Traditional seawater chemical oxygen demand (COD) monitoring methods are based on manual operations, which require various operating procedures and long duration of measurement, are prone to secondary pollution and hence unsuitable for in-situ monitoring. In this paper, we developed a prototype of in-situ seawater COD monitoring sensor based on UV-Vis absorption spectroscopy, and integrating it to a buoy for coastal trials. During the trials, several measures were applied to reduce the influence of biofouling, including coating sensor housing with an environment-friendly anti-fouling paint, and designing a motorized underwater wiper for optical window cleaning. The in-situ COD sensor had been continuously working underwater for more than 6 months, obtaining 1536 sets of seawater UV-Vis absorption sectrum.
We developed two underwater fluorimeters (VIS&UV) for in-situ assessments of aquatic fluorescence constituents. Two prototypes had been developed to assess chlorophyll a and BOD5, respectively, and were deployed under a buoy platform for long-term field tests. Design considerations include exciting light use efficiency, weak fluorescence signal detection, ambient light suppression, corrosion resistance and anti-biofouling. The prototypes demonstrated excellent linearity in response to fluorescence emissions in laboratory calibrations and good environment suitability during the field tests. We had obtained a large amount of observational data and maintenance experience.
Suspension assay using optically color-encoded microbeads is a novel way to increase the reaction speed and multiplex
of biomolecular detection and analysis. To boost the detection speed, a hyperspectral imaging (HSI) system is of great
interest for quickly decoding the color codes of the microcarriers. Imaging Fourier transform spectrometer (IFTS) is a
potential candidate for this task due to its advantages in HSI measurement. However, conventional IFTS is only popular
in IR spectral bands because it is easier to track its scanning mirror position in longer wavelengths so that the
fundamental Nyquist criterion can be satisfied when sampling the interferograms; the sampling mechanism for shorter
wavelengths IFTS used to be very sophisticated, high-cost and bulky. In order to overcome this handicap and take better
usage of its advantages for HSI applications, a new wide spectral range IFTS platform is proposed based on an optical
beam-folding position-tracking technique. This simple technique has successfully extended the spectral range of an IFTS
to cover 350-1000nm. Test results prove that the system has achieved good spectral and spatial resolving performances
with instrumentation flexibilities. Accurate and fast measurement results on novel colloidal photonic crystal microbeads
also demonstrate its practical potential for high-throughput and multiplex suspension molecular assays.
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