A novel and highly sensitive nanocatalytic surface plasmon resonance-scattering analytical platform for detection of trace Pb ions

Highly Ordered, Plasmonic Enhanced Inverse Opal Photonic Crystal for Ultrasensitive Detection of Staphylococcal Enterotoxin B

Although there is considerable interest in self-assembly of ordered, porous "inverse opal" structures for optical, electronic, and chemical applications, uncontrolled defect formation limits the usefulness of such materials. Herein, we develop a highly ordered and plasmonic enhanced sensing inverse opal photonic crystal (IOPC) material. The co-assembly of the colloidal template with the matrix material avoids the need for liquid penetration into the preassembled colloidal crystals and minimizes the associated rupture and inhomogeneity of the resulting IOPC. Au nanoparticles (Au NPs) not only act as a "bridge" between recognition elements (aptamers) and IOPCs, but also can amplify optical signals. Furthermore, the enhancement mechanism of Au NPs is simulated by COMSOL. During the detection process, the optical signal of the sensing Au-Apt IOPC responds to the Staphylococcal enterotoxin B with a concentration ranging from 10^-2 to 10³ pg mL^-1, and the limit of detection is 2.820 fg mL^-1. Spiked real sample detection indicates that the as-proposed method possessed good accuracy. The sensing Au-Apt IOPC provides an extensive biosensor platform to detect a variety of toxic and harmful substances through replacing the aptamer by other recognition elements, such as antibodies or receptors.

Fullerol Nanocatalysis and Trimodal Surface Plasmon Resonance for the Determination of Isocarbophos

Fullerol (C₆₀OH) has been shown to catalyze the trisodium citrate (TSC)-silver nitrate reaction to generate Ag nanoparticles (AgNPs). These AgNPs exhibit significant nanoplasmic surface-enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS), and absorption (Abs). When an aptamer (Apt) adsorbs on the C₆₀OH surface, catalysis is inhibited, and the intensities of SERS, RRS, and Abs decrease. In the presence of isocarbophos (IPS), Apt forms a stable complex (Apt-IPS) and releases C₆₀OH. As a result, SERS, RRS, and Abs intensities increase with increasing IPS concentration. Accordingly, a new SERS, RRS, and Abs trimodal method using Apt-labeled fullerol was established for the determination of IPS. Of the three spectral methods, SERS was the most sensitive, while the Abs method was the most cost-effective.

A dual-model SERS and RRS analytical platform for Pb(II) based on Ag-doped carbon dot catalytic amplification and aptamer regulation

Several carbon dots doping with diferent elements (Ca, Ag, Au) were fabricated and their catalytic properties had been investigated in this paper. It was found that the Ag-doped carbon dots (CDAg) had played a role of mimic enzyme on the reaction of HAuCl4-H2O2 and generated nanogold particles with surface enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) effects. The aptamer (Apt) can be adsorbed on the CDAg surface and cause the catalysis weakening. When the target Pb(II) was added, it would combine with the Apt to produce firm complexes Pb-Apt and desorb CDAg, which caused its catalytic effect restore. The formed nanogold had a strong RRS peak (at 375 nm) and a high SERS peak (at 1615 cm-1) in the presence of molecular probe (Victoria blue B, VBB). The dual-model signals of SERS and RRS increased linearly with Pb(II) concentration increase within the scope of 0.006-0.46 μmol/L and 0.01-0.46 μmol/L. And their detection limits respectively were 0.0032 μmol/L and 0.0048 μmol/L Pb(II).

A simple gold nanoplasmonic SERS method for trace Hg2+ based on aptamer-regulating graphene oxide catalysis

The as-prepared graphene oxide (GO) exhibited a strong catalytic effect on reduction of HAuCl₄ by trisodium citrate to form gold nanoplasmons (AuNPs) with a strong surface-enhanced Raman scattering (SERS) effect at 1615 cm^-1 in the presence of molecular probe Victoria blue 4R (VB4r). SERS intensity increased with nanocatalyst GO concentration due to the formation of more AuNP substrates. The aptamer (Apt) of Hg²⁺ can bind to GO to form Apt-GO complexes, which can strongly inhibit nanocatalysis. When target Hg²⁺ is present, the formed stable Hg²⁺ -Apt complexes are separated from the GO surface, which leads to GO catalysis recovery. The enhanced SERS signal was linear to Hg²⁺ concentration in the range 0.25-10 nmol/L, with a detection limit of 0.08 nmol/L Hg²⁺ . Thus, a new gold nanoplasmon molecular spectral analysis platform was established for detecting Hg²⁺ , based on Apt regulation of GO nanocatalysis.

Colorimetric sensor for cimetidine detection in human urine based on d-xylose protected gold nanoparticles

A simple, novel, and rapid colorimetric sensor for cimetidine (Cim) detection based on d-xylose protected gold nanoparticles (d-x@AuNPs) has been developed for the first time.

DNAzyme sensors for detection of metal ions in the environment and imaging them in living cells

The on-site and real-time detection of metal ions is important for environmental monitoring and for understanding the impact of metal ions on human health. However, developing sensors selective for a wide range of metal ions that can work in the complex matrices of untreated samples and cells presents significant challenges. To meet these challenges, DNAzymes, an emerging class of metal ion-dependent enzymes selective for almost any metal ion, have been functionalized with fluorophores, nanoparticles and other imaging agents and incorporated into sensors for the detection of metal ions in environmental samples and for imaging metal ions in living cells. Herein, we highlight the recent developments of DNAzyme-based fluorescent, colorimetric, SERS, electrochemical and electrochemiluminscent sensors for metal ions for these applications.

SERS spectral study of HAuCl4-cysteine nanocatalytic reaction and its application for detection of heparin sodium with label-free VB4r molecular probe

In the presence of nanocatalyst, L-cysteine reduce HAuCl₄ rapidly to form gold nanoparticles (AuNP), and a quick nanocatalytic preparation procedure was established for Au/AuNP sol with highly active surface enhanced Raman scattering (SERS) effect and good stability. The nanoreaction was also studied by absorption, resonance Rayleigh scattering (RRS), transmission electron microscopy (TEM) and energy spectra. In the selected conditions, the analyte heparin sodium (HS) could react with victoria blue 4 R (VB4r) to form associated complexes which have very weak SERS effect to make the SERS signals decrease. The SERS signals at 1617 cm⁻¹ reduced linearly with HS concentration increasing. Upon addition of FeCl₃, it hydrolyzed to form stable Fe(OH)₃ sol platform that carried SERS active Au/AuNPs to enhance the sensitivity. Accordingly, we established a SERS quantitative analysis method in the sol substrate of Fe(OH)₃-Au/AuNPs, with a linear range of 0.5–75 ng/mL HS and a detection limit of 0.2 ng/mL. HS in real samples was determined, with a relative standard deviation of 2.65–7.63% and a recovery of 99.3–101%.