Selectivity Improvements and Response Time Scale of Porous Silicon Conductometric Gas Sensors

Özdemir, Serdar; Gole, James L.

doi:10.1149/1.3484113

Cited by 9 publications

(9 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Nanostructure modification of PSi interfaces has been shown to be an effective method to adjust the sensor response to a range of chemical analytes for the purpose of developing an array of uniquely interacting interfaces. ,,,− To further explore the dipole interactions of the PSi sensors with organic solvents, interactions were compared for PSi sensors treated with nanostructured metal oxide depositions. Au x O and SnO x nanostructures were selected for deposition as they represent a range from weak to strong acidity − , and in dipole moments.…”

Section: Results and Discussion: Signatures Of Organic Solventsmentioning

confidence: 99%

Detection of Liquid Organic Solvents on Metal Oxide Nanostructure Decorated Porous Silicon Interfaces

Baker

Gole

2016

ACS Sens.

Self Cite

View full text Add to dashboard Cite

We study the interaction of liquid organic solvents within the pores of n- and p-type porous silicon (PSi) interfaces. Several polar (acetone, methanol, ethanol, isopropanol, and water), borderline (chloroform), and nonpolar (toluene and isoprene) molecular solvents have been characterized on distinct n- and p-type pore structures, as analyzed using scanning electron microscopy. Fundamental to these studies has been the generation of Nyquist diagrams comparing the behavior for both dry and solvent treated interfaces for each system studied. The results of these studies on an undecorated PSi interface suggest a closer correlation with the dipole moments associated with the applied organic solvents rather than their dielectric response. This is supported by the observed interaction of the considered solvents with metal oxide (Au x O (x ≫ 1) and SnO x ) decorated PSi interfaces where nanostructured metal oxide-solvent dipole–dipole interactions appear to be manifest. In correlation with the Nyquist plots and the establishment of equivalent circuit models, we evaluate the real-time capacitance and conductance. These studies suggest the viability of array-based sensing for the considered organic solvents.

show abstract

Section: Results and Discussion: Signatures Of Organic Solventsmentioning

confidence: 99%

Detection of Liquid Organic Solvents on Metal Oxide Nanostructure Decorated Porous Silicon Interfaces

Baker

Gole

2016

ACS Sens.

Self Cite

View full text Add to dashboard Cite

show abstract

“…This behavior is in agreement with a simple 1D diffusion model simulation of the system which we have previously used to obtain a first order characterization of the naked PS gas sensor. 27 This simple model solves the 1D diffusion equation numerically by comparing with the experimental sensitivity. We have evaluated the order of magnitude dimensions of the diffusion into the hybrid PS porous layer, and the relative time scales of both Fickian and Knudsen diffusion.…”

Section: Resultsmentioning

confidence: 99%

“…The results presented in Figures 3-9 for the transduction of NO 2 with both untreated and fractional nanostructure treated n-type porous silicon clearly indicate a very much more dynamic reversible interaction for acids and bases with majority electron carriers than with holes. 1,3,27 Further, the influence of the nanostructured metal oxides, fractionally deposited to the PS interface, appears to be notably more pronounced for n-type systems than it is for p-type systems. This may be at least, in part, due to the effective masses.…”

Section: Discussionmentioning

confidence: 98%

“…The possibility exists to reverse the process of electron extraction whenever an acid is countered by Note that upon the introduction of NO 2 the resistance of the system "bottoms-out" as conductance is maximized. 27 The green saw-teeth boxes indicate the anaylte concentration and the range over which this concentration is exposed to the sensor interface. The numbers inside the graphs denote the ppm concentration of these exposures.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Dynamic Interaction of NO₂with a Nanostructure Modified Porous Silicon Matrix: Acidity, Sensor Response, and the Competition for Donor Level Electrons

Laminack¹,

Pouse²,

Gole

2012

ECS J. Solid State Sci. Technol.

View full text Add to dashboard Cite

We describe a reversible response matrix and the dynamic interplay, as a moderately acidic NO 2 analyte interacts at room temperature with a TiO 2 , SnO x , Cu x O (x = 1,2), and A x O (x 1) metal oxide nanostructure deposited n-type nanopore coated microporous porous silicon (PS) interface. A significant variable response matrix is measured and the dynamic nature of analyte-interface processes characterizing the semiconductor-analyte interaction as NO 2 couples to the decorated semiconductor majority charge carriers. The competition for electrons between NO 2 and the TiO 2 decorated PS interface leads to distinct variations in sensor response as a function of increased TiO 2 concentration and displays a time variance as the extraction of electrons by NO 2 reaches a limiting charge carrier depletion and the decorated PS surface becomes electron withdrawing. This dynamic reversal is also demonstrated by distinct time-dependent PS interface responses to NO 2 and NO where the degree of electron extraction reaches a maximum and is again countered by the depleted n-type PS. Electron depleted SnO x and Au x O treated PS interfaces display a significant remnant effect as the decorated surface can become electron withdrawing for extended periods, forming a stronger acid and extracting electrons from NO 2. Exposure to NH 3 also demonstrates the remnant effects of depletion.We have outlined 1 an approach to "nanostructure directed electron transduction vs. chemisorption" on a sensor/microreactor interface. The fractional deposition of nanostructured metal oxide islands is used to modify sensitive surface layers created utilizing a hybrid nanopore covered microporous matrix formed on "p-or n-type" silicon. The core of this approach is the Inverse Hard / Soft acid / base (Table I) interaction model (IHSAB). This model provides a general approach to optimally design sensors with improved and variable sensitivity and conversion efficiency for a variety of gases, in an array-based format, 5 by correlating the tenants of acid/base interaction and the properties of extrinsic semiconductors. [1][2][3][4] In the present study, we demonstrate not only the variable surface sensitivities that are introduced by the playoff between the untreated extrinsic semiconductor interface and the matrix of fractionally deposited nanostructured islands, but also the dynamic time-dependent response that exemplifies the manner in which these nanostructure decorated interfaces interact with the analyte NO 2 , striking at the heart of the competitive electron dynamics that characterizes these systems.The IHSAB principle correlates with a basis in directed electron transduction with minimized chemisorption,and is in complement to the HSAB principle for hard/soft acid/base interactions first put forth by Pearson et al. 6 and later correlated with density functional theory (DFT) 7,8 and Chemical Reaction Theory 9 by Pearson, Parr, 7,8 Cohen et al. 9 and others. 10 In contrast to the HSAB principle which outlines a means to form strong ionic or covalent b...

show abstract

“…The selective response to each gas is based upon IHSAB theory [2,7,35,67]. A number of papers review the capabilities of porous silicon (PS) sensors [35,47,67,68]. The selection of these nanostructured metal oxide island coating provides a reversible interaction they introduce is dictated by the newly developed IHSAB model.…”

Section: Examples Of Selective Monitoringmentioning

confidence: 99%

Nanostructure directed interfaces created from nanoparticle island sites deposited to microporous arrays and forming sensor platforms

Gole¹,

Laminack²,

Boudreaux³

2017

Front Nanosci Nanotech

View full text Add to dashboard Cite

Novel nanostructured island sites are made to decorate a microporous/nanoporous array. These island sites are formed from a variety of easily produced nanostructured metal oxides deposited from solution. Sensor platforms are distinct from and do not require film-based coating. The nanostructure directing acidic metal oxide sites which vary in their Lewis acidity decorate micropores and control the electron transduction process. The interaction of analytes with these island sites varies in a predictable manner and can be modified through in-situ functionalization of their Lewis acidity. The microporous structure allows rapid Fickian diffusion of analytes to the active nanostructure island sites whose reversible interaction dominates the sensor response as it requires low energy consumption. Highly accurate repeat depositions are not required. We require that the island sites are deposited at sufficiently low concentration so as not to interact electronically with each other. The response time of these interfaces is more rapid than film-based depositions, which require a more lengthy diffusion time. The sensors are reversible. The nanoporous structure prevents sintering of these island centers at elevated temperatures. The concentration of detection centers can be made to produce an optimum matrix of enhanced sensor responses, force a dominant distinct analyte-interface physisorption (rather than chemisorption). The produced semiconductor interface is easily functionalized to create an enhanced range of nanoparticle semiconductor sites. The matrix provides a sensitive means of transferring electrons that are easily detected. The sensors operate at room temperature as well as elevated temperatures. Low energy magnetic field signal enhancement can be achieved with transition metals. Contaminated sensors can be readily rejuvenated. Pulsed mode operation ensures low analyte consumption and high analyte selectivity and further provides the ability to rapidly assess false positive signals using Fast Fourier Transfer techniques, Solar pumped sensors requiring low light levels (≤ 1 Watt) have been demonstrated. Water vapor contamination can be greatly if not entirely reduced. The modelling of sensor response with a new Fermi energy distribution -based response isotherm is found to be superior to other isotherms. Sensors operate can be made to operate efficiently for two gases simultaneously. Modes of extending these studies to multiple gas arrays are considered.

show abstract

Selectivity Improvements and Response Time Scale of Porous Silicon Conductometric Gas Sensors

Cited by 9 publications

References 9 publications

Detection of Liquid Organic Solvents on Metal Oxide Nanostructure Decorated Porous Silicon Interfaces

Detection of Liquid Organic Solvents on Metal Oxide Nanostructure Decorated Porous Silicon Interfaces

Dynamic Interaction of NO₂with a Nanostructure Modified Porous Silicon Matrix: Acidity, Sensor Response, and the Competition for Donor Level Electrons

Nanostructure directed interfaces created from nanoparticle island sites deposited to microporous arrays and forming sensor platforms

Contact Info

Product

Resources

About

Selectivity Improvements and Response Time Scale of Porous Silicon Conductometric Gas Sensors

Cited by 9 publications

References 9 publications

Detection of Liquid Organic Solvents on Metal Oxide Nanostructure Decorated Porous Silicon Interfaces

Detection of Liquid Organic Solvents on Metal Oxide Nanostructure Decorated Porous Silicon Interfaces

Dynamic Interaction of NO2with a Nanostructure Modified Porous Silicon Matrix: Acidity, Sensor Response, and the Competition for Donor Level Electrons

Nanostructure directed interfaces created from nanoparticle island sites deposited to microporous arrays and forming sensor platforms

Contact Info

Product

Resources

About

Dynamic Interaction of NO₂with a Nanostructure Modified Porous Silicon Matrix: Acidity, Sensor Response, and the Competition for Donor Level Electrons