As banned veterinary drugs, many pesticides, including malachite green (MG), pose a risk of carcinogenesis. Due to its low price and strong antiseptic qualities, MG has been used illegally in fisheries. As a result, MG residues are usually detected in fresh fish. To evaluate MG residues, currently, approaches include high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS) and other methods are used, and the detections are performed using a small volume of aquaculture water. However, such traditional detections rely on large and expensive equipment, which are cumbersome, and their processes are complicated, time-consuming and expensive. Consequently, these traditional methods cannot meet the needs of on-site detection of pesticides in markets, which are with features of large circulation, fast speed and low price. In recent years, with the emergence of surface-enhanced Raman scattering SERS) and portable Raman spectrometers, a rapid on-site detection method for trace pesticide molecules becomes possible. Herein, the SERS technology uses surface plasmon of metallic nanostructures to sense molecules located nearby, thus obtaining information of molecular species and concentrations. In order to achieve an extremely low limit of detection(LOD), generally, the coffee ring effect or other means are used on SERS substrates to enrich molecules into a certain region sufficiently. When a droplet contact the substrate for a hydrophilic substrate, the liquid spreads on the surface, leading to a long perimeter of its coffee ring and a decrease in molecular distribution concentration. While when a superhydrophobic substrate is used for molecule enrichment, due to its small surface adhesion, droplets are unable to be fixed and would roll on the surface, thus shall significantly increase the difficulty of operation. Taking detection of trace residues of MG molecule as an example, due to the noisy environment caused by people in the market, collisions occur from time to time, and due to the lack of professional experiment platforms in the market, it is not desirable to use a superhydrophobic SERS substrate to detect pesticide molecules under this condition. A SERS substrate based on parahydrophobic nanostructures is proposed for rapid on-site trace detection of MG molecules in this work. Compared with previous superhydrophobic substrates, parahydrophobic substrates presented herein is able to firmly grasp droplets to be measured, which perfectly solves the problem that in on-site detections, droplets roll on conventional supehydrophobic substrates. In addition, compared with the hydrophilic substrates, due to a large contact angle of the parahydrophobic substrate, the area of the coffee ring can be reduced by 5. 73 times, thus enriching concentration of the molecules can be largely increased, which as a result, can ultimately reduce LOD by at least two orders of magnitude. In short, the parahydrophobic SERS substrate proposed in this work is expected to be applied in rapid on-site detections of trace pesticide molecules.

Surface-enhanced Raman scattering (SERS) devices with advantages of being non-destructive, ultra-sensitive, and real-time are of significance. For now, most SERS devices are constructed on non-transparent substrates. When such non-transparent SERS devices are used to detect analytes with high concentrations, laser can only be incident from their front-sides. It means that incident laser needs to penetrate analyte molecules to reach metallic nanostructures at the bottom, so laser energy used to excite surface plasmon resonance (SPR) of metallic nanostructures is attenuated, and accordingly, SERS spectral signals are also attenuated; besides, SERS spectral signals cannot be efficiently returned to the charge-coupled device (CCD) due to the blocking of analyte molecules, so that the signals are greatly reduced and in some cases, they cannot be detected at all. In contrast, when a transparent SERS device is adopted, the analyte molecules are placed on front-side of the device and Raman laser is incident from the back-side. In this way, analyte molecules with high concentration have minimal influence on incident laser and SERS spectral signals, so better spectral signals can be obtained. In this work, a polyimide(PI) layer was spin-coated on a quartz substrate, and then the substrate was bombarded by oxygen plasma without masks. After that, nanofiber masks were formed on the quartz substrate. Later on, quartz nanocone forests were formed by a reactive-ion-etching (RIE) step. Subsequently, metallic nanoparticles were sputtered on the nanocones, thus, a transparent SERS device was obtained. For this SERS transparent device, Raman laser can be incident from front-side and back-side of the device during the test. The preliminary experimental results showed that for Rhodamine 6G (R6G), in a concentration range of 10(-3) similar to 10(-6) mol . L-1, the SERS spectra from the back-side were with higher intensities than those from the front-side. In addition, repeatability of the device detected from the back-side was further studied. These results demonstrated the feasibility of the device in practical biochemical detection applications. This work is expected to extend the applications of SERS technique in the field of analyte detections.

In this work, a pattern-free and high-throughput droplet platform with low reagent consumption, and applicable for on-site preliminary screening of ions is proposed. The droplet platform is composed of nanowire-nanopillar double-layer forests with features of superhydrophobicity and high adhesion, and it can tightly capture analyte droplets with a large contact angle. The platform is fabricated simply by plasma-treating of polyimide, silicon etching, and decoration of hexamethyldisilazane (HMDS) molecules. Based on such a droplet platform, detection of chromium ions through chromogenic reaction is successfully realized. It is expected that such a platform can be used for on-site ion screening with various concentrations and species.

In this work, a surface-enhanced Raman scattering (SERS)-active droplet with three-dimensional (3D) hot spots prepared from a superhydrophobic SERS substrate, which is inspired by the nut wizard strategy, was developed for ultrasensitive detection in complex liquid environments. The SERS substrate was composed of silver-capped parylene C-coated carbon nanoparticles (Ag-PC@CNPs). Such a SERS substrate was prepared by candle-soot deposition to provide a porous carbon nanoparticle layer followed by deposition of a parylene C film to protect the CNPs and then sputtering of silver nanoparticles. Similar to a nut wizard, a droplet rolling on the Ag-PC@CNP-coated substrate picked up the Ag-PC@CNPs. In this way, a self-concentrated and extremely sensitive SERS-active droplet sensor with 3D hot spots was formed. The sensor did not require precise laser focusing and showed relatively high repeatability and much higher sensitivity than those of a corresponding SERS substrate with two-dimensional hot spots. The sensor also achieved high sensitivity and specificity in complex liquid environments; in addition, bovine serum albumin with a concentration as low as 1 pM can be achieved. Consequently, an extremely simple, flexible, and highly sensitive SERS detection technique applicable to liquid biopsy analysis is anticipated.

In this work, a biomimetic chip with patterned wettability, capable of harvesting fog and detecting trace molecules in the fog is proposed. Such a chip consists of micropatterns of nanofiber forests on a silicon substrate, and it is prepared using an extremely simple process composed of only photolithography and plasma treatment. Due to condensation-assisted wetting of the superhydrophilic nanofiber forest micropatterns, such a chip can achieve fluorescence analysis of molecules with a concentration down to 10 -8 M. It is expected that such a chip can achieve real-time and highly sensitive detection of fog quality in fields of medical diagnosis and environmental monitoring.

In this work, a crystal-clear SERS-droplet is proposed, inside of which hot-spots are evenly distributed in three-dimension. Such a droplet is prepared by rolling an aqueous droplet on a superhydrophobic SERS substrate composed of carbon nanoparticles (CNPs) and their protecting nanolayer of Parylene C (PC). Such a CNP-PC stacked SERS substrate is fabricated simply by flame deposition of CNPs, chemical vapor deposition of a PC nanolayer, and noble-metal sputtering. Due to the three-dimensional (3D) distribution of hot-spots, such a SERS-droplet is about 18.5 times more sensitive than a similar SERS substrate involving only two-dimensional hot-spots, and achieves an enhancement factor as large as 6.6 ×10 7 . Besides, ascribe to even distribution of the hot-spots, the SERS-droplet has a relatively high repeatability.

In this work, quartz nanocone forests are prepared by adopting two steps of reactive ion etchings. Subsequently, metal nanoparticles are sputtered on the nanocone forests, thus a transparent surface-enhanced Raman scattering (SERS) device is obtained. With such a transparent SERS device, laser can be incident from back-side of the device, thus is able to avoid influence of cap layers, fluids and analyte molecules on laser propagation and signal collections. In addition, ascribe to excellent light transmittance of the quartz substrate, spectra from the back-side show even higher intensity than those from the front-side, especially at conditions of large analyte concentrations. This indicates a way to broaden detection ranges for microfluidic SERS devices.

In this work, transparent nanowire forests(NWFs) with different morphologies and densities are fabricated using silane coupling agent(SCA) as a promotor and regulator in a plasma repolymerization technique. The NWFs prepared in two-dimensional surface microchannels are with a large surface area and show superhydrophilicity, leading to a strong ability of liquid self-driving and biomolecule capturing; As is demonstrated, when the NWFs are integrated on a transparent substrate for bio-detections, light can be incident from their back sides to stimulate and collect signals without requirement of complex optical path systems. Besides, the NWF-based bio-detection devices have much higher fluorescence intensity than conventional immunochromatographic test strips, implying applications of the transparent self-driving devices in fast and ultra-sensitive bio-detections.