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In this study, nanofertilizer effectiveness of urea/APTMS-modified zeolite as a slow release fertilizer nitrogen from urea was evaluated. The natural zeolite is activated by 1% of HF with a temperature of 120°C and a zeolite surface has been modified with aminopropyltrimethoxysilane (APTMS) 5%. Zeolite was activated with APTMS-modified zeolite characterized by X-ray diffraction spectroscopy (XRD), surface area analyzer (SAA) and UV-Vis spectroscopy. Modification of activated zeolite with APTMS result in decrease in pore size as well as crystalinity. While the aminopropyl group was well defined with FTIR spectra, pore size measurenment using SAA obtained APTMS-modified pore size was 7.74 nm; while a maximum adsorption capacity of urea was 3.668 mg/g. Slow release urea of APTMSmodified zeolite was evaluated and observed by the increasing of urea absorbance at a wavelength of 190 nm in aqueous media. The experiment result showed that urea without zeolite was released up to 100% limit at 10 min observations, while the urea impregnated with APTMS-modified zeolite in 1 M NaCl media was released up to 100% at 120 min observation times. Meanwhile, the APTMS-modified zeolite in aqueous media was released only about 56.24% at 120 min. The result conclude that the APTMSmodified zeolite is capable of retarding the release of urea and potential to be developed as a control release of nitrogen from urea.

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Synthesis of graphene oxide (GO) material with variations in permanganate/graphite ratio has been carried out. This research purposes to study the impact of increasing oxidizing agents to graphite on the chemical structure and properties of the GO material produced. All GOs were synthesized using the improved Tour method with three variations of permanganate/graphite ratios of 5, 6, and 7. The results obtained include GO-5, GO-6, and GO-7, respectively, having a d spacing value of 0.843; 0.891; 0.894 nm by XRD analysis and 0.768; 0.756; 0.772 nm by SAED analysis. Based on the FTIR data, all GO materials bring up the peaks of oxygen-functionalized carbon absorption such as O–H, C–H sp3, C=O, C–O–C of ether and ester, and C-OH for carboxylic acids and alcohols. The oxidation levels (O/C ratio taken from EDX data) of GO-5, GO-6, and GO-7 are 0.67, 0.88, and 1.50, respectively. SEM images display the appearance of an exfoliated layer with a wrinkled and irregular surface. TEM images show thin and transparent layers. The main peaks with the highest absorbance at the wavelength around 230-240 nm, meanwhile the band gap energy produced was 3.53; 3.71; 3.55 eV for GO-5, GO-6, and GO-7, respectively.