Organic Thin-film Transistor Sensors Research Articles

Axial Phenoxylation of Aluminum Phthalocyanines for Improved Cannabinoid Sensitivity in OTFT Sensors.

Cannabis producers, consumers, and regulators need fast, accurate, point-of-use sensors to detect Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) from both liquid and vapor source samples, and phthalocyanine-based organic thin-film transistors (OTFTs) provide a cost-effective solution. Chloro aluminum phthalocyanine (Cl-AlPc) has emerged as a promising material due to its unique coordinating interactions with cannabinoids, allowing for superior sensitivity. This work explores the molecular engineering of AlPc to tune and enhance these interactions, where a series of novel phenxoylated R-AlPcs are synthesized and integrated into OTFTs, which are then exposed to THC and CBD solution and vapor samples. While the R-AlPc substituted molecules have a comparable baseline device performance to Cl-AlPc, their new crystal structures and weakened intermolecular interactions increase sensitivity to THC. Grazing-incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM) are used to investigate this film restructuring, where a significant shift in the crystal structure, grain size, and film roughness is detected for the R-AlPc molecules that do not occur with Cl-AlPc. This significant crystal reorganization and film restructuring are the driving force behind the improved sensitivity to cannabinoids relative to Cl-AlPc and demonstrate that analyte-semiconductor interactions can be enhanced through chemical modification to create more responsive OTFT sensors.

Enhancement of ammonia gas sensitivity and selectivity by depleted layer of PBTTT-C14/MoS2-QDs heterojunction based thin film transistor

A highly sensitive, room temperature operating ammonia (NH3) gas sensor has been fabricated by using PBTTT-C14/MoS2-QDs heterojunction based organic thin film transistor (OTFT). Thin film of PBTTT-C14/MoS2-QDs has been fabricated by low cost and high yield ‘floating film transfer method’ (FTM). Initially, hydrothermally synthesized MoS2 quantum dots (QDs) were added in PBTTT-C14 polymer to make a composite ink, which was used for film fabrication. This polymer/QDs based film has been used as a channel of a top contact-bottom gated organic thin film transistor. Various concentration of NH3 ranging from 0.5 to 50 ppm has been exposed on the channel to determine the sensitivity and the selectivity of the device. For comparison, a reference OTFT has been fabricated under the same condition by using pristine PBTTT-C14 thin film. It has been observed that the response of the polymer/QDs heterojunction device is ∼ 85 % at 50 ppm which is ∼ 3 times higher compared to reference device in higher concentration range of NH3. This enhancement becomes possible due to the NH3 sensitive depletion layer of polymer/QDs heterojunction. This OTFT sensor shows high selectivity to the NH3 gas with good linearity to the concentration, which can fulfill basic requirements for practical utilization.

OTFT Biosensor on Flexible Substrates for Human Health Monitoring: a Review

With the development of the Internet of Things era, smart wearable devices have gradually entered people’s daily life, and these devices have provided great convenience to human beings in terms of real-time detection of human health and information transmission. Smart wearable electronic devices have also been gradually developed from smart bracelets, smart watches, and smart glasses into fibers or textiles. Organic thin-film transistor (OTFT) as a key component of flexible electronic devices has an important role in signal amplification, signal filtering, signal transmission, signal reception, and storage. In this article, we introduce the recent progress of OTFT based on 2-D film and 1-D fiber from the substrate of OTFT and focus on the preparation method and performance of OTFT based on 1-D fiber from the conductive fiber. In addition, some practical applications of OTFT sensors in human health detection are introduced. Index Electronic textiles, organic thin-film transistor (OTFT), smart wearables.

Insight into OTFT Sensors Using Confocal Fluorescence Microscopy.

Confocal fluorescence microscopy provides a means to map charge carrier density within the semiconductor layer in an active organic thin film transistor (OTFT). This method exploits the inverse relationship between charge carrier density and photoluminescence (PL) intensity in OTFTs, originating from exciton quenching following exciton-charge energy transfer. This work demonstrates that confocal microscopy can be a simple yet effective approach to gain insight into doping and de-doping processes in OTFT sensors. Specifically, the mechanisms of hydrogen peroxide sensitivity are studied in low-voltage hygroscopic insulator field effect transistors (HIFETs). While the sensitivity of HIFETs to hydrogen peroxide is well known, the underlying mechanisms remain poorly understood. Using confocal microscopy, new light is shed on these mechanisms. Two distinct doping processes are discerned: one that occurs throughout the semiconductor film, independent of applied voltages; and a stronger doping effect occurring near the source electrode, when acting as an anode with respect to a negatively polarized drain electrode. These insights offer important guidance to future studies and the optimization of HIFET-based sensors. More importantly, the methods reported here are broadly applicable to the study of a range of OTFT-based sensors. This work demonstrates that confocal microscopy can be an effective research tool in this field.

Hydrogenated Graphene Based Organic Thin Film Transistor Sensor for Detection of Chloride Ions as Corrosion Precursors

Corrosion monitoring and management has been at the center of structural health monitoring protocols due to its damaging effects on metallic structures. Current corrosion prevention and management programs often fail to include environmental factors such as Cl− ions and surface wetness. Early detection of these environmental factors can prevent the onset of corrosion and reduce repair and maintenance-related expenses. There is growing interest in creating solution-processed thin film environmental sensors with high sensitivity to corrosion precursors, low-cost fabrication, and small footprint, rendering them viable candidates for investigation as potential corrosion sensors that could be easily integrated into existing structures and screen printed or patterned directly into surface coatings. In this work, we have implemented C60-based n-type organic thin film transistors (OTFTs) with functionalized graphene oxide for humidity sensing and functionalized graphene nanoparticles for Cl− ion detection, using low-cost solution processing techniques. The reduced graphene oxide (rGO)-coated OTFT humidity sensor is designed for the qualitative estimation of surface moisture levels and high levels of humidity, and it exhibits a relative responsivity for dry to surface wetness transition of 122.6% to surface wetness, within a response time of 20 ms. We furthermore implemented an in-house synthesized hydrogenated graphene coating in conjunction with a second OTFT architecture for Cl− ions sensing which yielded a sensitivity of 4%/ppm to ultrafine ionic concentrations, over an order of magnitude lower than the range identified to cause corrosion in aircraft structures.

Organic Thin‐Film Transistors as Cannabinoid Sensors: Effect of Analytes on Phthalocyanine Film Crystallization

AbstractWith a growing international trend of Cannabis legalization, there is a present need for on‐the‐spot, low cost, and rapid detection of cannabinoids. Here, relationships between thin‐films of phthalocyanines (Pcs) with a variety of central, peripheral, and axial substituents and their response to the cannabinoid Δ9‐tetrahydrocannabinol (THC), with and without a cannabinoid‐sensitive chromophore (Fast Blue BB) are investigated through organic thin‐film transistor (OTFT) performance. X‐ray diffraction and UV–vis absorption spectroscopy measurements demonstrate significantly altered film morphologies and the formation of new crystal orientations in response to analytes, which are corroborated by scanning electron microscopy. Electron paramagnetic resonance further corroborates shifting crystal structures in response to THC and also reveals the formation and promotion of Pc radical species through THC‐metal coordination. With exposure to THC, aluminum chloride Pc generates the largest physical film changes as well as the largest changes in OTFT performance. These findings suggest that the semiconductor thin‐film morphologies in Pc‐based OTFT sensors are not static in the presence of analytes and that the sensing response is driven both by strong analyte‐Pc coordination and bulk film restructuring to accommodate these interactions.

Gold nanorods doping induced performance improvement of room temperature OTFT NO2 sensors

Solution-processed organic thin-film transistors (OTFTs) are regarded as the promising candidates for low-cost gas sensors due to their advantages of high throughput, large-area and sensitive to various gas analytes. Microstructure control of organic active layers in OTFTs is an effective route to improve the sensing performance. In this work, we report a simple method to modify the morphology of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) thin films via doping gold nanorods (Au NRs) for enhancing the performance of the corresponding OTFT sensors for nitrogen dioxide (NO2) detection. With the optimized doping ratio of Au nanorods, the TIPS-pentacene OTFT snesors not only exhibit a 3-fold increase in mobility, but also obtain a high sensitivity of 70% to 18 ppm NO2 with a detection limit of 270 ppb. The microstructures and morphologies of the modified TIPS-pentacene thin film characterized by atomic force microscopy and field scanning electron microscope. The experimental results indicate that the proper addition of Au NRs could effectively regulate the grain size of TIPS-pentacene, and therein control the density of grain boundaries during the crystallization, which is essential for the high-performance gas sensors.

Microstructure control of organic semiconductors via UV-ozone for high-sensitivity NO2 detection

Developing high sensitive organic semiconductors (OSCs) in organic thin-film transistors (OTFTs) is the key for OTFT based gas sensors. Herein, we report a simple processing route of highly sensitive OSCs for high performance OTFT based nitrogen dioxide (NO2) sensors, where the active OSC layer is based on ultraviolet-ozone (UVO) treated poly(3-hexylthiophene-2,5-diyl) (P3HT). Compared to conventional P3HT based OTFT sensors, the reported device exhibits a remarkable improvement of the gas response from 350% to 30000%. The studies in morphologies, chemical compositions and microstructures of the UVO-treated films reveal that a large number of carrier traps generated in the P3HT films is the decisive reason for the enhancement of sensing performance. Moreover, the optimized device shows great potential of practical applications on the stand points of sensitivity, selectivity, reusability and the ability of recovery, as well as limit of detection of ~7.3 ppb. This simple method provides an innovative understanding for the role of the carrier traps in sensing performance and demonstrates a bright future for developing high performance OTFT gas sensors.

Stimuli-responsive polymer as gate dielectric for organic transistor sensors

Abstract Temperature is a characteristic often correlated with environmental and health issues. This paper presents an organic thin film transistor (OTFT) based temperature sensor having a detection range of 30–45 °C, which, therefore, encompasses the human body temperature. The OTFT sensor featured thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and pentacene as the gate dielectric and semiconductor, respectively. The PNIPAM film possessed a dielectric constant of 4.2 with very low leakage current density. The OTFT exhibited high electrical performance, with a hole mobility (μ) of 0.90 ± 0.04 cm2 V−1 s−1, a threshold voltage (Vth) of −15.4 ± 1.16 V, and an on/off ratio of 104. Significant changes in the drain current and the values of Vth and μ occurred when the temperature of the device was varied within the range 30–45 °C at an interval of 0.5 °C. The operating principle for this temperature sensor was based on the structural transformation of the PNIPAM dielectric and the enhanced charge transport of the pentacene semiconductor upon varying the temperature. Flexible OTFTs fabricated on polyethylene terephthalate substrate displayed hole mobilities as high as 0.39 ± 0.01 cm2 V−1 s−1, values of Vth of −18.6 ± 0.45, and on/off ratios of 102, and were workable for over 100 bending cycles.

Phase Separation of P3HT/PMMA Blend Film for Forming Semiconducting and Dielectric Layers in Organic Thin-Film Transistors for High-Sensitivity NO2 Detection.

Formation of the semiconductor/dielectric double-layered films via vertical phase separations from polymer blends is an effective method to fabricate organic thin-film transistors (OTFTs). Here, we introduce a simple one-step processing method for the vertical phase separation of poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(methyl methacrylate) (PMMA) blends in OTFTs and their applications for high-performance nitrogen dioxide (NO2) sensors. Compared to the conventional two-step coated OTFT sensors, one-step processed devices exhibit a great enhancement of the responsivity from 116 to 1481% for 30 ppm NO2 concentration and a limit of detection of ∼0.7 ppb. Studies of the microstructures of the blend films and the electrical properties of the sensors reveal that the devices formed by the one-step vertical phase separation have better capability for the adsorption of NO2 molecules. Moreover, a careful adjustment of the blend ratio between P3HT and PMMA can further improve the performance of the NO2 sensors, ranging from sensitivity to selectivity and to the ability of recovery. This simple one-step processing method demonstrates a potential possibility for developing high-performance, low-cost, and large-area OTFT gas sensors.

Pyrene-SH functionalized OTFT for detection of Hg2+ ions in aquatic environments

Abstract Mercury ion (Hg2+) sensor based on bottom gate top contact organic thin film transistor (OTFT) was fabricated. The OTFT channel area was functionalized with pyrene that contain thiol group, which has strong binding affinity toward Hg2+ ion. The OTFT sensor exhibited a charge mobility of 0.28 cm2 V−1 s−1, a threshold voltage of −22.3 V and on-to-off ratio 103. The sensor shows high selectivity to Hg2+ ion over other two valence metal ions. OTFT sensor exhibited high sensitivity to Hg2+ ion, indicated by increasing of drain current after exposed to different concentration of Hg2+ ion ranging from 1 mM to 0.01 μM. Moreover, the OTFT sensor capability for practical application was also demonstrated by sensing the present of 25 μM of Hg2+ ion in tap, drinking and seawater samples.

Functionalized Organic Thin Film Transistors for Biosensing.

The rise of organic bioelectronics efficiently bridges the gap between semiconductor devices and biological systems, leading to flexible, lightweight, and low-cost organic bioelectronic devices suitable for health or body signal monitoring. The introduction of organic semiconductors in the devices can soften the boundaries between microelectronic systems and dynamically active cells and tissues. Therefore, organic bioelectronics has attracted much attention recently due to the unique properties and promising applications. Organic thin film transistors (OTFTs), owing to their inherent capability of amplifying received signals, have emerged as one of the state-of-the-art biosensing platforms. The advantages of organic semiconductors in terms of synthetic freedom, low temperature solution processing, biocompatibility, and mechanical flexibility render OTFTs ideal transducers for wearable electronics, e-skin, and implantable devices. How to realize highly sensitive, selective, rapid, and efficient signal capture and extraction of biological recognition events is the major challenge in the design of biosensors. OTFTs are prone to converting the presence or change of target analytes into specific electrical signals even in complex biological systems. More importantly, OTFT sensors can be conveniently functionalized with chemical or biological modifications and exhibit substantially improved device sensitivity and selectivity as well as other analytical figure of merits, including calibration range, linearity, and accuracy. However, the stability and reproducibility of the organic devices need to be further improved. In this Account, we first introduce the unique features of OTFTs for bioelectronic applications. Two typical OTFT configurations, including organic electrochemical transistor (OECT) and electrolyte gated organic field effect transistor (EGOFET), are highlighted in their sensing applications mainly due to the operation of the devices in electrolytes and the combination of ionic and electronic charge transports in the devices. These devices are potentiometric transducers with low working voltages (<1 V) and high sensitivity, and are thus suitable for wearable applications with low power consumption. Second, the functionalization strategies on channel materials, electrolytes, and gate electrodes based on various modification methods and sensing mechanisms are discussed in sequence. In an OECT- or EGOFET-based biosensor, the device performance is particularly sensitive to the physical properties of the two interfaces, including channel/electrolyte and gate/electrolyte interfaces. Any change in the potential drop or capacitance of either interface can influence the channel current substantially. Therefore, the functionalization of the interfaces is critical to the sensing performance. In particular, when an electrochemically active material is modified on the interfaces, the reaction of the analyte catalyzed by the modified material can influence the interface potential and lead to a channel current response much stronger than that of a conventional electrochemical measurement. So the biosensors are much more sensitive than typical analytical methods due to the signal amplification of the transistors. Third, the processing techniques including screen printing and inkjet printing and the possibility for mass production are discussed. The applications of organic transistors in wearable electronics and healthcare monitoring systems, especially the fabric OECT-based biosensors for noninvasive detection, are presented. It is expected that the versatile organic transistors will enable various compact, flexible and disposable biosensors compatible with wearable electronics.

Electrical and Ammonia Gas Sensing Properties of PQT-12/CdSe Quantum Dots Composite-Based Organic Thin Film Transistors

The electrical and ammonia gas sensing properties of poly (3, 3”’-dialkylquaterthiophene) (i.e., PQT-12) and CdSe quantum dots (QDs) composite-based back-gated organic thin film transistors (OTFTs) fabricated on SiO2 coated heavily doped p-Si substrates by solution method have been investigated in this paper. The properties of pristine PQT-12 and PQT-12/CdSe QDs composite films have been investigated by transmission electron microscopy and atomic force microscopy. To investigate the effect of colloidal CdSe QDs on the characteristics of PQT-12-based OTFTs, the performance of pristine PQT-12-based OTFT has been compared with that of the PQT-12/CdSe QDs composite-based OTFT. The field effect mobility, threshold voltage, on/off current ratio, and subthreshold swing of the PQT-12/CdSe QDs composite-based OTFT are $4.2\times 10^{-3}$ cm2/Vs, −14.4 V, $1.9\times 10^{3}$ , and 5.2 V/dec while the corresponding values for pristine PQT-12-based OTFT are $1.4\times 10^{-3}$ cm2/Vs, −22.1 V, $3.6\times 10^{2}$ , and 7.9 V/dec, respectively. When the devices are exposed to ammonia gas, an estimated gas response of ~51% is obtained for PQT-12/CdSe QDs composite-based OTFT whereas the gas response of ~41% is achieved for the pristine PQT-12 OTFT sensor. The improved gas response in the PQT-12/CdSe QDs composite-based OTFT is attributed to enhanced charge transfer due to the CdSe QDs as compared with the pristine PQT-12-based OTFT.

Diketopyrrolopyrrole-based polymer transistors for hazardous volatile organic compound detection

Abstract Here, we report on highly sensitive OTFT sensors based on ultrathin poly[[2,5-bis(2-octyldodecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl]-alt-[[2,2′-(2,5-thiophene)bis-thieno(3,2-b)thiophene]-5,5′-diyl]] (DPPT-TT) organic thin film transistors (OTFTs) for detection of volatile organic compounds (VOCs). The flexible ultrathin DPPT-TT-OTFT sensors show high sensitivity of ∼87% in the exposed ammonia compared to ethanol and ethylene gases, which is ascribed to severe hole trapping in the semiconducting channel. Additionally, the gas sensor exhibit intense alteration of the OTFT performance parameters, including turn-on voltage, threshold voltage, and on and off current to common VOCs, such as 2-propanol, trichloroethylene, and 1,2-dichloroethane. In particular high sensitivity with good reversibility is achieved in the exposed 2-propanol.This work demonstrates that OTFTs with the dye-based conjugated polymers have great potential to realize real-time monitoring of various hazardous VOCs.

Interfacial modifying layer-driven high-performance organic thin-film transistors and their nitrogen dioxide gas sensors

Organic thin-film transistors (OTFTs) based on bottom-gate bottom-contact configuration were fabricated by inserting two kinds of modifying layers at the interface of source/drain electrode and organic semiconductor, while nitrogen dioxide (NO2) sensing capability was also evaluated based on the obtained OTFTs. Compared to OTFT without interfacial layer, the field-effect mobility (μ) was enhanced from 0.018 cm2/Vs to 0.15 cm2/Vs by incorporating with MoOx interfacial layer. Moreover, when exposed to 30 ppm NO2, the saturation current and μ of OTFT with MoOx interfacial layer increase 22.7% and 26.7%, respectively, while in original OTFT, the values are only 3.0% and 3.7%, respectively. The mechanism of performance improvement of OTFT sensor was systematically studied by focusing on the interface of source/drain electrode and organic semiconductor. The reduced contact resistance leads to higher μ, meanwhile, pentacene morphology modulation on MoOx contributes to better diffusion of NO2 molecules. As a result, higher μ and more diffused gas molecules enhance the gas sensing property of the transistor.

Two novel methods for evaluating the performance of OTFT gas sensors

Two methods were proposed to evaluate the performance of organic thin film transistor (OTFT) gas sensors. A back-gated OTFT gas sensor with poly(3-hexylthiophene) (P3HT)/zinc oxide (ZnO) nanorods composite films as the active layer and gas sensing layers were prepared for nitrogen dioxide (NO2) detection. The electrical parameters of OTFTs based on pure P3HT film and P3HT/ZnO-nanorods composite films were calculated and analyzed. The response characteristics of gas sensor to NO2 were studied. It can be found that the response of OTFT gas sensor was inaccurate according to conventional definition. The effects of humidity and temperature on the response of sensors were evaluated. However, OTFT, as a multiparameter sensor, can provide more information to evaluate the gas sensing properties. The variation of Vth of OTFT gas sensor was associated with the content of ZnO-nanorods and the concentration of NO2. The variation mechanism of Vth was analyzed as well. The results indicated the variation of Vth as the response of sensor was reliable. The variation of Vth was attributed to the impact introduced by NO2 molecules on the charge carrier motion. In addition, the slope of fitting line (ΔI versus logt) was proposed as a new method to evaluate the gas properties of OTFT sensors. The calculated results illustrated that the sensitivity can be magnified compared to the variation of Vth and increased 40.2% due to appropriate amount of ZnO-nanorods doping.

An electrical characterisation system for the real-time acquisition of multiple independent sensing parameters from organic thin film transistors

Abstract. The presence of multiple independent sensing parameters in a single device is the key conceptual advantage of sensor devices based on an organic thin film transistor (OTFT) over simple organic chemiresistors. Practically, however, these multiple parameters must first be extracted from the electrical characteristics of the OTFTs and, thus, they are not immediately apparent. To exploit the advantage of OTFT sensors, we require a measurement technology to extract these parameters in real time. Here, we introduce an efficient, cost-effective system that is a faster and more compact alternative to the expensive and cumbersome laboratory-based instruments currently available. The characterisation system presented here records the electric behaviour of OTFTs in the form of its "saturated transfer characteristics" multiple times per second for virtually unlimited periods of time, with the option to multiplex up to 20 devices in parallel. By applying a bespoke algorithm to the measured transfer characteristics, the system then extracts, in real time, several underlying transistor parameters (on- and off-current, threshold voltage, and charge carrier mobility). Tests were conducted on the example of a poly(thieno[3,2-b]thiophene) (PBTTT) OTFT exposed to ethanol vapour. The system extracts the underlying OTFT parameters with very low noise without introducing apparent correlations between independent parameters as an artefact.

Detection of saliva-range glucose concentrations using organic thin-film transistors

We describe the development of a glucose sensor through direct incorporation of an enzyme (glucose oxidase) into the gate of an organic thin film transistor (OTFT). We show that glucose diffusion is the key determinant of the device response time and present a mechanism of glucose sensing in these devices that involves protonic doping of the transistor channel via enzymatic oxidation of glucose. The integrated OTFT sensor is sensitive across 4 decades of glucose concentration; a range that encompasses both the blood and salivary glucose concentration levels. As such, this work acts as a proof-of-concept for low-cost printed biosensors for salivary glucose.

On the mode of operation in electrolyte-gated thin film transistors based on different substituted polythiophenes

Organic Thin Film Transistors (OTFT), gated through an aqueous electrolyte, have extensively been studied as sensors in various applications. These water-gated devices are known to work both as electrochemical (Organic ElectroChemical Transistor – OECT) and field-effect (Organic Field-Effect Transistor – OFET) devices. To properly model and predict the response of water-gated OTFT sensors it is important to distinguish between the mechanism, field-effect or electrochemical, by which the transistor is modulated and thus how the gate signal can be affected by the analyte. In this present study we explore three organic polymer semiconductors, poly-(3-hexyl-thiophene) (P3HT), poly-(3-carboxy-pentyl-thiphene) (P3CPT) and a co-polymer P3HT–co-poly-(3-ethoxypentanoic acid-thiophene) (monomer ratio 1:6, P3HT–COOH15) in water-gated OTFT structures. We report a set of transistor characteristics, including standard output parameters, impedance spectroscopy and current transients, to investigate the origin of the mode of operation in these water-gated OTFTs. Impedance characteristics, including both frequency and voltage dependence, were recorded for capacitor stacks corresponding to the gate/electrolyte/semiconductor/source structure. It is shown that P3HT as well as P3HT–COOH15 both can function as semiconductors in water gated OTFT devices operating in field-effect mode. P3CPT on the other hand shows typical signs of electrochemical mode of operation. The –COOH side group has been suggested as a possible anchoring site for biorecognition elements in EGOFET sensors, rendering P3HT–COOH15 a possible candidate for such applications.

Star-shaped self-assembly of an organic thin film transistor sensor in the presence of Cu2+ and CN− ions

In this study we developed organic thin film transistors (OTFTs) for the sensing of metal ions and anions through the self-assembly of a pentacene/Schiff base pyrene derivative. Our bilayer OTFTs displayed attractive device parameters: an electron mobility (μ) of 0.12cm2V−1s−1, a threshold voltage (Vth) of 22.20V, and a five-orders-of-magnitude on/off ratio. This device was sensitive toward Cu2+ among 13 metal cations and toward CN− among nine anions, as measured through changes in the values of Vth and Ioff in the presence of Cu2+ cations and a change in the value of Isat in the presence of CN− anions. We observed selectivity toward both of these ions in mixed ion solutions, with sensitivity over different concentrations (from 20 to 350μM for Cu2+; from 100 to 350μM for CN−) as well as in sea water. The pyrene derivative self-assembled through pyrene–pyrene* coordination in the presence of Cu2+ ions; the rods of the pyrene derivative broke into smaller pieces upon formation of benzoxazole rings in the presence of CN− ions, as confirmed using atomic force microscopy and fourier transform attenuated total reflection spectroscopy.