Nanocrystalline TiO₂/SnO₂ heterostructures for gas sensing

• Barbara Lyson-Sypien,
• Anna Kusior,
• Mieczylaw Rekas,
• Jan Zukrowski,
• Marta Gajewska,
• Katarzyna Michalow-Mauke,
• Thomas Graule,
• Marta Radecka and
• Katarzyna Zakrzewska

Beilstein J. Nanotechnol. 2017, 8, 108–122, doi:10.3762/bjnano.8.12

• the range of 3–27 nm. Tin exhibits only the oxidation state 4+. The H2 detection threshold for the studied TiO2/SnO2 heterostructures is lower than 1 ppm especially in the case of SnO2-rich samples. The recovery time of SnO2-based heterostructures, despite their large responses over the whole

• heterostructures exhibit larger responses to gases over the whole measuring range, it appears that their recovery time, τ, for the sensor to reach 90% of the initial electrical resistance, R0, is much longer than that of TiO2-rich heterostructures at higher H2 concentrations (Figure 6). In the case of 90 mol

• % SnO2/10 mol % TiO2 (1100 ppm H2), τ is about 2500 s, whereas for 10 mol % SnO2/90 mol % TiO2 (1100 ppm H2), τ is less than 30 s. The longer recovery time of SnO2-rich sensors can be attributed to a constricted gas desorption that probably results from the differences in the microstructure evidenced by

Sensitive detection of hydrocarbon gases using electrochemically Pd-modified ZnO chemiresistors

• Elena Dilonardo,
• Michele Penza,
• Marco Alvisi,
• Gennaro Cassano,
• Cinzia Di Franco,
• Francesco Palmisano,
• Luisa Torsi and
• Nicola Cioffi

Beilstein J. Nanotechnol. 2017, 8, 82–90, doi:10.3762/bjnano.8.9

• whole investigated concentration range the response and recovery processes were faster on Pd-modified ZnO NRs. This behavior can be attributed to the presence of Pd NPs, which catalyze the sensing process. Moreover, the response time was faster than the recovery time, in both cases, Pd-modified and

• chemical composition of pristine and Pd-functionalized ZnO NRs, annealed at 550 °C. The value for O–Zn refers to the atomic percentage of oxygen bound to zinc. Comparison of the response time (tResponse) and recovery time (tRecovery) between pristine and Pd-modified ZnO NRs at various C4H10 concentrations

Nanostructured SnO₂–ZnO composite gas sensors for selective detection of carbon monoxide

• Paul Chesler,
• Cristian Hornoiu,
• Susana Mihaiu,
• Cristina Vladut,
• Jose Maria Calderon Moreno,
• Mihai Anastasescu,
• Carmen Moldovan,
• Bogdan Firtat,
• Costin Brasoveanu,
• George Muscalu,
• Ion Stan and
• Mariuca Gartner

Beilstein J. Nanotechnol. 2016, 7, 2045–2056, doi:10.3762/bjnano.7.195

• decontaminated by heating the sensor in the carrier gas for a period equal (at least) to the recovery time. The S2 sensor was found to be sensitive even to low concentrations of CO (5 ppm) as seen in Figure 14, with a response value of 1.21. Other working temperatures were tested for the S2 sensor to verify if

Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals

• Ivan Shtepliuk,
• Jens Eriksson,
• Volodymyr Khranovskyy,
• Tihomir Iakimov,
• Anita Lloyd Spetz and
• Rositsa Yakimova

Beilstein J. Nanotechnol. 2016, 7, 1800–1814, doi:10.3762/bjnano.7.173

• the absolute value of adsorption energy. At the same time, we believe that the general trend in adsorption of heavy metals by graphene surface will not be changed. Another important aspect is the recovery time. According to the transition state theory [61], the recovery time may be written as follows

• : where T is the temperature, kB is Boltzmann’s constant and ν0 is the frequency of the desorption event, and Eads is the adsorption energy. An increase in adsorption energy will cause an increased recovery time. In fact, in the case of strong adsorption, the recovery time will be too long for the sensor

• signal to return to its initial value in a reasonable time. This is not applicable for real-time sensors. Our findings suggest that the recovery time of the sensor for Pb detection will be longer than that of the sensors for determination of Hg and Cd. This is mainly associated with the difference in the

Nanostructured TiO₂-based gas sensors with enhanced sensitivity to reducing gases

• Wojciech Maziarz,
• Anna Kusior and
• Anita Trenczek-Zajac

Beilstein J. Nanotechnol. 2016, 7, 1718–1726, doi:10.3762/bjnano.7.164

• nitrogen oxides and in the presence of acetone. The effect of surface modification on the response and recovery time was studied. Experimental Sample preparation The sensing materials were prepared by thermal and chemical oxidation of Ti foils (d = 0.127 mm, 99.7%, Sigma-Aldrich). Titanium was cut into 20

• the response to a specific gas was the highest. Then, the measurements at constant temperature with varied gas concentrations were carried out. For all the measurements, the sampling time was 2 s. The response time, tres, and recovery time, trec, are defined as the time required for changes in

• place at temperatures higher than adsorption, longer recovery time can be easily explained. According to Basu and Basu [42] there are two ways to increase the kinetics of desorption and hence lower the recovery time, that is to raise the temperature or to inject oxygen at a higher concentration. In

NO gas sensing at room temperature using single titanium oxide nanodot sensors created by atomic force microscopy nanolithography

• Li-Yang Hong and
• Heh-Nan Lin

Beilstein J. Nanotechnol. 2016, 7, 1044–1051, doi:10.3762/bjnano.7.97

• -recovery approaches. It is found that a sensor with a smaller ND has better performance than a larger one. A response of 31%, a response time of 91 s, and a recovery time of 184 s have been achieved at a concentration of 10 ppm for a ND with a size of around 80 nm. The present work demonstrates the

• in Supporting Information File 1.) The response time tres is defined as the time required for the current to decrease to 10% of the initial current during NO exposure. The results are 91, 86, and 81 s for 10, 15, and 20 ppm, respectively, and plotted in Figure 4b. The recovery time trec is defined as

• the time required for the current to increase to 90% of the original current when NO is being pumped out. The results are 184, 363, and 477 s for 10, 15, and 20 ppm, respectively, and also plotted in Figure 4b. Response and recovery time both increase as the concentration rises. Since there are more

Nanoscale effects in the characterization of viscoelastic materials with atomic force microscopy: coupling of a quasi-three-dimensional standard linear solid model with in-plane surface interactions

• Santiago D. Solares

Beilstein J. Nanotechnol. 2016, 7, 554–571, doi:10.3762/bjnano.7.49

• paragraph for multifrequency AFM), it is worth noting that although tip–sample impacts are in principle much simpler for single-frequency AFM, during a scanning experiment, there is an interplay between scanning speed, cantilever oscillation frequency and the recovery time of the surface, such that tip

Bacteriorhodopsin–ZnO hybrid as a potential sensing element for low-temperature detection of ethanol vapour

• Saurav Kumar,
• Sudeshna Bagchi,
• Senthil Prasad,
• Anupma Sharma,
• Ritesh Kumar,
• Rishemjit Kaur,
• Jagvir Singh and
• Amol P. Bhondekar

Beilstein J. Nanotechnol. 2016, 7, 501–510, doi:10.3762/bjnano.7.44

• ,b shows the response of the ZnO-TF/bR and ZnO-NR/bR structures for the consecutive concentration increase (50 ppm, 100 ppm, 200 ppm) at 70 °C. The response time for the ZnO-TF/bR and ZnO-NR/bR structures was observed to be 11 and 4.3 min, respectively, and the recovery time was 1.7 and 1.5 min

Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases

• Elena Dilonardo,
• Michele Penza,
• Marco Alvisi,
• Cinzia Di Franco,
• Francesco Palmisano,
• Luisa Torsi and
• Nicola Cioffi

Beilstein J. Nanotechnol. 2016, 7, 22–31, doi:10.3762/bjnano.7.3

• general and ZnO nanomaterials in particular are promising as sensing layer in chemiresistive gas sensors, although their limited selectivity, high response/recovery time, high-power consumption, and lack of long-term stability have limited their use in more demanding applications [24]. Nowadays, many

• decreasing steps and finally a recovery time of 30 min to restore the sensor signal to the initial value under dry air flow and to clean the test cell and sensor surface. The sensor response to a given gas concentration is defined as the relative resistance change, ΔR/Ri (%), where ΔR is the change in

• equilibrium resistance value. The recovery time is defined as the time necessary to reach the 90% of the original resistance value in air without the gaseous analyte. Results and Discussion Chemical and structural properties The surface chemical composition of pristine and Au-doped ZnO nanocomposites annealed

Increasing throughput of AFM-based single cell adhesion measurements through multisubstrate surfaces

• Miao Yu,
• Nico Strohmeyer,
• Jinghe Wang,
• Daniel J. Müller and
• Jonne Helenius

Beilstein J. Nanotechnol. 2015, 6, 157–166, doi:10.3762/bjnano.6.15

• washed with measurement media to exchange coating buffers and remove loosely bound protein from the surface. Throughout the experiments, the PDMS mask remained on Petri Dish. After a recovery time of at least 45 min in the measurement media [20], cell suspensions were pipetted onto the BSA well and cells

Synthesis of boron nitride nanotubes and their applications

• Saban Kalay,
• Zehra Yilmaz,
• Ozlem Sen,
• Melis Emanet,
• Emine Kazanc and
• Mustafa Çulha

Beilstein J. Nanotechnol. 2015, 6, 84–102, doi:10.3762/bjnano.6.9

• humidity sensor system. The adsorption–desorption tests showed that the AgNP–BNNT material had a potentially fast response/recovery time of 100/15 s for the detection of relative humidity at room temperature [90]. The use of Ni-encapsulated BNNTs in optomagnetic-based sensors with respect to their magnetic

Advances in NO₂ sensing with individual single-walled carbon nanotube transistors

• Kiran Chikkadi,
• Matthias Muoth,
• Cosmin Roman,
• Miroslav Haluska and
• Christofer Hierold

Beilstein J. Nanotechnol. 2014, 5, 2179–2191, doi:10.3762/bjnano.5.227

• current understanding of the NO2–nanotube interaction is far from complete. A brief review of the reports so far will be made before further discussing their effects on the electrical characteristics of the CNFET. Several experimental reports have shown that the undisturbed recovery time of a nanotube

• the substrate provide more favorable sites for adsorption, where the NO2 molecules may have a higher binding energy. However, suspended nanotubes have also been shown to be sensitive to NO2 [30][53], and the recovery time even in the absence of a substrate appears to be comparable. This suggests that

• to gas exposure. This excludes other possibilities such as substrate-assisted adsorption and response from the contacts suggesting that the nanotube itself is indeed sensitive even in the absence of other contributing mechanisms. Furthermore, the long recovery time is observed here as well

Room temperature, ppb-level NO₂ gas sensing of multiple-networked ZnSe nanowire sensors under UV illumination

• Sunghoon Park,
• Soohyun Kim,
• Wan In Lee,
• Kyoung-Kook Kim and
• Chongmu Lee

Beilstein J. Nanotechnol. 2014, 5, 1836–1841, doi:10.3762/bjnano.5.194

• the other hand, Figure 5a and Figure 5b show that both the response time and recovery time of the ZnSe nanowires at room temperature towards 5 ppm NO2 gas tend to decrease with the UV illumination intensity. These high responses at room temperature highlight the strong influence of UV irradiation on

• sensing performance could be enhanced when used at room temperature under UV illumination. The response of the ZnSe nanowires increased from 0 to ≈234% with increasing UV illumination intensity from 0 to 1.2 mW/cm2 and the response time and recovery time of the ZnSe nanowires tended to decrease with

Effects of palladium on the optical and hydrogen sensing characteristics of Pd-doped ZnO nanoparticles

• Anh-Thu Thi Do,
• Hong Thai Giang,
• Thu Thi Do,
• Ngan Quang Pham and
• Giang Truong Ho

Beilstein J. Nanotechnol. 2014, 5, 1261–1267, doi:10.3762/bjnano.5.140

• smaller than a concentration value of 1 vol % (ca. 10,000 ppm). Figure 6 shows the characteristic of the sensor response to the H2 concentration of 25% LEL at 250 °C. The results show that the response time of the sensor is in the range of 10–20 s and the recovery time is around 10 s. Thus, this sensor is

Highly NO₂ sensitive caesium doped graphene oxide conductometric sensors

• Carlo Piloto,
• Marco Notarianni,
• Mahnaz Shafiei,
• Elena Taran,
• Dilini Galpaya,
• Cheng Yan and
• Nunzio Motta

Beilstein J. Nanotechnol. 2014, 5, 1073–1081, doi:10.3762/bjnano.5.120

• exposure to 0.091, 0.18, 0.36, 0.732 and 1.44 ppm NO2 are shown in Figure 6b. The GO-Cs sensor reacts after few tens of seconds to the NO2 even at very low concentrations, down to 180 ppb. In terms of recovery time, for concentrations below 1 ppm, few minute exposures to dry air is enough to restore the

• original resistivity value. For higher concentrations, the recovery is longer, suggesting that the amount of Cs doping can be optimized to make a balance between the sensitivity and recovery time. This is in agreement with what observed by other researchers [25][46]. As shown in Figure 6c, the GO-Cs sensor

• , response and recovery time. (a) Low magnification and (b) high magnification SEM images of graphite oxide flakes. AFM and KPFM images of (a) and (b) a GO flake (2 × 2 μm); (c) and (d) a GO-Cs flake (1.4 × 1.4 μm). (a) XPS survey spectrum of GO (blue line) and GO-Cs (red line); High resolution XPS C1s

Gas sensing with gold-decorated vertically aligned carbon nanotubes

• Prasantha R. Mudimela,
• Mattia Scardamaglia,
• Oriol González-León,
• Nicolas Reckinger,
• Rony Snyders,
• Eduard Llobet,
• Carla Bittencourt and
• Jean-François Colomer

Beilstein J. Nanotechnol. 2014, 5, 910–918, doi:10.3762/bjnano.5.104

• room temperature), prompt response, short recovery time and reasonable reversibility and stability [2][3][4][6]. A further advance in the development of CNT gas sensing devices was the use of vertically aligned CNTs (VA-CNTs). In this case the sensing device benefits from the unidirectional electrical

Conducting composite materials from the biopolymer kappa-carrageenan and carbon nanotubes

• Ali Aldalbahi,
• Jin Chu,
• Peter Feng and
• Marc in het Panhuis

Beilstein J. Nanotechnol. 2012, 3, 415–427, doi:10.3762/bjnano.3.48

• that the change of gas concentration was instantaneous, which is a prerequisite condition for the accurate measurements of response and recovery time of the sensor. Effect of increasing concentration on (a) the viscosity and (b) the shear stress versus shear rate of KC solutions. The lines in (a) and