Carbon dots (C-Dots) from mangosteen peel has been synthesized by pyrolysis method. Synthesis of C-Dots is done using precursor solution which is prepared from extract of mangosteen peel as carbon source and urea as passivation agent. C-Dots is successfully formed with absorbance spectra at wavelength 350-550 nm. Urea affects to the formed C-Dots, while the absorbance and the luminescent spectra are independent toward urea. C-Dots from extract of mangosteen peel has size in range *2-15 nm. The absorbance peaks of C-Dots shows significant wavelength shift at visible region as the increasing of synthesized temperature. Shift of wavelength absorbance indicates the change of electronic transition of C-Dots. Meanwhile, the luminescent of C-Dots can be controlled by synthesized temperature as well. C-Dots luminescent were increasing as higher synthesized temperature. It was shown by the shift of wavelength emission into shorter wavelength, 465 nm at 200°C, 450 nm at 250°C, and 423 nm at 300°C. Synthesized temperature also affects size of C-Dots. It has size *10-15 nm at 200°C, *7-11 nm at 250°C and *2-4 nm at 300°C. In addition, temperature corresponds to the structure of carbon chains and C-N configuration of formed C-Dots from mangosteen peel extract.
This research aims to describe the anxiety of grade 9 students to solve geometry problems based on the IDEAL stages, that is, identify, define, explore, act, and look back. The subjects were three students who each had one student at each level, namely, visualization, analysis, and informal deduction. The data were collected through tests and interviews. To guarantee the validity and reliability of the research, the triangulation technique was used. The findings and conclusions were as follows: students' visualization anxiety could be observed in the explore stage, which was caused by their confusion to use the Pythagorean theorem in which only one side was known, and in the act stage, which was caused by the thinking barrier as they were unable to write the solution and add the explanation; students' analysis anxiety could be observed in the act stage, which was caused by their confusion to ponder over the working time and the use of a wrong method, and in the look-back stage, which was caused by their uncertainty and worry for giving incorrect answers; and students' informal deduction anxiety appeared in the act stage, which was caused by the thinking barrier as they were unable to describe the use of proportion of base and perpendicular of a right triangle.
The objective of this study is to describe students’ creative thinking skills in terms of Adversity Quotient. Students of tenth grade math and science studies were given an AQ questionnaire to find out their personality types. Three students from each personality type of quitters, campers, and climbers were given tests to find out their creative thinking skills. The procedure of this study refers to the qualitative content analysis method: (1) giving questionnaires and tests, (2) presenting in detail about students’ mathematical performance, and (3) in-depth interviews. It was known from 97 subjects who were given questionnaire, 6 students are quitters’, 2 peoples switched from quitters to campers, 48 campers, 36 campers to climbers and 5 climbers. Three quitters and campers didn’t fulfill with creative skill qualifications. Whereas for the climbers’ showed fluency and flexibility.
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