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Djulia Onggo
Kelompok Keilmuan Kimia Anorganik dan Fisik, Fakultas Matematika dan Ilmu Pengetahuan Alam, Institut Teknologi Bandung
Biochemistry, Genetics & Molecular Biology Chemical Engineering, Chemistry & Bioengineering Chemistry Education Materials Science & Nanotechnology Mathematics

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General Principles in Electrospray Mass Spectrometry: A New Technique in Mass Spectral Analysis Djulia Onggo; Daud K. Walanda; Robert C. Burns; Geoffrey A. Lawrance; Ellak I. von Nagy-Felsobuki
Jurnal Matematika & Sains Vol 3, No 2 (1998)
Publisher : Institut Teknologi Bandung

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Electrospray mass spectrometry analyzes ions which have been generated in the gas-phase from electrically charged droplets obtained by nebulizing a solution. While the generation of an aerosol by electrospray was published by Zeleny in 1917, it was not until approximately some seven decades later when it was successfully interfaced to a mass spectrometer, thereby extending significantly the use of mass spectrometry in inorganic, biological and trace element research. The mechanism of ion generation by electrospray is still not definitively understood nor is the limitation of its linear dynamic range with respect to analyte concentration. This review will describe the general principles underlying this new technique.
Uji Selektivitas dan Penentuan Rekoveri Akhir pada Pemisahan Logam Emas dengan Metode Agregasi Hidrofobik Suharta Suharta; N. M. Surdia; Buchari Buchari; Djulia Onggo
Jurnal Matematika & Sains Vol 5, No 1 (2000)
Publisher : Institut Teknologi Bandung

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STUDI APLIKASI METODE POTENSIOMETRI PADA PENENTUAN KANDUNGAN KARBON ORGANIK TOTAL TANAH The separation of substance by hydrophobic aggregation method is always started from colloidal particles. The flaws of this technique are especially in the selectivity and recovery. This research was developing of gold separation by hydrophobic aggregation method where it was started from solution system. Complex of [AuCl4]- was chosen in this solution system. The gold selectivity from cations {Ag(I), Cu (II), Fe (III), Zn (II), Pb(II)}, and anions {SO4 2-, NO3-, Br-, I-} was studied. As a result, this method can be separated of gold with height selectivity. The selectivity is restrained by pH, and the optimum pH is 2,0. The recovery of gold with DTMAB, TTMAB, and HTMAB surfactant is 92,60 ± 0,89 %; 90,30 ± 1,32 %; and 89,40 ± 1,51 % respectively.
Penggunaan Differential Thermal Analysis (DTA) Pada Penentuan Aktivitas Dan Reaktivitas Katalis Fe2O3, Co3O4, NiO, CuO, dan LaMO3 (M=Fe, Co, dan Ni) Untuk Oksidasi CO Menjadi CO2 Djulia Onggo; Hamzah Fauzi
Jurnal Matematika & Sains Vol 4, No 1 (1999)
Publisher : Institut Teknologi Bandung

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The catalyst activity of Fe2O3, Co3O4, NiO, CuO, and LaMO3 (M = Fe, Co, and Ni) has been determined using Differential Thermal analysis apparatus. The increased temperature rate has been used at 25oC per min. in the atmosphere of 40% CO, 40% N2 and 20% O2. Mixture gases. The analysis result shows that the order of catalytic activity is Co3O4 > CuO > Fe2O3 > NiO > LaCoO3 > LaFeO3 > LaNiO3. Beside of catalytic activity, this method can be used to determine the starting temperature of carbon monoxide oxidation reaction, which refer to the catalytic reactivity. The order of catalytic reactivity is Co3O4 > CuO > NiO > Fe2O3 > LaCoO3 > LaNiO3 > LaFeO3.
Transisi Spin dalam Spesies Turunan Tris[2-(Pirazol-3-il)piridina]besi(II) Djulia Onggo; Kristian H. Sugiyarto
Jurnal Matematika & Sains Vol 4, No 2 (1999)
Publisher : Institut Teknologi Bandung

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Complexes [Fe(3-pp)3][X]2.2H2O, where 3-pp = (2-(pyrazol-3-yl)pyridine, and X = I, Br, NO3, and CF3SO3, and X2 = [Fe(CN)5(NO)], have been isolated and characterized in terms of magnetic, Mössbauer, and electronic spectral properties. All the dihydrate salts which were isolated from aqueous solution are red brown, and heating up to 110 - 1600C results in decomposition for all salts except for the triflate which gives complete dehydration to the anhydrous yellow salt. At room temperature, the magnetic moment of the dihidrate salts are slightly higher than the purely low-spin value (2,0-2,5 BM). The magnetic moments change gradually parallel to the change in temperature within 90 - 363K, and this is associated with the continuous spin state - singlet (1A1)quintet (5T2) - transition in iron(II). For the yellow anhydrous triflate salt, the spin state transition occurs dramatically, being discontinuous and associated with hysteresis (Tc↓ = 229K, Tc↑= 241K ; ∆Tc = 12K ). The triflate salt also shows a termochromic nature, being yellow at room temperature and dark red-brown at low temperature.
Synthesis and Magnetic Properties of a Fe-Mn-Cr Multinuclear Complex with 4-Amino-1,2,4-triazole and Oxalate Ligands Iis Siti Jahro; Djulia Onggo; Ismunandar Ismunandar; Susanto Imam Rahayu; Esther Jacoba Martha Vertelman; Petra van Koningsbruggen
Jurnal Matematika & Sains Vol 11, No 3 (2006)
Publisher : Institut Teknologi Bandung

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A multinuclear Fe-Mn-Cr complex with 4-amino-1,2,4-triazole (NH2trz) and oxalate (ox) ligands has been synthesized successfully. The formula of the [Fe(NH2trz)3][ClO4][MnCr(ox)3].4H2O complex has been obtained based on the metal and C, H, N contents. The presence of water molecules, metal-ligand bonding and bridge ligand in the multinuclear complex has been confirmed by its infrared spectrum. The compound crystallizes in the hexagonal system with cell parameters of a = b = 18.695 Å and c = 57.351 Å. The compound shows a gradual spin crossover for iron(II) in the [Fe(NH2trz)3]2+ with transition temperature (T1/2) of 205 K. The antiferromagnetic interaction between Cr(III) and Mn(II) ions in the [MnCr(ox)3]n n- network is observed from the Weiss constant (θ) of -2.3 K.
Studi Teoretis Struktur Elektronik dan Sifat Transisi Spin Kompleks [Fe(dpa)2(NCS)2] Yusthinus Thobias Male; Djulia Onggo; Muhamad Abdulkadir Martoprawiro; Ismunandar Ismunandar
Jurnal Matematika & Sains Vol 14, No 3 (2009)
Publisher : Institut Teknologi Bandung

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The computational method B3LYP*/6-31G(d) has been used for predicting the mononuclear spin transition (ST) complexes properties, i.e. [Fe(dpa)2(NCS)2] with cis and trans isomers. Computational results showed that in vacuum and methanol, cis-[Fe(dpa)2(NCS)2] isomer gave a reasonable value of ∆Eel for ST. In methanol, the cis isomer was more stabilized because that isomer showing more higher dipole moments (21,59 D) than the trans isomer and unsubstituted complex, [Fe(dpa)3]2+ (5,70 and 0,03 D). This results showed that if those complexes were synthesized, in the ambient temperature they have high spin properties but only cis-[Fe(dpa)2(NCS)2] isomer has ST properties. Analysis of main atomic orbitals populations showed that the electronic ground bands and the next ground bands are assigned to ligand-to-ligand charge-transfer (LLCT) transitions because of the charge transfer from NCS-ligand to the main ligand. It can be concluded that computational method B3LYP*/6-31G(d) gives more predictive power to mononuclear ST complex.
MONITORING KESTABILAN DISPERSI MULTI WALL CARBON NANOTUBE DALAM SURFAKTAN HEXADECYLTRIMETHYL AMMONIUM BROMIDE Holia Onggo; Djulia Onggo; R. Yudianti
Jurnal Sains Materi Indonesia Vol 13, No 2: FEBRUARI 2012
Publisher : Center for Science & Technology of Advanced Materials - National Nuclear Energy Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (873.717 KB) | DOI: 10.17146/jsmi.2012.13.2.4715

Abstract

MONITORING KESTABILAN DISPERSI MULTI WALL CARBON NANOTUBE DALAM SURFAKTAN HEXADECYLTRIMETHYL AMMONIUM BROMIDE. Kestabilan dispersi Multi Wall Carbon Cano Tube (MWCNT) dalam larutan yang mengandung Hexadecyl trimethyl Ammonium Bromide (CTAB) diamati dengan UV spektrofotometer. Dispersi MWCNT dalam larutan CTAB dengan rasio massa 1: 2 dibuat dengan bantuan ultrasonic vibracell pada amplitude 60% dengan variasi waktu sonikasi 60menit, 90menit dan 120 menit. Pengaruh waktu sonikasi dan waktu penyimpanan terhadap kestabilan dispersi diamati dengan mengukur absorbansi dispersi dengan UV spektrofotometer. Perubahan morfologi MWCNT akibat gelombang ultrasonik yang ditimbulkan oleh ultrasonic vibracell diamati dengan Scanning/ Transmission Electron Microscope (S/TEM). Meningkatnya waktu sonikasi menyebabkan laju dispersi MWCNT meningkat ditunjukan dengan berkurangnya diameter dan panjang MWCNT. Penambahan surfaktan CTAB yang berlebihan dalam larutan menyebabkan proses sonikasi menjadi tidak efektif. Kestabilan dispersi MWCNT dapat bertahan selama 20 hari.
Kompleks Besi(II) Dengan Ligan 3-BPP : Review Fitriani Fitriani; Djulia Onggo; Irma Mulyani
Jurnal Kartika Kimia Vol 4 No 1 (2021): Jurnal Kartika Kimia
Publisher : Department of Chemistry, Faculty of Sciences and Informatics, University of Jenderal Achmad Yani

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26874/jkk.v4i1.74

Abstract

The change of two different spin electronic states under the influence of temperature, pressure and light irradiation is known as the Spin Transition or Spin Crossover (SCO) phenomenon. Spin transition exists on octahedral complexes with an intermediate ligand field, one of the ligands is 2,6-bis (pyrazol-3-yl)pyridine or 3-bpp. Spin transition complexes were intensively investigated because they are highly potential candidates for electronic materials, such as sensors, molecular switches and information storages. The iron(II) complex with 3-bpp ligand has shown SCO characteristics including different transition pattern and transition temperature which were influenced by type of the counter anions. The iron(II) complexes with different types of counter anions have exhibited SCO phenomenon, due to the effect of temperature with abrupt transition. However, the presence of hydrate water in the iron(II) complex results in the higher temperature transition. In addition of that, the transition pattern has changed from the abrupt transition into the gradual transition types. Several studies of SCO properties of the complex Fe(II)-3-bpp reported that the transition type and the temperature transition were influenced by the type of counter anion and the amount of hydrate molecules. With various transition patterns and transition temperatures, the potential of Fe(II)-bpp complexes as SCO materials is more interesting to explored. Keywords: Iron(II) Complex, 3-bpp Ligand, Spin Crossover
Co-Authors Bohari M. Yamin Buchari Buchari Daud Karel Walanda Ellak I. von Nagy-Felsobuki Esther Jacoba Martha Vertelman Fitriani Fitriani Geoffrey A. Lawrance Hamzah Fauzi Holia Onggo Iis Siti Jahro Irma Mulyani Ismunandar Ismunandar . Kristian H. Sugiyarto Muhamad Abdulkadir Martoprawiro N. M. Surdia Petra van Koningsbruggen R. Yudianti Robert C. Burns Suharta Suharta Susanto Imam Rahayu Yusthinus T. Male