Detection And Application Of Small Aldehydes Based On Photonic Crystal Sensing Films

Aldehydes are a kind of important chemical raw materials and widely used in industrial manufacture and daily life.However,they seriously threaten people's life and health due to their carcinogenicity and mutagenicity,such as formaldehyde,acetaldehyde,etc.Although the commonly used analytical methods,such as chromatography,electrochemical analysis,quartz crystal microbalance method,colorimetric and fluorimetric methods,can effectively detect aldehydes,they are mainly based on specialized analytical instruments and complicated to operate.In recent years,photonic crystals have been used as the sensing platform to realize the sensing and detection of different target molecules through photonic stopband manipulation or fluorescence enhancement effect.In this dissertation,high-efficiency detection of small aldehydes has been achieved by the photonic crystals sensing platform.It includes two aspects.First,the functionalized three-dimensional photonic crystal(PC)hydrogelis used as the sensing platform to realize the highly effective colorimetric detection of formaldehyde.The nucleophilic addition reaction between the modified amino group in the hydrogel network and the carbonyl group of the aldehyde changes the osmotic pressure of the hydrogel,thereby changing the volume of the hydrogel to swell or shrink.That causes an interspacing change of photonic crystal microspheres,resulting in the photonic stopband shift and the corresponding color change of the hydrogel film.The other one is that three-dimensional macroporous inverse opal PCs are used as sensing platform.Organic small molecules which can interact with aldehydes to produce fluorescent products are infiltrated into the voids of the inverse opals.Slow photon effect of PCs is used to enahce the fluorescence and high-efficiency fluorescence detection of formaldehyde and acetaldehyde has been realized.The main contents are as follows:1.The opal-type polystyrene-poly(acrylic acid-acrylamide)three-dimensional PC hydrogel film was prepared by the"sandwich"method,followed by modification with ethylenediamine to obtain a colorimetric sensing film that can efficiently detect formaldehyde.The amino group on the polymer chain of the PC hydrogel reacts with formaldehyde to increase the crosslink density of the hydrogel,resulting in volume shrinkage of the hydrogel and decrease in microsphere spacing of the PC.That causes the the blue shift of the photonic stopband and the color change of the hydrogel film,achieving the visual detection of formaldehyde.The hydrogel sensing film modified by 30 m M of ethylenediamine changes from dark red to cyan after 10 min and the maximum value of the stopband bule shift is 163 nm.The limit of detection(LOD)of 0.34 n M can be acquired.The PC hydrogel film realizes the highly selective and sensitive detection of formaldehyde,providing a method for the visual detection of formaldehyde in real life.2.The SiO₂ inverse opal PCs with a three-dimensional macroporous structure were fabricated by the sacrificial template method,followed by infiltration of a pyrene derivative PEA to obtain a formaldehyde-sensitive and fluorescence-enhanced PC sensing film.Utilizing the specific Aza-Cope rearrangement reaction of allylamine of PEA and formaldehyde to generate a strong fluorescent product emitted at 480 nm,we choosed a PC whose blue band edge of stopand overlapped with the fluorescence emission wavelength.By virtue of the fluorescence enhancement property derived from slow photon effect of PC,formaldehyde was detected higly selectively and sensitively(LOD,1.38 n M).Furthermore,the rapid detection of formaldehyde(within 1 min)is realized due to the interconnected three-dimensional macroporous structure of the inverse opal PC and its high specific surface area.The prepared sensing film can be used for the detection of formaldehyde in air and aquatic products.3.A naphthalimide derivative infiltrated(HBD)SiO₂ inverse opal PC fluorescent sensing film was constructed,provideing a multifunctional detection platform for formaldehyde and acetaldehyde in air,aquatic products and biological cells.The nucleophilic addition product between the amine group of the naphthimide derivative and aldehydes emit a strong fluorescence around 550 nm,which can selectively detect formaldehyde and acetaldehyde.The significant enhancement in fluorescence intensity is because the fluorescence wavelength is located at the blue band edge of the photonic stopband of the sample.The slow photon effect of the PC enhances the fluorescence and improves the detection sensitivity.The LODs of formaldehyde and acetaldehyde are 10.6n M and 7.3 n M,respectively,increasing 3 orders of magnitude compared with that in the solution system.Furthermore,the three-dimensional macroporous inverse opal structure allows the sensor to respond quickly within 1 minute.In addition,the prepared PC sensing film can be reused by simply cleaning in an acidic aqueous solution after response.Therefore,the prepared HBD-infiltrated SiO₂ inverse opal PC sensing film realizes rapid,highly sensitive,highly selective,and reversible detection of formaldehyde and acetaldehyde.It can be used as a multi-detection platform of formaldehyde and acetaldehyde in air,aqueous solutions and living cells.The fluorescence sensing method is based on organic small molecule functionalized PCs,and can be widely used in the development of different target analytes sensors by designing new functional organic compounds.