Judul: Sintesis Partikel Nanobesi dengan Bioreduktor Polifenol dari Ekstrak Kulit Delima Merah
Abstrak: Partikel nano besi (nZVI) digunakan dalam proses remediasi lingkungan dan pengolahan air baku. Reduktor NaBH4 yang digunakan dalam sintesis nano besi menghasilkan material yang mudah teroksidasi dan beraglomerasi. Penggunaan polifenol sebagai bioreduktor menghasilkan material yang lebih stabil. Penelitian ini bertujuan menyintesis nZVI dengan reduktor NaBH4 (C-nZVI), polifenol dari ampas teh dan kulit delima (G-nZVI), membandingkan kualitas pada masing-masing nZVI, serta menentukan efektivitas G-nZVI kulit delima mendegradasi bahan organik terlarut. Sintesis material nano besi menggunakan metode reduksi garam FeCl3 dalam pelarut air. Material C-nZVI yang dihasilkan berupa serbuk hitam sedangkan G-nZVI berupa serpihan hitam. Nilai band gap energi ketiga material memprediksi ukuran yang nano. Ketiga material memiliki semua gugus sebagai kesatuan utuh nZVI. Difraktogram difraksi sinar-X pada ketiga material belum memperlihatkan fase kristal secara jelas. Distribusi dan rerata ukuran partikel G-nZVI kulit delima lebih baik daripada G-nZVI ampas teh. Nilai potensial zeta membuktikan kedua material G-nZVI bersifat stabil dalam pelarut air. Degradasi optimum bahan organik terlarut, yakni 98% oleh G-nZVI kulit delima dicapai setelah dua jam inkubasi., Nano zero valent iron (nZVI) has been used in environment remediating and raw water processing. NaBH4 reductor, used in iron nanoparticle synthesis, produced easily oxidised and agglomerate material. Using polyphenol as a bioreductor produced a more stabilised material. This study aims to synthesise nZVI using NaBH4 (C-nZVI), polyphenol from spend tea and pomegranate peel (G-nZVI) reductors, compare the quality of each material, and determine the effectiveness of dissolved organic matter reduction by pomegranate peel G-nZVI. The iron nanoparticle was synthesised by the method of FeCl3 salt reduction in a water solvent. C-nZVI material was produced as a black powder while G-nZVI materials were black flakes. The band gap energy values of those three materials predict that materials had reached the nano size. All three materials had intact nZVI unitary groups. X-ray diffractogram did not clearly show the core phase crystals. Distribution and mean of material size of the pomegranate peel G-nZVI was better than spend tea G-nZVI. Both zeta potential G-nZVI attest that the materials were stable in the water medium. Optimum dissolved organic matter degradation, namely 98%, by G-nZVI pomegranate peel was reached after two hours of incubation.
Keyword: bahan organik terlarut, kulit delima, partikel nano besi, polifenol

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: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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