefore, in this study an alternative method that is cheaper and environmentally friendly has no impact on the environment. It actually helps reduce household waste. The results of the antibacterial ability showed that the nanoparticles that had been synthesized with a concentration of 1 mM dan 1,5 mM were found to be effective against the species of bacteria Stapylococcus Aureus.
Keyword: antimicrobial test, green synthesis, kaffir lime, nanoparticles

Judul: Analysis of Unequal Income Distribution with Cobb-Douglas Production Function
Abstrak: This paper studies the economic growth model by Moav (2002). Moav model shows the existence of unequal income distribution between low-income with high-income community. That kind of unequal income distribution is caused by uneven distribution of income. On this Moav model, there is one area called the threshold. Threshold becomes a benchmark to determining whether a society is categorized into low- or high- income community. The production function used in this paper is the Cobb-Douglas function. The dynamics of this model is described as difference equation of low-income, threshold, and high-income community. Simulation study on the model is carried out using Maple 13 and Mathematica 7.0 software. Overall, from the observed case, high-income community will reach a stable condition earlier, followed by the threshold, and then the low-income community.
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