Electrochemical Sensors based on Gold-Silver Core-Shell Nanoparticles Combined with a Graphene/PEDOT:PSS Composite Modified Glassy Carbon Electrode for Paraoxon-ethyl Detection

Herein, a nonenzymatic detection of paraoxon-ethyl was developed by modifying a glassy carbon electrode (GCE) with gold-silver core-shell (Au-Ag) nanoparticles combined with the composite of graphene with poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS). These core-shell nanoparticles (Au-Ag) were synthesized using a seed-growth method and characterized using UV-vis spectroscopy and high-resolution transmission electron microscopy (HR-TEM) techniques. Meanwhile, the structural properties, surface morphology and topography, and electrochemical characterization of the composite of Au-Ag core-shell/graphene/PEDOT:PSS were analyzed using infrared spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS) techniques. Moreover, the proposed sensor for paraoxon-ethyl detection based on Au-Ag core-shell/graphene/PEDOT:PSS modified GCE demonstrates good electrochemical and electroanalytical performance when investigated with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry techniques. It was found that the synergistic effect between Au-Ag core-shell nanoparticles and the composite of graphene/PEDOT:PSS provides a higher conductivity and enhanced electrocatalytic activity for paraoxon-ethyl detection at an optimum pH of 7. At pH 7, the proposed sensor for paraoxon-ethyl detection shows a linear range of concentrations from 0.2 to 100 μM with a limit of detection of 10 nM and high sensitivity of 3.24 μA μM-1 cm-2. In addition, the proposed sensor for paraoxon-ethyl confirmed good reproducibility, with the possibility of being further developed as a disposable electrode. This sensor also displayed good selectivity in the presence of several interfering species such as diazinon, carbaryl, ascorbic acid, glucose, nitrite, sodium bicarbonate, and magnesium sulfate. For practical applications, this proposed sensor was employed for the determination of paraoxon-ethyl in real samples (fruits and vegetables) and showed no significant difference from the standard spectrophotometric technique. In conclusion, this proposed sensor might have a potential to be developed as a platform of electrochemical sensors for pesticide detection.

PEMBUATAN MINUMAN ISOTONIK DAN SUSU COKLAT SEBAGAI OLAHAN BUAH KELAPA DI DESA BALE KECAMATAN TANANTOVEA Jaya Hardi, Ruslan, Abd. Rahman Razak dan Ahmad Ridhay

Desa Bale merupakan salah satu daerah yang terletak di Kabupaten Donggala, Sulawesi Tengah. Penduduk di Desa Bale umumnya sebagai petani kelapa. Pembuatan produk olahan kelapa yang inovatif masih sangat kurang di Desa Bale. Minuman isotonik dan susu coklat santan kelapa dapat menjadi produk olahan baru bagi masyarakat setempat. Tujuan kegiatan ini adalah untuk menambah keterampilan masyarakat di desa Bale dalam mengolah air kelapa tua dan santan kelapa menjadi produk yang menarik dan memiliki nilai jual yang menjanjikan. Metode yang digunakan pada kegiatan ini adalah penyuluhan yang diikuti dengan demonstrasi. Hasil dari kegiatan yang dilakukan adalah keterampilan masyarakat mitra di desa Bale bertambah dalam membuat minuman isotonik dan susu coklat santan kelapa dengan menggunakan metode yang sederhana dan murah. Hasil pengukuran tingkat kepuasan menunjukkan bahwa 80% peserta atau mitra sangat puas terhadap pelaksanaan kegiatan pengabdian. Masyarakat mitra siap untuk mengembangkan produk olahan hasil pelatihan dalam bentuk produk yang siap dipasarkan.

KARAKTERISASI ENZIM KITINASE DARI ISOLAT BAKTERI TERMOFILIK B1211 ASAL AIR PANAS BORA

Penelitian ini bertujuan untuk mengkarakterisasi enzim kitinase dari bakteri termofilik asal sumber air panas Bora. Isolat bakteri B1211 digunakan pada produksi enzim kitinase pada media MSM cair yang diperkaya dengan konsentrasi koloidal kitin 1% pada suhu inkubasi 60oC selama 3 hari. Aktivitas enzim kitinase dianalisis berdasarkan standar N-asetil-D-glukosamin untuk kondisi suhu dan pH optimum, pengaruh substrat, dan pengaruh ion logam. Hasil penelitian menunjukkan enzim kitinase memiliki suhu optimum, pH optimum, dan konsentrasi substrat terbaik, masing-masing 600C, pH 7, dan 2%. Kinetika enzim kitinase memiliki Vmaks dan Km, yaitu 0,72 U/mL dan 0,01 mg/mL. Ion logam Hg2+, Zn2+, Al3+, dan Cu2+ berfungsi sebagai activator, sedangkan ion Li3+, Ca2+, dan K+ cenderung sebagai inhibitor terhadap enzim kitinase.Kata kunci: bakteri termofilik, isolat B1211, kitinase, karakterisasi

SINTESIS O-KARBOKSIMETIL KITOSAN PADA BERBAGAI KONSENTRASI NaOH DAN SUHU REAKSI SERTA APLIKASINYA SEBAGAI ANTIBAKTERI

The research about the influence of NaOH concentrations and reaction temperature to O-Carboxymethyl Chitosan (O-CMC) synthesis and it is antibacterial application was done. This research intent on detect NaOH concentration and reaction temperature that resulting of O-CMC with highest of yield, solubility, and substitution degrees, and also to find out FTIR spectrum and antibacterial activity of O-CMC. The produce of O-CMC was done by using a Completely Randomized Design (CRD) with the variation of NaOH concentration of 20%, 30%, 40%, 50%, and 60%, and also reaction temperature of 20, 30, and 40oC. The result was showed that on the NaOH concentration of 60% (w/v) and temperature of 30oC was resulted highest of yield, solubility, and substitution degrees of 41.5%, 31 g/L, and 0.67, respectively. FTIR spectrum was showed that bending vibration of primary amine (-NH2) give two bands for O-CMC. The broadest inhibition area of O-CMC (1.43 cm) was showed on Salmonella sp.Keywords: chitosan, O-CMC, substitution degree, antibacterial