Chloroauric acid trihydrate (HAuCl4?3H2O), HMIs and neverless 11-mercaptoundecanoic acid (MUA, Figure 2) were obtained from Sigma (St. Louis, MO, USA). Deionized water (18.2 M��) produced by the Milli-Q system was used throughout the experiments.Figure Inhibitors,Modulators,Libraries 2.11-Mercaptoundecanoic acid (MUA) molecule (C11H22O2S).2.2. Preparation of Au NanoparticlesFifteen (15) nm Au nanoparticles (AuNPs) were prepared by citrate reduction of HAuCl4 which is similar to Grabar’s method [20]. 1% trisodium citrate solution (4 mL) was added to a boiling solution of HAuCl4 (99 mL deionized water and 1 mL 1% HAuCl4). The mixture was kept boiling and stirring for about 30 min until the color of the aqueous change from yellow to red. After that, the solution was cooled to room temperature while being stirred continuously and then the prepared AuNPs was stored at 4 ��C.
2.3. Modification of AuNPsThe modification of AuNPs with 11-mercaptoundecanoc acid (MUA-AuNPs) was carried out mainly as reported [18] with some changes as follows: aqueous solution Inhibitors,Modulators,Libraries (500 ��L) consisting of MUA (2.4 mM) and an equivalent amount of sodium hydroxide (2.4 mM) were added to 15 nm Au nanoparticle suspension (500 ��L). The mixed solution was stirred with the speed of 450 rpm in 80 ��C for 1 h on the Thermo mixer (Eppendorf, Hamburg, Germany). After cooling down to room temperature, the mixture was centrifuged twice (10,000 rpm, 10 mins, 4 ��C) and the supernatant was replaced with deionized water.2.4. Fabrication of Microfluidic ChipsMicrofluidic chips with Y shape and zigzag microchannels were firstly fabricated according to standard photolithographic methods [21].
Then a negative master was prepared Inhibitors,Modulators,Libraries on the silicon wafer by SU-8 photoresist, and a plasma etcher was used to realize the passivation of the master. The prepared master Inhibitors,Modulators,Libraries was placed in a glass bottom dish. After that, PDMS prepolymer (10:1 v/v mixture) was degassed and cast onto the master. After heating for 2 h at 80 ��C, the PDMS was removed from the substrate and the holes punched with corresponding metal pipes. We used a flat PDMS slab (3 mm thick) as the substrate that bonding with the prepared PDMS layer to form the channels for chemical reaction. The dimensions of the finished microchannels in the chip are 100 ��m (width) �� 30 ��m (height), and the whole chip are 3.5 cm (width) �� 5 cm (length).2.5.
Preparation and Inletting of the RegentAfter degassing at 10 kPa for 1 h, the microfluidic chip was Anacetrapib immediately sealed with adhesive tape except for the inlet reservoirs to be ready for Pb2+ detection. The MUA modified AuNPs and different test samples were added into two inlet reservoirs using micropipette.3.?Results and Discussions3.1. Colorimetric Analysis in SolutionOur AuNP-based HMI sensor was based selleck inhibitor on the colour change caused by the surface plasmon resonance effect on AuNP aggregation.