In this study, we report the synthesis of the magnetite/silica nanocomposites and their structural and functional groups, magnetic properties, morphology, antimicrobial activity, and drug delivery performance. The X-ray diffraction characterization showed that magnetite formed a spinel phase and that silica formed an amorphous phase. The particle sizes of magnetite increased from 8.2 to 13.2 nm with increasing silica content, and the particles were observed to be superparamagnetic. The nanocomposites tended to agglomerate based on the scanning electron microscopy images. The antimicrobial activity of the magnetite/silica nanocomposites revealed that the increasing silica content increased the inhibition zones by 74%, 77%, and 143% in case of Gram-positive bacteria (B. subtilis), Gram-negative bacteria (E. coli), and fungus (C. albicans), respectively. Furthermore, doxorubicin was used as the model compound in the drug loading and release study, and drug loading was directly proportional to the silica content. Thus, the increasing silica content increased the drug loading owing to the increasing number of OHÀ bonds in silica, resulting in strong bonds with doxorubicin. Based on this study, the magnetite/silica nanocomposites could be applied as drug delivery vehicles.

Fe3O4@SiO2 nanocomposites have been synthesized using the Stöber method. X-ray diffraction data analysis showed the addition of SiO2 changed the diffraction pattern peak which represented the existence of Fe3O4 and SiO2 nanoparticles. Based on the elemental analysis, it can be seen that Si compositions on the samples were 14.7 % (S1), 19.8% (S2), and 20.4% (S3). It strengthens the existence of Fe3O4 and SiO2 nanoparticles on the sample. Furthermore, the infrared spectrum showed that Fe3O4 and SiO2 molecular functional groups were recorded at the wavenumber of 548 cm−1 with Fe-O-Si bond. Furthermore, Fe-O bond was recorded at the wavenumber of 461 cm−1. Meanwhile, Si-O-Si and Si-O bonds were detected at the wavenumbers of 1102 cm−1 and 949 cm−1 respectively. Furthermore, the data from UV-Vis characterization presented the peak shifted towards a higher angle of the wavelength which indicated that there is a phenomenon of changes in band gap particle size along with increased content of SiO2.

In this study, a new antimicrobial agent was developed through a synthesis of Fe3O4/SiO2/Ag double nanocomposites using the sol–gel method. The prepared samples were characterized using XRD, SEM, FTIR, UV-Vis, VSM, and antibacterial test. The data analysis results for the Fe3O4/SiO2/Ag composites showed that Fe3O4, SiO2, and Ag constructed respective spinel cubic, orthorhombic, and amorphous structures in nanometric size. The saturation magnetization of Fe3O4/SiO2/Ag nanocomposites decreased due to the increase in the Ag content. Interestingly, the Fe3O4/SiO2/Ag nanocomposites presented excellent microbial activity. Ag deposition on the Fe3O4/SiO2 surface enhanced the antimicrobial activity of nanocomposites because Ag oxidized to Ag[Formula: see text] ion to produce a toxic effect in the cells of microorganisms. Furthermore, the Ag[Formula: see text] ion created the –S–Ag bond chain and deactivated the microorganism cells. Furthermore, surface plasmon resonance of Ag had an impact on the formation of photo-induced electrons, which produced superoxide radical anions, [Formula: see text] generating a collapsing force that causes the death of microorganisms.

Penelitian ini bertujuan untuk mengetahui tingkat penguasaan konsep pada materi tekanan hidrostatis dan hukum pascal. Penelitian ini menggunakan metode deskriptif dengan teknik sampling berupa purposive sampling (sample dengan tujuan tertentu). Terdapat 19 soal penguasaan konsep dengan 10 soal pilihan ganda beralasan dan 9 soal pernyataan benar atau salah disertai alasan. Soal-soal penguasaan konsep tersebut disebar ke 109 mahasiswa pendidikan fisika angkatan 2018 dan 2019. Berdasarkan analisis data, kesulitan mahasiswa terletak pada pengaplikasian persamaan dan penguasaan prinsip-prinsip yang bekerja pada tekanan hidrostatis. Mahasiswa hanya memahami bahwa suatu objek yang memiliki kedalam yang sama, juga memiliki tekanan yang sama. Namun sayangnya, syarat dari keadaan tersebut diabaikan. Lebih lanjut, mahasiswa juga mengalami kesulitan untuk menentukan gaya-gaya yang bekerja di dalam bejana. Hal ini diketahui berdasarkan jawaban dari soal soal penguasaan konsep. Dimana 12% dari mahasiswa tidak mampu menjawab dan memberikan alasan yang tepat. Sedangkan 88% sisanya memberi jawaban yang salah.

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