A new SERS quantitative analysis strategy for ultratrace chloramphenicol with Fe3O4@MIP nanocatalytic probe.

Three functional magnetic nanocatalytic probe, which integrates recognition, catalytic amplification, and separation enrichment, is a new approach to construct a simple, fast, highly selective, and sensitive analytical method. In this article, a new magnetic nanosurface molecularly imprinted polymer nanoprobe (Fe3O4@MIP) with trifunctionality was rapidly prepared using a microwave-assisted method with magnetic Fe3O4 nanoparticles as a substrate, chloramphenicol (CAP) as a template molecule, and methacrylic acid as a functional monomer. The characterized nanoprobe was found that could specifically recognize CAP, strongly catalyze the new indicator nanoreaction of fructose (DF)-HAuCl4. The gold nanoparticles (AuNPs) exhibit strong resonance Rayleigh scattering (RRS) and surface enhanced Raman scattering (SERS) effects. Upon addition of CAP, the SERS/RRS signals were linearly weakened. Accordingly, a new SERS/RRS analysis platform for highly sensitive and selective determination of CAP was constructed. The SERS linear range was 0.0125-0.1 nmol/L, with detection limit (DL) of 0.004 nmol/L CAP. Furthermore, it could be combined with magnet-enriched separation to further improve the sensitivity, with a DL of 0.04 pmol/L CAP. The SERS method has been used for the determination of CAP in real samples, with relative standard deviations of 2.37-9.89 % and the recovery of 95.24-107.1 %.

A new strategy for RRS-based determination of phosphate with a bifunctional Fe3O4 magnetic nanoparticle surface molecularly imprinted polydopamine probe.

In this paper, a magnetic nanoparticle surface molecularly imprinted polydopamine RRS probe Fe3O4@MIP was prepared using phosphomolybdic acid (PMo) as the template, Fe3O4 magnetic nanoparticles as the substrate and dopamine hydrochloride (PD) as the monomer and crosslinking agent for the determination of PO43-. Under acidic conditions, phosphomolybdic acid is formed by the reaction of PO43- with ammonium molybdate (MSA), which can be imprinted with the Fe3O4@MIP probe surface and reduced to phosphomolybdic blue (PMoB) by ascorbic acid (Aa). Strong resonance Rayleigh scattering energy transfer (RRS-ET) occurs between the probe and PMoB, resulting in a decrease in the RRS signal value. A new, simple and selective RRS method for the determination of PO43- in water samples was developed. The linear range of this method is 1-22.5 µmol L-1, and the detection limit (DL) is 0.49 µmol L-1. Furthermore, the magnetic enrichment ability of Fe3O4@MIP is discussed. Experimental data show that even 0.2 µmol L-1 of phosphate can be detected within a 20% error range.

A new surface molecularly imprinted polyacrylamide nanoprobe for trace Cr(VI) with RRS technique.

This article was used potassium dichromate as the template molecule, silver nanoclusters as the nano matrix, acrylamide as the monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent, and azodiisobutyronitrile (AIBN) as the initiator to prepare a new silver nanocluster surface MIP (AgNCs@MIP) nanoprobe for chromate. Upon addition of Cr(VI), it selectively adsorbs on the surface of AgNCs@MIP nanoprobes. The dichromate ion absorption peak at 350 nm overlaps with the AgNCs@MIP RRS peak at 370 nm, resulting in strong RRS energy transfer (RRS-ET) and a decrease in the RRS intensity. The decreased RRS intensity is directly proportional to the concentration of dichromate ions in the range of 0.0025-0.015 µmol/L, with a detection limit of 0.8 nmol/L. Therefore, a simple, fast, sensitive and selective RRS method for the determination of trace Cr(VI) in mineral water has been established, with a relative standard deviation of 9.2-9.8 % and recovery of 95.20 %-103.60 %.

A Dimode Scattering Method for Ultratrace Dinitrofuran Detection with Nanopalladium Molecularly Imprinted Polymer Nanocatalytic Probe.

With four nanoparticles as the nanomatrix, dinotefuran (DNF) as the template molecule, N-isopropylacrylamide as the functional monomer, trimethylolpropane and trimethacrylate as the cross-linker, four nanosurface molecularly imprinted polymer (MIP) bifunctional probes were prepared by microwave synthesis. It was found that palladium nanosurface MIP (Pd@MIP) not only recognized DNF but also had the strongest catalytic effect on the new nanogold indicator reaction of acrylic acid-HAuCl4, which was evaluated quickly with the slope procedure developed by us. The generated gold nanoparticles (AuNPs) not only possessed the resonance Rayleigh scattering (RRS) effect but also strong surface-enhanced Raman scattering (SERS) activity. The combination of Pd@MIP with DNF enhanced the catalytic effect by coupling the nanosurface electrons with π-electrons, thus enhancing both scattering signals. A new Pd@MIP nanoprobe catalytic-SERS/RRS dual-mode analytical platform was developed for the specific and sensitive detection of DNF. The linear ranges of the SERS and RRS methods were 0.075-0.75 and 0.1-0.75 nmol/L, and the limits of detection were 0.03 and 0.06 nmol/L, respectively. The standard deviations were 0.54-2.39%, and the recoveries were 93-105%.

A new PdMOF-loaded molecularly imprinted polyaniline nanocatalytic probe for ultratrace oxytetracycline with SERS technique.

In this paper, a new Pd metal organic framework (PdMOF) surface molecularly imprinted polyaniline nanocatalytic probe (PdMOF@MIP) with dual functions of recognition and catalysis was synthesized. It is found that the PdMOF@MIP nanoprobe can not only identify OTC but also catalyze the new nanoreaction of NaH2PO2-HAuCl4 to generate gold nanoparticles (AuNPs), and the generated AuNPs could be traced by surface-enhanced Raman scattering (SERS). When OTC specifically binds to PdMOF@MIP to generate PdMOF@MIP-OTC conjugate, its catalytic effect is weakened and the analytical signal is reduced linaerly. Accordingly, a new, highly sensitive, selective and simple SERS/RRS/Abs trimode detection platform for OTC was constructed. The linear range of SERS was 0.0625 ng/mL âˆ¼ 1.75 ng/mL and the limit of detection was 0.015 ng/mL. This new nanocatalytic probe detection strategy can also be used for the selective detection of other antibiotics such as tetracycline and doxycycline, respectively. In addition, the nanocatalytic mechanism has been investigated.

A new copper nanocluster surface molecular imprinted polymethacrylic acid probe for ultratrace trichlorophenol based on in situ-generated nanogold SPR effects.

A new coinage metal nanocluster surface molecularly imprinted polymethacrylic acid nanoprobe (NC@MIP) for the selective determination of 2,4,6-trichlorophenol (TCP) was prepared via microwave synthesis using 2,4,6-trichlorophenol as a template molecule, copper nanoclusters (CuNC) as a nanosubstrate, and methacrylic acid as a polymer monomer. It was found that the copper nanocluster MIP (CuNC@MIP) shows the strongest catalytic performance for the reduction of HAuCl4 by hydrazine hydrate for the on-site generation of gold nanoparticles (AuNPs) with the surface plasmon resonance (SPR) effects of resonance surface-enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) as well as absorption (Abs). When TCP was added, the CuNC@MIP nanoprobe and TCP-formed CuNC@MIP-TCP nanoenzyme with stronger catalytic activity generated more AuNPs, and the trimodal analytical signal was enhanced linearly. Therefore, a new SERS/RRS/Abs trimodal sensing platform for TCP was constructed, which was simple, rapid, sensitive, and selective. For each mode, the linear ranges were 0.0075-0.075, 0.010-0.10, and 0.010-0.10 nmol L-1, and the detection limits were 0.0010, 0.021, and 0.043 nmol L-1, respectively. The relative deviation of TCP in different water quality was 0.47%-2.5% and the recovery rate was 94.6%-108.6%.

A new and highly efficient CuMOF-based nanoenzyme and its application to the aptamer SERS/FL/RRS/Abs quadruple-mode analysis of ultratrace malachite green.

Malachite green (MG) is highly toxic, persistent, and carcinogenic, and its widespread use is a danger to the ecosystem and a threat to public health and food safety, making it necessary to develop new sensitive multimode molecular spectroscopy methods. In this work, a new copper-based nanomaterial (CuNM) was prepared by a high-temperature roasting using a copper metal-organic framework (CuMOF) as precursor. The as-prepared CuNM was characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), and BET surface area analysis. CuNM was found to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce the oxidation product TMBOX; however, subsequently, the MG aptamer (Apt) could be adsorbed on the CuNM surface by intermolecular interaction, which would inhibit the catalytic performance. After the addition of MG to be tested, the CuNM previously adsorbed by the Apt was transformed into its free state, thus restoring its catalytic activity. This new nanocatalytic indicator reaction could be monitored by surface-enhanced Raman scattering (SERS)/resonance Rayleigh scattering (RRS)/fluorescence (FL)/absorption (Abs) quadruple-mode methods. The SERS determination range was 0.004-0.4 nmol L-1 MG, with a limit of detection of 0.0032 nM. In this way, a rapid, stable, and sensitive method for the determination of MG residues in the environment was established.

A new N/Fe doped carbon dot nanosurface molecularly imprinted polymethacrylate nanoprobe for trace fipronil with SERS/RRS dimode technique.

The N and Fe doped carbon dot (CDNFe) was prepared by microwave procedure. Using CDNFe as the nano-substrate, fipronil (FL) as the template molecule and α-methacrylic acid as the functional monomer, the molecular imprinted polymethacrylic acid nanoprobe (CDNFe@MIP) with difunction was synthesized by microwave procedure. The CDNFe@MIP was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier infrared spectroscopy, and other techniques. The results show that the nanoprobe not only distinguish FL but also has a strong catalytic effect on the HAuCl4-Na2C2O4 nanogold indicator reaction. When the nanoprobes specifically recognize FL, their catalytic effect is significantly reduced. Since the AuNPs generated by HAuCl4 reduction have strong surface-enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) effects, a SERS/RRS dual-mode sensing platform for detecting 5-500 ng/L FL was constructed. The new analytical method was applied to detect FL in food samples with a relative standard deviation (RSD) of 3.3-8.1 % and a recovery rate of 94.6-104.5 %.

A novel highly active AgMOF-based silver single-atom catalyst and its application to the aptamer SERS/RRS for the determination of aflatoxin B1.

A novel highly active silver single-atom catalyst (AgSAC) was prepared by a microwave-assisted solvothermal method using silver covalent organic frameworks (AgMOF) as precursors. It was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared (IR), and surface-enhanced Raman scattering (SERS). The experiment found that AgSAC has excellent catalytic performance and can heavily catalyze the nano-reaction of chloroauric acid-malic acid (HAuCl4-H2Mi) to generate gold nanoparticles (AuNPs). The produced AuNPs have strong SERS, resonance Rayleigh scattering (RRS) and surface plasmon resonance absorption (Abs) signals. Aflatoxin B1 aptamer (AptAFB1) can be adsorbed to the surface of AgSAC through electrostatic interaction, to reduce the catalytic activity of AgSAC and the SERS/RRS/Abs signal of the system. When the target molecule (AFB1) was added, it will specifically bind to AptAFB1 and release AgSAC, restoring the catalytic activity of AgSAC, thereby restoring the SERS/RRS/Abs signal of the system. Based on this, a simple and sensitive aptamer sensing analysis platform for trace AFB1 was established, and a reasonable catalytic amplification mechanism of AgSAC was proposed. The SERS method exhibited the highest sensitivity, with a linear range of 0.005-0.225 µg/L and a detection limit of 0.002 µg/L.

A novel bifunctional molecularly imprinted polymer-based SERS/RRS dimode nanosensor for ultratrace acetamiprid.

A new acetamiprid (AP) molecularly imprinted polymer (MIP) nanosol was synthesized with α-methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinker and 2,2'-azobisisobutyronitrile as initiator, under the microwave irradiation. It was characterized by transmission electron microscopy, specific surface area and pore size analysis, and molecular spectroscopy. The bifunctional MIP nanomaterial not only had the recognition of AP but also had a strong catalysis of the nanogold dimode indicator reaction of chloroauric acid-dopamine. The generated gold nanoparticles (AuNPs) had strong surface-enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) effects, and the two kinds of signals enhanced linearly with imprinted molecule AP increasing. Accordingly, a novel SERS/RRS nanosensor platform was constructed to detect 0.25-20 pmol/L and 0.5-50 pmol/L AP by SERS and RRS monitoring respectively. Moreover, a reliable nanocatalytic mechanism was proposed.

Identification of the active compounds in the Yi-Fei-San-Jie formula using a comprehensive strategy based on cell extraction/UPLC-MS/MS, network pharmacology, and molecular biology techniques.

BACKGROUND: Chinese herbal formulae has multiple active constituents and targets, and the good clinical response is encouraging more scientists to explore the bio-active ingredients in such complex systems. Yi-Fei-San-Jie formula (YFSJF) is commonly used to treat patients with lung cancer in South China; however, its bio-active ingredients remain unknown. PURPOSE: We investigated the bio-active ingredients of the YFSJF using a novel comprehensive strategy. METHODS: A549 cell extraction coupled with ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS/MS) was used for the screening of potential bio-active ingredients. Network pharmacology approach and molecular dynamics simulation were performed for the screening of targets. Surface plasmon resonance (SPR) assay and molecular biology techniques were used to verify the targets. RESULTS: Nine A549 cell membrane-binding compounds were identified through cell extraction/UPLC-MS/MS. Five compounds, namely ginsenoside Ro, ginsenoside Rb1, ginsenoside Rc, peimisine, and peimine were cytotoxic to A549 cells, and they were considered the bio-active ingredients of the YFSJF in vitro. Network pharmacology analysis revealed that TGFBR2 is the key target and the TGFß pathway is the key pathway targeted by YFSJF in non-small cell lung cancer. Peimisine showed an affinity to TGFBR2 using molecular docking and dynamic stimulation, which was confirmed using surface plasmon resonance spectroscopy. The molecular biology-based analysis further confirmed that peimisine targets TGFBR2 and can reverse A549 epithelial-mesenchymal transition by inhibiting the TGFß pathway. CONCLUSION: Taken together, cell extraction/UPLC-MS/MS, network pharmacology, and molecular biology-based analysis comprise a feasible strategy to explore active ingredients in YFSJF.

A stable and sensitive Au metal organic frameworks resonance Rayleigh scattering nanoprobe for detection of SO3 2- in food based on fuchsin addition reaction.

A stable Au metal organic frameworks (AuMOF) nanosol was prepared. It was characterized by electron microscopy and molecular spectral techniques. In pH 6.8 PBS buffer solution, AuMOF nanoprobes exhibit a strong resonance Rayleigh scattering (RRS) peak at 330 nm. After basic fuchsin (BF) adsorbing on the surface of AuMOF, the RRS energy of the nanoprobe donor can be transferred to BF receptor, resulting in a decrease in the RRS intensity at 330 nm. Both sulfite and BF taken place an addition reaction to form a colorless product (SBF) that exhibit weak RRS energy transfer (RRS-ET) between AuMOF and SBF, resulting in the enhancement of the RRS peak. As the concentration of SO3 2-increases, the RRS peak is linearly enhanced. Thus, a new and sensitive RRS-ET method for the detection of SO3 2- (0.160-5.00 µmol/L) was developed accordingly using AuMOF as nanoprobes, with a detection limit of 0.0800 µmol/L. This new RRS method was applied to determination of SO3 2- in food and SO2 in air samples. The recoveries of food and air samples were 97.1-106% and 92.9-106%, and the relative standard deviation (RSD) was 2.10-4.80% and 2.10-4.50%, respectively.

Ti3C2@Pd nanocatalytic amplification-polypeptide SERS/RRS/Abs trimode biosensoring platformfor ultratrace trinitrotoluene.

A new MXene supported Pd nanoparticles (Ti3C2@Pd) nanosol with good stability and strong catalysis was prepared by the two-step procedure. Experiment was found that Ti3C2@Pd could strongly catalyze the reduction of HAuCl4 by H2O2 to produce gold nanoparticles (AuNPs), with strong surface enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS) and surface plasmon resonance absorption (Abs). Coupled this new SERS/RRS/Abs trimode nanocatalytic indicator reaction with specific TNT polypeptide (PTTNT), a facile and selective trimode polypeptide biosensoring platform was established for the detection of ultratrace TNT, with a linear range of 1.1-66, 1.1-66 and 4.4-66 pmol/L TNT, and detection limit (DL) of 0.69, 0.97 and 3.36 pmol/L by SERS, RRS and Abs assay respectively. It has been used to detect TNT in wastewater and soil samples, with recovery of 98.7-106% and RSD of 6.22-8.77%. In addition, this biosensoring platform can be also used to assay glyphosate and estradiol, respectively.

A cholesterol benzoate RRS probe for the determination of trace ammonium ions.

The measurement of NH4+ has attracted considerable attention with the increase of NH4+ emissions in sewage caused by human activities. So far, a variety of photometric and fluorescence methods for the detection of NH4+ have been researched and summarized, but there is no report about the use of liquid crystals (LCs) cholesteryl benzoate (CB) as a resonance Rayleigh scattering (RRS) probe to determine ammonium ions. In the NaAc-HAc buffer solution with pH = 4.80, the yellow compounds 3,5 diacetyl-1,4 dihydrolutidine (DDL) generated by the reaction of NH4+ with acetylacetone (AT) and formaldehyde (HCHO) act as the energy receiver and CB as the donor. Because the RRS spectrum of CB overlaps with the DDL absorption spectrum, resonance Rayleigh scattering energy transfer (RRS-ET) occurs. When the NH4+ concentration increased, the generated DDL increased, and the RRS-ET also increased, so the RRS intensity of the system at 395 nm decreased. For this reason, a fast and sensitive CB RRS-ET method was established to apply to the detection of NH4+ in water. The detection range was 1.00 × 10-3 - 4.66 µg/mL, and the detection limit was 6.62 × 10-3 µg/mL. Using this method to analyze and detect NH4+ in environmental water samples, the precision and recovery rate were between 1.30-9.30% and 95.5-109.9%, respectively. Therefore, this method has the advantages of sensitivity and simplicity.

A novel aptamer RRS assay platform for ultratrace melamine based on COF-loaded Pd nanocluster catalytic amplification.

Two COFs of BzBD and BzBD loaded Pd nanoclusters (BzBDPd) were prepared using 1,3,5-benzenetricarboxaldehyde (Bz), benzidine (BD) and CO reducing agent, and were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), infrared spectroscopy (IR) and other techniques. BzBDPd can strongly catalyze the new and stable Au@NiP nanoreaction that exhibit a strong resonance Rayleigh scattering (RRS) peak at 538 nm and a surface plasmon resonance (SPR) absorption peak at 395 nm, and the sensitive and facile RRS technique was used to study the indicator reaction. Combining the nanocatalytic amplification reaction with specific aptamer (Apt) of some target molecules such as melamine (ML), urea (UR) and bisphenol A (BPA), a simple, sensitive and selective Apt RRS assay platform was established. The linear range of the RRS detection platform for melamine is 0.0025-0.04 nmol/L, and the detection limit (DL) is 1.96 × 10-4 nmol/L. In addition, ML in real sample was analyzed, the stability of BzBD, BzBDPd, PdNPs and the catalytic mechanism of COFPd were also considered.

On-signal amplification of silver nanosol RRS/SERS aptamer detection of ultratrace urea by polystyrene nanosphere catalyst.

The catalytic amplification signal of polystyrene nanosphere (PN) is used to conveniently fabricate the resonance Rayleigh scattering (RRS)/surface-enhanced Raman scattering (SERS) dual-mode method to sensitively and selectively detect urea in food. PN has strong catalysis of the slow nanoreaction of citrate-Ag(I) to produce yellow silver nanoparticles (AgNP), which exhibit strong RRS effect and SERS effect with molecular probes. When aptamer (Apt) is present, the Apt is adsorbed on the PN surface, the catalysis is weakened, the AgNP is reduced, and the SERS/RRS signal is weakened. After adding urea to exhibit specific Aptamer reaction, the Apt is desorbed from the PN surface and the catalysis is restored. As urea increase, the desorbed PNs increase to produce more AgNPs indicator to increase SERS/RRS signal. The increase value △I of SERS/RRS is linearly to urea concentration. Therefore, a sensitive and selective SERS/RRS dual-mode method for urea is established based on aptamers-regulated the catalysis of PNs. This method is applied to the detection of urea in milk with satisfactory results. The relative standard deviation is 3.9-6.8% and the recovery rate is 94.5-102%.

Sensitive Aptamer SERS and RRS Assays for Trace Oxytetracycline Based on the Catalytic Amplification of CuNCs.

A new method for the determination of oxytetracycline (OTC) has been established by coupling the catalytic amplification reaction of copper nanoclusters (CuNCs) with the aptamer reaction. CuNCs prepared by a wet chemical method have the catalytic activity for the formation of gold nanoparticles (AuNPs) resulting from a HAuCl4-ethanol (En) reaction. The experimental results showed that OTC aptamer (Apt) can be adsorbed on the surface of CuNCs in a non-specific way, thus inhibiting its catalytic activity. When OTC was added to the solution, the OTC-Apt complex was generated by a specific reaction, which made the CuNCs desorb and restore their catalytic activity. With the increase of OTC, the recovery of the catalytic activity of CuNCs is strengthened, the reaction speed is accelerated, and the number of AuNPs is increased. The generated AuNPs exhibited surface enhanced Raman scattering (SERS) signals at 1615 cm-1 in the presence of Vitoria blue 4R (VB4R) molecular probes, and a resonance Rayleigh scattering (RRS) peak at 586 nm. There is a good linear relationship between the intensities of SERS, or RRS, and OTC concentration at the range of 37.5-300 ng/L or 37.5-225 ng/L, respectively. A new SERS and RRS assay for the determination of trace OTC based on the regulation of CuNCs catalysis was established.

Aptamer Turn-On SERS/RRS/Fluorescence Tri-mode Platform for Ultra-trace Urea Determination Using Fe/N-Doped Carbon Dots.

Sensitive and selective methods for the determination of urea in samples such as dairy products are important for quality control and health applications. Using ammonium ferric citrate as a precursor, Fe/N-codoped carbon dots (CDFeN) were prepared by a hydrothermal procedure and characterized in detail. CDFeN strongly catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to turn on an indicator molecular reaction, forming an oxidized tetramethylbenzidine (TMBox) probe with surface-enhanced Raman scattering, resonance Rayleigh scattering, and fluorescence (SERS, RRS, and FL) signals at 1,598 cm-1, 370 nm, and 405 nm, respectively. The urea aptamer (Apt) can turn off the indicator reaction to reduce the tri-signals, and the addition of urea turns on the indicator reaction to linearly enhance the SERS/RRS/FL intensity. Thus, a novel Apt turn-on tri-mode method was developed for the assay determination of ultra-trace urea with high sensitivity, good selectivity, and accuracy. Trace adenosine triphosphate and estradiol can also be determined by the Apt-CDFeN catalytic analytical platform.

Single-atom Fe catalytic amplification-gold nanosol SERS/RRS aptamer as platform for the quantification of trace pollutants.

Bisphenol A (BPA), as a typical endocrine disruptor, poses a serious threat to human health. Therefore, it is urgent to establish a rapid, sensitive, and simple method for the determination of BPA. In this paper, based on the aptamer-mediated single-atom Fe carbon dot catalyst (SAFe) catalyzing the HAuCl4-ethylene glycol (EG) nanoreaction, a new SERS/RRS di-mode detection method for BPA was established. The results show that SAFe exhibits a strong catalytic effect on the HAuCl4-EG nanoreaction, which could generate purple gold nanoparticles (AuNPs) with resonance Rayleigh scattering (RRS) signals and surface-enhanced Raman scattering (SERS) effects. After the addition of BPA aptamer (Apt), it could encapsulate SAFe through intermolecular interaction, thus inhibiting its catalytic action, resulting in the reduction of AuNPs generated and the decrease of RRS and SERS signals of the system. With the addition of BPA, Apt was specifically combined with BPA, and SAFe was re-released to restore the catalytic ability; the generated AuNPs increased. As a result of this RRS and SERS signals of the system recovered, and their increment was linear with the concentration of BPA. Thus, the quantification of 0.1-4.0 nM (RRS) and 0.1-12.0 nM (SERS) BPA was realized, and the detection limits were 0.08 nM and 0.03 nM, respectively. At the same time, we used molecular spectroscopy and electron microscopy to study the SAFe-HAuCl4-ethylene glycol indicator reaction, and proposed a reasonable SAFe catalytic reaction mechanism. Based on Apt-mediated SAFe catalysis gold nanoreaction amplification, a SERS/RRS di-mode analytical platform was established for targets such as BPA.

A nanosol SERS/RRS aptamer assay of trace cobalt(ii) by covalent organic framework BtPD-loaded nanogold catalytic amplification.

The determination of heavy metal ions has always been a hot topic in the field of environmental analysis. In this study, a new covalent organic framework-loaded gold nanoparticle (AuCOF) nanocatalytic amplification signal strategy was developed to determine trace Co2+ in water. The COF of BtPD was synthesized from 1,3,5-benzene tricarboxaldehyde and p-phenylenediamine, and a new kind of AuBtPD nanosol was prepared by reduction of HAuCl4 to AuNPs on the BtPD carrier. It has strong catalysis of the new indicator reaction of sodium formate reducing HAuCl4 to AuNP sol with strong resonance Rayleigh scattering (RRS) at 370 nm and surface enhanced resonance Raman scattering (SERS) activity at 1614 cm-1 in the presence of a Victoria blue 4R (VB4R) molecular probe. Combining the nanocatalytic reaction to amplify the dual-scattering signals and specific aptamer (Apt) of cobalt ions, a new, fast, stable, sensitive and specific dual mode method for detecting Co2+ was established; the RRS signal I 370nm and SERS signal I 1614cm-1 show a linear relationship with the concentration of 0.033-1 nmol L-1 Co2+ and with a limit of detection (LOD) of 0.02 nmol L-1. The two methods have been applied to the determination of Co2+ in industrial wastewater, tap water and river water, and the results are satisfactory.