Judul: Kajian Potensi Rimpang Curcuma sebagai Agen Pereduksi dan Kitosan sebagai Agen Penstabil pada Sintesis Nanopartikel Perak
Abstrak: Sintesis nanopartikel perak dengan metode kimia mempunyai beberapa kelemahan, diantaranya tidak ramah lingkungan. Rimpang tanaman Curcuma dapat menjadi alternatif agen pereduksi. Salah satu faktor yang berperan dalam tanaman Curcuma sebagai agen pereduksi adalah kandungan total fenoliknya. Senyawa fenol dapat bertindak sebagai agen pereduksi dalam reduksi logam menjadi nanopartikel logam. Tujuan penelitian ini untuk mengidentifikasi potensi rimpang Curcuma khususnya temu putih, temu hitam, temu kunci, temu giring, temu mangga, dan kurkumin sebagai agen pereduksi perak menjadi nanopartikel perak (AgNp) berdasarkan kandungan total fenolik rimpang tanaman tersebut dan kitosan sebagai agen penstabil AgNp. Karakteristik AgNp yang dianalisis meliputi ukuran partikel, polidispersitas (PdI), dan potensial zeta serta mekanisme kitosan sebagai agen penstabil pada AgNp. Kitosan dapat meningkatkan aktivitas biologis AgNp, kompatibilitas AgNp, dan dapat memodifikasi muatan permukaan AgNp sehingga dapat diaplikasikan secara lebih luas., The synthesis of silver nanoparticles by chemical methods has several disadvantages, including not being environmentally friendly. Curcuma rhizome can be an alternative natural reducing agent. One of the factors that play a role in Curcuma plants as reducing agents is the total phenolic content. Phenol compounds can act as reducing agents in the reduction of metal into metal nanoparticles. The purpose of this study was to identify the potential of Curcuma rhizome, especially white ginger, black turmeric, fingerroot, temu giring, mango ginger, and curcumin as a reducing agent for silver nanoparticles (AgNp) based on the total phenolic content of these plants rhizomes, and to study chitosan as a stabilizing agent for AgNp. The characterizations analyzed included particle size, polydispersity (PdI), and zeta potential as well as the mechanism of chitosan as a stabilizing agent in AgNp. Chitosan can increase AgNp biological activity, increase nanoparticle compatibility, and can modify the surface of AgNp so that they can be applied more widely.
Keyword: chitosan, Curcuma, nanoparticles, silver nanoparticles

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: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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