Use of Dichlorodimethylsilane to Produce Polydimethylsiloxane as a Substitute for Vitreous Humour: Characteristics and In Vitro Toxicity.

Polydimethylsiloxane (PDMS) is a substitute for vitreous humour in vitreoretinal surgery and is usually produced from octamethylcyclotetrasiloxane (D4). In Indonesia, both commercial PDMS and D4 are limited and expensive. Dichlorodimethylsilane (DCMS) can be an alternative to produce PDMS. DCMS is cheaper and easier to obtain than D4. However, more extra effort is needed in order to produce PDMS from DCMS. Therefore, this study aimed to produce PDMS from DCMS by varying the ratio of DCMS precursor to dichloromethane (DCM) solvent at ratios of 1:1 and 1:4 through the hydrolysis-condensation method under neutral conditions. The PDMS produced had medium- (2.06 Pa·s) and high viscosity (3.59 Pa·s), with densities ranging from 0.96 to 0.99 g/mL. The refractive index was 1.4034-1.4036 and surface tension was 21 × 10-3 N/m, while they were able to transmit ~100% visible light, which were similar values to the commercial PDMS characteristics. PDMS samples were characterized using IR and NMR spectroscopy, which confirmed they were of PDMS type. The most optimum DCMS:DCM ratio was 1:1 due to the medium-viscosity PDMS type that could be produced. The in vitro HET-CAM toxicity test showed that samples were non-irritant, similar to PDMS produced from D4. PDMS from DCMS was non-toxic and ready to be used as a vitreous humuor substitution.

Different Roles between PEDOT:PSS as Counter Electrode and PEDOT:Carrageenan as Electrolyte in Dye-Sensitized Solar Cell Applications: A Systematic Literature Review.

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) has been mostly used as a counter electrode to give a high performance of dye-sensitized solar cell (DSSC). Recently, PEDOT doped by carrageenan, namely PEDOT:Carrageenan, was introduced as a new material to be applied on DSSC as an electrolyte. PEDOT:Carrageenan has a similar synthesis process as PEDOT:PSS, owing to their similar ester sulphate (-SO3H) groups in both PSS and carrageenan. This review provides an overview of the different roles between PEDOT:PSS as a counter electrode and PEDOT:Carrageenan as an electrolyte for DSSC applications. The synthesis process and characteristics of PEDOT:PSS and PEDOT:Carrageenan were also described in this review. In conclusion, we found that the primary role of PEDOT:PSS as a counter electrode is to transfer electrons back to cell and accelerate redox reaction with its superior electrical conductivity and high electrocatalytic activity. PEDOT:Carrageenan as an electrolyte has not shown the main role for regenerating the dye sensitized at the oxidized state, probably due to its low ionic conductivity. Therefore, PEDOT:Carrageenan still obtained a low performance of DSSC. Additionally, the future perspective and challenges of using PEDOT:Carrageenan as both electrolyte and counter electrode are described in detail.

Green Template-Mediated Synthesis of Biowaste Nano-Hydroxyapatite: A Systematic Literature Review.

Hydroxyapatite (HA) is a well-known calcium phosphate ingredient comparable to human bone tissue. HA has exciting applications in many fields, especially biomedical applications, such as drug delivery, osteogenesis, and dental implants. Unfortunately, hydroxyapatite-based nanomaterials are synthesized by conventional methods using reagents that are not environmentally friendly and are expensive. Therefore, extensive efforts have been made to establish a simple, efficient, and green method to form nano-hydroxyapatite (NHA) biofunctional materials with significant biocompatibility, bioactivity, and mechanical strength. Several types of biowaste have proven to be a source of calcium in forming HA, including using chicken eggshells, fish bones, and beef bones. This systematic literature review discusses the possibility of replacing synthetic chemical reagents, synthetic pathways, and toxic capping agents with a green template to synthesize NHA. This review also shed insight on the simple green manufacture of NHA with controlled shape and size.

Study of Magnetic Properties and Relaxation Time of Nanoparticle Fe3O4-SiO2.

The magnetic properties and relaxation time of Fe3O4 nanoparticles, and their encapsulation with silicon dioxide (Fe3O4-SiO2), have been successfully investigated by analyzing the temperature dependence of magnetization (M(T)) and the time dependence of magnetization (M(t)), using the SQUID magnetometer measurement. The M(T) measurement results can determine the magnetic parameters and magnetic irreversibility of Fe3O4 and Fe3O4-SiO2 samples. The values of Curie constant (C), effective magnetic moment (µeff), and Weiss temperature (θP) are 4.2 (emu.K.Oe/mol), 5.77 µB, and -349 K, respectively, for the Fe3O4 samples, and 81.3 (emu.K.Oe/mol), 25.49 µB, and -2440 K, respectively, for the Fe3O4-SiO2 samples. After encapsulation, the broadening peak deviation decreased from 281.6 K to 279 K, indicating that the superparamagnetic interactions increased with the encapsulation process. The magnetic parameters and irreversibility values showed that the superparamagnetic properties increased significantly after encapsulation (Fe3O4-SiO2). From the results of the M(t) measurement, it was found that there was a decrease in the magnetic relaxation time after the encapsulation process, which indicated that the distribution of the nanoparticle size and anisotropy energy increased.

Physical Characterization and In Vitro Toxicity Test of PDMS Synthesized from Low-Grade D4 Monomer as a Vitreous Substitute in the Human Eyes.

Polydimethylsiloxane (PDMS) is one of the most superior materials and has been used as a substitute for vitreous humor in the human eye. In previous research, we have succeeded in producing PDMS with low and medium viscosity using octamethylcyclotetrasiloxane (D4) monomer with a low grade of 96%. Both have good physical properties and are comparable to commercial product PDMS and PDMS synthesized using D4 monomer with a high grade of 98%. An improvement of the synthesis process is needed to ensure that PDMS synthesized from a low-grade D4 monomer under specific synthesis conditions can repeatedly produce high-quality PDMS. Apart from good physical properties, the PDMS as a substitute for vitreous humor must also be safe and not cause other disturbances to the eyes. Here, we reported the process of synthesizing and characterizing the physical properties of low- and medium-viscosity PDMS using a low-grade D4 monomer. We also reported for the first time the in vitro toxicity test using the Hen's Egg Test Chorioallantoic Membrane (HET-CAM) test method. We have succeeded in obtaining PDMS with viscosities of 1.15 Pa.s, 1.17 Pa.s, and 1.81 Pa.s. All samples have good physical properties such as refractive index, surface tension, and functional groups that are similar to commercial PDMS. The HET-CAM test results showed that all samples did not show signs of irritation indicating that samples were non-toxic. From the results of this study, it can be concluded that PDMS synthesized from a low-grade D4 monomer under specific synthesis conditions by the ROP method is very safe and has the potential to be developed as a substitute for vitreous humor in human eyes.

Observation of Cu Spin Fluctuations in High-Tc Cuprate Superconductor Nanoparticles Investigated by Muon Spin Relaxation.

The nano-size effects of high-Tc cuprate superconductor La2-xSrxCuO4 with x = 0.20 are investigated using X-ray diffractometry, Transmission electron microscopy, and muon-spin relaxation (µSR). It is investigated whether an increase in the bond distance of Cu and O atoms in the conducting layer compared to those of the bulk state might affect its physical and magnetic properties. The µSR measurements revealed the slowing down of Cu spin fluctuations in La2-xSrxCuO4 nanoparticles, indicating the development of a magnetic correlation at low temperatures. The magnetic correlation strengthens as the particle size reduces. This significantly differs from those observed in the bulk form, which show a superconducting state below Tc. It is indicated that reducing the particle size of La2-xSrxCuO4 down to nanometer size causes the appearance of magnetism. The magnetism enhances with decreasing particle size.