An ultraviolet-enhanced
(UV-enhanced) nitric oxide (NO) sensor
based on silver-doped zinc oxide (ZnO) nanoflowers is developed using
a low-cost hydrothermal method. The results indicate that silver (Ag)
ions were doped into the ZnO nanostructure successfully, thus changing
the morphology. In the high-resolution transmission electron microscopy
images, we also found that some Ag ions were separated out onto the
surface of the ZnO nanoflowers and that the Ag-doped and Ag nanoparticles
improved the sensing property. The NO sensing property increased from
73.91 to 89.04% through the use of a UV light-emitting diode (UV-LED).
The response time was approximately 120 s without the UV-LED, and
the UV-enhanced Ag-doped ZnO nanoflower sensor exhibited a reduced
response time (60 s). The best working temperature could be reduced
from 200 to 150 °C using UV light illumination, and it was found
that the NO response increased by 15.13% at 150 °C. The UV photoresponse
of the Ag-doped ZnO nanoflowers and the mechanisms by which the improvement
of NO sensing property occurred through the use of UV light illumination
are discussed. The property of the gas sensor can be calibrated using
a self-photoelectric effect under UV light illumination. These interesting
UV-enhanced Ag-doped ZnO nanoflowers are viable candidates for practical
applications.
In this study, metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors (PDs) based on Cu-doped ZnO (CZO) nanorods (NRs) were fabricated and investigated. The CZO NRs were prepared on a Corning glass substrate by the chemical bath deposition (CBD) method with photolithography processes. It was found that the diameter and length of ZnO NRs increased with Cu-doped concentration. The X-ray diffraction (XRD) analysis showed that the growth of NR arrays along the c-axis was hexagonal wurtzite crystal. Compared with pure ZnO NRs, it can be seen that the main UV peak (378 nm) of photoluminescence (PL) spectra showed a blue-shift phenomenon with the increase of Cu-doped concentration. Additionally, it was found that the rise and recovery time of such a fabricated PD were shortened under the UV illumination. The UV sensing properties of the CZO PDs were improved since the trapping and de-trapping of electrons by Cu-related complexes were faster than the adsorption and desorption of oxygen molecules. With a 3 V applied bias and 380 nm UV illumination, the optimal sensitivity of our PDs is 196.6.
In this study, a flexible and stable
pH sensor based on aluminum-doped zinc oxide nanosheets (Al-doped
ZnO NSs) was developed by a low-cost hydrothermal method. The results
obtained from this study indicated that Al ions could be doped successfully
into the ZnO nanostructure, which could change the morphology and
improve the pH-sensing properties. The pH sensitivity of Al-doped
ZnO nanosheets reached 50.2 mV/pH with a correlation coefficient of
around 0.99468 when compared with that of ZnO film (34.13 mV/pH) and
pure ZnO nanowires (45.89 mV/pH). The test range of pH values was
widened by Al-doping, and the Al-doped ZnO NS sensor could detect
the pH value ranging from 2 to 12. It was observed that in a more
acidic environment, especially at pH 2, the sensor, Al-doped ZnO nanosheet,
was strongly stable over 12 weeks of testing. It was noted that the
response time was utterly fast and the response time of the sensors
for each pH standard buffer solutions was around 0.3 s. Thus, the
response time and performance were quite stable. The microchannel
provided a novel testing method for the pH sensor, where the liquid
to be tested was just 5 mL. Hence, it was suggested to be useful for
many medical diagnoses and treatments. The benefits of Al-doped ZnO
nanosheet pH sensor were high sensitivity, good long-term usage, good
flexible property, and requirement of a small amount of test liquid,
which could make the sensors viable candidates for practical applications.
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