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"Penelitian ini mengembangkan pembuatan biosensor elektrokimia menggunakan nanopartikel core-shell Fe3O4@Au yang dimodifikasi hemoglobin pada Screen Printed Carbon Electrode (SPCE) untuk mendeteksi akrilamida. Fe3O4NP (~4,9 nm) dan core-shell Fe3O4@Au (~5-6,4 nm) berhasil disintesis melalui metode dekomposisi termal. Hasil ini dikonfirmasi oleh analisis UV-Visible Spectrometer (UV-Vis), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) dan Transmission Electron Microscopy (TEM). Studi awal elektrokimia hemoglobin optimum didapatkan pada ABS 0,1 MpH 6 dengan konsentrasi optimal hemoglobin sebesar 2 mg/mL. Fe3O4@Au yang termodifikasi Hb memiliki ukuran yang lebih besar, dikarakterisasi dengan Scanning Electron Microscopy (SEM), FTIR, dan Zeta Potensial. Kinerja Fe3O4@Au/Hb dievaluasi untuk mendeteksi akrilamida dilakukan dengan metode Cyclic Voltammetry (CV) pada rentang potensial -0,8-0,8 V, scanrate 50 mV/s didapatkan koefisien regresi linear R2 = 0,98 pada rentang konsentrasi 0-1 μM dengan Limit of Detection (LOD) sebesar 0,136 μM dan sensitivitas sebesar 0,4411 μA/μM. Selain itu, studi interferensi dilakukan untuk beberapa senyawa sederhana lainnya seperti asam askorbat, melamin, glukosa, kafein dan natrium asetat. Pengukuran akrilamida pada real sampel berupa kopi bubuk dilakukan secara elektrokimia dengan biosensor ini dan divalidasi dengan metode standar High Performance Liquid Performance (HPLC).

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This work reports an investigation on the fabrication of electrochemical biosensor based on hemoglobin-modified core-shell Fe3O4@Au nanostructures on screen printed carbon electrode for the detection of acrylamide. Here, both Fe3O4NP (~4.9 nm) and core-shell Fe3O4@Au (~5-6.4 nm) nanostructures were successfully synthesized via thermal decomposition method. These results are discussed by analysis of UV-Visible Spectrometers (UV-Vis), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). Preliminary electrochemical investigation at ABS pH 6 also revealed that the optimum amount of hemoglobin immobilization were obtained at ABS 0.1 M pH 6 with an optimal hemoglobin concentration of 2 mg/mL. Hb modified Fe3O4@AuNP has a larger size, characterized by Scanning Electron Microscopy (SEM), FTIR, and Zeta Potential. The performance of Fe3O4@Au/Hb was evaluated to detect acrylamide using the Cyclic Voltammetry (CV) method in the potential range of -0.8-0.8 V, a scanrate of 50 mV/s obtained a linear regression coefficient R2=0.98 in the concentration range 0-1 μM with a Limit Detection (LOD) 0.136 μM and sensitivity 0.4411 μA/μM. In addition, studi interference is made for a number of simple compounds such as ascorbic acid, melamine, caffeine and sodium acetate. The measurement of acrylamide in real samples consisting of ground coffee was carried out by electrochemistry with this biosensor and validated by the standard High Performance Liquid Performance (HPLC) method."

"Avidin merupakan glikoprotein tetrametrik yang belakangan ini banyak dikembangkan aplikasinya karena sifatnya yang menguntungkan, terutama dalam bidang biomedis. Senyawa yang dapat digunakan sebagai agen pengenal dalam sensor avidin adalah biotin. Biotin diketahui dapat berikatan seara spesifik dengan avidin (Kd ~10−15 M). Nanopartikel core-shell dapat digunakan sebagai bahan label magnetik yang dapat menunjang pembentukan sensor. Pada penelitian ini, dilakukan sintesis Fe3O4@Au-sisteamin dan studi literatur Fe3O4@Au-sisteamin sebagai template pengikatan biotin untuk sensor avidin. Nanopartikel Fe3O4 di sintesis menggunakan metode ko-presipitasi sedangkan Fe3O4@Au di sintesis melalui deposisi-presipitasi dimana dari kedua metode ini mempermudah pemisahan antara nanopartikel dengan larutan menggunakan magnet eksternal. Nanokomposit hasil sintesis dikarakterisasi dengan spektroskopi Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), dan Transmission Electron Microscope (TEM). Hasil yang diperoleh menunjukkan rata-rata nanopartikel Fe3O4 dan Fe3O4@Au sebesar 3,724 ± 0,561 nm dan 13,801 ± 4,147 nm. Hasil FT-IR memunculkan spektra pada bilangan gelombang 550-700 cm-1 yang mengindikasikan bahwa sisteamin berikatan secara kovalen dengan shell Au.

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Avidin is a tetrametric glycoprotein that has been developed recently for many applications because of its beneficial properties, especially in the biomedical field. The compound that can be used as a recognition agent in avidin sensing is biotin. Biotin is well-known to bind specifically with avidin (Kd ~ 10−15 M). In this research, the synthesis of Fe3O4@Au-cysteamine and the literature study of Fe3O4@Au-cysteamine as a biotin binding template for avidin sensor have been done. Fe3O4 nanoparticles (Fe3O4 NPs) were synthesized using the co-precipitation method while Fe3O4@Au were synthesized through precipitation-deposition. Both methods facilitate separation between the nanoparticles and the solution using an external magnet. The synthesized nanocomposites were characterized by Fourier Transform Infrared (FTIR) spectroscopy, X-Ray Diffraction (XRD), and Transmission Electron Microscope (TEM). The results obtained showed that the average Fe3O4 and Fe3O4@Au nanoparticles were 3.724 ± 0.561 nm and 13.801 ± 4.147 nm. The FT-IR spectra also showed that there was peak at 550-700 cm-1 which indicate that cysteamine binds covalently to the Au shell."

"ABSTRAKSenyawa turunan spiropiperidin berhasil disintesis meggunakan -diketon asam barbiturat/dimedon, formaldehid serta turunan anilin melalui kondensasi Mannich. Dua reaksi dinilai menghasilkan senyawa target senyawa 1 dan senyawa 3 , sementara satu reaksi lain menghasilkan dihidropiridin senyawa 2 . Hasil dikonfirmasi menggunakan karakterisasi FTIR, UV-Vis dan LC-MS. Sintesis senyawa menggunakan nanokatalis Fe3O4 dari proses dekomposisi termal karat besi dengan asam palmitat dalam pelarut paraffin. Paraffin sebagai pelarut memiliki titik didih tinggi dan dapat menggantikan pelarut umum seperti n-oktadekana. Penggunaan karat dan parrafin meningkatkan nilai ekonomis katalis yang dihasilkan. Karakterisasi FTIR pada katalis menunjukkan keberadaan asam palmitat sebagai capping agent mengelilingi Fe3O4. Data XRD memberikan ukuran rata-rata kristal 42,758 nm, sementara gambar TEM mengkonfimasi bentuk kristal berupa kubus dan unsur penyusunnya. Karakterisasi PSA memberikan indeks polidispersitas 0,391 dan Z-average 48,94. Dua senyawa hasil sintesis dioptimasi dalam suhu, waktu reaksi dan jumlah katalis berat yang berbeda. Hasil optimasi reaksi untuk senyawa 1 15-phenyl-2,4,10,12,15-pentaazadispiro[5.1.5.3]-hexadecane-1,3,5,9,11,13-hexa-one memberikan kondisi optimum pada suhu 50 oC, 4 jam reaksi dan 7,5 katalis dengan rendemen 69,30 . Sementara senyawa 2 10-4 chlorophenyl -9,10-dihydropyrido[2,3-d;6,5-d rsquo;]-dypyrimidine-2,4,6,8 1H,3H,5H,7H -tetra-one optimum pada suhu 50 oC, 4 jam dan 5 katalis dengan rendemen 72,34 . Studi penggunaan ulang katalis dilakukan pada senyawa 1 dan memberikan kecendrungan penurunan hasil rendemen dalam lima kali pengulangan.

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ABSTRACT Spiropiperidine derivatives have been successfully synthesized using diketone such as barbituric acid dimedone, formaldehyde and aniline derivatives through Mannich condensation. Two reactions considered produced the targeted compounds compound 1 and compound 3 , while the other reaction produced dihydropyridine compound 2 . These results were confirmed using FTIR, UV Vis and LC MS. These compounds were synthesized using heterogenic Fe3O4 catalyst which was obtained from rust capped palmitic acid in paraffin solvent. Paraffin was chosen as solvent due to its high boiling point which was suitable to replace common solvents n octadecane. The use of rust and paraffin would increase catalyst rsquo s economic value. FTIR characterization of catalyst showed the presence of palmitic acid as capping agent surrounding Fe3O4. XRD data gave average crystal size of 42.758 nm, while the TEM image confirmed the crystal structure as cube and its constituent elements. PSA result gave polydispersity index of 0.391 and Z average 48,94. Two compounds were optimized under various of temperatures, times and amount of catalyst weight . Optimization condition for compound 1 15 phenyl 2,4,10,12,15 pentaazadispiro 5.1.5.3 hexadecane 1,3,5,9,11,13 hexa one came as 50 oC, 4 hours of time reaction and 7.5 catalyst with 69.30 of yield. Meanwhile compound 2 10 4 chlorophenyl 9,10 dihydropyrido 2,3 d 6,5 d 39 dypyrimidine 2,4,6,8 1H, 3H, 5H, 7H tetra one at 50 oC, 4 hours of time reaction and 5 catalyst yielded 72,34 . The study of reusable catalyst was conducted on compound 1 and resulted the yield rsquo s descending rsquo s tendency in each five times of repetitions."

"ABSTRACTSenyawa turunan spirooxindole adalah senyawa heterosiklik yang berasal dari bahan alam dan memiliki berbagai aktivitas biologis seperti antioksidan dan antibakteri. Senyawa ini telah berhasil disintesis dengan kondensasi Knoevenagel dan adisi Michael multi komponen satu pot. Sintesis senyawa turunan spirooxindole dapat ditingkatkan efisiensi waktunya dengan menggunakan katalis heterogen berupa grafena oksida/Fe3O4. Pada penelitian ini, senyawa turunan spirooxindole telah disintesis dengan menggunakan prekursor 1,3-diketon yang bervariasi seperti asam barbiturat, etil asetoasetat, dan dimedon. Berdasarkan hasil optimasi reaksi, diperoleh kondisi optimum pada suhu 60oC , waktu 45 menit, dan berat katalis sebesar 15%. Persen yield yang didapat pada kondisi optimum terdapat pada senyawa 1 sebesar 90.86%, senyawa 2 sebesar 93.03%, dan senyawa 3 sebesar 65.456%. Karakterisasi produk hasil sintesis dan katalis grafena oksida/Fe3O4 telah dikonfirmasi menggunakan KLT, FT-IR, spektrofotometer UV-Vis, GC-MS, SEM/EDX, dan XRD. Pada senyawa turunan spirooxindole, hasil sintesis dilakukan uji aktivitas antioksidan dengan nilai IC50 untuk produk senyawa 1 sebesar 392,20 ppm, senyawa 2 sebesar 1010,61 ppm, dan senyawa 3 sebesar 452,51 ppm. Uji antibakteri yang juga dilakukan pada senyawa turunan spirooxindole didapati bahwa hanya Senyawa 1 yang menunjukkan sifat antibakteri pada bakteri S.aureus dan E.coli.

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ABSTRACTSpirooxindole derivative compounds are heterocyclic compounds that come from nature product and have many biological activities like antioxidant and antibacteria. These compounds have been successfully synthesized with Knoevenagel condensation and Michael addition multicomponent reaction in one pot. Time efficiency in these reactions can be increased using heterogeneous catalyst called graphene oxide/Fe3O4. These derivatives of spirooxindole compound synthesized with variation of 1,3 diketone precursor such as barbituric acid, ethyl acetoacetate, and dimedone. Based on the optimization result, optimum condition obtained in 60 oC, 45 minutes, and catalyst weight 15%. Yield percentage that obtained in optimum condition from compound 1 was 90.86%, compound 2 was 93.03%, and compound 3 was 65.456%. Analyzation and characterization of the product and graphene oxide/Fe3O4 catalyst have been confirmed using TLC, FT-IR, UV-Vis spectrophotometer, GC-MS, SEM/EDX, and XRD. In spirooxindole derivatives, the result of synthesis was tested by antioxidant activity with  IC50 value for product of compound 1 equal to 392,20 ppm, compound 2 equal to 1010,61 ppm, and compound 3 equal to 452,51 ppm. Antibacterial test which also have been done showed that compound 1 is the only compound showed antibacterial characteristic with S.aureus and E.coli bacteria."

"Pencemaran lingkungan adalah salah satu masalah serius disebabkan pembuangan limbah berbahaya dan beracun dari industri–industri yang tidak teregulasi. Salah satu material yang banyak digunakan sebagai zat warna adalah sunset yellow pada industri tekstil yang berdampak buruk, menyebabkan risiko kesehatan seperti depresi, kerusakan ginjal, kerusakan hati, dan kanker. Pada penelitian ini telah dilakukan sintesis nanokomposit Nanochitosan/Fe₃O₄−SrSnO₃ untuk mendegradasi zat warna sunset yellow. Nankomposit Nanochitosan/Fe₃O₄−SrSnO₃ dikarakterisasi dengan Fourier–transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–Vis), X–ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high–resolution transmission electron microscopy (HRTEM), Brunauer–Emmet–Teller (BET) dan ultraviolet visible–diffuse reflectance (UV–DRS). Pengaruh Fe₃O₄ terhadap sisi aktif SrSnO₃ telah dipelajari dan energi celah pita dari SrSnO₃ menjadi 2,4 eV dengan komposisi Fe₃O₄/SrSnO₃ (3:1) dengan persen degradasi sebesar 88,45% . Nanochitosan ditambahkan sebagai support meningkatkan aktivitas dari nanokomposit Fe₃O₄−SrSnO₃ dengan persen dgradasi 97,42%. Nanokomposit yang optimal yang digunakan untuk analisis kinetika reaksi dan isoterm adsorpsi adalah dengan kondisi massa 0,04 gram, pH 10, dan waktu selama 75 menit. Kinetika reaksi mengikuti psuedo first order dengan konstanta laju reaksi 0,058 dan sesuai dengan isoterm adsorpsi Langmuir

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Environmental pollution is one of the most serious problems caused by the disposal of hazardous and toxic waste from unregulated industries. One material that is widely used as a dye is sunset yellow in the textile industry which has adverse effects, causing health risks such as depression, kidney damage, liver damage, and cancer. In this study, Nanochitosan/ Fe₃O₄−SrSnO₃ nanocomposite has been synthesized to degrade sunset yellow dye. Nanochitosan/ Fe₃O₄−SrSnO₃ nanocomposites were characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmet-Teller (BET) and ultraviolet visible-diffuse reflectance (UV-DRS). The effect of Fe3O4 on the active side of SrSnO₃ was studied and the band gap energy of SrSnO₃ became 2.4 eV with Fe₃O₄/SrSnO₃ composition (3:1) with a percent degradation of 88.45%. Nanochitosan added as support increases the activity of Fe₃O₄−SrSnO₃ nanocomposite with 97.42% degradation percent. The optimal nanocomposite used for the analysis of reaction kinetics and adsorption isotherms was with a mass condition of 0.04 grams, pH 10, and time for 75 minutes. The reaction kinetics followed first order psuedo with a reaction rate constant of 0.058 and fit the Langmuir adsorption isotherm."

"Akrilamida merupakan senyawa neurotoksin yang berpotensi menyebabkakan penyakit kanker yang terbentuk akibat pemaparan suhu yang tinggi saat proses memasak pada makanan dan beresiko pada kesehatan manusia. Penelitian ini akan menghasilkan sensor akrilamida yang sensitif dan selektif berdasarkan penurunan arus HbFe3+ menjadi HbFe2+ hasil interaksi akrilamida dengan hemoglobin. Sensor akan memodifikasikan hemoglobin pada permukaan Fe3O4@Au yang disintesis menggunakan metode ko-presipitasi dan dikarakterisasi menggunakan FTIR, TEM, SEM-EDX, dan XRD. Biosensor ini akan menggunakan elektroda screen-printed carbon electrode (SPCE) karena praktis, memungkinkan biomolekul untuk immobilisasi ke permukaan elektroda, dan selektif. Studi komputasi melalui simulasi docking menunjukan pH 7.4 pada suhu 310 K merupakan kondisi optimum Hb untuk berinteraksi dengan akrilamida berdasarkan menghasilkan ΔGbinding -2.8934 pada binding site α N-Terminal Valin dan nilai Pkd sebesar 4.8755x10-4, hal ini divalidasi oleh studi elektrokimia diperoleh ABS pH 7.4 0,1 M dan konsentrasi Hb 2 mg / l mealalui pengukuran menggunakan voltametri siklik (CV) menghasilkan kondisi yang optimum dengan rentang potensial -1.0 V – 1.0 V dan scan rate 50 mV/s. Pengukuran standar akrilamida menunjukkan linieritas yang cukup baik (R2 > 0,9794) pada rentang konsentrasi 0.01 μM – 0.09 μM. dengan limit of detection (LOD) sebesar 0.02 μA dan sensitivitas sebesar 276.47 μA/μM. Validasi kadar akrilamida dilakukan menggunakan High Performance Liquid Performance (HPLC) pada sampel kopi bubuk luwak yang juga diukur secara elektrokimia menggunakan CV. Akrilamida dalam sampel kopi luwak menggunakan sensor menunjukkan hasil 4.6 ppm yang mendekati hasil pengukuran dengan HPLC 4.3 ppm.

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Acrylamide is a neurotoxic compound that has the potential to cause cancer which is formed due to exposure to high temperatures during the cooking process on food and is a risk to human health. This research will produce a sensitive and selective acrylamide sensor based on the reduction of current HbFe3+ to HbFe2+ as a result of the interaction of acrylamide with hemoglobin. The sensor will modify the hemoglobin on the surface of Fe3O4@ Au which was synthesized using the co-precipitation method and characterized using FTIR, TEM, SEM-EDX, and XRD. Fe3O4 is used to remove the supernatant of acrylamide in a solution. This biosensor will be using a screen-printed carbon electrode (SPCE) electrode because it is single-use, allows biomolecules to be immobilized to the electrode surface, and selective. Computational studies through docking simulations show pH 7.4 at 310 K is the optimum condition for Hb to interact with acrylamide with ΔGbinding value -2.8934 at the α N-Valine Terminal binding site and a Pkd value is 4.8755x10-4, this is validated by electrochemical studies were ABS pH 7.4 0.1 M and a Hb concentration of 2 mg / l was obtained through measurement using cyclic voltammetry (CV) resulting in optimum conditions with a potential range of -1.0 V - 1.0 V and a scan rate of 50 mV / s. The acrylamide standard measurement showed fairly good linearity (R2> 0.9794) at a concentration of 0.01 μM - 0.09 μM with a limit of detection (LOD) is 0.02 μA and the sensitivity of the sensor is 276.47 μA / μM. Validation of acrylamide levels was carried out using High-Performance Liquid Performance (HPLC) on Luwak coffee ground coffee samples which were also measured electrochemically using CV."

"Nanohybrid iron oxide titanium dioxide copper oxide dengan tiga variasi molar 1 1 1 1 3 1 dan 1 5 1 telah disintesis menggunakan metode sol gel Pengukuran X Ray Diffraction XRD Field Emission Scanning Electron Microscopy FESEM Energy Dispersive X rays EDX UV Vis Spectroscopy dan Vibrating Sample Magnetometer VSM digunakan untuk menentukan sifat struktur morfologi nilai energy gap optik dan sifat magnetik dari sampel nanohybrid Pengujian aktivitas fotokatalitik sampel nanohybrid dilakukan dengan mengamati degradasi warna methylene blue MB dibawah pemaparan cahaya ultraviolet dan tampak Hasil menunjukkan keberadaan copper oxide seiring dengan peningkatan rasio molar titanium dioxide mempengaruhi aktivitas fotokatalitik nanohybrid Nanohybrid dengan rasio molar 1 5 1 menunjukkan aktivitas fotokatalitik yang paling baik untuk pemaparan dengan cahaya ultraviolet sedangkan untuk pemaparan dengan cahaya tampak didapatkan dengan rasio molar 1 1 1 Selain itu fotokatalis nanohybird dapat dipisahkan setelah proses reaksi menggunakan magnet eksternal Penambahan scavenger menunjukkan hole memiliki peranan penting dalam proses degradasi methylene blue

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Iron oxide titanium dioxide copper oxide nanohybrids with three different molar ratios 1 1 1 1 3 1 and 1 5 1 were successfully prepared by sol gel method X Ray Diffraction XRD Field Emission Scanning Electron Microscopy FESEM Energy Dispersive X rays EDX UV ndash Vis spectroscopy and Vibrating Sample Magnetometer VSM techniques were employed to determine the structure morphology optical gap energy and magnetic properties of the as prepared samples Photocatalytic examination of the nanohybrids was carried out using aqueous solution of methylene blue MB under ultraviolet and visible light irradiation The results demonstrate that the increase molar ratio of titanium dioxide and the addition of copper oxide to iron oxide titanium dioxide cooper oxide has remarkable influence on the photocatalytic activity The nanohybrids with 1 5 1 molar ratio has superior activity in degradation of MB under ultraviolet light while under visible light the maximum degradation is reached by sample with molar ratio 1 1 1 Furthermore the photocatalysts can be separated from the reaction system simply by applying an external magnetic Active species on photocatalytic activity were investigated by measuring the photocatalytic degradation in the presence of scavenger The results suggested that holes play the most important role in degradation of methylene blue."

"ABSTRAKShape Memory Polyurethane (SMPU) telah disintesis dari penambahan polyethylene glycol (PEG-6000) sebagai segmen lunak dan 4,4'-Methylenebis (Cyclohexyl isocyanate) (HMDI) sebagai segmen keras serta 1,1,1-Trimethylol propane (TMP) sebagai chain extender. SMPU lalu ditambahkan nanopartikel Fe3O4 berukuran 20-50 nm untuk meningkatkan sifat kemagnetan. Untuk mengkonfimasi bentuk ikatan antarmuka komposit SMPU digunakan FTIR (Fourier Transform Infrared Spectroscopy). FE-SEM digunakan untuk mengetahui interface dari filler dan matriks SMPU. Konfirmasi nilai kemagnetan menggunakan VSM (vibrating sampel magnetometer) dan pengujian tarik menggunakan microtensile menunjukkan bahwa penambahan Fe3O4 dengan persentase 11 wt% menghasilkan nilai kemagnetan dan sifat mekanik tertinggi.

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ABSTRACTShape Memory Polyurethane (SMPU) has been synthesized by reacting polyethylene glycol (PEG-6000) as softsegment, 4,4'-Methylenebis (Cyclohexyl isocyanate) (HMDI) as hardsegment and 1,1,1-Trimethylol propane (TMP) as chain extender. SMPU was added by Fe3O4 as filler to provide magnetical property. Magnetite which had confirmed by Scanning Elctron Magnetic (SEM) have size 20-50 nm. Functional group was investigated by FTIR (Fourier Transform Infrared Spectroscopy). The magnetic behavior of the nanocomposites was observed by vibrating sample margnetometer (VSM). FE-SEM is used to acknowledge interface between filler and Shape Memory Polyurethane (SMPU) matrix. Mechanical properties tested by microtensile testing showed adding 11% Fe3O4 obtaining magnetic and nanocomposites SMPU resulted in improved materials with higher magnetical and mechanical properties."

"Kami menunjukkan penelitian secara teoretik pada kenaikan nilai magnetisasi dari sistem nanopartikel Fe3O4 dengan adanya penambahan reduced Graphene Oxide (rGO). Data eksperimen telah menunjukkan bahwa magnetisasi sistem nanopartikel Fe3O4 -rGO meningkat dengan peningkatan jumlah rGO sampai sekitar 5 wt%, tetapi menurun kembali dengan bertambah lebih banyaknya jumlah rGO. Kami mengajukkan bahwa kenaikan terjadi dipengaruhi oleh adanya pembalikan spin pada Fe3+ dalam bagian tertrahedral dibantu oleh kekosongan oksigen di perbatasan partikel Fe3O4 . Kekosongan oksigen diinduksi oleh adanya lapisan rGO yang menarik atom oksigen dari permukaan partikel Fe3O4 disekitarnya. Untuk memahami peningkatan mag- netisasi, kami mengkontruksi model Hamiltonian berdasarkan tight-binding untuk sistem nanopartikel Fe3O4 dengan konsentrasi kekosongan oksigen dikontrol melalui konten rGO. Kami menghitung magnetisasi sebagai fungsi dari medan magnet eksternal untuk berbagai variasi wt% rGo. Kami menggunakan metode dynamical mean-field theory dan melakukan perhitungan pada temperatur ruangan. Hasil kami untuk ketergantungan rGO wt% dari magnetisasi saturasi menunjukkan hasil yang sangat sesuai dengan data eksperimen dari sistem nanopartikel Fe3O4 -rGO yang ada. Hasil ini mungkin dapat menkonfirmasi bahwa model kami telah membawa ide paling penting yang dibutuhkan untuk menjelaskan fenomena kenaikan magnetisasi diatas.

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We present a theoretical study on the enhancement of magnetization of Fe3O4 nanoparticle system upon addition of reduced Graphene Oxide (rGO). Experimental data have shown that the magnetization of Fe3O4 -rGO nanoparticle system increases with increasing rGO content up to about 5 wt%, but decreases back as the rGO content increases further. We propose that the enhancement is due to spin-flipping of Fe3+ in the tetrahedral sites assisted by oxygen vacancies at the Fe3O4 particle boundaries. These oxygen vacancies are induced by the presence of rGO flakes that adsorb oxygen atoms from Fe3O4 particles around them. To understand the enhancement of the magnetization we construct a tight-binding based model Hamiltonian for the Fe3O4 nanoparticle system with the concentration of oxygen vacancies being controlled by the rGO content. We calculate the magnetization as a function of the applied magnetic field for various values of rGO wt%. We use the method of dynamical mean-field theory and perform the calculations for a room temperature. Our result for rGO wt% dependence of the saturated magnetization shows a very good agreement with the existing experimental data of the Fe3O4 -rGO nanoparticle system. This result may confirm that our model already carries the most essential idea needed to explain the above phenomenon of magnetization enhancement."

"Pada penelitian ini, dua jenis graphene graphene dan nanographene platelets NGP dipergunakan sebagai supporting adsorbent dan juga katalis untuk proses degradasi limbah pewarna. Material graphene dan NGP dipergunakan untuk men-support kemampuan adsorpsi dari material nanopartikel Fe3O4. Kemampuan adsorpsi dari nanopartikel Fe3O4 meningkat dengan penambahan material NGP dan graphene. Penambahan material graphene pada Fe3O4 menunjukan kemampuan adsorpsi yang paling baik dibandingkan dengan penambahan material NGP. Material NGP dan graphene juga dipergunakan untuk meningkatkan kemampuan fotokatalitik nanokomposit Fe3O4/ZnO/CuO FZC dibawah penyinaran cahaya ultraviolet UV dan cahaya tampak serta kemampuan sonophotocatalytic dibawah radiasi UV ultrasound US dan cahaya tampak US . Penambahan material graphene menghasilkan kemampuan adsorpsi dan aktivitas fotokatalitik dikarenakan memiliki luasan area yang lebih besar serta oxygen functional group dari material graphene. Penambahan material NGP dan graphene juga mampu menghambat laju rekombinasi elektron dan hole dikarenakan kemampuan graphene dan NGP untuk bertindak sebagai electron acceptor. Hal tersebut berdampak terhadap peningkatan kemampuan aktivitas katalitik dari sampel. Sifat fisis dari seluruh material dianalisis menggunakan X-ray diffractions XRD , energy dispersive X-ray EDX , transmission electron microscope TEM , UV-Vis diffuse reflectance spectroscopy, Fourier transform Infra-red FT-IR spectroscopy Raman spectroscopy, Brunauer ndash;Emmett ndash;Teller BET , differential thermal analysis and thermogravimetric analysis DTA/TGA , vibrating sample magnetometer VSM.

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In this study, two types of Carbon nanographene platelets NGP and graphene has been used as supporting adsorbent and catalyst for waste water removal. Both NGP and graphene were used to support the adsorption ability of Fe3O4 nanoparticles. The adsorption ability of Fe3O4 was increase with the incorporation of NGP and graphene. The incorporation of graphene resulted in the higher adsorption ability of the samples. Moreover, NGP and graphene also used to support the photocatalytic performance under UV and visible light irradiation as well as sonophotocatalytic under UV ultrasound US and visible US of Fe3O4 ZnO CuO FZC nanocomposites. The incorporation of graphene has better adsorption and catalytic performance than the incorporation of NGP due to the higher specific surface area and also the oxygen functional group in graphene materials. The incorporation of NGP and graphene has an ability to prevent recombination electron and hole due to both NGP and graphene could act as electron acceptors. It impacts on the improvement the catalytic performance. The combination of The physical properties of the samples was investigated using X ray diffractions XRD , energy dispersive X ray EDX , transmission electron microscope TEM , UV Vis diffuse reflectance spectroscopy, Fourier transform Infra red FT IR spectroscopy, Raman spectroscopy, Brunauer ndash Emmett ndash Teller BET , differential thermal analysis and thermogravimetric analysis DTA TGA , vibrating sample magnetometer VSM."