Materials Science Forum Vol. 1114

Abstract: The performance of a commercial GMR with a double-chip configuration has been investigated for detecting nanotag. Fe₃O₄ magnetic nanoparticles (MNPs) as tags were synthesized by co-precipitation method based on green synthesis using Moringa oleifera (MO) extract. Fe₃O₄ showed a soft ferromagnetic material and a magnetic saturation of 55.0 emu/g. MNPs-ethanol solution are dropped onto the surface of each chip of the sensing element. As a comparison, the performance of a single-chip configuration is also investigated. Obtained bias magnetic field used as a magnetic field sensing double-chip sensor is 3.8 Oe smaller than the single-chip sensor, which is 4.3 Oe, confirmed by the shift in the value of the first derivative order. Configuration of double-chip sensor in detecting Fe₃O₄ has a smaller LoD of 2.4 mg/mL compared to the single-chip configuration of 3.8 mg/mL. Therefore, Green-synthesized Fe₃O₄ as biocompatible magnetic tags in combination with commercial GMR sensors using double-chip configuration is promising for magnetic-based biosensor applications in driving more responsive detection and enabling portability by using a smaller energy source.

Abstract: Detection of magnetic nanoparticles (MNP_S) label is essential to determine the performance of giant magnetoresistance (GMR) sensors in biosensing technology. This research identifies the potency of green-synthesized Fe₃O₄/Chitosan on GMR sensors, which has never been explored. MNP_S label was synthesized by the coprecipitation method based on the green synthesis route because cost-effective, non-toxic, and reduces waste production. Chitosan is considered the best polymer candidate as a stabilizer of Fe₃O₄ because they are biodegradable, biocompatible, and hydrophilic. The characteristics of Fe₃O₄/Chitosan with several concentrations and the effect on sensor signals were investigated. Measurement of Fe₃O₄/Chitosan using a spin-valve based sensor with a Ta (2nm)/Ir₂₀Mn₈₀(10nm)/Co₉₀Fe₁₀(3nm)/Co₈₄Fe₁₀B₄(10nm)/Ta (5nm) structure on Si/SiO₂ substrate. Fe₃O₄/Chitosan has a spherical shape with an inverse spinel cubic structure. The crystallite sizes of Fe₃O₄/Chitosan (1:1) and Fe₃O₄/Chitosan (2:1) are 7.9 and 7.5 nm, respectively. Fourier transforms infrared spectra of Fe₃O₄/Chitosan showed the NH₂ bending at 1560 cm⁻¹, C-O-C stretching at 1386 cm⁻¹, and Fe-O stretching at 580 cm⁻¹. The results indicate that chitosan effectively coated the surface of Fe₃O₄. The sensitivity of the GMR sensor increased to 0.04 mV/mg/mL and 0.05 mV/mg/mL, in the case of Fe₃O₄/Chitosan (1:1) and Fe₃O₄/Chitosan (2:1). The increase in the sensitivity was caused by the decrease in diamagnetic material composition, crystallite size and the increase in the saturation magnetization of Fe₃O₄/Chitosan. Green-synthesized Fe₃O₄/Chitosan can be detected by GMR sensor by providing a low external magnetic field within the 60s and reach ruthless performance as a magnetic label to be applied to biosensors application in the future.

Abstract: This study reports on the effect of Gd concentrations on the properties of Gd-doped ZnO films. The films were prepared using co-sputtering method at room temperature. Characterization tools such as X-ray diffraction (XRD), atomic force microscopy (AFM), and vibrating sample magnetometer (VSM) were used to analyze the properties of the prepared films. XRD results observed that all the films are well crystalline and designated to the hexagonal wurtzite structure of ZnO with no secondary phases, which confirmed the successful of doping the Gd into ZnO. Topography analysis from AFM discovered the increase of Gd concentrations of Gd-doped ZnO films leads to the increase in grain size and rougher surface of the films. The magnetization of the films effectively depends on the Gd concentrations, which the diamagnetic behavior changed to ferromagnetic behavior upon Gd doping. A film with higher Gd doping concentration is more effective than lower Gd doping in terms of saturation magnetization (M_s), coercivity (H_c) and remanent magnetization (M_r). These findings revealed that optimizing the Gd concentration is very crucial in enhancing the magnetic properties of Gd-doped ZnO films.

Abstract: The application of an external electric field to the surface plasmon resonance (SPR) system of green-synthesized magnetite (Fe₃O₄) nanoparticles (MNPs) is very promising for increasing the SPR detection signal. Electro-optic surface plasmon resonance (EOSPR) behavior of MNPs has been successfully carried out. The EOSPR system was investigated using the Kretschmann configuration with the prism/Au thin film/MNPs/air layer arrangement and applying an electric voltage of 0 V, 2 V, 4 V, and 6 V. In this study, we synthesized MNPs using the green synthesis approach from moringa oleifera extract. The benefits of green synthesis include being safe, affordable, clean, and ecologically friendly processes. X-ray diffraction results obtained crystal size of the MNPs is about 9.2 nm with inverse spinel face-centered cubic crystal structure. Fourier transforms infrared characterization showed the presence of Fe-O bonds at wave numbers 569 cm^-1 and 629 cm^-1, indicating that MNPs were successfully formed. The saturation magnetization of the samples is 55.3 emu/g. The SPR angle of the SPR system Prism/Au thin film/air without the addition of MNPs is 44.66°. After being deposited by MNPs and induced by a voltage of 0 V, 2 V, 4 V, and 6 V, the SPR angles changed to 44.87°, 44.90°, 44.95° and 45.12°. The addition of MNPs and an external electric field causes the SPR angle to increase. The results of this study can provide new insights into the development of optical devices that can be manipulated electrically and have the potential for future biosensor applications.

Abstract: Bone cement is an indispensable material in orthopedic medicine. In Indonesia, the fulfillment of bone cement needs still depends on imports from other countries. Polymethyl methacrylate (PMMA) is one of the main ingredients of bone cement which can be made from suspension polymerization of methyl methacrylate monomer (MMA). Therefore, this study aims to develop a technique for producing bone cement from PMMA. The production of bone cement consists of (1) the manufacture of PMMA, (2) the mixing of solid mixtures, (3) the mixing of solid mixtures and liquid mixtures, and (4) the molding of bone cement composites. The concentrations of barium sulfate (BaSO₄) used were 7%, 9%, and 11% by weight. Composite products were analyzed by Scanning Electron Microscopy (SEM), Proton Nuclear Magnetic Resonance (H-NMR), and Compressive Strength. The increase of BaSO₄ can trigger more smooth surface of bone cement composite. The tacticity from H-NMR shows that the bone cement dominantly consists of syndiotactic (58.83-59.91%) molecular arrangement. The highest compressive strength was 84.2 MPa which was obtained in 9% BaSO4 weight.

Abstract: Poly (methyl methacrylate) or PMMA is an acrylic material has been used widely as a denture base material. The denture base materials should exhibit good mechanical properties and dimensional stability in moist environment. Hydroxyapatite (HAp) as a filler is added to improve the mechanical properties of the denture base. Process for the manufacture of denture base composites consists of a synthesis of polymethyl methacrylate (PMMA) with suspension polymerization process, treatment filler hydroxyapatite, mixing component powder and liquid, molding and curing process. hydroxyapatite concentrations used were 0%, 1.5%, 3%, 4.5%, 6%, 7.5% and 9%. Characterization of PMMA product resulted an average particle size of 48.7 microns, dominant percentage of taxicity in atactic 39.5% and syndiotactic 60.7%. In the FTIR spectra, no impurity compounds were detected in PMMA products. The highest tensile strength value was found in hydroxyapatite which contained 6%, which was 63.87 MPa according to the PMMA standard for denture base.

Abstract: The decrease in kidney function is caused by an increase in creatinine and urea levels in the blood; this is the cause of chronic kidney failure (GGK) in patients. Hemodialysis membrane technology is an alternative treatment for chronic renal failure by separating dissolved components in the blood, such as creatinine and urea, using dialysate fluid by passing through the membrane pores. Therefore, the characteristics of hemodialysis membranes become essential to meet the requirements of a dialyzer. This study aimed to compare the features of the resulting hemodialysis membrane with several commercial membranes. In this study, there were four kinds of commercial membranes used, namely F8HPS, FX80, LO PS 15, and Nipro Elisio 15-H, were compared with membrane products that have variations in the composition of polyethylene (PES) using N-methyl-2-pyrolidone (NMP) solvents are 22.5; 24; and 25%. The membrane manufacturing method uses nonsolvent-induced precipitation (NISP). The resulting hollow fiber membrane is characterized by surface morphology using a scanning electron microscope (SEM), functional groups (FT-IR), and tensile test analysis (DMA). The results showed that the composition of PES/NMP is 25%, close to the characteristics of Nipro Elisio 15-H.

Abstract: In this study, composite films were prepared from modified taro starch with the addition of duck bone gelatin using varying percentages (0%, 5%, 15%, 25%, 35% of the total solids weight) by solution casting method. The mixing of duck bone gelatin on taro starch films was studied as a new approach for composite films from natural materials that are environmentally friendly and have good physical properties. This study aimed to obtain information on the effect of the percentage variation of duck bone gelatin on the composite film on the density, transparency, crystallinity and thermal properties. The results of revealed that the addition of duck bone gelatin concentration had no significant effect (p>0.05) on the density of the composite films, but had a significant effect (p<0.05) on the transparency and termal properties. Crystallinity analysis using X-ray diffraction (XRD) technique showed that the composite films product has a semicrystalline structure with low crystallinity. DSC scan showed that the composite film with the addition of 5% duck bone gelatin gave high thermal stability values ​​with melting temperature (T_m) 181.86°C and melting enthalpy (ΔH_m) 252.73 J/g. The TGA results confirmed that the thermal stability of the composite film at the concentration of 5% duck bone gelatin had a weight loss of 37.48 % in the temperature range (296.74-500°C).

Abstract: The rapid development of the timber industry has caused the total capacity of the Indonesian timber industry to exceed the ability of production forests to provide raw materials sustainably. One of the industries that require a supply of wood as its main raw material is the furniture industry. The raw materials for furniture that are commonly used are logs and planks. In recent years, there has been the development of new materials that use natural fibers as polymer reinforcement, which can be used to replace wood materials. The material is a natural fiber composite. Composite materials reinforced with natural fibers are widely used in aerospace, automotive, circuit boards and other applications. One of the natural fibers that can be used as a composite is straw fiber. This high proportion of cellulose in straw fiber can be used for several things, one of which is composite materials. The utilization of rice straw fiber and epoxy as raw materials for making composites is an alternative to overcoming the increasing demand for wood. The purpose of this study was to determine and analyze the effect of volume fraction and alkalization treatment on the physical and mechanical characteristics of straw fiber composites, also to determine and analyze the effect of adding a coating of PE/SiO₂ on the hydrophobic characteristics of straw fiber composites. The physical and mechanical properties of the composites were evaluated based on the SNI 03-2059-2006 and SNI-01-4449-2006 standard. The volume fractions used are 40%, 50%, and 60%. The length of the fiber used is 5 mm. And the alkalization variables used were 5% and 10% NaOH with 4 and 8 hours of immersion. The compressive strength decreased by adding fiber volume fraction and increased by higher treatment alkalization. The coating method can produce composite with the contact angle value of more than 90^o.