Agus Subagio

Dye-sensitized solar cell based carbon nanotube as counter electrode

The counter electrode using Carbon nanotube (CNT) has been successfully fabricated by the doctor blade method and their performances were investigated. We found that increasing mass of the CNT powder in binder increases electrocatalytic activity which this beneficial to conversion efficiency of the Dye-sensitized solar cell (DSSC). The photovoltaic performance of the DSSCs with 0.01, 0.02 and 0.04 gr of the CNT obtained overall conversion efficiencies of 0.32%, 0.74% and 0.91%, respectively. The results suggest that the CNT counter electrode has potential as alternative to the Pt free counter electrode for DSSC.

AC-MnO2-CNT Composites for Electrodes of Electrochemical Supercapacitors

Electrodes for electrochemical supercapacitors were fabricated by doctor blade method of composite of activated carbon (AC), MnO2 and carbon nanotubes (CNTs). The AC-MnO2-CNTs composites were synthesized by solution processing method with pH variation of 3, 7 and 11. The composites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and impedance spectroscopy. The XRD pattern shown the crystalline structure and the SEM image observed that the distribution of CNTs was homogeneous between carbon particles. The electrodes were fabricated for supercapacitor cells with 316L stainless steel as current collector and 1 M Na2SO4 as electrolyte. An electrochemical characterization was performed by using an electrochemical impedance spectroscopy (EIS) method using a LCR Hi-Tester HIOKI 3522 instrument and the results showed an increase in the value of specific capacitance at the AC-MnO2-CNT on the acid reaction condition.

Effect of Co‐doping on Microstructural, Crystal Structure and Optical Properties of Ti1−xCOxO2 Thin films Deposited on Si Substrate by MOCVD Method

Ti1−xCOxO2 thin films have been grown on n‐type Si(100) substrates by metal organic vapor deposition (MOCVD) using titanium (IV) isopropoxide (TTIP) and tris (2,2,6,6‐tetramethyl‐3, 5‐heptanedionato) cobalt (III) as metal organic precursors. The parameter deposition, such as: bubbler temperature of TTIP Tb(Ti) = 50 °C; substrate temperature Ts = 450 °C; bubbler pressure Pb(Ti) = 260 Torr; flow rate of Ar gas through TTIP precursor Ar(Ti) = 100 sccm (standard cubic centimeters per minute) and flow rate of oxygen gas O2 = 60 sccm were found as optimal deposition parameters. The thin films deposited were have rutile (002) crystal plane, whereas those deposited at other parameter were mixing of anatase and rutile phases. Co dopant with concentration of up to 5.77% was not changes the structure of TiO2. Increase of Co incorporated in thin films was decreasing of band‐gap energy.

Nanosilver microalgae biosynthesis: cell appearance based on SEM and EDX methods

Microbial contamination has caused public health problems in the world population. This problem has spurred the development of methods to overcome and prevent microbial invasion. The extensive use of antibiotics has facilitated the continued emergence and spread of resistant organisms. Synthesized of silver nanoparticle (AgNPs) on microalgae Chlorella pyrenoidosa offer environmentally safe antimicrobial agent. The present study is focused on the biosynthesis of AgNPs using microalgae C. pyrenoidosa. The research methods was conducted by insertion of nanosilver particle into microalgae cells with and without agitation to speed up the process of formation nanosilver microalgae. The formation of microalgae SNP was analyzes by UV-Vis spectrophotometer, Scanning Electron Micrograph (SEM) and Energy-dispersive X-ray spectroscopy (EDX) methods. The research result showed that nanosilver microalgae biosynthesis using the agitation treatment was exhibited better performance in particle insertion and cell stability, comparing with no agitation treatment. However, synthesis of nanosilver microalgae tend to reduce the cell size.

Application of Inorganic Fertilizer With NanoChisil and Nanosilica on Black Corn Plant Growth (Zea Mays L.)

Corn is one of the most important sources of carbohydrate and protein in Indonesia, while black corn has not been widely known. One way to increase the growth of black corn plants is to optimize the use of fertilizer, i.e. by a combination of NPK fertilizer with NanoChisil or Nanosilica fertilizer. NanoChisil is a fertilizer with chitosan and silica, while nanosil fertilizer is a fertilizer with silica content. Both of these fertilizers are nano-sized. NPK is a fertilizer with nutrient contents of Nitrogen, Phospor and Potassium. This study aims to determine the combination effect of NPK fertilizer with NanoChisil or Nanosilica on the growth of black corn plants. This research used Completely Randomized Design (CRD). The treatments used were P0 control (without fertilization); P1 (25% NanoChisil 75% NPK combination); P2 (25% Nanosilica 75% NPK combination); P3 (100% NanoChisil); P4 (100% Nanosilica). The study consisted of 5 treatments with 5 repititions. The research parameters consist of plant height, number of leaves, wet weight, dry weight, and the stomata amount. The data analysis used is Analysis of Variance (ANOVA) if the difference is evident, the analysis is continued by Duncan Multiple Range Test (DMRT) at 95% significant level. The results showed the use of NPK fertilizer combination with NanoChisil and NPK fertilizer with Nanosilica have an effect to increase plant height, number of leaves, wet weight, and dry weight. The allocation of 25% NanoChisil 75% NPK is most optimal in increasing plant height, number of leaves, wet weight, and dry weight.

Synthesis and characterization carboxyl functionalized Multi-Walled Carbon Nanotubes (MWCNT-COOH) and NH2 functionalized Multi-Walled Carbon Nanotubes (MWCNTNH2)

A making of MWCNTs-COOH has been conducted to improve the compatibility of carbon nanotubes and MWCNTs-NH2, in order to have conductive properties. The MWCNTs- COOH study was performed, using the first reflux method using HNO3 for 6 hours heated with 60°C (concentrated HNO3 ratio with MWCNTs is 1: 5), followed by the second reflux using SOCl2 for 5 hours heated to 70°C (concentrated HNO3 ratio with MWCNTs is 1: 3). Meanwhile, the making of MWCNTs-NH2 used homogenization process, used magnetic stirrer, with comparison between MWCNTs-COOH with Etanadiamine 1: 2000, for 8 hours at 40oC. Both products were analyzed using Fourier transform infrared (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). The C-O bond on MWCNTs-COOH is indicated by absorption at wavelength 1672.28 cm-1 and O-H bond at 3431.36 cm-1 N-H bond on MWCNTs-NH2 shown at wavelength 1440.83. The SEM analysis indicates that both products have a tubular surface morphology.

The effect of temperature deposited on the performance of ZnO-CNT-graphite for supercapacitors

Carbon nanotubes (CNTs), graphite are now widely studied as the electrodes of supercapacitor, owing to their high conductivity, large surface area, chemical stability, etc. A lot of research has been focused on Carbon/metal oxide nanocomposite electrode for Electrode supercapacitor because it will increase the total capacitance. In this research, ZnO nanoparticles were deposited onto substrate CNT:Graphite in different temperatures such as 300°, 350°, and 400°C. The characterization of the crystal size using X-Ray Diffraction (XRD) patterns showed ZnO material peak was detected a ZnO crystallite. The size of ZnO crystallite in 300°, 350°, and 400°C consecutively is 101.1; 103.4; and 116.7 nm. The test results are Electrochemical impedance spectrometry (EIS) high electrical conductivity values obtained on the composition of ZnO-CNT-graphite with a temperature of 350°C 4.6 (S/m); and (2) the highest value of capacitance in 300°C is 1.23 F/g.

Characterization of CNT-MnO2 nanocomposite by electrophoretic deposition as potential electrode for supercapacitor

Energy crisis that occured in Indonesia suggests that energy supply could not offset the high rate request and needs an electric energy saving device which can save high voltage, safety, and unlimited lifetime. The weakness of batteries is durable but has a low power density while the capacitor has a high power density but it doesn’t durable. The renewal of this study is CNT-MnO2 thin film fabrication method using electrophoretic deposition. Electrophoretic deposition is a newest method to deposited CNT using power supply with cheap, and make a good result. The result of FTIR analysis showed that the best CNT-MnO2 composition is 75:25 and C-C bond is detected in fingerprint area. The result is electrode thin film homogen and characterized by X-ray diffraction (XRD) peaks 2θ=26,63° is characterization of graphite, and 2θ=43,97° is characterization of diamond Carbon type and measured by Scherrer formula results 52,3 nm material average size .EIS test results its capacitance about 7,86 F. from the data it ca...

Sintesis dan Karakterisasi TiO2 Terdoping Nitrogen (N-Doped TiO2) dengan Metode Sol–Gel

Energi celah pita yang lebar dari semikonduktor TiO 2 yang setara dengan cahaya ultraviolet (l<380 nm) membatasi aplikasi fotokatalitik hanya terbatas pada daerah ultraviolet dan tidak pada daerah cahaya tampak (l = 400 nm–700 nm). Pada penelitian ini dilakukan sintesis TiO 2 teremban nitrogen yang dipreparasi melalui metode sol-gel. Prekursor TiCl 4 digunakan sebagai sumber titanium dioksida dan CO(NH 2 ) 2 sebagai sumber nitrogen dan divariasi pada jumlah konsentrasi N dengan variasi 20 g, 30 g, 40 g dan 50 g. Refluks dilakukan pada suhu 100 o C selama 7 jam dilanjutkan dengan pengeringan selama 3 jam pada suhu 100 o C, dan kalsinasi pada suhu 500 o C selama 7 jam . Karakterisasi N- doped TiO 2 dilakukan menggunakan X-ray Diffraction (XRD), Fourier Transform–Infra Red spectroscopy (FTIR), dan UV- Visible diffuse reflectance spectra (UV-Vis DRS). Berdasarkan data XRD diketahui bahwa kristal N- doped TiO 2 berstruktur anatase dengan indeks Miller 101. Spektra FTIR menunjukkan pergeseran serapan vibrasi O-Ti-O pada bilangan gelombang 400-1050 cm -1 , diperkirakan sebagai akibat terbentuknya ikatan N-Ti-O. Spektrum DRS-UV–tampak menunjukkan penurunan energi celah pita dari TiO 2 yakni 3,2 eV. Dapat disimpulkan bahwa penambahan konsentrasi nitrogen mengakibatkan penurunan energi celah pita, pada variasi 20g sebesar 3,12 eV, 30 g sebesar 3,09 eV, 40 g sebesar 3,082 eV, dan 50 g sebesar 3,08 eV.

Study of Mg‐doped GaN Thin Films Grown on c‐Plane Sapphire Substrate by Plasma Assisted Metalorganic Chemical Vapor Deposition Method

Mechanism of doping of Mg in GaN thin film grown on c‐plane sapphire substrate by plasma assisted‐metalorganic chemical vapor deposition (PA‐MOCVD) method have been investigated. The growth was carried out at temperature of 680 °C, which flow rate of Cp2Mg as dopant source was varied of 0.003; 0.006; 0.009 and 0.012 sccm. The Van der Pauw technique, X‐ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize their electric, crystallographic and morphology properties. Hole concentrations of up to 1019 cm−3 have been observed for Mg‐doped GaN films without any post‐growth annealing. The XRD analysis showed change of the FWHMs for the (0002) orientation plane from Mg‐doped GaN films. The difference of the atomic radius between Ga and Mg atoms causes lattice distortion in crystal. This lattice distortion generates dislocation and causes growth of the layer to be three‐dimensional as showed on SEM images.