TABLE 5.1

The LOC Detection Techniques, Principles, and Nanomaterials Applied

Transducer

Detection technique

Principles

Nanomaterials

Optical

Colorimetric

• The color changes are caused by a reaction between the

analyte sample and the recognition element.

• Evaluate qualitatively (by the naked eye) or quantitively (by

smartphones or flatbed scanners)

Aggregation of AuNPs or AgNPs

nanoparticles

Surface Plasmon

Resonance (SPR)

• Observe and measure the changes in the refractive index of

metal nanoparticles causes by the reaction between the

analyte sample and the recognition element.

• Aggregation of metal nanoparticles causes shifting in the SPR

peak to a longer wavelength

Aggregation of AuNPs or AgNPs

nanoparticles

Fluorescence

• Measure the fluorescence property of the reaction between

analyte and recognition element to absorb light at a specific

wavelength and emit it at a longer wavelength

Fluorescence signal enhancement by

AuNPs, AgNPs, Graphene QDs,

Carbon QDs, SiNPs

Chemiluminescence (CL)

• Measure the electromagnetic radiation caused by a reaction

of analyte and recognition element in the visible or near IR

region resulting by a redox reaction between two CL regents

CL signal enhancement by Graphene

NPs, AuNPs, PtNPs, IONPs, and

NiNPs

Electrochemical

Amperometric

• Measure an oxidation or reduction current caused by the

chemical reaction of analyte and recognition element under a

constant potential supplied over a period of time

Amperometric signal enhancement by

AuNPs, AgNPs, PtNPs, Graphene NPs.

MWCNT, GO NPs

Voltammetric

• Measure the current dependence on potential changes caused

by chemical reaction of analyte and recognition element

• Potential changes in various ways; potential scan, potential

step, and stripping voltammetry

Current signal enhancement by AuNPs,

AgNPs, PtNPs, Graphene NPs.

MWCNT, GO NPs, MnO2

Impedimetric

• Measure the electrical impedance signal caused by chemical

reaction of analyte and recognition element

Signal enhancement by AuNPs, PtNPs

MWCNT, GO NS, IONPs, SnO2

Electrical

Field-effect transistor

Measure the change of conductance caused by the reaction of

analyte and recognition element

Conductivity enhancement is caused by

AuNPs, AgNPs, Graphene NPs. ZnO,

IONPs, MnO2 NP, SnO2 NP

Abbreviation: QDs: quantum dots; SiNPs: silicone nanoparticles; PtNPs: platinum nanoparticles; IONPs: iron oxide nanoparticles; NiNPs: nickel nanoparticles;

MWCNT: multiwalled carbon nanotube; GO NPs: graphene oxide nanoparticles; MnO2: manganese dioxide nanoparticles; SnO2 NPs: tin oxide nanoparticles.

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Bioelectronics