Yoki Yulizar

Secomultiflorane-type triterpenoid acids from stem bark of Sandoricum koetjape

Abstract Bryononic acid and two new ring-A secotriterpenoids were isolated from Sandoricum koetjape stem bark and their structures elucidated by NMR spectrometry.

Investigation of crystal structure influence on spectroscopic and photoluminescent properties of terbium-picrate triethylene glycol complex.

The [Tb(Pic)(2)(H(2)O)(EO3)](Pic)·0.5(EO3) complex, for which EO3 and Pic stand for triethylene glycol and picrate anion, respectively, was successfully prepared and characterized. The Tb(III) complex was crystallized in triclinic structure with space group P1¯. The Tb(III) ion was coordinated to nine oxygen atoms from one EO3 ligand, one water molecule, and two Pic anions. The photoluminescent (PL) spectrum of the complex displayed characteristic narrow bands arising from intraconfigurational transitions of the Tb(III) ion. The strongest emission was centred at 544 nm ((5)D(4)→(7)F(5)), which was responsible for the green emission. The short acyclic chain length of the EO3 ligand, lanthanide contraction, and a bulky picrate anion affected the PL intensity, coordination environment around the Tb(III) ion, and crystal structure of the inner-sphere [Tb(Pic)(2)(H(2)O)(EO3)](+) moiety. The unique crystal structure in the Tb complex contained a half mole of triethylene glycol solvated. The complex had a high thermal stability due to the role of π-π stacking interactions of the Pic anions. The appearance of an emission from the ligands suggests that the photoluminescence of ligands cannot be quenched by coordination to the Tb(III) ion in its complex, so the intramolecular energy transfer process from the triplet state of the ligands (T(1)(L)) to the resonant emissive energy level of Tb(III) is not effective.

The shape conversion of silver nanoparticles through heating and its application as homogeneous catalyst in reduction of 4- nitrophenol

The shape conversion of silver nanoparticles (AgNPs) through heating and its application as a homogeneous catalyst in the reduction of 4-nitrophenol is reported here. Synthesis of AgNPs by reduction of AgNO3 using NaBH4 and sodium citrate as reducing agent were successfully conducted. The addition of PVP was used as stabilizing agent. The synthesized AgNPs were heated at 95 °C and observed using UV-Vis spectrophotometer, transmission electron microscopy (TEM), Fourier-transformed infrared (FTIR) spectroscopy and particle size analyzer (PSA). Characteristics of AgNPs before heated were blue with UV- Vis absorbance spectrum at λmax = 786 nm and the shape was pseudo nano prism sized ± 28 nm. During the heating process, the color changed gradually from blue (λmax = 786 nm) to orange (λmax = 486 nm) and also its shape from nano prism to nanodisk. Silver nano prism has a lattice constant, 4.160 A, larger than the silver nanodisk, 4.081 A, which was possibly achieved through rearrangement of silver atoms on the surface of AgNPs. Both silver nanodisk and nano prism were tested as a homogeneous catalyst for the reduction of 4-nitrophenol (4- NP) with NaBH4.

Spectroscopic, Structural, and Morphology of Nickel Oxide Nanoparticles Prepared Using Physalis angulata Leaf Extract

Green synthesis of nickel oxide nanoparticles (NiO NPs) using Physalisangulata leaf extract (PALE) as weak base sources and stabilizing agents has been reported. Chemical bonding and vibration spectroscopy, crystallographic structure, optical band gap, particle size and microscopic studies of NiO NPs were also investigated. Ni-O vibration modes of NiO NPs were analyzed by FTIR and Raman instrument at ~400 and ~900 cm-1 wavenumber. XRD pattern of NiO NPs confirmed cubic crystal structure with space group Fm-3m. Optical band gap of NiO NPs determined by using Tauc plot method was about 3.42 eV. Particle size analyzer showed size distribution of NiO NPs was 64.13 nm which confirm NiO formed in nanoscale. Electron microscopic studies of NiO NPs were observed by using scanning electron microscopy and transmission electron microscopy.

Green Method for Synthesis of Gold Nanoparticles Using Polyscias scutellaria Leaf Extract under UV Light and Their Catalytic Activity to Reduce Methylene Blue

The aqueous fraction of Polyscias scutellaria leaf extract (PSE) has been used as a reducing agent and stabilizer in the green synthesis of gold nanoparticles (AuNPs). UV-Vis spectrophotometry, particle size analyzer (PSA), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy-selected area electron diffraction (TEM-SAED), and X-ray diffraction (XRD) were used to characterize AuNPs. The AuNPs have a size of 5–20 nm and have a face centered cubic (fcc) crystal structure and are stable for 21 days. Phenolic compounds, which are secondary metabolites of PSE, act as an active compound to reduce Au3+ ion to Au0, as well as stabilize the AuNPs through their surface interaction with carbonyl and hydroxyl groups of phenols. AuNPs exhibit excellent catalytic activity for the reduction of methylene blue with NaBH4. The reduction of methylene blue using AuNPs catalysts is a pseudo-first-order reaction with a reduction rate constant ( ) of 0.0223 min−1.

Fe(II)-MSA functionalized Au nanoparticle on natural zeolites as effective reducing agent for Cr(VI) ions

Hexavalent chromium (Cr(VI)) ions are typical species found in wastewater released from various industries, e.g. electroplating, leather tanning, and canning industries, which causes serious risks to the environment. Therefore, Cr(VI) ions should be reduced into a less-toxic species, i.e. Cr(III) [1, 2]. This present investigation deals with the preparation of Indonesian natural zeolite (INZ) modified by Au nanoparticles and Fe(II)–mercaptosuccinic acid (MSA) complexes as reducing agents for Cr(VI) to Cr(III) ions. These materials were characterized using XRD, SEM – EDS, UV-Vis DRS, and FTIR. It was revealed that Au nanoparticles play a role as bridging agent of INZ and Fe(II)–MSA. The purpose of this modification is to provide flexible and easily accessible reducing sites, i.e. Fe(II) in heterogeneous system. Therefore, the reducing materials can be easily separated at the end of reaction. The reduction of Cr(VI) ions was indicated by the decay of absorbance at λmax of 350 nm based on the measurement usi...