Abstrak. Dalam rangka mengurangi pemakaian bahan kimia berbahaya, kini telah mulai dikembangkan penggunaan bahan alami pada proses pembentukan nanopartikel. Pada penelitian ini, biosintesis nanopartikel ZnO dilakukan menggunakan ekstrak kulit Ananas comosus sebagai agen capping sekaligus agen pereduksi. Seng nitrat digunakan sebagai prekursor dari ion seng, sedangkan kulit nanas dibuat menjadi ekstrak untuk dimanfaatkan kandungan antioksidannya. Sampel ZnO dipelajari sifat fisisnya dari hasil karakterisasi X-ray diffraction (XRD), scanning electron microscopy (SEM) dan spektroskopi UV-Vis. Berdasarkan pola XRD, nanopartikel ZnO memberikan fasa kristal heksagonal wurtzite dengan ukuran kristal 14 nm. Morfologi SEM masing-masing sampel didapatkan berbentuk bunga atau micro-nanoflower dengan ukuran diameter rata-rata 510 nm dan 560 nm untuk sampel 0,01 M dan 0,025 M. Hasil spektrum absorbansi UV-Vis menunjukkan peningkatan puncak penyerapan cahaya dengan penambahan konsentrasi seng nitrat. Berdasarkan informasi sifat fisis ini, sampel ZnO berpotensi diaplikasikan sebagai material fotokatalis.Abstract. In order to reduce the use of hazardous chemicals, the use of natural ingredients has now been developed in the process of forming nanoparticles. In this study, biosynthesis of ZnO nanoparticles was carried out using Ananas comosus peel extract as capping agent and reducing agent. Zinc nitrate was used as a precursor to zinc ion. The physical properties of ZnO samples were studied from the characterization result of scanning electron microscopy (SEM), UV-Vis spectroscopy, and X-ray diffraction (XRD). The SEM morphology of each different sample was obtained in the form of micro-nanoflower with an average diameter  of 510 nm and 560 nm for 0.01 M and 0.025 M samples, respectively. The UV-Vis absorbance spectrum results showed an increase in the light absorption peak as  zinc nitrate concentration increased. According to the XRD pattern, the ZnO nanoparticles possessed an hexagonal wurtzite crystal phase with a crystal size of 14 nm. Based on this information on physical properties, the ZnO sample has the potential to be applied as a photocatalyst material.

Sucrose is a type of sugar that is widely used in various types of foods and beverages. In Indonesia, sucrose consumption reaches 2.8 million tons on average per year. Effects of consuming too much sucrose can increase the risk of various diseases such as diabetes, dental caries and obesity. The level of maximum amount of sucrose that is safe for the body equal to 10% of the total energy or the equivalent of 50 g/person/day, so that the required detection system and the identification of the sucrose concentration. In this work, the identification process was carried out using an amperometric biosensor based on the yeast Saccharomyces cerevisiae as a bioreceptor. Measurements were made by immobilizing yeast cells and analyte samples into the biosensor electrodes and observed based on cellular respiration activity which was expressed as a parameter of dissolved oxygen (DO). The biosensor response is generated in the form of an output potential value, then processed using principal component analysis (PCA) to produce a sucrose concentration classification point with a percentage of variance of the two main components of 98.77% which states that the sensor is able to identify sucrose concentrations.

This research investigated the effect of synthesis pH on the microstructure and morphology of the zinc oxide (ZnO) particles prepared using pineapple (Ananas comosus) peel extract. In this study, ZnO powder were synthesized at different pH, i.e. 8, 9, 10, 11, and 12. ZnO samples were characterized using UV-Vis spectroscopy, Fourier Transform InfraRed spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The UV-Vis absorbances spectroscopy shows the optical absorption peak of the ZnO sample occurred in a wavelength range of 300-360 nm, with bandgap energy of ∼3.22 eV. The FT-IR spectrum shows the peak of Zn-O absorption at the wavenumber of 437.55 cm-1 and the reduction of aromatic compounds with increasing of pH. The micrograph of ZnO particles synthesized at different pH shows that the pH affected the size and shape of ZnO. Micro-sized particles with a granular shape have been found at pH 8, and 9, a spherical shape have been found at pH 10, while micro-sized flower-shaped particles have been found at pH 11 and 12. The XRD pattern reveals a wurzite hexagonal ZnO crystal phase with the hkl plane of (101) as the strongest peak, as well as the purity of the sample increasing as the pH value rises. As the conclusion, synthesis pH has a significant impact on the optical, structural, and morphological properties of ZnO biosynthetic powder.

No abstract

This paper presents a simple biosensor for observing the dissolved oxygen (DO) production in water. The measuring process is implemented using the biochips G connected with a biosensor module and electronic circuit to detect the changes of dissolved oxygen in real time measurement. Initial test was completed to observe the biochip response to the different oxygenated water solution. A light and dark experiment with ON/OFF phase of 20 minutes illumination period was realized to stimulate the green algae Chlorella vulgaris photosynthesis process to DO rate. The results show Biochip G using algae Chlorella vulgaris response to environmental changing conditions in the form of relationship between output voltage and DO rate the solution.