Chapter 5 Light-addressable potentiometric sensors (LAPS): recent trends and applications

Wagner, Torsten; Schöning, Michael J.

doi:10.1016/s0166-526x(06)49005-x

Cited by 37 publications

(21 citation statements)

References 150 publications

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“…To record the temporal change of the ion concentration in the solution, the LAPS device was operated in the CC mode, where the bias voltage was controlled by a feedback loop to maintain a fixed photocurrent. 7 2.2. Materials and Solutions.…”

Section: Methodsmentioning

confidence: 99%

Layer-by-Layer Assembly of Carbon Nanotubes Incorporated in Light-Addressable Potentiometric Sensors

et al. 2009

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The integration of carbon nanotubes in conjunction with a chemical or biological recognition element into a semiconductor field-effect device (FED) may lead to new (bio)chemical sensors. In this study, we present a new concept to develop field-effect-based sensors, using a light-addressable potentiometric sensor (LAPS) platform modified with layer-by-layer (LbL) films of single-walled carbon nanotubes (SWNTs) and polyamidoamine (PAMAM) dendrimers. Film growth was monitored for each layer adsorbed on the LAPS chip by measuring current-voltage (I/V) curves. The morphology of the films was analyzed via atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM), revealing the formation of a highly interconnected nanostructure of SWNTs-network into the dendrimer layers. Constant current (CC) measurements showed that the incorporation of the PAMAM/SWNT LbL film containing up to 6 bilayers onto the LAPS structure has a high pH sensitivity of ca. 58 mV/pH. The biosensing ability of the devices was tested for penicillin G via adsorptive immobilization of the enzyme penicillinase atop the LbL film. LAPS architectures modified with the LbL film exhibited higher sensitivity, ca. 100 mV/decade, in comparison to ca. 79 mV/decade for an unmodified LAPS, which demonstrates the potential application of the CNT-LbL structure in field-effect-based (bio)chemical sensors.

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Section: Methodsmentioning

confidence: 99%

Layer-by-Layer Assembly of Carbon Nanotubes Incorporated in Light-Addressable Potentiometric Sensors

et al. 2009

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“…When SPIM is operated with a fixed light source and the double layer and surface state capacitances are negligible, the detectable photocurrent I can be modelled with an equivalent circuit ( Figure 6) and written with the simplified equation [33]: (1) Where is the photon-induced current; and are the capacitances of the insulator and the depletion layer in the silicon. The behaviour of a LAPS substrate can be approximated with a pure capacitance in photocurrent measurements.…”

Section: Figure 5a Presents the Spim Image Of (Pss/pah) 2 -Aunps-(pssmentioning

confidence: 99%

“…Hence it can be assumed that the capsule surface within the laser focus can be considered as a homogeneous dielectric with defined thickness and dielectric constant, which can also be modelled as a capacitance. The expression for the ratio of maximum photocurrents without ( ) and with microcapsules ( ) can be simplified as below [33]:…”

Section: Figure 5a Presents the Spim Image Of (Pss/pah) 2 -Aunps-(pssmentioning

confidence: 99%

The effect of gold nanoparticles on the impedance of microcapsules visualized by scanning photo-induced impedance microscopy

Wang

Campos

et al. 2016

Electrochimica Acta

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Abstract:Polyelectrolyte microcapsules have attracted great interest in drug delivery applications, and microcapsules modified with gold nanoparticles have been used in this way with triggered release when a laser can be used to remotely open shells through light-induced local heating. The electrical impedance of unmodified microcapsules has been studied due to its implications for their permeability, however, the impedance of functionalised microcapsules has not yet been investigated. Herein, the impedance of microcapsules modified with gold nanoparticles was studied for the first time. It was shown that the modification of microcapsules with gold nanoparticles leads to a much greater impedance than would be expected from the increase in the thickness caused by the presence of a layer of gold nanoparticles alone. The impedance of gold nanoparticle modified capsules was measured using scanning photo-induced impedance microscopy 2 (SPIM), which is based on photocurrent measurements at an electrolyte-insulatorsemiconductor (EIS) field-effect structure. High resolution and good sensitivity were achieved using a two-photon effect for charge carrier excitation and organic monolayer modified silicon on sapphire (SOS) as the SPIM substrate. SPIM allowed impedance imaging of collapsed microcapsules with unprecedented detail. SPIM images of capsules labelled with gold nanoparticles (AuNPs) showed a good agreement with the corresponding optical images, including the creases resulting from the collapse of the hollow shells. The significant increase in impedance caused by the impregnation with AuNPs was also verified by conductive Atomic Force Microscopy (C-AFM) measurements in the dry state.

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“…The metabolism of eukaryotes and microorganisms can be simplified as a series of various chemical and biological processes including the response to their surrounding environment. Hence, the determination of the metabolic activity of microorganisms is a relevant indicator to evaluate events in biotechnology, like fermentation steps of biomass in a biogas tank , cell growth investigations, biomedical and pharmaceutical studies, or tissue repair processes . Disturbances in the cellular metabolism can cause unexpected process malfunctions preventing a system from working properly.…”

Section: Introductionmentioning

confidence: 99%

Determination of the extracellular acidification of Escherichia coli K12 with a multi‐chamber‐based LAPS system

Dantism

Takenaga

Wagner

et al. 2016

Physica Status Solidi (a)

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On-line monitoring of the metabolic activity of microorganisms involved in intermediate stages of biogas production plays an important role to avoid undesirable "down times" during the biogas production. In order to control this process, an on-chip differential measuring system based on the lightaddressable potentiometric sensor (LAPS) principle combined with a 3D-printed multi-chamber structure has been realized. As a test microorganism, Escherichia coli K12 (E. coli K12) were used for cell-based measurements. Multi-chamber structures were developed to determine the metabolic activity of E. coli K12 in suspension for a different number of cells, responding to the addition of a constant or variable amount of glucose concentrations, enabling differential and simultaneous measurements.Multi-chamber differential measurement setup based on the LAPS principle; RE, reference electrode.

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Chapter 5 Light-addressable potentiometric sensors (LAPS): recent trends and applications

Cited by 37 publications

References 150 publications

Layer-by-Layer Assembly of Carbon Nanotubes Incorporated in Light-Addressable Potentiometric Sensors

Layer-by-Layer Assembly of Carbon Nanotubes Incorporated in Light-Addressable Potentiometric Sensors

The effect of gold nanoparticles on the impedance of microcapsules visualized by scanning photo-induced impedance microscopy

Determination of the extracellular acidification of Escherichia coli K12 with a multi‐chamber‐based LAPS system

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