Work Function Type Sensors Research Articles

Sensing characteristics of novel borospherenes towards sulfur-containing gases: electronic and work function-type sensor

Using density functional theory (DFT), the researchers in this study investigated the potential uses of C4B32 nanocluster in detecting gases such as CS2, H2S, SO2 and COS. The study's results revealed that these gases have varying degrees of stability in the order of SO2 being the most stable, followed by COS, CS2 and H2S. Additionally, the study found a correlation between the electric dipole moment and adsorption energy of the molecules. In this study, the density of states, natural bond orbitals, energetic and electrical properties, and structure optimisation were all investigated using the PBE-D3/6-31G* basis set. The researchers also suggested that C4B32 nanocluster may as an electronic-type and Φ-type sensor in detecting H2S and SO2. According to the study's findings, C4B32 nanocluster cannot be used as a Φ-type sensor for COS and CS2, but they can be used to identify SO2 and H2S when CS2 and COS are present. The C4B32 nanocluster displayed a fast recovery time for H2S and SO2 desorption at room temperature, measuring 69 × 10−6 μs and 3.97 s, respectively, indicating its capacity to perform well in the environment.

The First-Principles investigation of sensing and removal applications of nitrobenzene using pristine and Sc decorated B9N9 nanoring

Nitrobenzene (NB), an aromatic organic compound widely used in various industries, has several environmental risks. Due to its risks, reliable sensing mechanisms are crucial. In the present work, we investigated the potential of the pristine and Sc decorated B9N9 nanoring as a sensor for detection of the toxic NB molecule using density functional theory (DFT). We have analyzed the structural parameters, adsorption energy (Ead), highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), HOMO-LUMO gap, density of states (DOS) spectra, Mulliken charge transfer, dipole moment, IR spectra, non-covalent interactions (NCI) iso-surfaces, recovery time (τ) and work function (φ) before and after the adsorption of NB onto pristine and Sc decorated B9N9 nanorings. Our analysis revealed that the NB interacted optimally with the pristine B9N9 nanoring, as evidenced by changes in electronic properties and Ead value of −0.58 eV. However, the Sc decorated B9N9 nanoring indicated a strong interaction with NB with Ead of −4.09 eV at a proximal distance of 2.12 Å. Furthermore, our study demonstrated that the pristine B9N9 nanoring could be used as both an “electronic sensor” and “φ-type sensor”. Additionally, to esteem rapid recovery for practical feasibility, we calculated τ for both the pristine and Sc decorated B9N9 nanoring. The short τ of the pristine nanoring indicates its suitability as NB sensor. In contrast, the longer τ of the Sc decorated nanoring suggests its applicability for NB storage or its removal from the surroundings. Overall, our findings underscore the potential of pristine B9N9 nanoring as effective NB sensor and removal. We hope that our study will assist experimentalists to develope a reliable B9N9 nanoring based sensor for the detection of NB molecules.

Exploration of SF6 and its decomposed gases in adsorption and sensing (four modified WSe2 monolayers at quantum level)

As SF6 is the most widely used high-voltage insulating gas, the monitoring of its decomposition products to ensure the stable operation of GIS equipment and the treatment of leakage have been two important research topics. This work is based on the first principles of adsorption and sensing characterization of SF6 and its decomposed gases (HF, H2S, SO2, SOF2, SO2F2) using four modification strategies on the surface of WSe2. The energy parameters such as transfer charge, density of states, adsorption energy, band gap, and work function are calculated for each system. The results show that the electrical conductivity of the system is greatly enhanced when defect modification is employed, and the band gap is changed from 2.018 eV to 0.008 eV (W@WSe2) and 1.271 eV (Se@WSe2). The CoO and TiO2 doped WSe2 showed excellent adsorption of SF6 (−7.818 eV) and SOF2 (−14.263 eV), respectively, which is of great significance for SF6 gas leakage treatment. In addition, the results of work function calculations indicate that CoO-WSe2 has potential as a work function type sensor for these six gases. Finally, by calculating the desorption time (τ), we systematically explored whether the four modified materials have the characteristics to be used as recyclable resistive type sensors under different temperature environments. Our work will help to explore the adsorption performance and sensing characteristics of WSe2 monolayers with different modifications for SF6 and its decomposed gases, which is crucial for the protection of GIS equipment in power systems.

The adsorption of sulfur mustard chemical warfare agent on the Ga12N12 and Ca12O12 nanocages; A systematic DFT study

This work presents a systematic DFT study of the potential of Ca12O12 and Ga12N12 nanocages for detecting and removing the sulfur mustard. Sulfur mustard was chemically adsorbed on the surface of Ca12O12 and Ga12N12 nanocages. Moreover, the Ga12N12 nanocage exhibited a significantly greater capacity for removing sulfur mustard than Ca12O12 because of stronger sulfur mustard adsorption. QTAIM analysis showed that partial covalent bonds are responsible for the strong sulfur mustard adsorption on Ga12N12, while sulfur mustard adsorbs on Ca12O12 by strong non-covalent interactions. According to NBO, the work function of Ga12N12 nanocage was considerably reduced exposure to sulfur mustard, indicating that Ga12N12 may be a suitable work function type sensor for detecting sulfur mustard. Comparing the UV–visible spectra of bare nanocages with those of the nanocages adsorbing sulfur mustard revealed that the sulfur mustard adsorption didn't visibly alter the spectra of the nanocages but increased the number of absorption lines.

Transition metal-functionalized porphyrin-like C70 fullerenes as sensors and adsorbents of formaldehyde- DFT, NBO, and QTAIM study

C70 fullerenes are effective formaldehyde sensors and adsorbents, with nitrogen or boron doping significantly increasing their sensitivity in detecting formaldehyde gas. C70 fullerenes doped with nitrogen atoms are effective in removing formaldehyde from the air. In this work, the potential of transition metal- (Ti, Cr, Fe, Ni, and Zn) functionalized porphyrin C70 fullerenes (MF-PC70Fs) for sensing and removing formaldehyde were investigated using DFT, QTAIM, and NBO. The HOMO-LUMO gaps for Ti, Cr, Fe, Ni, and Zn-functionalized materials were computed, resulting in values of 1.27, 0.07, 1.84, 1.84, and 1.80 eV, respectively. The absorption energies of formaldehyde onto MF-PC70Fs were computed, revealing that the PC70Fs functionalized with Ti had the highest adsorption strength, while those functionalized with Ni had the lowest. The HOMO-LUMO gap of Cr- and Fe-functionalized PC70Fs was significantly changed after adsorbing formaldehyde. Accordingly, they may be used as conductivity-type sensors for detecting formaldehyde. Also, Cr-, Fe-, and Zn-functionalized PC70Fs can be used as formaldehyde work function type sensors. According to the calculated time recovery of MF-PC70Fs, Fe- and Zn-functionalized PC70Fs are more favourite materials than Cr-functionalized in formaldehyde sensors.

Metal-decorated siligene as work function type sensor for NH3 detection: A DFT approach

In this work, we employed density functional theory calculations to investigate the feasibility of X-decorated (X = Li, Na, K, Mg, Ca, Sc, Ti, and Pd) two-dimensional siligene (2D SiGe) for ammonia (NH3) sensing through variations of its work function. The results indicated that NH3 molecule is physisorbed on pristine 2D SiGe. Moreover, Li, Na, K, Sc, Ti, Pd and Ca atoms are chemisorbed on the 2D SiGe, while Mg is barely adsorbed. Likewise, NH3 tends to be adsorbed on the metal atoms of the decorated 2D SiGe with adsorption energies between −0.13 eV and−1.47 eV. The changes observed in the work functions of Na-, Mg-, Ca-, Sc-, and Pd-decorated 2D SiGe upon NH3 may allow its detection. Moreover, the results indicate that only the recovery times of 2D SiGe decorate with Na, K, Ca and Pd atoms could allow for their use as reusable sensors of NH3, while 2D SiGe decorated with Li, Mg, Sc and Ti could be used to trap NH3. From the results of work functions and recovery times on metal decorated 2D SiGe, it is concluded that Pd, Ca, and Na-decorated 2D SiGe are the most suitable material for sensing NH3 molecules.

Metal-Decorated Siligene as Work Function Type Sensor for NH3 Detection: A DFT Approach

Metal-Decorated Siligene as Work Function Type Sensor for NH3 Detection: A DFT Approach

Theoretical study of the adsorption of BMSF-BENZ drug for osteoporosis disease treatment on Al-doped carbon nanotubes (Al-CNT) as a drug delivery vehicle

The adsorption energy of the BMSF-BENZ adsorbed complexes was investigated to understand the non-local dispersion interactions, with many other chemical parameters related to this subject like HOMO and LUMO, energy gap, and the time needed for the BMSF-BENZ to be desorbed from the nanotube (recovery time). Our study reveals that Al-CNT is a promising adsorbent for this drug as Eads of BMSF-BENZ/Al-CNT complexes are -22.09, -38.68, -12.89, -31.01, -27.31, -21.90, and -21.42 kcal/mol in the gas phase on the active atoms of the BMSF BENZ (Br, N8, N9, N58, O35, O41, and S), respectively. In addition, the spontaneous and favorable interaction between the BMSF BENZ and all nanoparticles was confirmed by investigating Gibbs free energy and quantum theory of atoms in molecule analysis (QTAIM) so that it can be used as an electrochemical sensor or biosensor. Furthermore, to more visualize the nature of intermolecular bonding and the strength of interaction between the BMSF-BENZ drug molecule and the nanotube, QTAIM has been widely studied in the case of drug delivery purposes. Al-CNT (4,0) can be extended as a drug delivery system and the work function type sensor.

Defective boron carbide monolayer as a chemical sensor for dopamine drug

By implementing density functional theory method, we studied the dopamine (DA) drug adsorption onto pristine and double-vacancy defected BC3 (DV-BC3) monolayer in order to evaluate the potential application of this nanostructure as a sensing material. The sensitivity of the perfect BC3 nanosheet was negligible toward DA identification of the compound. The adsorption energy of the DA drug on the DV-BC3 surface was calculated to be −29.03 kcal/mol. The electrical band gap and the work function of DV-BC3 decreased from 1.75 and −4.49 to 0.95 eV and −3.27 eV, respectively, after the DA adsorption process. This illustrates the potential application of the DV-BC3 nanosheet as the electronic and work function type sensor, while the perfect BC3 may be only an electronic sensor. A major shift in the adsorption energy was predicted as the solvent dielectric constant increased.

Fluorouracil drug sensing characteristics of pristine and Al-doped BC3 nanosheets: Quantum chemical study

The electronic sensitivity of pristine and Al-doped BC3 nanosheets toward a typical anticancer drug namely, 5-fluorouracil (5FU) was investigated using density functional theory calculations. It was found the pristine BC3 tendency toward 5FU molecules is not noticeably high, and the obtained adsorption energy is about −4.42 kcal/mol. Additionally, the evaluated electronic properties of pristine BC3 are not mainly affected by the 5FU drug as well. The Al-doping significantly enhances the reactivity and sensitivity of the sheet toward 5FU. The 5FU adsorption results in a noticeable reduction of the HOMO-LUMO gap of the Al-doped BC3 from 1.34 to 1.04 eV, increasing the electrical conductivity. It shows that the Al-doped sheet may be a promising candidate as an electronic sensor for 5FU detection, unlike the pristine BC3. Also, the work function of Al-doped BC3 is mainly affected by 5FU adsorption which significantly changes the field emission electron current from its surface, demonstrating that it may be also a work function type sensor for 5FU detection. The Al-doped BC3 sheet benefits from a short recovery time of 8.80 ms for 5FU desorption.

Tunable adsorption behavior of small molecule on GeP monolayer by applied strain and electric field

The sensing properties of GeP monolayer to small gas molecule (CO, CO2, O2, H2O, NH3, NO and NO2) have been investigated by performing first-principle calculations. Based on calculated adsorption distance, adsorption energy and charge transfer, we find that GeP monolayer is the most sensitive to NO2 and NO molecules, and all gas molecules act as acceptors to gain electrons from GeP monolayer. The adsorption energy of NO2 is smaller than that of NO molecule, which implies that NO2 is more easily desorbed from GeP. And different work function changes also indicate the possibility to identify NO2 and NO in an oxygen-free environment. Moreover, we apply uniaxial and biaxial strains to GeP monolayer and find that a small biaxial compressive strain can effectively enhance the sensitivity of work function type sensor based GeP to NO2 molecule without increasing recovery time. We also discuss the effect of external vertical electric field on the adsorption performance of NO2 molecule. The negative electric field can significantly increase the adsorption strength, charge transfer and work function change of NO2-GeP system. Our results indicate that GeP monolayer is a potential candidate for NO2 gas sensor.

A DFT study on the detection of isoniazid drug by pristine, Si and Al doped C70 fullerenes

Abstract Using density functional theory calculations, the electronic sensitivity and reactivity of pristine, Al and Si doped C70 fullerenes are inspected toward anti-tuberculosis isoniazid (IS) drug. We found that the IS prefers to be physically adsorbed on the pristine C70 via its O-head with adsorption energy about −1.3 kcal/mol and no effect on the C70 electrical conductivity. Substituting a C atom of C70 by Al and Si atoms, the C70 reactivity meaningfully increases, and the predicted adsorption energies are about −67.9 and −51.3 kcal/mol, respectively. The HOMO-LUMO gap (Eg) and work function of Al–C70 are not sensibly affected by the IS drug. While because of a large HOMO destabilization in the Si–C70 upon the IS adsorption, the Eg of Si–C70 largely decreases from 2.24 to 1.12 eV, increasing its electrical conductivity which can generate an electrical signal. This signal is connected to the presence of IS in the environment. Therefore, we concluded that the Si–C70 may be a promising electronic sensor for the IS drug detection. Similar to the case of Al–C70, the Fermi level and work function of Si–C70 are not sensibly affected by IS adsorption, indicating that the Si–C70 can be used only as an electronic sensor not a work function type sensor.

Amantadine antiparkinsonian drug adsorption on the AlN and BN nanoclusters: A computational study

To find a sensor for Amantadine (AM) antiparkinsonian drug, we studied its interaction with Al12N12 and B12N12 nanoclusters by density functional theory calculations. The AM molecule attaches via its –NH2 group to the Al or B atoms of Al12N12 or B12N12 with Gibbs free energy change about −31.5 or −26.1 kcal/mol. Increasing the AM concentration, the interaction becomes weaker due to steric effects. The AM adsorbs on the Al12N12 and B12N12 with two different mechanisms, including electrostatic and charge transfer, respectively. The AM significantly reduces the Al12N12 work function from 4.50 to 3.66 eV, increasing the electron field emission. Thus, the AlN cluster may be a work function type sensor. Upon the AM adsorption on the BN cage, the HOMO level is largely destabilized, reducing the Eg from 6.84 to 5.01 eV which largely increases the electrical conductivity. This indicates that the BN cluster may be a potential electronic sensor.

Electronic and Work Function-Based Sensors for Acetylsalicylic Acid Based on the AlN and BN Nanoclusters: DFT Studies

Using density functional theory calculations, we investigated the potential application of Al12N12 and B12N12 nanoclusters as an electronic or work function type sensor for acetylsalicylic acid (ASA) drug detection. The drug tends to be adsorbed on the surface of both AlN and BN clusters via its –COOH group with adsorption energies about − 62.8 and − 21.9 kcal/mol, respectively. The AlN nanocluster is neither electronic nor work function based sensor for ASA because of a low sensitivity, and a huge recovery time (~ 9.8 × 1038 s). But the response of BN nanocluster is completely different, and its electrical conductivity is largely increased in the presence of ASA drug due to the large stabilization of LUMO level. We concluded that the BN nanocluster may be a promising candidate to detect the ASA drug with a short recovery time about 109 s and a high electronic sensitivity. As the work function of the BN nanocluster is not affected by the ASA adsorption, it cannot be used as a work function type sensor.

Utility of extrinsic [60] fullerenes as work function type sensors for amphetamine drug detection: DFT studies

Detection of illicit drugs is of increasing interest for police and drug communities because of their abuse. Using density functional calculations, we investigated the interaction of amphetamine (AA) drug with the pristine, B, Al, Ga (group IIIA), Si, and Ge (IIV group) doped C60 fullerenes. The AA cycloaddition from its phenyl ring to the [6–6] bonds of C60 is more favorable than that to the [5–6] bonds, in good agreement with experiment. When an AA molecule is adsorbed from its –NH2 group on the C60 fullerene, its work function is significantly decreased, showing a good sensitivity but the adsorption energy (−0.4 kcal/mol) is very small. Replacing a carbon atom of C60 by the impurity atoms, the interaction between the AA and the C60 is largely improved (adsorption energy ∼ −38.6 to −65.6 kcal/mol). Upon the adsorption of AA on the doped fullerenes, the Fermi level is largely shifted to higher energy, especially in the case of Si and Ge-doped fullerenes, and thus, the work function decreases by about 22.7 and 24.9%, respectively. The electron emission largely increases which can be converted to an electronic noise. However, the Si and Ge-C60 fullerenes are work function-type sensors for AA drug.

Influence of the morphology of platinum combined with β-Ga 2O 3 on the VOC response of work function type sensors

Polycrystalline β-Ga 2O 3/platinum thick films can be used as a novel sensing layer for the detection of VOC (volatile organic compounds) in sensors based on the readout of the work function (Kelvin probe, Floating Gate FET). An intermittent short thermal activation at 175 °C enables a subsequent room temperature operation. The supposed mechanism is based on the formation of oxygen species during this thermal activation. After cooling down to room temperature those species remain on the surface for some hours to days. The sensing mechanism at room temperature is assumed to be based on a reaction of reducing gases with this oxygen species resulting in a change of the work function due to the change of the surface properties. The addition of platinum as catalyst is necessary to obtain a response to various VOC. Pt clusters with varying size are investigated which are responsible for improving the VOC sensitivity. Therefore platinum on micro- and nanoscale was used. The best variants are capable to detect small concentrations (ppb–ppm) of different VOC (aldehydes, alcohols, esters, ketones, and hydrocarbons) as well as toxic CO well below their odor or toxicity threshold. Meaningful responses are still present some days after the thermal activation.

Stepwise improvement of (hetero-) polysiloxane sensing layers for CO 2 detection operated at room temperature by modification of the polymeric network

Gas sensors based on the work function read out of (hetero-) polysiloxane sensing layers containing primary amino groups (–NH 2) can be used for the detection of CO 2. The sensing mechanism is assumed to be an acid/base reaction between primary amino groups and CO 2. In literature, both a bicarbonate formation and a carbamate formation are discussed. To investigate the reaction with CO 2, different polymers based on modified polysiloxanes are examined. It is shown that the CO 2 response of work function type sensors can be systematically improved by modifying the polymeric network on the one hand (adjoining primary amino groups) and by increasing the hydrophobicity on the other hand. The findings summarized in this paper indicate the possibility for new ambient temperature CO 2 sensors with short response (<1 min) and recovery times (<5 min), a high long-term stability (months to years) as well as a high SNR (signal noise ratio) of ca. 25 (exposure from 400 ppm up to 4000 ppm CO 2). Furthermore, the fast establishment of the chemical equilibrium is remarkable when humidity is changed in atmosphere.

The influence of interfaces and interlayers on the gas sensitivity in work function type sensors

It is known that barium carbonate can act as CO2 sensitive material in work function type gas sensors in ambient condition. The reaction is due to the formation of bicarbonate species at the surface. The cross-sensitivity to other acidic gases as NO2 was up to now regarded and described in terms of similar reactions on the carbonate surface. In this work it was found that the NO2 sensitivity is due to reactions on the back metalisation of the carbonate film. Using different layer systems different sensitivities can therefore be switched on and off according to the needs in special applications. The design of specialised sensor systems is possible on the base of the results found in this work.

Investigation of the reaction mechanisms in work function type sensors at room temperature by studies of the cross-sensitivity to oxygen and water: the carbonate–carbon dioxide system

Thin films and screen-printed films of BaCO 3 react to changes of CO 2 in wet synthetic air at room temperature with a change of the work function as measured by the Kelvin method. The reaction is due to the formation of hydrogen carbonate ions on the surface. In this work, the reaction mechanism is investigated by studying the cross-sensitivities to oxygen and humidity in the temperature range between 25°C and 250°C. At low temperatures between 25°C and 100°C, the reaction involves water whereas at temperatures above 200°C, the reaction is driven by the presence of oxygen. In both cases, the reaction can be described in terms of a Nernst equation. In the low-temperature region, however, the (thickness-independent) potential type of reaction is superimposed by a (thickness-dependent) capacitance type of reaction to humidity like in the well-known capacitive humidity sensors.

TiN in work function type sensors: a stable ammonia sensitive material for room temperature operation with low humidity cross sensitivity

In this work, it was found that exposure of TiN to ammonia (400 ppb–100 ppm) in wet synthetic air at room temperature leads to a reversible decrease of Δ Φ. There is a change of the work function of −30 meV/decade of increasing ammonia concentration at room temperature. The response time ( t 90) to 1 ppm is ≤1 min. The sensitivity is a typical room temperature effect as it decreases at higher temperatures up to 100°C. The reaction has a low cross sensitivity to humidity, as — first — the sensitivity to ammonia does not depend on the relative humidity and — second — the work function change due to humidity changes is as low as −2 meV for an increase of 10% in relative humidity. The Diffuse Reflectance Infrared Fourier Transform Spectra (DRIFT-spectra) indicate that the adsorption of ammonia is correlated with a decrease of OH species on the surface. All data are compared to the gas reactions of TiO 2.