The Synthesis of Alginate-Capped Silver Nanoparticles under Microwave Irradiation

Synthesis of silver nanoparticles (Ag-NP) was successfully performed within a few minutes by microwave irradiation of the precursor salt (AgNO3) and alginate mixed solution in one pot. Herein, alginate molecules acted as both a reducing and stabilizing agent for the preparation of the silver nanoparticles. The obtained nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, particle size analysis (PSA), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The pH and concentration ratio of the alginate/metal precursor salt greatly influenced the particle size and its distribution of Ag-NP. The higher the pH the higher the nucleation rate and the larger the electrostatic stabilization, while both of them were responsible for producing a smaller particle size and a narrower size distribution. A higher concentration ratio also yielded a smaller particle size and a narrower size distribution, but above the optimum ratio, the trend was conversely changed due to the reducing capability of the alginate, which was dominant above the optimum ratio, thus creating a high density of nuclei, allowing aggregation to occur. A lower ratio not only led to a higher tendency to produce larger particles, but also a higher probability of anisotropic particle shape formation due to the lack of reducing capability of the alginates

The Study of Phosphate Release from Artificial Sediment into Water Body Using Diffusive Gradient in Thin Film (DGT) Device in Oxic Condition

The phenomenon of phosphate release in sediments into water bodies under oxic environment has been investigated using the Diffusive Gradient in Thin Film (DGT) technique. This research consists of several stages: polymer synthesis and DGT probe assembly, sediment sampling, DGT deployment in oxic conditions, and phosphate analysis from DGT adsorption results. Acrylamide polymer was successfully synthesized with a composition 15% acrylamide; N-N'-methylenebisacrylamide 0.1% and ferrihydrite as binding gels. DGT probes were assembly by placing a 16 x 3.2 cm polyacrylamide gel, binding gels and filter membranes on the DGT probes. The sediment sample was taken from the Bogor Botanical Gardens at the coordinates 6°36’00.6” S; 106°47’51.0” E. The DGT probe was placed in sediment samples for 1, 3 and 7 days in oxic conditions. After the prescribed time, the binding gel was removed and cut every 1 cm depth, then eluted using 0.25 M H2SO4 and the phosphate concentration was measured using spectrophotometry method. The results showed that the phosphate concentration tends to be higher with the increasing incubation time and depth. Maximum CDGT phosphate released on day 1, day 3 and day 7 were 1.00 µg/L at a depth of 14 cm, 6.61 µg/L at a depth of 14 cm, and 20.92 µg/L at a depth of 11 cm respectively. This ensures that the phosphate in water bodies comes from biogeochemical processes that occur in sediments and is successfully measured through DGT techniques

Morphological, Thermal and Oxygen Barrier Properties Plasticized Film Polylactic Acid

Introducing plasticizer poly(ethylene glycol) (PEG400) was applied into poly(lactic acid) (PLA) to produce film matrix packaging by direct casting. Non mechanical properties were carried out plasticized PLA including morphology, crystallinity structure and degree, thermal properties and oxygen barrier properties. Plasticized PLA revealed improving surface structure of PLA film matrix form fractures and homogenous film were achieved at 5% PEG 400. Chromatogram PLA and plasticized PLA were categorized crystal structure an α-form crystal. Intercalated and exfoliated structure did not occur significantly due to dispersion PEG 400 in the matrix but indicated dispersion structure. Thermal properties did not improve plasticized PLA significantly for both glass temperature and melting temperature. PEG 400 accelerated crystal formation that increased the crystallinity degree from 17.71% to 34.64%. Plasticized PLA enhanced permeability value about 20% while largest fraction PEG400 reduced ability to prevent from oxygen through pass the film. The oxygen barrier properties was significantly affected degree of crystalline in the film with a correlation number 0.85

The Interaction Of Co2+-Ammonia Modelling: The Comparative Study Between Ab Initio And Electron Correlation Methods = Pemodelan Interaksi Co24-Amoniak: Perbandingan antara Metode Ab Initio dan Korelasi Elektron

ABSTRACT Research on comparison between Hartree-Fock method and electron correlation methods as well as the effect of size of basis sets on representing interaction of Co2+-NH3 observed from complex energy parameters and optimum geometric parameters have been carried out. The first step is screening basis sets based on charge transfer effect and BSSE value. The selected basis set does not yield charge transfer at 1,4 A < rco2._N < 8 A, and yield small BSSE value. Electron correlation methods used are Moller-Plesset order 2 (MP2), Moller-Plesset order 3 (MP3), Configuration Interaction, Doubles (CID), dan Configuration Interaction, Singles and Doubles (CISD) whereas the basis set used is the result of the screening. LANL2DZ ECP-6-31G* and LANL2DZ ECP-6-311++G(3df,3pd) basis sets are used with Unrestricted Hartree-Fock (UHF) and Moller-Plesset order 2 (MP2) methods to study the effect of size of basis sets. The result of the research showed that the best basis set is LANL2DZ ECP for Co2+ and 6-31G* for NH3. The application of electron correlation method and large basis set can increase the quality of interaction representation of Co2+- NH3. Moller-Plesset (MP) perturbation method gives larger contribution to correlation energy than Configuration Interaction (CI) method. Keywords: solvation modelling, ammonia, cobal

THE INTERACTION OF Co²⁺-AMMONIA MODELLING: THE COMPARATIVE STUDY BETWEEN AB INITIO AND ELECTRON CORRELATION METHODS

Research on comparison between Hartree-Fock method and electron correlation methods as well as the effect of size of basis sets on representing interaction of Co2+-NH3 observed from complex energy parameters and optimum geometric parameters have been carried out.The first step is screening basis sets based on charge transfer effect and BSSE value. The selected basis set does not yield charge transfer at 1,4

Theoretical Analysis of Interaction Energy in Alginate-Capped Gold Nanoparticles Colloidal System

Stability of Au/alginate nanocomposite was theoretically evaluated by computing various interactions energy which contributes in the system, including attraction and repulsion interaction. The results revealed that both polymer and electrostatic charges played a significant role in the stabilization, but the steric repulsion comes from polymer chain is a more effective stabilization mechanism than the electrostatic repulsion. Higher pH yielded in stronger electrostatic repulsion but when the alginate thickness is low the resulting nanocomposite was less stable in a long time period. Interaction energies for Au/alginate nanocomposite colloidal system was up to ~60 kT for alginate thickness of 1 nm, at very short particle-particle separation distance (< 1 nm). As the alginate thickness can be controlled by adjusting the alginate concentration, it can be concluded that the high stability of Au/alginate nanocomposite can be achieved by employing an appropriate amount of alginate concentration

Microwave-Assisted Synthesis of Alginate-Stabilized Gold Nanoparticles

An efficient and rapid method for preparation of Au nanoparticles (Au-NP) has been developed by direct microwave irradiation of metal precursor and alginate mixed solution in a single step. Here, alginate molecules act as both the reducing and stabilizing agents of Au-NP. The obtained nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, particle size analyzer, fourier transform infrared spectroscopy, and transmission electron microscopy. The nanoparticles have a spherical form and perfectly capped with alginate when using alginate and chloro auric acid (HAuCl4) precursor in the concentration range of 0.50 to 0.75% (w/v) and 0.40 mM, respectively. The use of a lower concentration of alginate and/or higher concentration of HAuCl4 caused agglomeration to occur, thereby resulting in a bigger size of Au-NP and red shifting of surface plasmon resonance (SPR) peak to a higher wavelength

Microwave-Assisted Synthesis of Alginate-Stabilized Gold Nanoparticles

An efficient and rapid method for preparation of Au nanoparticles (Au-NP) has been developed by direct microwave irradiation of metal precursor and alginate mixed solution in a single step. Here, alginate molecules act as both the reducing and stabilizing agents of Au-NP. The obtained nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, particle size analyzer, fourier transform infrared spectroscopy, and transmission electron microscopy. The nanoparticles have a spherical form and perfectly capped with alginate when using alginate and chloro auric acid (HAuCl4) precursor in the concentration range of 0.50 to 0.75% (w/v) and 0.40 mM, respectively. The use of a lower concentration of alginate and/or higher concentration of HAuCl4 caused agglomeration to occur, thereby resulting in a bigger size of Au-NP and red shifting of surface plasmon resonance (SPR) peak to a higher wavelength

LEAD BIOSORPTION USING BIOMASS FROM KETAPANG LEAF

Waste containing of lead (Pb) is very dangerous for the environment. However, waste treatment process has been introduced to minimize the waste, either by precipitation process or ionic exchange resin. In addition, researchers have shown that ketapang leaves (Terminalia catappa) can be potentially used in waste water treatment. It has been used as water treatment media for fresh water aquarium. Moreover, this research was aimed to find out the potential of ketapang leaves biosorption for waste treatment that has been polluted by heavy metal, such as lead, by investigating the characteristics of biosorption, kinetics and thermodynamics. Maximum conditions of pH, ketapang leaves dose, contact time, and temperature were also investigated in this research. The result showed that biomass of ketapang leaves has potential as biosorbent. Nevertheless, the absorbtion was highly affected by dependent to pH, Pb concentration, adsorbent mass, contact time, and temperature, in which the maximum limits are 3; 5 mg/L; 0.5 gram; 4 hours; 40 ºC; respectively. Reaction rate, moreover, was running on order one and was fulfilled the principle of Langmuir. Ketapan leaves have a low activation energy making it suitable to be used as an alternative adsorbent Pb absorption of waste containing Pb