Density of States of a Nanoscale Semiconductor Interface as a Transduction Signal for Sensing Molecules

Abstract

Nanoscale inorganic semiconductors (with interfacial thickness <10 nm) have superior stability compared to soft organic compounds and are important for the development of enhanced reagentless sensing devices. As a proof of concept, this study demonstrated that the density of states of a copper oxide mixed valence semiconducting nanoscale film can be suitably designed as a transducer signal for reagentless sensing of phenol.

Quantum rate dynamics and charge screening at the nanoscale level

“…4, the nature of C q at nanoscale interfaces (in its inverse or direct form) can be employed to detect and quantify the NS1 protein (redox-active monolayer interface), 10 which is a biomarker for dengue virus (DENV), or phenol (semiconductive interface). 15 The supercapacitive phenomena seem more evident in the presence of redox reactions, presenting a large specific capacitance of approximately 1400 F g À1 in the case of the redox-active film, compared to 27 F g À1 for the semiconductive film (see S6, ESI † for more details).…”

Quantum rate as a spectroscopic methodology for measuring the electronic structure of quantum dots

“…Hence, the concentration of the electrolyte used in the analysis is important for a suitable electric field screening. According to the previous works about the application of QRS methodology in graphene, 12 organic molecules 27 and inorganic semiconducting nanofilms, 13 electrolyte concentrations typically ranges from 1 to 10 mM.…”

“…8 QRS is an electric spectroscopy method that is fundamentally based on the quantum rate theoretical principles. 9–11 For instance, besides the application of the principles to characterize single-layer graphene, 8,12 it has also been possible to access the DOS of mixed metal-oxide films 13 and organic assemblies, 14 such as molecular redox-active films. 11 Furthermore, quantum rate theory has been useful for the study of quantum electrochemical principles, 11,15 for example demonstrating that charge transfer resistance is essentially a specific setting of the quantum conductance principle.…”

Reagentless Quantum-Rate-Based Electrochemical Signal of Graphene for Detecting SARS-CoV-2 Infection Using Nasal Swab Specimens

“…Briefly, C μ is a series combination of two capacitances, electrostatic ( C e ) and quantum ( C q ), such that 1/ C μ = 1/ C e + 1/ C q . The term C e is associated with the spatial Coulombic separation of charge, and hence, it depends on the geometric configuration of the charge distribution, and C q is associated with the occupation of available quantum states in the interface and is proportional to the electronic density of states (DOS) (d n /dμ) of molecular or nanoscale entities within the interface, that is, C q = e 2 (d n /dμ), where n denotes the number of occupied states in the molecular or nanoscale assemblies per electrochemical potential μ state of the electrode. , For a nanoscale or molecular structure attached to the electrode embedded in an electrolytic medium, C e is much higher than C q (because 1/ C e ∼ 0), and hence, C μ is governed by C q over the electrostatic C e such that C μ ∼ C q . , Typically, capacitive biosensors following the C μ ∼ C q regime require control of the nanoscale active structures within <5 nm of the interface for sensitive detection of chemical and/or biological differences induced by variances in their surroundings.…”

“…The listed characteristics of electrochemical capacitive biosensors were successfully demonstrated in sensing studies of different disease biomarkers and molecules of environmental interest, such as C-reactive protein (CRP), 5,6 human prostatic acid phosphatase, 6 D-dimer, 7 dengue non-structural protein 1, 8 and related antibodies 9 and phenolic compounds in water. 10 The transduction mechanism of electrochemical capacitive interfaces is based on the dominance of a quantum capacitive C q component over the total and equivalent electrochemical capacitance C μ signal of the interface, a governance that occurs whenever the structure of the interface is properly designed on the nano-or molecular scale. Briefly, C μ is a series combination of two capacitances, electrostatic (C e ) and quantum (C q ), such that 1/C μ = 1/C e + 1/C q .…”