Microbial Contamination of Photographic and Cinematographic Materials in Archival Funds in the Czech Republic

In this study we investigated the microbial contamination of 126 samples of photographic and cinematographic materials from 10 archival funds in the Czech Republic. Microorganisms were isolated from the light-sensitive layer by swabbing it with a polyurethane sponge. Microbial isolates were identified by MALDI-TOF MS (bacteria) or by phenotype testing and microscopy (fungi). Bacterial contamination was more abundant and more diverse than fungal contamination, and both were significantly associated with archives. The most frequently isolated fungal genera were Cladosporium, Eurotium, Penicillium, Aspergillus and Alternaria. The most frequently isolated bacteria were Gram-positive genera such as Staphylococcus, Micrococcus, Kocuria, Streptococcus and Bacillus. This bacterial and fungal diversity suggests that air is the main vehicle of contamination. We also analysed the impact of the type of material used for the carrier (paper, baryta paper, cellulose acetate and nitrate or glass) or the light-sensitive layer (albumen, gelatine, collodion and other) on the level and diversity of microbial contamination. Carriers such as polyester and cellulose nitrate may have a negative impact on bacterial contamination, while paper and baryta paper may have a partially positive impact on both fungal and bacterial contamination.

A Study on the Interface Diffusion of In2O3/ITO Multilayer Thin-Film Thermocouple

In2O3/ITO multilayer thin film thermocouple is a new type of semiconductor thin-film thermocouple, which has broad application prospects. The interface diffusion between the layers is the main cause of its thermal oxidation failure. In this paper, an interface diffusion model of multilayer films is established based on Fick's second law. A sample of In2O3/ITO thin-film thermocouple was prepared, then designed and conducted high temperature test. According to the test results, the diffusion of substances between the film layers was analyzed. Based on the established interface diffusion model, a simulation calculation is carried out. The influence of interface diffusion on the life of In2O3 and ITO sensitive layer was quantitatively analyzed.

Improving the Sensitivity of Chipless RFID Sensors: The Case of a Low-Humidity Sensor

This study is supposed to introduce a valid strategy for increasing the sensitivity of chipless radio frequency identification (RFID) encoders. The idea is to properly select the dielectric substrate in order to enhance the contribution of the sensitive layer and to maximize the frequency shift of the resonance peak. The specific case of a chipless sensor suitable for the detection of humidity in low-humidity regimes will be investigated both with numerical and experimental tests.

NH3 Sensor Based on rGO-PANI Composite with Improved Sensitivity

This work reports on a reduced graphene oxide and poly(aniline) composite (rGO-PANI), with rGO clusters inserted between PANI chains. These clusters were formed due the plasticizing effect of N-methyl-2-pyrrolidone (NMP) solvent, which was added during the synthesis. Further, this composite was processed as thin film onto an interdigitated electrode array and used as the sensitive layer for ammonia gas, presenting sensitivity of 250% at 100 ppm, a response time of 97 s, and a lowest detection limit of 5 ppm. The PANI deprotonation process, upon exposure to NH3, rGO, also contributed by improving the sensitivity due its higher surface area and the presence of carboxylic acids. This allowed for the interaction between the hydrogen of NH3 (nucleophilic character) and the -COOH groups (electrophilic character) from the rGO surface, thereby introducing a promising sensing composite for amine-based gases.

Electrode Modified with Tin(IV) Oxide Nanoparticles and Surfactants as Sensitive Sensor for Hesperidin

Tin(IV) oxide nanoparticles in combination with surfactants were used as a sensitive layer in a sensor for hesperidin. The effect of the surfactant’s nature and concentration on the hesperidin response was evaluated. The best parameters were registered in the case of 500 µM cetylpyridinium bromide (CPB) as a dispersive agent. The SEM and electrochemical data confirmed the increase in sensor surface effective area and electron transfer rate. The sensor gave a linear response to hesperidin in the ranges of 0.10–10 and 10–75 µM with a detection limit of 77 nM. The approach was successfully tested on orange juices and validated using ultra-HPLC.

Ternary Oxidized Carbon Nanohorns/TiO2/PVP Nanohybrid as Sensitive Layer for Chemoresistive Humidity Sensor

The relative humidity (RH) sensing response of a chemoresistive sensor using a novel ternary hybrid nanocomposite film as a sensing element is presented. The sensitive layer was obtained by employing the drop-casting technique for depositing a thin film of nanocomposite between the electrodes of an interdigitated (IDT) structure. The sensing support structure consists of an IDT dual-comb structure fabricated on a oSi-SiO2 substrate. The IDT comprises chromium, as an adhesion layer (10 nm thickness), and a gold layer (100 nm thickness). The sensing capability of a novel thin film based on a ternary hybrid made of oxidated carbon nanohorns–titanium dioxide–polyvinylpyrrolidone (CNHox/TiO2/PVP) nanocomposite was investigated by applying a direct current with known intensity between the two electrodes of the sensing structure, and measuring the resulting voltage difference, while varying the RH from 0% to 100% in a humid nitrogen atmosphere. The ternary hybrid-based thin film’s resistance increased when the sensors were exposed to relative humidity ranging from 0 to 100%. It was found that the performance of the new chemoresistive sensor is consistent with that of the capacitive commercial sensor used as a benchmark. Raman spectroscopy was used to provide information on the composition of the sensing layer and on potential interactions between constituents. Several sensing mechanisms were considered and discussed, based on the interaction of water molecules with each component of the ternary nanohybrid. The sensing results obtained lead to the conclusion that the synergic effect of the p-type semiconductor behavior of the CNHox and the PVP swelling process plays a pivotal role in the overall resistance decrease of the sensitive film.

Low Power Multisensors for Selective Gas Detection

The aim of this work is the realization of a generic gas multisensor device based on MOX sensitive layer. We designed and modeled a novel detection system with several heating zones associated with three sensors supported on a membrane with a few micrometers of thickness. The design was optimized to overcome the problems of response stability and selectivity and to reduce power consumption. The heat repartition and the power consumption in relation to the membrane thickness were studied by finite element simulations. The results show that a membrane thickness of 4 µm decreases the heater temperature by more than 100 K versus 2 µm thickness. Ethanol detection performances were studied. The thermoelectrical characterization concluded that the three detection areas can be heated at 533 K with a power of 53 mW. One sensor was tested in ethanol. The sensor response in 1 ppm and 100 ppm of ethanol in a 50% relative humidity atmosphere was 1.4 and 9.2, respectively. We demonstrated that this detection device can detect ethanol with high sensitivity and stability in dry and humid air with reduced power consumption resulting in 18 mW per sensor.

A room-temperature ultrasonic hydrogen sensor based on a sensitive layer of reduced graphene oxide

It is challenging to increase the sensitivity of a hydrogen sensor operating at room temperature due to weak sorption and tiny mass of hydrogen. In this work, an ultrasonic sensor is presented for detecting hydrogen, which is composed of a 128° YX-LiNbO3 substrate and a reduced graphene oxide (RGO) sensitive layer with a platinum catalyzer. By optimizing the depositing parameters of RGO and platinum, a considerably high sensitivity is achieved at room temperature. A frequency shift of 308.9 kHz is obtained in 100 ppm hydrogen mixed with argon, and a frequency shift of 24.4 kHz is obtained in 1000 ppm hydrogen mixed in synthetic air. It is demonstrated that in addition to strong sorption of the sensitive layer, the coaction of mass load and conductivity variation is key to high sensitivity of the sensor. By establishing the original conductivity of the sensitive layer within the “conductivity window” for enhancing electrical response, we improve the sensitivity of the ultrasonic sensor, which is available for detecting hydrogen with an extremely low concentration of 5 ppm.