Nano biosensors for neurochemical monitoring

Meyyappan M. 나노기술연구협의회 2015 Nano Convergence Vol.2 No.18

Neurochemicals such as dopamine (DA) and serotonin (S-HT) are linked to disorders such as Parkinson’s disease, epilepsy, addiction and many others. Detection of and monitoring these neurochemicals in vivo and in vitro has become important in treating various disorders. The electroactive nature of DA and S-HT has enabled employing electrochemical techniques to detect them at low concentrations, and a variety of electrodes and approaches have been reported. The use of nanomaterials such as carbon nanotubes, graphene and nanowires has been advocated in recent years for the sensitive detection of neurochemicals. This article reviews the advances in nano biosensors for this application and discusses the future outlook and challenges.

The effect of Ga content on In_2xGa_2−2xO₃ nanowire transistor characteristics

Suh, Misook,Meyyappan, M,Ju, Sanghyun IOP Pub 2012 Nanotechnology Vol.23 No.30

<P>We have investigated the change in structural and electrical properties of In<SUB>2x</SUB>Ga<SUB>2−2x</SUB>O<SUB>3</SUB> nanowires (x = 1, 0.69 and 0.32) grown with varied indium (In) and gallium (Ga) contents. The as-grown In<SUB>2x</SUB>Ga<SUB>2−2x</SUB>O<SUB>3</SUB> nanowires kept the cubic crystal structure of In<SUB>2</SUB>O<SUB>3</SUB> intact even when the atomic percentages of Ga were increased to 31% (x = 0.69) and 68% (x = 0.32) in comparison to the total amount of In and Ga. However, as Ga added to In<SUB>2</SUB>O<SUB>3</SUB> structure was substituted with In, the lattice constant decreased and, consequently, the main peaks observed in x-ray diffraction in the direction of (222), (400) and (440) shifted by around ∼0.08°. The average threshold voltage values for the In<SUB>2x</SUB>Ga<SUB>2−2x</SUB>O<SUB>3</SUB> nanowire transistors were −9.9 V (x = 1), −6.6 V (x = 0.67) and −5.6 V (x = 0.32), exhibiting a more positive shift and the sub-threshold slope increased to 0.53 V /dec (x = 1), 0.33 V /dec (x = 0.67) and 0.27 V /dec (x = 0.32), showing an improved switching characteristic with increasing Ga. </P>

LaF₃ electrolyte-insulator-semiconductor sensor for detecting fluoride ions

Cho, Hyeonsu,Kim, Kihyun,Meyyappan, M.,Baek, Chang-Ki Elsevier Sequoia 2019 Sensors and actuators. B Chemical Vol.279 No.-

<P><B>Abstract</B></P> <P>Electrolyte-insulator-semiconductor (EIS) sensor is commonly considered for chemical and biosensing applications due to its small size and simple fabrication method. Here, we demonstrate a fluoride-sensitive EIS sensor using thermally-deposited polycrystalline lanthanum fluoride (poly LaF<SUB>3</SUB>) film as sensing membrane, which is cheaper than single-crystal LaF<SUB>3</SUB>. The sensing characteristics are analyzed for poly LaF<SUB>3</SUB> layers deposited at different temperatures, and the EIS sensors with the sensing membrane formed at 500 °C exhibit excellent sensing response to fluoride ions with a high sensitivity of 52.3 mV/pF and low limit of detection of 1.9 ppb. This limit of detection is lower than previously reported values in the literatures. In addition, the poly LaF<SUB>3</SUB> film deposited at 500 °C has good stability with a low hysteresis voltage of 5.1 mV and a small drift rate of 0.67 mV/h. These superior metrics come from a rather well crystallized LaF<SUB>3</SUB> structure including denser surface grains, enhanced preferential crystalline (002) plane, and improved stoichiometric composition. Furthermore, the sensors show a good selectivity over other ions such as NO<SUB>3</SUB> <SUP>−</SUP> and SO<SUB>4</SUB> <SUP>2−</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We fabricated fluoride-sensitive EIS sensor using thermally deposited poly LaF<SUB>3</SUB> membrane. </LI> <LI> The effect of deposition temperature on the structural and sensing properties of poly LaF<SUB>3</SUB> was investigated. </LI> <LI> Poly LaF<SUB>3</SUB> sensor formed at 500 °C exhibits high sensitivity, low limit of detection, small hysteresis voltage and small drift rate. </LI> <LI> The improved sensing characteristics come from excellent membrane quality. </LI> </UL> </P>

Improving social media data quality for effective analytics: an empirical investigation based on E-BDMS

B. Karthick,T. Meyyappan 한국전산응용수학회 2023 Journal of applied mathematics & informatics Vol.41 No.5

Social media platforms have become an integral part of our daily lives, and they generate vast amounts of data that can be analyzed for various purposes. However, the quality of the data obtained from social media is often questionable due to factors such as noise, bias, and incompleteness. Enhancing data quality is crucial to ensure the reliability and validity of the results obtained from such data. This paper proposes an enhanced decision-making framework based on Business Decision Management Systems (BDMS) that addresses these challenges by incorporating a data quality enhancement component. The framework includes a backtracking method to improve plan failures and risk-taking abilities and a steep optimized strategy to enhance training plan and resource management, all of which contribute to improving the quality of the data. We examine the efficacy of the proposed framework through research data, which provides evidence of its ability to increase the level of effectiveness and performance by enhancing data quality. Additionally, we demonstrate the reliability of the proposed framework through simulation analysis, which includes true positive analysis, performance analysis, error analysis, and accuracy analysis. This research contributes to the field of business intelligence by providing a framework that addresses critical data quality challenges faced by organizations in decision-making environments.

Photostable Zn₂SnO₄ Nanowire Transistors for Transparent Displays

Lim, Taekyung,Kim, Hwansoo,Meyyappan, M.,Ju, Sanghyun American Chemical Society 2012 ACS NANO Vol.6 No.6

<P>Although oxide nanowires offer advantages for next-generation transparent display applications, they are also one of the most challenging materials for this purpose. Exposure of semiconducting channel areas of oxide nanowire transistors produces an undesirable increase in the photocurrent, which may result in unstable device operation. In this study, we have developed a Zn<SUB>2</SUB>SnO<SUB>4</SUB> nanowire transistor that operates stably regardless of changes in the external illumination. In particular, after exposure to a light source of 2100 lx, the threshold voltage (<I>V</I><SUB>th</SUB>) showed a negative shift of less than 0.4 V, and the subthreshold slope (SS) changed by ∼0.1 V/dec. ZnO or SnO<SUB>2</SUB> nanowire transistors, in contrast, showed 1.5–2.0 V negative shift in <I>V</I><SUB>th</SUB> and an SS change of ∼0.3 V/dec under the same conditions. Furthermore, the Zn<SUB>2</SUB>SnO<SUB>4</SUB> nanowire transistors returned to their initial state immediately after the light source was turned off, unlike those using the other two nanowires. Thus, Zn<SUB>2</SUB>SnO<SUB>4</SUB> nanowires achieve photostability without the application of a black material or additional processing, minimizing the photocurrent effect for display devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-6/nn300401w/production/images/medium/nn-2012-00401w_0008.gif'></P>

Control of Semiconducting and Metallic Indium Oxide Nanowires

Lim, Taekyung,Lee, Sumi,Meyyappan, M.,Ju, Sanghyun American Chemical Society 2011 ACS NANO Vol.5 No.5

<P>Oxide semiconductors are candidates for chemical sensors, transparent electrodes, and electronic devices. Here, we have investigated metal-to-semiconductor transitions during In<SUB>2</SUB>O<SUB>3</SUB> nanowire growth with variations in the O<SUB>2</SUB> gas rate. Photoluminescence and current–voltage characteristics of In<SUB>2</SUB>O<SUB>3</SUB> nanowire transistors have been used to understand the transition behavior. The proportion of metallic nanowires to semiconducting nanowires significantly changes from 80:20 to 25:75 when the O<SUB>2</SUB> fraction in argon increases from 0.005% to 0.2%. We believe that excessive oxygen vacancies at low O<SUB>2</SUB> gas rates increase the conductivity and thereby the number of nanowires with metallic characteristics. With an increase in oxygen flow, the oxygen vacancies in the nanowires are substituted with oxygen and the subsequent reduction in oxygen vacancies increases the number of semiconducting nanowires. The threshold voltage of transistors fabricated with semiconducting nanowires shifts in a positive direction by about +3.3 eV between nanowires grown with 0.005% and 0.2% oxygen. The results here indicate that electrical and optical characteristics of oxide nanowires can be controlled by the amount of oxygen during growth instead of relying on conventional postgrowth high-temperature annealing or other postprocessing techniques.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-5/nn200390d/production/images/medium/nn-2011-00390d_0004.gif'></P>

Nanowires in Thermoelectric Devices

Keivan Davami,이정수,Meyya Meyyappan 한국전기전자재료학회 2011 Transactions on Electrical and Electronic Material Vol.12 No.6

The low efficiency of bulk thermoelectric materials has limited the widespread application of thermoelectric power generation. Theoretical and experimental investigations indicate that materials prepared in the form of nanowires show higher thermoelectric coefficients, thus promising to revolutionize the field. This article reviews the basics of thermoelectric power generation, conventional devices, the role of nanowires and the current status of the field.

Synthesis of ZnTe nanostructures by vapor–liquid–solid technique

Devami, Keivan,Kang, Daegun,Lee, Jeong-Soo,Meyyappan, M. Elsevier 2011 Chemical physics letters Vol.504 No.1

<P><B>Graphical abstract</B></P><P><ce:figure id='f0040'></ce:figure></P><P><B>Research highlights</B></P><P>► ZnTe nanowire growth using VLS technique. ► Morphology largely depends on temperature. ► Reactor modeling to gain understanding and for growth optimization.</P> <P><B>Abstract</B></P><P>We have synthesized nanowires of ZnTe using a vapor–liquid–solid approach and found the morphology to be dependant upon the growth temperature. Widely varying structures ranging from cylindrical and tapered nanowires to nanoribbons are obtained depending on the substrate location, gas flow rate and pressure all of which change the temperature distribution within the reactor. The reactor is also modeled to understand the impact of temperature on growth morphology.</P>

Nanoscale memory devices

Chung, Andy,Deen, Jamal,Lee, Jeong-Soo,Meyyappan, M IOP Pub 2010 Nanotechnology Vol.21 No.41

<P>This article reviews the current status and future prospects for the use of nanomaterials and devices in memory technology. First, the status and continuing scaling trends of the flash memory are discussed. Then, a detailed discussion on technologies trying to replace flash in the near-term is provided. This includes phase change random access memory, Fe random access memory and magnetic random access memory. The long-term nanotechnology prospects for memory devices include carbon-nanotube-based memory, molecular electronics and memristors based on resistive materials such as TiO<SUB>2</SUB>. </P>

Coal as a carbon source for carbon nanotube synthesis

Moothi, K.,Iyuke, S.E.,Meyyappan, M.,Falcon, R. Pergamon Press ; Elsevier Science Ltd 2012 Carbon Vol.50 No.8

This article reviews the recent advances on the various processes used in the synthesis of carbon nanotubes (CNTs) from different types of coal (anthracite, bituminous, etc.) and on the role played by coal as carbon source in the production of CNTs. The molecular solid coal is inexpensive and widely available in comparison to the most widely used solid carbon precursor, graphite (a lattice solid) and high purity hydrocarbon gas sources. An account is given on the different processes involved in the synthesis of various CNTs (single and multi-walled, bamboo-shaped, branched, etc.) from different types of coal (anthracite, bituminous, etc.). Both arc-discharge and thermal plasma jet produce high quality CNTs but fundamental disadvantages limit their use as large-scale synthesis routes. Chemical vapour deposition appears to be promising but further experimental work is necessary in order to develop an understanding of the complex factors governing the formation of different carbon nanomaterials from coal. Successful utilization of CNTs in various applications is strongly dependent on the development of simple, efficient and inexpensive technology for mass production and coal as a carbon source has the potential to meet the needs.