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The stable and highly catalytic Fe metal–organic framework (FeMOF) nanosol was prepared and characterized by electron microscopy, and energy and molecular spectral analysis. It was found that FeMOF strongly catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce TMBox, which had a fluorescence (FL) peak at 410 nm. When silver nanoparticles were added, it exhibited strong resonance Rayleigh scattering (RRS) activity and surface-enhanced Raman scattering (SERS) effect. This new FeMOF nanocatalytic trimode indicator reaction was combined with the glyphosate aptamer reaction to establish a new SERS/RRS/FL trimode biosensor for glyphosate. The sensor can be used for the analysis of environmental wastewater, and a new method for detecting glyphosate content in wastewater is proposed. The linear range of the sensor is 0.1–14 nmol/L, the detection limit is 0.05 nmol/L, the recovery is 92.1–97.5%, and the relative standard deviation is 3.6–8.7%. [ABSTRACT FROM AUTHOR]

A neodymium metal–organic framework (MOFNd) was prepared using 1H-pyrazole-3,5-dicarboxylic acid (H3pdc) and 2-pyrazinecarboxylic acid as ligands. Through the addition of HAuCl4 as a precursor and NaBH4 as a reducing agent, a new MOFNd-loaded nanogold (AuNPs) (Au@MOFNd) nanosol with good stability and high catalytic activity was conveniently prepared via a solvothermal-reduction method and characterized. It was found that the indicator reaction of reducing HAuCl4 by Na2SO3 to generate AuNPs was slow. Au@MOFNd strongly catalyzes this nanoreaction, and the produced AuNPs exhibit a strong resonance Rayleigh scattering (RRS) peak at 370 nm, and a strong surface-enhanced Raman scattering (SERS) peak at 1617 cm−1 with the addition of the molecular probe Victoria blue 4R (VB4r). A novel SERS/RRS di-mode quantitative analysis method for glyphosate (GLY) was established by coupling this new Au@MOFNd catalytic indicator reaction with the aptamer (Apt) reaction of GLY, with SERS and RRS detection limits of 0.02 nM and 0.3 nM, respectively. It has been applied to the analysis of soil samples with a recovery rate of 93.0%–106.5% and precision of 2.2%–4.1%, and the results were satisfactory. [ABSTRACT FROM AUTHOR]

A nanosurface molecular imprinted polymer nanoprobe (AuNC@MIP) for dichromate (Cr 2 O 7 2-) was synthesized by microwave irradiation, using gold nanoclusters (AuNC) as a nanosubstrate, Cr 2 O 7 2- as template molecule, 4-vinylpyridine (4-VP) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking, and 2,2′-azobisisobutyronitrile (AIBN) as initiator. It was characterized by molecular spectral technique, electron microscope and X-ray photoelectron spectroscopy. The nanoprobe was found to exhibit a strong resonance Rayleigh scattering (RRS) effect at 370 nm. In the presence of diphenylcarbazide (DPC), the RRS-energy transfer (RRS-ET) was enhanced with the increase of Cr 2 O 7 2- concentration, and the RRS signal intensity at 370 nm was decreased linearly, with a linear range of 2.5–75 nmol/L Cr 2 O 7 2- and the limit of detection (LOD) of 2.47 nmol/L. Accordingly, a new RRS-ET method for the simple, sensitive and selective detection of trace Cr 2 O 7 2- was developed. As a comparison, the nanosurface MIP probes were prepared with different particle-size nanoparticle gold (AuNP) substrate and different functional monomers. [Display omitted] • Gold nanocluster surface molecularly imprinted polymers was synthesized using the microwave irradiation. • AuNC@MIP binding to Cr 2 O 7 2- produces resonance Rayleigh scattering-energy transfer effect (RRS-ET) strongly. • A new RRS nanoprobe for trace Cr 2 O 7 2- was established. • The RRS method is simple, highly sensitive and selective. [ABSTRACT FROM AUTHOR]

In pH 3.1 HCOOH-HCOONa buffer solution, liquid crystal 5CB was used as the probe to generate a strong resonance Rayleigh scattering (RRS) peak at 450 nm. Gold nanoparticles (AuNPs) could catalyse the reaction of phosphomolybdic acid (PMo)-formic acid (FA) to form phosphomolybdenum blue (PMoB), which caused the RRS strength of PMo at 450 nm to decrease linearly. Hg2+ could have an electrostatic substitution reaction with AuNPs, thereby inhibiting the catalytic effect of AuNPs, and the RRS peak was enhanced. In the range of 2.5 × 10−9 mol/L–4.5 × 10−8 mol/L Hg2+, as the concentration of Hg2+ increased, the catalytic effect of AuNPs gradually weakened, and the peak value of RRS at 450 nm (ΔI) was linearly increased. The regression equation is ΔI450nm = 27.988C−5.6159, and the detection limit is 1.0 nmol/L. The method has been used to detect Hg2+ in wastewater with satisfactory results. [ABSTRACT FROM AUTHOR]

AbstractNanosurface-imprinted polymer nanoprobes (Fe3O4@MIP) were prepared by microwave synthesis using Fe3O4 as a nanosubstrate, aspirin as a template, α-methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent, and 2,2'-azobisisobutyronitrile (AIBN) as an initiator. Characterization of Fe3O4@MIP revealed that the spectral probe exhibited strong resonance Rayleigh scattering (RRS) for aspirin. With the increase in aspirin concentration, the RRS energy transfer (RRS-ET) was enhanced, and the signal at 370 nm decreased, providing a linear range from 0.25 to 12.5 μmol/L and a detection limit (DL) of 0.08 μmol/L. The developed protocol was used for the determination of aspirin in drugs with recoveries from 93.2 to 102.6. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Liquid crystal nanosurface imprinted polymers were prepared by microwave procedure. • CBU@MIP not only recognized ML but also catalyzed the new nanogold indicator reaction of HAuCl 4 -SF. • A SERS and RRS dimode analytical platform was established for ultratrace ML. • The SERS/RRS platform has high sensitivity, selectivity and accuracy. In this paper, a new dimode scattering spectral method for rapid detection of ultratrace melamine (ML) in dairy products was established by coupling nanosurface molecular imprinting technology with nanocatalytic amplification reaction of liquid crystal particles. It was found that liquid crystal cholesteryl butyrate (CBU) nanosurface imprinted polymers (CBU@MIP) not only recognized ML but also catalyzed the nano indicator reaction of HAuCl 4 -sodium formate to produce gold nanoparticles with surface-enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) effect. When ML was added, it specifically combined with CBU@MIP to form CBU@MIP-ML conjugates with strong catalytic activity, and SERS and RRS signals increased linearly with the detection limits of 0.0072 pmol/L and 0.093 pmol/L respectively. The method was applied to the determination of ML in dairy products and plastic tablewares with relative standard deviation (RSD) of 2.2–4.4 % and 1.6–4.7 %, and recovery of 95.4 %-108.3 % and 95.9–108.6 % respectively. [ABSTRACT FROM AUTHOR]

The development of rapid, simple, and highly sensitive analytical methods for detecting pesticide residues is crucial for safeguarding the environment and human health. In this study, MXeneTi 3 C 2 Tx nanosheets are used to load a titanium-based metal-organic framework (Ti-MOFs) and imidacloprid peptide (PT IMI), and a novel bifunctional nanoprobe (TN@Ti-MOFs/PT) is prepared by irradiation in a domestic microwave oven and stirring at room temperature. Powder X-ray diffraction, transmission electron microscope and Fourier transform infrared spectrometer are used to characterize the prepared nanomaterials. It is found that TN@Ti-MOFs/PT not only specifically recognizes imidacloprid (IMI), but also catalyzes the nanogold indicator reaction to generate gold nanoparticles (AuNP) in an 80 ℃ constant temperature water bath. The generated AuNP can be directly used as an optical probe for resonance Rayleigh scattering (RRS) at wavelength of 370 nm. In the presence of the Victoria blue 4 R molecule probe, it shows a robust surface enhanced Raman scattering (SERS) signal at wavelength number of 1617 cm−1. When the target molecule IMI is added, it can interact with the PT IMI specific base sequence, resulting in PT chain shedding from the TN@Ti-MOFs/PT nanoprobe surface, exposing abundant redox sites and accelerating the redox charge transfer, resulting in AuNP increase and SERS/RRS signal enhancement. As a result, a highly sensitive and specific PT-based dual-mode biosensing platform is developed for the detection of trace IMI, with a linear range of 0.01–0.25 ng/mL and a detection limit of 0.0011 and 0.0039 ng/mL by SERS and RRS assays, respectively. To demonstrate its practical application, the platform is used to detect IMI in vegetable samples, with relative deviations of 1.36–5.86% and recoveries of 95.0–107%. Additionally, the mechanism of nanocatalysis enhancement is also investigated. [Display omitted] • TN@Ti-MOFs could strongly catalyzed the GLA-HAuCl 4 indicator reaction. • The TN@Ti-MOFs/PT nanoprobe possessed catalytic and recognition properties. • A novel SERS/RRS dual-mold assay platform for imidacloprid was constructed. • The nanocatalytic enhancement mechanism of TN@Ti-MOFs was investigated. [ABSTRACT FROM AUTHOR]

Co-doped carbon dots are new multifunctional carbon nanomaterials. Their fast preparation and new analytical applications such as in continuous detection and resonance Rayleigh scattering (RRS) probes are of interest to people. Herein, the N/Au co-doped carbon dots (CDN/Au) were prepared quickly by a microwave synthesis method using fructose as the carbon source and urea and HAuCl4 as dopants, and it exhibited an excellent RRS effect at 555 nm. Based on both silicate (SiO32−) and phosphate (PO43−) reacting with ammonium molybdate to form silicomolybdate heteropoly acid (SiMo) and phosphomolybdate heteropoly acid (PMo), PMo decomposed by the addition of citric acid, and SiMo/PMo combined with CDN/Au to show good RRS analytical properties, and a new strategy was developed to detect SiO32− and PO43− by the CDN/Au probes continuously. With the increase of SiO32− (PO43−), SiMo (PMo) reacted with CDN/Au probes to form more big particles which resulted in the RRS intensity enhancement at 555 nm, and had a good linear relationship with the SiO32− (PO43−) concentration in the range of 1.11 μg L−1–19.98 μg L−1, with detection limits of 0.3 μg L−1 SiO32− and 0.3 μg L−1 PO43−. Accordingly, a new RRS method was established for continuous detection of SiO32− and PO43− using CDN/Au as the probe. [ABSTRACT FROM AUTHOR]

The stable Cu 2 O nanocubic (Cu 2 ONC) sol was prepared, based on graphene oxide (GO) catalysis of glucose-Fehling's reagent reaction, and its absorption and resonance Rayleigh scattering (RRS) spectra, transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were examined. Using the as-prepared Cu 2 ONC as RRS probe, and coupling with the neomycin sulfate (NEO) complex reaction, a new, simple, sensitive and selective RRS-energy transfer (RRS-ET) method was established for detection of neomycin sulfate, with a linear range of 1.4–112 μM and a detection limit of 0.4 μM. The method has been applied to the detection of neomycin sulfate in samples with satisfactory results. [ABSTRACT FROM AUTHOR]

The stable silver nanorod (AgNR) sol in red was prepared by the two-step procedure of NaBH 4 –H 2 O 2 and citrate heating reduction, and it exhibited a strong resonance Rayleigh scattering (RRS) peak at 346 nm. In pH 3.8 HAc–NaAc buffer solution, tea polyphenols (TP) reacted with ammonium molybdate (AM) to form yellow organic molybdate (OM) as receptor that was closed to the donor of AgNR, the RRS energy transfer (RRS-ET) takes place, owing to the overlapping between the AgNR RRS spectra and OM absorption spectra. When TP concentration increased, the RRS intensity decreased due to the RRS-ET increasing. So, a simple and sensitive AgNR surface plasmon RRS-ET analytical platform was fabricated to detect trace TP in the range of 0.05–0.85 μg/mL, with a detection limit of 0.03 μg/mL TP. The TP in tea samples was analyzed by this RRS-ET analysis platform, with satisfactory results. [ABSTRACT FROM AUTHOR]

In the KOH medium, the as-prepared gold nanorods (AuNR) were aggregated to AuNR aggregates that exhibited strong resonance Rayleigh scattering (RRS) at 440 nm. Formaldehyde reacted with 4-amino-3-hydrazino-5-mercap-1,2,4-triazole (AHMT) to form a purplish red compound 6-mercapto-S-triazole [4,3-b]-S-tetrazole with strong hydrophobic ability that as receptors were closed to the surfaces of AuNR aggregates as donors. When the system was irradiated, the RRS-energy transfer (RRS-ET) takes place, which results in the RRS signal quenching at 440 nm. With the increase of formaldehyde concentration, the formed receptors increased, and the RRS intensity quenched linearly at 440 nm due to the RRS-energy transfer enhancing. The quenched intensity responds linearly with formaldehyde concentration in the range of 0.25-48 μmol/L. Thus, a new AuNR surface plasmon RRS-ET method was developed for the determination of trace formaldehyde, with satisfactory results. [ABSTRACT FROM AUTHOR]

In pH 4.0 acetate buffer solution, fluorine ions react with fluorine reagent (FR) and La(III) to generate blue ternary complex that exhibited strong absorption at about 370 nm. Upon addition of graphene oxide/nanogold (GO/NG) as resonance Rayleigh scattering (RRS) spectral probe with strong RRS peak at 370 nm, the color changed to gray, and the RRS intensity decreased with the increase of fluorine ion concentration due to the RRS energy transfer (RRSET) from GO/NG to the complex. Under the selected condition, the decreased RRS peak Δ I 370nm was linear to fluorine ion concentration in the range of 6.0 × 10 −8 –1.3 × 10 −5 mol/L, with a detection limit of 3.0 × 10 −8 mol/L F − . This RRSET method was applied to the analysis of fluorine in toothpaste and water samples, with satisfactory results. [ABSTRACT FROM AUTHOR]

Highly sensitive and selective resonance Rayleigh scattering (RRS) and surface enhanced resonance Raman scattering (SERRS) spectral detection technique are developed by combining the functional nucleic acid including aptamer and DNAzyme, and nanoparticle such as gold/silver (NG/NS) aggregation and catalysis reaction. The recent progress of resonance scattering spectral technologies including RRS and SERRS are reviewed in this paper. [ABSTRACT FROM AUTHOR]

In pH 7.2 Tris-HCl buffer solution, the substrate strand DNA (SDNA) was hybridized to the enzyme strand DNA (EDNA) forming a double strand DNA (dsDNA). The SDNA in dsDNA could be cleaved by lead(II) to release a cleavaged single-stranded (ssDNA) that prevented the gold nanoparticles (AuNPs) from forming a stable AuNPs-ssDNA conjugate. The unconjugated AuNPs were aggregated to form AuNP aggregation (AuNPsA) that appeared as a resonance Rayleigh scattering (RS) peak at 532 nm. When the lead(II) concentration increased, the AuNPs-ssDNA increased, the AuNPsA decreased, the color changed from blue to red, and the RS intensity at 532 nm decreased. The decreased RS intensity ΔI 532 nm was linear to the lead(II) concentration in the range of 0.67–60 nmol/L, with a detection limit of 0.3 nmol/L. The AuNPs-ssDNA exhibited a strong catalytic effect on the reaction between chloroauric acid and vitamin C (VC) that can be detected by an RS method at 620 nm. When the lead(II) concentration increased, the intensity at 620 nm increased, and the increased intensity ΔI 620 nm was linear to the lead(II) concentration in the range of 1.33–120 pmol/L, with a detection limit of 0.5 pmol/L. The proposed method was applied to detect lead(II) in water samples, with satisfactory results. [ABSTRACT FROM AUTHOR]

The aptamer (ssDNA) was used to label nanogold (NG) particle to fabricate an aptamer-nanogold (NGssDNA) probe for melamine. The probe was stabile in pH 6.6 NaHPO-NaHPO buffer solutions and in the presence of high concentration of electrolyte. Upon addition of melamine, it interacted with the probe to form big NGssDNA-melamine aggregations that led to the resonance Rayleigh scattering (RRS) intensity at 566 nm increased greatly. The increased RRS intensity (ΔI) is linear to melamine concentration in the range of 1.89-81.98 μg/L, with a detection limit of 0.98 μg/L melamine. The unreacted probe in the aptamer reaction solution exhibited strong catalytic effect on the slow CuO particle reaction between glucose and Fehling reagent, but the catalytic activity of NG aggregations is very weak. When melamine concentration increased, the unreacted probe decreased, the RRS peak intensity at 614 nm decreased. The decreased RS intensity is linear to melamine concentration in the range of 0.63-47.30 ng/L melamine, with a detection limit of 0.38 ng/L. The aptamer-modified nanogold catalytic RRS assay was applied to determination of melamine in milk, with high sensitivity and selectivity, simplicity and rapidity. [ABSTRACT FROM AUTHOR]

In this paper, dicyandiamide (Dd) and p-benzaldehyde (Bd) were heated at 180 °C for 3 h to prepare a new type of stable covalent organic framework (COF) DdBd nanosol with high catalysis. It was characterized by molecular spectroscopy and electron microscopy. The study found that DdBd had a strong catalytic effect on the new indicator reaction of polyethylene glycol 600 (PEG600)-chloroauric acid to form gold nanoparticles (AuNPs). AuNPs have strong resonance Rayleigh scattering (RRS) activity, and in the presence of Victoria Blue B (VBB) molecular probes, they also have a strong surface-enhanced Raman scattering (SERS) effect. Combined with a highly selective oxytetracycline (OTC) aptamer (Apt) reaction, new dual-mode scattering SERS/RRS methods were developed to quantitatively analyze ultratrace OTC. The linear range of RRS is 3.00 × 10−3 –6.00 × 10−2 nmol/L, the detection limit is 1.1 × 10−3 nmol/L, the linear range of SERS is 3.00 × 10−3–7.00 × 10−2 nmol/L, and the detection limit is 9.0 × 10−4 nmol/L. Using the SERS method to analyze OTC in soil samples, the relative standard deviation is 1.35–4.78%, and the recovery rate is 94.3–104.9%. [ABSTRACT FROM AUTHOR]

Using citric acid (CA) and ethylenediamine (EDA) as precursors, stable nitrogen-doped carbon dots (CD) nanosols were prepared by microwave procedure and characterized in detail. It was found that CDNs catalyze ethanol (Et)-HAuCl4 to generate gold nanoparticles (AuNPs), which have strong surface plasmon resonance, Rayleigh scattering, (RRS) and a surface plasmon resonance (SPR) absorption (Abs) effect at 370 nm and 575 nm, respectively. Compled the new catalytic amplification indicator reaction with the specific As3+ aptamer reaction, a new RRS/Abs dual-mode aptamer sensor for the assay of trace As3+ was developed, based on the RRS/Abs signals increasing linearly with As3+ increasing in the ranges of 5–250 nmol/L and 50−250 nmol/L, whose detection limits were 0.8 nmol/L and 3.4 nmol/L As3+, respectively. This analytical method has the advantages of high selectivity, simplicity, and rapidity, and it has been successfully applied to the detection of practical samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel magnetic nanosurface MIP nanoprobe (Fe 3 O 4 @MIP) was synthesized. • Fe 3 O 4 @MIP efficiently catalyzed the AuNP reaction of HAuCl 4 -fructose. • A sensitive SERS/RRS dimode method was established with Fe 3 O 4 @MIP probe. • Fe 3 O 4 @MIP can be separated by magnet, to improve the sensitivity. 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 (Fe 3 O 4 @MIP) with trifunctionality was rapidly prepared using a microwave-assisted method with magnetic Fe 3 O 4 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)-HAuCl 4. 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 %. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is a commonly poisonous gas. It is important to detect CO in daily life. Herein, a new and sensitive surface enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) coupled di-mode method was developed for CO, based on gold nano-enzyme catalysis and gold nanoprobes. CO can react with HAuCl4 to generate gold nanoparticles (AuNPs) in pH 5.2 HAc-NaAc buffer. The generated AuNPs exhibited SERS activity at 1620 cm−1 in the presence of Vitoria blue B (VBB) molecular probes, and an RRS peak at 290 nm. Based on the AuNP bifunctional probes, the increased SERS and RRS intensities respond linearly with the concentration of CO in the range of 100–1500 ng/mL and 30–5230 ng/mL, respectively. To improve the sensitivity, the produced AuNPs were used as nano-enzyme catalysts for the new indicator reaction of HAuCl4-ethanol (En) to amplify the signal. The sensitive SERS method was coupled with the accurate RRS method to develop a sensitive and accurate SERS/RRS di-mode method for determination of 3.0–413 ng/mL CO, based on the AuNP-HAuCl4-En nanocatalytic reaction and its product of AuNPs as SERS and RRS bifunctional probes. [ABSTRACT FROM AUTHOR]

Carbon dots doped with N/Ce, N/Eu and N/Tb were prepared by a microwave based hydrothermal technique. The fluorescence of the N/Ce co-doped carbon dots (CDN/Ce) is strongest. They have excitation/emission maxima at 340/441 nm. CDN/Ce was characterized by scanning electron microscopy, infrared and fluorescence spectroscopy. On addition of the nucleic acid aptamer (Apt) against arsenic(III) in pH 7 solution, the blue fluorescence of the doped carbon dots is partially quenched due to electrostatic interaction. On addition of As(III), it will bind to the aptamer, and the carbon dots are released. Hence, fluorescence becomes gradually restored. In addition, the resonance Rayleigh scattering signal (measured at 340 nm) is reduced. This dual-mode assay works in the 0.5–5.8 μg·L−1 As(III) concentration range and has a 0.2 μg·L−1 detection limit. [ABSTRACT FROM AUTHOR]

[Display omitted] • COF-PTAuNC with recognition and catalytic amplification di-function was prepared. • COF-PTAuNC exhibits strong catalysis of the AuNP trimode indicator reaction. • A new nanocatalytic amplification-tetramode biosensor was established for Cd2+. • The method is simple, sensitive and selective. Nanoclusters (NCs) have extremely strong catalytic activity, but their stability is poor. Loading them on covalent-organic framework (COF) not only increase their stability but also hold strong catalysis. Furthermore, COF-loaded peptide nanoclusters have attracted wide spread attention due to specific recognition, strong catalytic amplification and good stability. Cd2+ was one of important metal of pollution, and it is of great significance to explore new peptide assay for Cd2+. This study was synthesized COF-loaded peptide AuNC (COF-PTAuNC) nanoprobes with recognition and catalysis functions using the peptide Csy-Pro-Pro-Cys-Trp-NH 2 (PT) as a template. The experiment found that COF-PTAuNC not only recognize Cd2+ but also had a strong catalytic effect on the indicator reaction of HAuCl 4 -sodium formate (Fo) to produce gold nanoparticles (AuNPs) to amplify the signal. The AuNPs has an absorption (Abs), resonance Rayleigh scattering (RRS) and surface enhanced Raman scattering (SERS) peak at 533 nm, 370 nm and 1618 cm−1 respectively. Using this new strategy, the concentration of Cd2+ in the range of 0.4–50 nmol/L had a linear relationship with the SERS intensity, and the detection limit (DL) was 0.16 nmol/L. This method has been used to detect Cd2+ content in water and rice samples, with recovery and relative standard deviation(RSD) of 91.8–109.8% and 1.2–8.7%, respectively. [ABSTRACT FROM AUTHOR]

In this experiment, using MXene quantum dot (MQD) as the core and thiamethoxam (TMX) as the template, a dual-functional surface molecularly imprinted polymer nanoprobe (MQD@MIP) for detecting of TMX was synthesized by microwave digestion procedure. And MQD@MIP was characterized in detail. It was found that this nanoprobe had dual function, which not only could specifically recognize TMX, but also could strongly catalyze the new indicator reaction of HAuCl 4 -maleic acid to produce gold nanoparticles (AuNPs). The AuNPs exhibit strong surface enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS) and surface plasmon resonance absorption (Abs) effect. Based on this, a new SERS/RRS/Abs trimode biosensoring platform was constructed for the determination of TMX, with a linear range of 1.0–150, 1.0–150, and 5.0–125 nmol/L TMX, and detection limit of 0.57 nmo/L, 0.84 nmol/L and 3.5 nmol/L, respectively. As a comparison, we used carbon dots (CDs) as the core to prepare surface molecularly imprinted polymers (CD@MIP) nanoprobe, and investigated the catalytic effect on the nanogold indicator reaction and the specific recognition effect on TMX. • MXene quantum dots were rapidly prepared by microwave irradiation. • A dual-functional nanosurface imprinted polymer nanoprobe was synthesized. • The nanoproble catalyze the new indicator reaction to generate AuNPs. • A new trimode biosensoring platform was established for determination of trace TMX. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Stable and highly catalytic MIP was prepared by microwave procedure. • A new HAuCl 4 -DA-MIP nanocatalytic indicator reaction with di-scattering monitoring was discovered. • The MIP had both catalytic and recognition properties. • A novel SERS/RRS dimode nanosensor was constructed. [ABSTRACT FROM AUTHOR]

The as-prepared gold nanoparticle (AuNP) exhibited strong catalysis of the nanoreaction between H 2 O 2 and HAuCl 4 to form gold nanoparticles (GNP) with nanoplasmonic surface-enhanced Raman scattering (SERS) at 1614 cm −1 , in the presence of Victoria blue B (VBB) molecular probes. Upon addition of the Pb 2+ aptamer, it adsorb on AuNP surface to inhibit the its nanocatalysis, and the SERS, surface plasmon resonance (SPR) absorption and resonance Rayleigh scattering (RRS) decreased due to the redox product of GNP nanoplasmonic effect decreasing. When Pb 2+ was added, the aptamer combined with it to form a very stable G-quadruplex and free AuNPs, which lead to the catalysis recovering, and the absorption, RRS and SERS intensity enhanced linearly. Hereby, a new and simple, sensitive and selective gold nanoplasmonic SERS platform was established for Pb 2+ , based on the aptamer-regulating GNP nanoplasmonic SPR effect. [ABSTRACT FROM AUTHOR]

The traditional preparation of MXeneTi 3 C 2 is complicated. Two-dimensional MXeneTi 3 C 2 nanosheets were prepared via in-situ generation of HF etching Ti 3 AlC 2 under the microwave irradiation. Gold nanocluster doped nanosheets sol (MXene@Au) with excellent stability and strong catalysis was synthesized with no product residue reducer CO. MXene@Au nanosol can catalyze mandelic acid-HAuCl 4 to produce gold nanoparticles, which can be traced via resonance Rayleigh scattering (RRS) and surface-enhanced Raman scattering (SERS). Coupled the dual-mode nanocatalytic indicator reaction with aptamer reaction, a high sensitivity, selectivity, facile SERS/RRS dual-mode biosensnoring assay platform has been constructed for isocarbophos (ICP). The linear range of SERS was 1.0 × 10−3-2.5 × 10−2 nmol/L, with a detection of limit 4.5 × 10−5 nmol/L (S/N = 3). It has been used to detect ICP in water samples, with a good recovery (95.5–104%) and a good relative standard deviation (5.2–9.6%). This new nanocatalytic amplification biosensoring strategy can also assay other organic pesticides including malathion, glyphosate, profenofos and carbendazim. In addition, the nanocatalytic mechanism was investigated. MXene doped AuNCs catalyze nanogold reaction combined with aptamer constructed a SERS/RRS/Abs catalytic amplification platform for assay of ICP. [Display omitted] • MXeneTi 3 C 2 nanosheets was first time prepared with the microwave irradiation. • MXene@Au strongly catalyzed the new AuNP reaction of mandelic acid-HAuCl 4. • New fast, sensitive and accurate SERS/RRS amplification platform was constructed. • Organophosphorus pesticide isocarbophos be detected via SERS/RRS amplification platform. • The nanocatalysis mechanism of MXene@Au was investigated. [ABSTRACT FROM AUTHOR]

A new MXene supported Pd nanoparticles (Ti 3 C 2 @Pd) nanosol with good stability and strong catalysis was prepared by the two-step procedure. Experiment was found that Ti 3 C 2 @Pd could strongly catalyze the reduction of HAuCl 4 by H 2 O 2 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 (PT TNT), 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. • MXeneTi 3 C 2 were rapidly prepared by microwave digestion procedure. • Ti 3 C 2 @Pd can strongly catalyze the reduction of HAuCl 4 by H 2 O 2 to produce AuNPs. • A SERS/RRS/Abs trimode biosensoring platform was established coupling AuNPs reaction with polypeptide. • The platform can be used to detect a variety of organic pollutants, such as TNT, GLY and E2. [ABSTRACT FROM AUTHOR]

A cerium metal organic framework-loaded silver nanocluster (MOF CeAgNC) is synthesized by a facile stirring procedure with trimesic acid, cerium nitrate, silver nitrate and NaBH 4 , which exhibites strong catalytic activity in the indicated reaction of HAuCl 4 -sodium lactate (SL). MOF CeAgNC can sensitively detect dopamine (DA) by surface-enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) techniques with a detection concentration range of 0.01–0.25 nmol/L and a detection limit of 0.008 nmol/L. Based on the specific binding of aptamer (Apt)-DA and the catalytic amplification strategy of MOF CeAgNC on HAuCl 4 -SL, a sensitive and convenient DA platform for dual-mode detection of SERS and RRS is constructed. In addition, the platform is successfully applied to detect DA in human serum with satisfactory recoveries (95.7–102%). [Display omitted] • A novel stable and highly catalytic MOF CeAgNC nanosol was prepared. • MOF CeAgNC had a strong catalytic effect on the HAuCl 4 -SL indicator reaction. • The SERS/RRS dual-mode detection method was constructed based on the reaction of aptamer and indicator. • The aptamer detection of DA was label-free, sensitive, and selective. [ABSTRACT FROM AUTHOR]

• Gold-doped carbon nitride dots were prepared by microwave procedure. • The fluorescence and RRS signals are linear to phosphate concentration. • The FL/RRS coupled dual-mode method was accurate and sensitive. The hydrophilic carbon nitride dots (CNDs) and gold-carbon nitride dots (CND Au) were prepared by microwave digestion instrument with citric acid, thiourea and chloroauric acid as precursors. The morphology and properties of the nanomaterial were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), resonance Rayleigh scattering (RRS), fluorescence (FL), Fourier transform infrared spectrometer (FTIR) and particle size analysis. The acidified ammonium molybdate and CNDs are combined to form complex by intermolecular forces, the system's fluorescence and RRS signals are decreased. After adding PO 4 3−, the ammonium molybdate and PO 4 3− form stable phosphomolybdate heteropoly acid (PMo) with hydrophobic properties, the PMo particles are separated from CNDs, and the released CNDs lead to the increase of FL signal. At the same time, PMo particles are simultaneously aggregate forming large particles, which are manifested by an increase in the RRS signal. We can establish a sensitive, rapid, selective method for the determination of trace PO 4 3− by combining RRS and FL signals. Within a certain range, the signals of the two methods show a linear relationship with the concentration of PO 4 3−. The linear range of dual-mode determination method is 1.4–21 nmol/L PO 4 3−, with a detection limit of 0.60 nmol/L. [ABSTRACT FROM AUTHOR]

New multifunctional nanomaterial preparation and its application to trace pollutant analysis are interesting to peoples. Using terbium metal-organic framework loaded gold nanoparticles (MOF Tb @Au) as the nanosubstrate and 3-aminopropyltriethoxysilane (APTES) as the functional monomer, a new bifunctional nanosurface molecularly imprinted polymer nanoprobe of MOF Tb @Au@MIP with strongly recognition and catalytic amplification functions was prepared by the microwave sol-gel procedure. It was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier infrared spectroscopy (FTIR) and other techniques. The nanoprobe was found to specifically recognize malathion (MAL) and catalyze the L-cysteine (Cys)-HAuCl 4 nanogold indicator reaction to amplify the molecular spectral signal. The gold nanoparticles (AuNPs) generated in the system show a strong surface-enhanced Raman scattering (SERS) effect, resonant Rayleigh scattering (RRS) peak and UV absorption (Abs) peak at 1615 cm−1, 370 nm and 520 nm, respectively. Based on this, a new SERS/RRS/Abs trimode method for the detection of MAL can be established. It has been applied to the analysis of cereal samples with satisfactory recoveries of 95.2–107.4% and precision of 3.76–9.06%. [Display omitted] • A new SMIP was synthesized with nanosubstrate of MOF@AuNP. • The SMIP has recognition and catalytic amplification difunction. • A new HAuCl 4 -cysteine-SMIP nanocatalytic indicator reaction was discovered. • A new SERS/RRS/Abs trimode analytical platform was developed to determine malathion. [ABSTRACT FROM AUTHOR]

A novel tetramode biosensor platform for trace Al3+ based-polypeptide loaded AuNC probe catalytic amplification. [Display omitted] • PTAuNC with recognition and catalytic amplification di-function was prepared. • PTAuNC exhibits strong catalysis of the TMB tetramode indicator reaction. • A new nanocatalytic amplification-tetramode biosensor was established for Al3+. • The method is simple, sensitive and selective. Nanoclusters have strong catalytic effect, but their stability was poor. Biomolecule functionalized gold nanoclusters (AuNC) have attracted extensive attention due to their good biocompatibility, stable physicochemical properties and strong catalytic activity. In this study, the peptide (PT) was used as a template to synthesize the PTAuNC nanoprobe with recognition and catalysis. The results show that PTAuNC has a strong catalytic effect on the indicator reaction of 3,3′,5,5′-tetramethylbenzidine (TMB)–H 2 O 2 to produce the oxidized TMB (TMBox). The TMBox had a strongest fluorescence (FL) peak at 410 nm and an absorption peak at 650 nm. Addition of nanosilver (AgNPs), it produced a strong surface enhanced Raman scattering (SERS) peak at 1616 cm−1 and a resonance Rayleigh scattering (RRS) peak at 370 nm. The new nanocatalytic indicator reaction was organically coupled with the PTAuNC-Al3+ recognition reaction, and a PTAuNC catalytic amplification SERS/RRS/FL/Abs tetramode biosensor platform for Al3+ was constructed. The Al3+ concentration in the range of 0.5–60 nmol/L had a good linear relationship with SERS intensity, with detection limit of 0.21 nmol/L. The method has been applied to the determination of Al3+ in water and food samples. The recovery and relative standard deviation (RSD) were 92.4–109.8% and 1.2–9.8%, respectively. [ABSTRACT FROM AUTHOR]

In pH 7.2 KH 2 PO 4 -NaOH buffer solution, graphene oxide (GO) has strong resonance Rayleigh scattering (RRS) effect at 400 nm, and amino acid reacted with ninhydrin to form blue-violet complex Ruhemann's purple (RP) with a absorption peak at 400 nm. RPs can strongly adsorbed on the surface of GO, and the RRS donor of GO probes coupled with the receptor of RP that reduced the RRS intensity at 400 nm due to the RRS-energy transfer (RRS-ET) from the GO to RP. With the increase of amino acid concentration, the RRS intensity quenched linearly at 400 nm due to the RRS-ET enhancing. The quenched intensity responds linearly with glutamic acid concentration in the range of 0.2–200 μmol L −1 , with a detection limit of 0.08 µmol L −1 . This simple and sensitive RRS-ET method was used to detect the content of amino acid in oral liquid, with satisfactory results. [ABSTRACT FROM AUTHOR]

Sb(III) was reduced to SbH 3 gas and introduced to the I 3 − -grapheme oxide (GO) or I 3 − -silver nanorod (AgNR)-Victoria blue B (VBB) solutions. Resonance Rayleigh scattering energy transfer (RRS-ET) occurred between the donor GO and the acceptor I 3 − due to the overlap between the absorption peak of I 3 − and RRS peak of GO. When I 3 − was reduced by SbH 3 , RRS-ET weakened and the RRS intensity enhanced. The increased RRS intensity was linear to Sb concentration in the range of 2.1–376.6 μg/L. In the I 3 − -AgNR-VBB solution, I 3 − combined with VBB to form VBB-I 3 and there was a weak surface-enhanced Raman scattering (SERS) effect. When SbH 3 reduced I 3 − , the SERS intensity increased due to the release of SERS active VBB. The enhanced SERS intensity was linear for Sb concentration in the range of 8.4–292.9 μg/L. The RRS-ET method was applied for determination of Sb in food with satisfactory results. [ABSTRACT FROM AUTHOR]

[Display omitted] • COF loaded-molybdate (COF Mo) was prepared by solvothermal procedure. • The strong RRS/Fluorescence-ET taken place on COF Mo surface. • The RRS/Flu dimode platform for PO 4 3− was sensitive and facile. A new covalent organic framework loaded-molybdate (COF Mo) nanomaterial was prepared simply by solvothermal procedure and characterized by electron microscopy and molecular spectral techniques. The COF Mo had a strong resonance Rayleigh scattering (RRS) signal at 465 nm and a fluorescence peak at 345 nm. When the PO 4 3− was added in the system, it reacted with the molybdate, which loaded on the surface of COF particles, to form stable phosphomolybdic acid occurring RRS/fluorescence-energy transfer, the RRS and fluorescence signals were decreased. The decreased RRS/fluorescence intensities were linear to the PO 4 3− concentration in the range of 0.053–3.2 nmol/L and 0.10–3.2 nmol/L, with a detection limit of 0.050 nmol/L and 0.090 nmol/L respectively. Accordingly, a new and facile RRS/fluorescence dimode method for detection of trace PO 4 3− was established, only one fluorometer was used. [ABSTRACT FROM AUTHOR]

In acidic solutions, Bi(III) was reduced by NaBH 4 to form BiH 3 gas. Using I 3 − graphene oxide (GO) as absorption solution, the BiH 3 gas reacted with I 3 − to form I − that resulted in the I 3 − concentration decreasing. In the absence of BiH 3 , the I 3 − concentration was high, and as receptors it was closed to the surfaces of GO which was as donors. Then the surface plasmon resonance Rayleigh scattering (RRS) energy of GO transfers to I 3 − heavily, and results in the RRS quenching severely. With the increase of the Bi(III) concentration, the receptors and the RRS energy transfer (RRS-ET) decreased, so the RRS intensity enhanced linearly at 370 nm. The RRS intensity was linear to the Bi(III) concentration in 0.05–5.5 μmol/L, with a detection limit of 4 ng/mL Bi. A new RRS-ET spectral method was developed for the determination of trace Bi(III). Using I 3 − as the absorption solution, silver nanorod (AgNR) as sol substrate and Vitoria blue B (VBB) as molecular probe, a SERS method was developed for detection of Bi. [ABSTRACT FROM AUTHOR]

A nanosilver RRS aptamer assay was proposed for trace glyphosate based on gold-doped polystyrene nanocatalytic amplification. [Display omitted] • The nanoreaction of Ag+-formate was used as new indicator. • Gold-doped polystyrene nanoenzyme strong catalyzed the nanoreaction. • The nanocatalytic amplification was coupled with glyphosate ampater. • The RRS assay was sensitive and selective. In this paper, carbon monoxide is used as a reducing agent to establish a new procedure for preparing gold-doped polystyrene nanoenzyme (Au@PN) sol, that was characterized by electron microscopy, molecular spectroscopy and other techniques. It can effectively catalyze the AgNO 3 -sodium formate (SF) reaction to generate silver nanoparticles with a significant resonance Rayleigh scattering (RRS) signal. A new RRS assay for detecting trace amounts of glyphosate (Gly) in soil was developed by combining the nanocatalytic amplification signal and the specific aptamer (Apt) reaction. The linear range is 0.5–20 nM, and the detection limit is 0.24 nM. On the one hand, it enriched the research of polystyrene nanoenzymes and expanded the application of polystyrene nanospheres. On the other hand, an Apt RRS assay platform for detecting other target molecules was constructed. [ABSTRACT FROM AUTHOR]

Two COFs of BzBD and BzBD loaded Pd nanoclusters (BzBD Pd) 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. BzBD Pd 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, BzBD Pd , PdNPs and the catalytic mechanism of COF Pd were also considered. [Display omitted] • A new COF doped with Pd nanoclusters (COF Pd) was synthesized. • COF Pd can strongly catalyze the Au@NiP alloy reaction. • A RRS platform was established coupling Au@NiP alloy nanoreaction with aptamer. • The RRS platform has high sensitivity, selectivity and accuracy. [ABSTRACT FROM AUTHOR]

Schematic presentation of RRS and SERS dual mode determination of ultratrace urea based on Apt mediated PN-AgNO 3 -Cit catalytic amplification reaction. [Display omitted] • PNs have catalysis of the AgNP reaction. • The Apt regulated the nanocatalytic amplification. • A SERS/RRS dual mode method was established to detect urea in milk. • The method has a high sensitivity and lower detection limit. 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%. [ABSTRACT FROM AUTHOR]

A fullerene carbon dot catalytic amplification-aptamer assay platform was fabricated for ultratrace As+3 utilizing SERS/RRS/Abs trifunctional Au nanoprobes. • C 60 was used as the precursor to prepare gold-doped carbon dots (CD Au). • CD Au strongly catalyzes the new AuNP reaction of fructose-HAuCl 4. • The AuNPs exhibits strong SERS/RRS/Abs effects. • The Apt-catalytic amplification platform was fast, convenient, sensitive and accurate. • The Apt-catalytic amplification platform can be used to detect As3+, Pb2+ and Hg2+. Under microwave conditions, Au-doped carbon dots (CD Au) were prepared using fullerene as a precursor, and characterized in details. It is found that CD Au can strongly catalyze the reaction of HAuCl 4 -fructose to generate gold nanoparticles (AuNPs). The new nanocatalytic reaction was studied by surface-enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS) and absorption (Abs) spectrometry. Based on the specific aptamer (Apt As)-As+3 reaction mediated the CD Au -HAuCl 4 -fructose nanoreaction, and the products of AuNPs as SERS/RRS/Abs trifunctional indicator nanoprobes, a new trimode Apt assay strategy was developed for detection of ultratrace As+3. A 0.07–0.70, 0.10–0.60 and 0.20–0.70 μg L−1 were determined by SERS, RRS and Abs, with detection limits (DL) of 0.04, 0.06, 0.10 μg L−1 respectively. The aptamer-regulation CD Au catalytic amplification platform can be also used to assay 1.7–13.3 nmol L−1 Pb2+ and 2.0–12 μmol L−1 Hg2+, with DL of 0.80 nmol L−1 and 0.90 μmol L−1 respectively. [ABSTRACT FROM AUTHOR]

• Catalysis of AuCOF on Ag nanoreaction was investigated by molecular spectral techniques. • An AuCOF catalytic amplification SERS/RRS aptasensor for detecting organic molecule was established. • The method has a high sensitivity and selectivity. A new Au nanocluster-doped covalent organic framework (AuCOF) was prepared and characterized by electron microscopy and molecular spectroscopy. Based on aptamer-mediated COF nanocatalytic amplification signal strategy, a dual-mode analytical platform of surface-enhanced Raman scattering/resonance Rayleigh scattering (SERS/RRS) was established to detect ultatrace small molecules. The catalysis of AuCOFs on AgNO 3 -citrate nanoreaction was investigated. The formed yellow silver nanoparticles (AgNPs) exhibit strong RRS and SERS effect. The aptamer (Apt) suppressed the catalysis of AuCOFs to cause the RRS and SERS signals decreasing. Upon addition of target organic molecule such as adenosine triphosphate (ATP), the specific aptamer reaction occurred to restore the catalysis of AuCOFs, which will generate more AgNPs, and resulting in a linear increase in the signals of RRS and SERS. On this basis, inelastic scattering SERS, elastic scattering RRS and SERS/RRS dual-mode biosensors were established for small organic molecules such as ATP, urea, and estradiol, which is of high sensitivity and good accuracy compared to the single mode scattering method. [ABSTRACT FROM AUTHOR]

Preparation of multifunctional codoped carbon dots, and their new analytical applications in surface-enhanced Raman scattering (SERS) quantitative analytical method are still challenge. To overcome these problems, the nitrogen/silver-codoped carbon dots (CD N/Ag) with highly catalytic amplification are prepared by microwave method, and characterized by spectrophotometry and electron microscopy. The results show that CD N/Ag can strongly catalyze trisodium citrate-HAuCl 4 reaction to generate red nanogold with resonance Rayleigh scattering (RRS) effect and SERS effect using Victoria blue B (VBB) as molecular probes. The CD N/Ag catalytic amplification and specific immunoreaction of clenbuterol (Clen) are coupled with highly sensitive SERS and accurate RRS to fabricate a new dual-spectroscopic strategy with a detection limit of 0.68 pg mL−1 Clen. Schematic diagram of detecting Clen by SERS/RRS dual-spectroscopy. Image 1 • The high catalytic activity CD N/Ag was synthesized by microwave method. • A novel SERS/RRS dual-spectroscopic immunosensor for ultratrace clenbuterol was established using CD N/Ag as catalyst. • The method has a high sensitivity and lower detection limit. [ABSTRACT FROM AUTHOR]

The nitrogen-doped carbon dot (CD UN) was rapidly prepared by microwave method, using trisodium citrate as carbon source and urea as nitrogen source, and was characterized by fluorescence, absorption, resonance Rayleigh scattering (RRS), infrared and electron microscopy. The CD UN produced a fluorescence peak at 450 nm and a RRS peak at 375 nm, with an excited wavelength of 375 nm. When the aptamer (Apt) was added, the CD UN was encapsulated by Apt and reduced its fluorescence and RRS intensities. When K+ was added, it reacts with Apt to form a stable G-quadruplex and free CD UN. The fluorescence and RRS di-model intensity was enhanced linearly with the concentration of K+. Accordingly, a simple, rapid and sensitive di-model molecular spectral method for the determination of 0.008–0.27 μmoL/L K+ has been developed, with a detection limit of 0.3 nmoL/L. Fluorescence and resonance Rayleigh scattering di-model probe for trace K+ coupled N-doped carbon dot and aptamer. Image 1 • N-doped carbon dots (CD UN) were prepared rapidly by microwave method. • The aptamer was coupled with CD UN fluorescence and RRS di-model probe. • The di-model intensity was linear to K+ concentration. • The di-model method is novel, sensitive and selective. [ABSTRACT FROM AUTHOR]