Two-dimension Array/hydrogel Composites With High Diffraction Intensity As Visual Sensors

The reported two-dimension (2D) array/hydrogel composites sensors have been limited to 2D monolayer polystyrene (PS) colloidal arrays, which have relatively weak diffraction intensity. The high reflective mirrors, such as A1 or Au mirror, were applied on such 2D colloidal crystal array/hydrogel composites sensors and the diffraction intensity was increased to some extent during the diffraction measurement and color identification process. This limited the practical applications of 2D array/hydrogel composites as visual sensor. In order to increase the diffraction intensity of 2D array/hydrogel composites sensors, the free standing 2D PS colloidal array/hydrogel composite films attached 2D PS colloidal arrays on hydrogel double surfaces,2D PS microsphere with Au shells array/hydrogel composite films and 2D Au nanosphere array/hydrogel composite films have been prepared and their enhanced optical diffraction have been investigated.(1) A free-standing 2D PS colloidal array/hydrogel composite film attached 2D PS colloidal array on its double surfaces was developed by s simple strategy, which could be acted as visual sensors with high diffraction intensity. The diffraction intensity of the hydrogel film attached 2D PS colloidal array on their double surfaces was stronger than the one that attached 2D colloidal array only to one surface due to multi-diffraction effect. Additionally, the colloidal array/hydrogel composite film attached 2D PS colloidal array on its double surfaces can overcome curly phenomenon of traditional hydrogel films loaded with colloidal monolayer on one side due to the balanced stress on their both surfaces. Such sensing hydrogel composite films with anti-curling performance and enhanced optical diffraction intensity are highly helpful to improve them to practical applications in visual detection.(2) A free-standing 2D PS microsphere array with Au nanoshells/hydrogel composite sensing film was prepared by attaching a 2D PS microsphere array with Au nanoshells onto a polyacrylic acid (PAAc) hydrogel film, which could be acted as visual sensors with high diffraction intensity. The 2D PS microsphere array with Au nanoshells was prepared by deposited a layer of Au on 2D PS microsphere array. The diffraction intensity of the 2D PS microsphere array with Au nanoshells/hydrogel composite was increased by about 30-fold than that of the 2D PS microsphere array/hydrogel composite film on the transparent substrate.(3) A free-standing 2D Au nanosphere array/PAAc hydrogel composite sensing film was prepared by attaching a 2D Au nanosphere array onto a PAAc hydrogel film, which could be used as visual sensors. These 2D Au nanosphere array/PAAc hydrogel composite films displayed visually diffraction color and much stronger diffraction intensity due to their periodic structures and large scattering cross section of Au nanosphere. Their diffraction intensity on quartz slide was increased by more than one order of magnitude (about 88 times) than that of 2D PS microsphere array/PAAc hydrogel composite film on Al miror to external stimuli, which solve the problem that 2D array/PAAc hydrogel composite films as visual sensors need high reflective mirrors. Such sensing hydrogel composite films with the strong diffraction signal are highly helpful to improve them to practical applications in visual detection. Additionally, the presented strategy could be extended to develop different visual sensors based on various functional hydrogel films.(4) 2D Au nanosphere array/poly(acrylamide-co-3-acrylamidophenylboronic acid) (P(AAm-co-PBA)) hydrogel composite films were prepared to detect glucose and HF acid. Analytes could be detected by the shift of diffraction wavelength and color change caused by volume change of hydrogel film. In glucose detection at high ionic strength, the problem that the diffraction peak blue-shifted first and then red-shifted with the increase of glucose concentraction was solved by using poly(vinyl alcohol) (PVA) as a volume resetting agent to secondary cross-link P(AAm-co-PBA) hydrogel film. Additonally,2D Au nanosphere array/P(AAm-co-PBA) hydrogel composite films have a good sensitivity to HF acid. They display color change (blue, green, red) with the increase of HF acid concentration form 0 mM to 7.0 mM and large shift of diffraction wavelength (from 481 nm to 921 nm, above 440 run) with the increase of HF acid concentration form 0 mM to 56.3 mM.A general summary about this thesis and the prospects for further work are presented.