Particle size dependence of relaxivity for silica-coated iron oxide nanoparticles

Tanveer Ahmad,배홍섭,이일수,장용민,이재준,홍성욱 한국물리학회 2012 Current Applied Physics Vol.12 No.3

We investigate the particle size dependence of the relaxivity of hydrogen protons in an aqueous solution of iron oxide (Fe3O4) nanoparticles coated in silica for biocompatibility. The T1 and T2 relaxation times for various concentrations of silica-coated nanoparticles were determined by a magnetic resonance scanner. We find that the relaxivity increased linearly with increasing particle size. The T2 relaxivity (R2) is more than 50 times larger than the T1 relaxivity (R1) for the nanoparticle contrast agent, which reflects the fact that the T2 relaxation is mainly influenced by outer sphere processes. The high R2/R1 ratio demonstrates that silica-coated iron oxide nanoparticles may serve as a T2 contrast agents in magnetic resonance imaging with high efficacy. We investigate the particle size dependence of the relaxivity of hydrogen protons in an aqueous solution of iron oxide (Fe3O4) nanoparticles coated in silica for biocompatibility. The T1 and T2 relaxation times for various concentrations of silica-coated nanoparticles were determined by a magnetic resonance scanner. We find that the relaxivity increased linearly with increasing particle size. The T2 relaxivity (R2) is more than 50 times larger than the T1 relaxivity (R1) for the nanoparticle contrast agent, which reflects the fact that the T2 relaxation is mainly influenced by outer sphere processes. The high R2/R1 ratio demonstrates that silica-coated iron oxide nanoparticles may serve as a T2 contrast agents in magnetic resonance imaging with high efficacy.

Valence and conduction band offset measurements in Ni0.07Zn0.93O/ZnO heterostructure

Tanveer Ahmad Dar,Arpana Agrawal,Pankaj Misra,Lalit M. Kukreja,Pranay Kumar Sen,Pratima Sen 한국물리학회 2014 Current Applied Physics Vol.14 No.2

We report valence and conduction band offset measurements in a pulsed laser deposited Ni0.07Zn0.93O/ ZnO heterostructure using X-ray photoelectron spectroscopy, valence band spectroscopy and ultraviolet visible spectroscopy. Neglecting the strain effect, the valence band offset was estimated to be 0.32 eV and the conduction band offset comes out to be 0.23 eV. Ratio between conduction band and valence band offset is 0.72. Core level shifting due to Ni doping has also been explained. Magnetotransport study of Ni0.07Zn0.93O film reveals that the charge carriers might be spin polarized at the interface of the heterojunction.

Silica-coated Iron-oxide Nanoparticles Synthesized as a T2 Contrast Agent for Magnetic Resonance Imaging by Using the Reverse Micelle Method

Tanveer Ahmad,홍성욱,장용민,이재준,이일수 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61

We synthesized iron-oxide (Fe3O4) nanoparticles by using the reverse micelle method and coated them with biocompatible silica. The coated nanoparticles were found to be spherical in the TEM images and showed a uniform size distribution with an average diameter of 10 nm. The T1 and the T2 relaxation times of hydrogen protons in aqueous solutions with various concentrations of silicacoated nanoparticles were determined by using a magnetic resonance (MR) scanner. We found that the T2 relaxivity was much larger than the T1 relaxivity for the nanoparticle contrast agent, which reflected the fact that the T2 relaxation was mainly influenced by outer sphere processes. The T2 relaxivity was found to be 15 times larger than that for the commercial Gd-DTPA-BMA contrast agent. This result demonstrates that silica-coated iron oxide nanoparticles are applicable as a T2 agent in magnetic resonance imaging.

An adroit unrelated question randomized response model with sundry strategies

Tanveer Ahmad Tarray,Zahoor Ahmad Ganie 한국전산응용수학회 2023 Journal of applied mathematics & informatics Vol.41 No.6

When sensitive topics such as gambling habits, drug addiction, alcoholism, tax evasion tendencies, induced abortions, drunk driving, past criminal involvement, and homosexuality are the focus of open or direct surveys, it becomes challenging to obtain accurate information due to non-response bias and response bias. People often hesitate to provide truthful answers. Warner introduced an ingenious method to address this issue. In this study, a new and unrelated randomized response model is proposed to eliminate misleading responses and nonresponses caused by the stigma associated with the attribute being investigated. The proposed randomized response model allows for the estimation of the population percentage with the sensitive characteristic in an unbiased manner. The characteristics and recommendations of the proposed randomized response model are examined, and numerical examples are provided to support the findings of this study.

Gold-Coated Iron Oxide Nanoparticles as a <i>T</i>₂ Contrast Agent in Magnetic Resonance Imaging

Ahmad, Tanveer,Bae, Hongsub,Rhee, Ilsu,Chang, Yongmin,Jin, Seong-Uk,Hong, Sungwook American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.7

<P>Gold-coated iron oxide (Fe3O4) nanoparticles were synthesized for use as a T2 contrast agent in magnetic resonance imaging (MRI). The coated nanoparticles were spherical in shape with an average diameter of 20 nm. The gold shell was about 2 nm thick. The bonding status of the gold on the nanoparticle surfaces was checked using a Fourier transform infrared spectrometer (FTIR). The FTIR spectra confirmed the attachment of homocysteine, in the form of thiolates, to the Au shell of the Au-Fe3O4 nanoparticles. The relaxivity ratio, R2/R1, for the coated nanoparticles was 3-fold higher than that of a commercial contrast agent, Resovist, which showed the potential for their use as a T2 contrast agent with high efficacy. In animal experiments, the presence of the nanoparticles in rat liver resulted in a 71% decrease in signal intensity in T2-weighted MR images, indicating that our gold-coated iron oxide nanoparticles are suitable for use as a T2 contrast agent in MRI.</P>

REVIEW OF EXPERIMENTAL STUDIES ON CO₂ ADSORPTION IN COAL

Tanveer AHMAD,Sang-Sup LEE 한국신재생에너지학회 2014 AFORE Vol.2014 No.-

활성탄의 물리적 특성에 따른 이산화탄소 흡착 특성

Ahmad Tanveer,박정민,최신앙,이상섭 한국청정기술학회 2018 청정기술 Vol.24 No.4

Effect of physical property of activated carbon on its carbon dioxide adsorption was investigated for the effective control of carbon dioxide. Pinewood sawdust and coal were used as raw materials of activated carbon. Specific surface area, micropore volume and mesopore volume of the prepared activated carbons were determined, respectively. The prepared activated carbons were analyzed for their adsorption capacity of carbon dioxide. The adsorption capacity was then presented with respect to the surface area, micropore volume and mesopore volume, respectively. As a result, the specific surface area and micropore volume of both pinewood and coal activated carbon were highly related to its carbon dioxide capacity. Its mesopore volume hardly affected its carbon dioxide capacity. Preparation of activated carbon with high specific surface area and micropore volume was found to be critical to the effective control of carbon dioxide. 효율적으로 이산화탄소를 처리할 수 있는 활성탄을 제조하기 위하여 활성탄의 물리적 특성이 이산화탄소 흡착에 미치는 영향을 조사하였다. 소나무 톱밥과 석탄이 활성탄의 원료로 사용되었고, 제조된 활성탄의 비표면적, 미세기공 부피, 중기공 부피를 분석하였다. 제조된 활성탄은 열중량 분석기를 이용하여 이산화탄소 흡착량을 결정하였다. 그리고 이산화탄소 흡착량결과를 활성탄의 비표면적, 미세기공 부피, 중기공 부피에 따라 분석하였다. 실험 결과, 소나무 톱밥 활성탄과 석탄 활성탄의 비표면적과 미세기공 부피는 이산화탄소 흡착량과 높은 연관성을 보인 반면에 중기공 부피는 이산화탄소 흡착에 거의영향을 미치지 않았다. 따라서 활성탄의 비표면적과 미세기공 부피를 극대화하는 것이 효율적인 이산화탄소 처리를 위해매우 중요한 요소로 나타났다.

Behavior of heavy metals in air pollution control devices of 2,400 kg/h municipal solid waste incinerator

Tanveer Ahmad,박정민,길상인,윤진한,이은도,김영운,이상섭 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.9

We analyzed the behavior of heavy metals, such as Cd, Cr, Cu, Ni, Pb, Zn, and Hg, in air pollution control devices of a municipal solid waste incinerator. For this study, a municipal solid waste incinerator with a burning capacity of 2,400 kg/h was selected. A semi-dry reactor (SDR), fabric filter, and wet scrubber were installed to serve as air pollution control devices. Flue gas was sampled upstream and downstream of each air pollution control device to determine the heavy metal concentrations therein. Ash was collected from the furnace, boiler, SDR, and fabric filter to determine the heavy metal concentration in the ash produced by each device. Each heavy metal was found to have a different fate in the incinerator and air pollution control devices. Cd and Pb were mostly present in the fabric filter ash, whereas Cr, Cu, and Ni were most prevalent in the bottom ash of the furnace and boiler, and Zn was present in the bottom and fabric filter ash at a ratio of 7 : 3. However, only a few percent of Hg was identified in the ash from the furnace, boiler, SDR, and fabric filter; the majority of Hg passed through the fabric filter and existed in an oxidized form. The wet scrubber exhibited high control efficiency for oxidized mercury, and the injection of commercial activated carbon at a rate of 0.2 g/Sm3 resulted in 93.2% mercury removal efficiency.

Combustion of Coal and Solid Waste using a Horizontal Combustor

( Tanveer Ahmad ),( Sang-sup Lee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2017 No.-

The aim of this work to investigate the distribution of mercury in the gas phase, bottom ash and fly ash during the combustion of coal and solid waste such as dried sludge and solid refuse fuel (SRF) because the solid waste can be used as alternative fuel. In our study, we used two types of continuous combustors including vertical and horizontal combustor at the same conditions. In vertical combustor, we can get only the bottom ash while in horizontal combustor we get both fly ash and bottom ash. For both combustors, the gaseous mercury was measured by using the Ontario Hydro Method. The results showed that a significant amount of emission of gas phase mercury occurs during the combustion of coal, dried sludge, and SRF. Among the fuels, SRF showed high mercury oxidation while dried sludge showed a high level of gaseous mercury emission in the flue gas.

Relaxivities of Hydrogen Protons in Aqueous Solutions of Gold-coated Manganese Ferrite Nanoparticles

Tanveer Ahmad,Yousaf Iqbal,배홍섭,이일수,홍성욱,장용민,이재준 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.11

Manganese ferrite nanoparticles were synthesized using the reverse micelle method and were coated with gold. TEM (transmission electron microscope) pictures showed that the shapes of the synthesized nanoparticles were almost spherical with an average diameter of 12 nm and a standard error of 4 nm. The bonding status of gold on the nanoparticle surfaces was checked using a Fourier transform infrared spectrometer (FTIR). The T1 and the T2 relaxation times of the hydrogen protons in aqueous solutions of the coated manganese-ferrite nanoparticles were determined using magnetic resonance imaging (MRI). The 1/T1 and the 1/T2 versus concentration curves for the nanoparticles showed a linear dependence. The T1 and the T2 relaxivities were found to be r1 =6.01 ± 0.12 and r2 = 83.3 ± 0.55 mM−1s−1. The ratio of r2/r1 was 13.9; this is larger than the ratios of r2/r1 for commercial T2 MRI contrast agents, indicating that the nanoparticles studied herein can serve as a T2 contrast agent with high efficacy.