Hemin-Functionalized InAs-Based High Sensitivity Room Temperature NO Gas Sensors

Abstract

We investigate the chemistry and kinetics of the surface functionalization of InAs with hemin aimed at demonstrating novel hemin-functionalized InAs planar resistors or molecularly controlled resistors (MOCSERs) with subparts per billion sensitivity to NO at 300 K. The high performance is a result of the strong coupling of the intrinsic surface-confined two-dimensional electron gas (2DEG) at the InAs surface with the surface-attached hemin molecules and their selective interactions with NO. The presence of the surface 2DEG in InAs is highly advantageous for sensing and obviates the need for high surface area to volume geometries conferred by nanowire structures. The chemistry and kinetics of surface attachment processes are investigated using X-ray photoelectron spectroscopy, atomic force microscopy, and spectroscopic ellipsometry, showing that the covalent attachment of hemin to both In and As sites modifies the band-bending of the InAs. In addition, the selective, reversible electronic interaction between hemin and NO molecules increases the InAs resistance, reducing the NO during the interaction. In addition to presenting the sensor performance characteristics, a chemical model based on the electron transfer from the 2DEG of InAs to the iron center of hemin, which reduces Fe(III) to the higher NO affinity Fe(II) state, is proposed.

Surface chemistry of porphyrins and phthalocyanines

“…An electrical gas sensor was based on a transistor with the gate electrode covered by a Zn porphyrin layer as the active material [81]. A similar approach was used in NO gas sensors on the basis of hemin on InAs planar resistors [130] and graphene field-effect transistors [82]. Porphyrin-based electrochemical sensors [131] have been reviewed by Malinski [132].…”

H-tailored surface conductivity in narrow band gap In(AsN)

“…Our findings will stimulate theoretical studies of H-diffusion and energy levels in mid-infrared III-N-Vs, where hydrogen, being either an unintentional or intentional dopant, affects surface electronic properties. 11 Furthermore, our results open up perspectives for employing mid-infrared In(AsN) in applications that exploit its n-type surface conductivity, ranging from gas sensing 12 to "all semiconductors" plasmonic waveguides 13 for midinfrared photonics. In particular, the controlled photodissociation of H-N donor complexes by a focused laser beam 4 or the selective H-incorporation by masking may provide a route for writing conducting paths and printed circuits on a single substrate.…”

“…9 In particular, the narrow band gap InAs semiconductor has an electron accumulation layer in the surface region with a Fermi level, E F , located well above the conduction band minimum. [10][11][12] Hydrogen, being either an unintentional or intentional dopant, can alter surface properties; 11 furthermore, the electronic behaviour of monoatomic-H can be modified by nitrogen through the formation of N-H donor complexes. 8 In this Letter, we exploit the combined effects of nitrogen and hydrogen in InAs and show that the n-type conductivity of the In(AsN) alloy can be significantly increased within a thin ($100 nm) channel below the surface by the controlled incorporation of H-atoms.…”

“…The channel retains a high electron mobility (l > 0.1 m 2 V À1 s À1 at low and room temperature) with an electron sheet density of 10 18 m À2 , significantly larger than in N-free InAs. This controlled modification of the surface conductivity and large increase in the electron sheet density by hydrogen could provide a platform for several applications, such as gas and molecular sensing 12 and "all semiconductor" plasmonic waveguides. 13 The nominally undoped In(AsN) epilayers (thickness d ¼ 1.0 lm and N-content, [N], of 0, 0.15, 1.1, and 1.9%) were grown by Molecular Beam Epitaxy (MBE) on a semiinsulating (SI) (100)-oriented GaAs substrate, which provides effective isolation for electrical measurements.…”

Structure and growth mechanism of self-assembled monolayers of metal protoporphyrins and octacarboxylphthalocyanine on silicon dioxide

“…Other studies show that the optical and electrical properties of conjugated macrocycle thin lms are extremely sensitive to adsorption of gas molecules (NO 2 , SO 2 , and CO 2 ), making them promising candidates for gas sensor applications [16][17][18][19][20][21] Among various strategies for the formation of macrocycle lms required for the design of these molecular devices, the leading advantage of self-assembly method is the covalent bonding between the molecules and the surface, which replaces weak van der Waals or hydrogen bonding as in the case of Langmuir-Blodgett lms. Therefore self-assembled thin lms offer very good chemical and physical stability.…”