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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]

Carbon dots (CDs) can be prepared from various organic (abundant) compounds that are rich in surfaces with –OH, –COOH, and –NH2 groups. Therefore, CDs exhibit good biocompatibility and electron transfer ability, allowing flexible surface modification and accelerated electron transfer during catalysis. Herein, CDs were prepared using a hydrothermal method with fructose, saccharose, and citric acid as C sources and urea as an N dopant. The as-prepared CDs were used to catalyze AgNO3–trisodium citrate (TSC) to produce Ag nanoparticles (AgNPs). The surface-enhanced Raman scattering (SERS) intensity increased with the increasing CDs concentration with Victoria blue B (VBB) as a signal molecule. The CDs exhibited a strong catalytic activity, with the highest activity shown by fructose-based CDs. After N doping, catalytic performance improved; with the passivation of a wrapped aptamer, the electron transfer was effectively disrupted (retarded). This resulted in the inhibition of the reaction and a decrease in the SERS intensity. When bisphenol A (BPA) was added, it specifically bound to the aptamer and CDs were released, recovering catalytical activity. The SERS intensity increased with BPA over the concentration range of 0.33–66.67 nmol/L. Thus, the aptamer-adjusted nanocatalytic SERS method can be applied for BPA detection. [ABSTRACT FROM AUTHOR]

A new, stable and high-catalytic activity ferrocene-doped polystyrene nanosphere (PNFer) sol was prepared by the hydrogel procedure and characterized by electron microscopy and molecular spectroscopy. Results show that the nanosol exhibits excellent catalysis of the new indicator nanoreaction between AgNO3 and sodium formate to generate nanosilver with strong surface-enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS) and surface plasmon resonance absorption (Abs) trimode molecular spectral signals. This new nanocatalytic amplification trimode indicator reaction was coupled with the G-quadruplex DNAzyme catalytic amplification of Pb2+ aptamer to fabricate a new SERS quantitative/RRS/Abs assay platform for the determination of ultratrace amounts of Pb2+. The Pb2+ content in water samples was analyzed with satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Abstract: The nanogold reaction between HAuCl4 and trisodium citrate (TCA) proceeded very slowly at 60°C in a water bath. The as‐prepared graphene oxide nanoribbons (GONRs) exhibited strong catalysis during the reaction to form gold nanoparticles (Au NPs) and appeared as a strong surface‐enhanced Raman scattering (SERS) peak at 1616 cm−1 in the presence of the molecular probe Victoria blue 4R (VB4r). With increase in GONR concentration, the SERS peak increased due to increased formation of Au NPs. Upon addition of dimethylglyoxime (DMG) ligand, which was adsorbed onto the GONR surface to inhibit GONR catalysis, the SERS peak decreased. When Ni2+ was added, a coordination reaction between DMG and Ni2+ took place to form stable complexes of [Ni (DMG)2]2+ and the release of free GONR catalyst that resulted in the SERS peak increasing linearly. A SERS quantitative analysis method for Ni2+ was therefore established, with a linear range of 0.07–2.8 μM, and a detection limit of 0.036 μM Ni2+. [ABSTRACT FROM AUTHOR]

Abstract: Using silver nanoparticles (AgNPs) as the nanocatalyst, l‐cysteine rapidly reduced HAuCl4 to make a stable gold nanoparticle sol (Ag/AuNP) that had a high surface‐enhanced Raman scattering (SERS) activity in the presence of Victoria blue 4R (VB4r) molecular probes. Under the selected conditions, chondroitin sulfate (Chs) reacted with the VB4r probes to form associated complexes that caused the SERS effect to decrease to 1618 cm−1. The decreased SERS intensity was linear to the Chs concentration in the range 3.1–500 ng/ml, with a detection limit of 1.0 ng/ml Chs. Accordingly, we established a simple and sensitive SERS quantitative analysis method to determine Chs in real samples, with a relative standard deviation of 1.47–3.16% and a recovery rate of 97.6–104.2%. [ABSTRACT FROM AUTHOR]

Stable silver nanosol (AgNP) was prepared by the light-wave procedure. Based on the Galvanic replacement reaction (GRR) of Au(III) on AgNP surface and using Victoria blue B (VBB) as molecular probes, a surface-enhanced Raman scattering (SERS) quantitative analysis of trace Au(III) was developed. VBB has no SERS signal in the dispersed AgNP sol substrate. Addition of NaCl, the VBB produced strong surface-enhanced Raman signals at 1381 cm −1 in the aggregated AgNP sol substrate. When Au(III) is present in the system, the surface Ag atoms interact with Au(III) to form Ag + and Au due to the potential difference, and the Au atom and AgCl deposited on the AgNP surface to reduce the SERS activity significantly and result in SERS signal quenching. The quenched SERS signal is linear to Au(III) concentration in the range of 25–625 nmol/L, with a detection limit of 8 nmol/L. The GRR system can be also monitored by resonance Rayleigh scattering (RRS) spectroscopy, Au can be detected by SERS and RRS methods, and the former is more sensitive. [ABSTRACT FROM AUTHOR]

Using AgNO3 as the precursor, stable silver nanochain (AgNC) sols, orange-red in color, were prepared using hydrazine hydrate. A strong surface plasmon resonance Rayleigh scattering (RRS) peak occurred at 420 nm plus two surface plasmon resonance (SPR) absorption peaks at 410 nm and 510 nm. Rhodamine S (RhS) cationic dye was absorbed on the as-prepared AgNC substrate to obtain a RhS-AgNC surface-enhanced Raman scattering (SERS) nanoprobe that exhibited a strong SERS peak at 1506 cm-1 and a strong RRS peak at 375 nm. Upon addition of the analyte sodium hexametaphosphate (HP), it reacted with RhS, which resulted in a decrease in the SERS and RRS peaks that was studied in detail. The decreased SERS and RRS intensities correlated linearly with HP concentration in the range of 0.0125-0.3 µmol/L and 0.05-1.0 µmol/L, with a detection limit of 6 nmol/L and 20 nmol/L HP respectively. Due to advantages of high sensitivity, good selectivity and simple operation, the RhS molecular probes were used to determine HP concentration in real samples. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In 0.19 mol/L acetic acid (HAc), a click reaction of 8-chloroquinoline/azide/phenylacetylene take places in aqueous solution without Cu(I) as a catalyst. 8-Chloroquinoline (CQN) exhibited a strong fluorescence peak at 430 nm that was quenched linearly as the concentration of azide increased from 20 to 1000 ng/mL. This quenching was due to consumption of CQN in the click reaction and a decrease in the number of efficiently excited photons due to the presence of triazole-quinoline ramification molecules with strong hydrophobicity. Using blue nanosilver sol as the substrate, CQN absorbed onto the surface of nanosilver particles, showing a strong surface-enhanced Raman scattering (SERS) peak at 1585 cm-1 that decreased linearly as the azide concentration increased from 8 to 500 ng/mL; the detection limit was 4 ng/mL. Thus, two new, simple and sensitive fluorescence and SERS methods have been developed for the determination of azide via the click reaction. Copyright © 2014 John Wiley & Sons, Ltd. [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]

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. [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]

The as-prepared co-doped N/Ag carbon dot (CDNAg) has strong catalysis of H2O2 oxidation of 3,3′-dimethylbiphenyl-4,4′-diamine (DBD). It forms an oxidation product (DBDox) with surface-enhanced Raman scattering (SERS) activity at 1605 cm−1 in the silver nanosol substrate, and a CDNAg catalytic amplification with SERS analytical platform can be structured based on aptamer (Apt) with the DBD oxidizing reaction. For example, the aptamer (Apt) of acetamiprid (ACT) can be adsorbed on the surface of CDNAg, resulting in inhibited catalytic activity, the reduced generation of DBDox, and a weakened SERS intensity. When the target molecule ACT was added, it formed a stable Apt-ACT complex and free CDNAg that restored catalytic activity and linearly enhanced the SERS signal. Based on this, we proposed a new quantitative SERS analysis method for the determination of 0.01–1.5 μg ACT with a detection limit of 0.006 μg/L. [ABSTRACT FROM AUTHOR]

Carbon dots (CD) have excellent stability and fluorescence activity, and have been widely used in fluorescence methods. However, there are no reports about using CD as catalysts to amplify SERS signals to detect trace sulfate. Thus, preparing CD catalysts and their application in SERS sulfate-sensing are significant. In this article, highly catalytic N-doped carbon dots (CDN) were prepared by a hydrothermal procedure. CDN exhibited strong catalysis of the gold nanoparticle (AuNP) reaction between HAuCl4 and H2O2. Vitoria blue 4R (VB4R) has a strong SERS peak at 1614 cm−1 in the formed AuNP sol substrate. When Ba2+ ions were added, they were adsorbed on a CDN surface to inhibit the CDN catalytic activity that caused the SERS peak decreasing. Upon addition of analyte SO42−, a reaction with Ba2+ produced stable BaSO4 precipitate and CDN, and its catalysis recovered to cause SERS intensity increasing linearly. Thus, an SERS method was developed for the detection of 0.02–1.7 μmol/L SO42−, with a detection limit of 0.007 μmol/L. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly catalytic and stable TbMOF@Au was prepared by solvothermal-reduction method. • The new SERS/RRS/Abs catalytic indicator reaction was utilized to amplify signal. • A triple-mode molecular spectral method was developed for MAL. • The detection limit of MAL is as low as 0.21 ng/mL. Terbium metal–organic framework (TbMOF) was prepared by microwave method with 1,3,5-benzenetricarboxylic acid as ligand. With HAuCl 4 as precursor and NaBH 4 as reducing agent, TbMOF-loaded gold nanoparticles (AuNPs) catalyst (TbMOF@Au 1) was prepared rapidly and characterized by transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. It was found that TbMOF@Au 1 has a strong catalytic effect on the HAuCl 4 -Cys nanoreaction, and the produced AuNPs have a strong resonant Rayleigh scattering (RRS) peak and surface plasmon resonance absorption (Abs) peak at 370 nm and 550 nm, respectively. With the addition of the molecular probe Victoria blue 4R (VB4r), AuNPs have a strong surface-enhanced Raman scattering (SERS) effect, the target analyte molecules are trapped in between the nanoparticles and a hot spot effect created in the process resulting in an extremely high SERS signal. A new SERS/RRS/Abs triple-mode analysis method for Malathion (MAL) was established by coupling this new TbMOF@Au 1 catalytic indicator reaction with MAL aptamer (Apt) reaction, and its SERS detection limit was 0.21 ng/mL. The SERS quantitative analysis method has been applied to the analysis of fruit samples with the recovery of 92.6–106.6 % and the precision of 2.72–8.16 %. [ABSTRACT FROM AUTHOR]

A new di-recognition nitrogen-doped carbon dot nanosurface aptamer molecularly imprinted polymer (CD NAg @MIPApt) nanocatalytic di-functional probe was prepared by microwave irradiation. The probe was utilized nitrogen-doped silver carbon dots (CD NAg) as the matrix, glyphosate (Gly) as the template molecule, α-methyl acrylate as the monomer, ethylene glycol dimethacrylate as the cross-linker, and aptamer as the biorecognition element. It could not only recognize Gly but also exhibits catalytic amplification function. It was found that CD NAg @MIPApt catalyzed the redox reaction of polyethylene glycol 400 (PEG400)-AgNO 3 to generate silver nanoparticles (AgNPs). The AgNPs indicator component exhibit the effects of surface-enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS) and surface plasmon resonance absorption (Abs). In the presence of Gly, it binds to the surface imprinted site of CD NAg @MIPApt, to reduce AgNPs generation due to the catalytic activity of CD NAg @MIPApt decreasing. Thus, the SERS/RRS/Abs signal values decreased linearly. The linear ranges of SERS/RRS/Abs assay were 0.1–2.5 nM, 0.25–2.75 nM and 0.5–5 nM respectively. The detection limits were 0.034 nM, 0.071 nM and 0.18 nM Gly. • A new CD NAg @MIPApt probe with di-recognition and di-function was prepared. • Apt was not only enhanced the sensitivity but also improved the selectivity. • The probe exhibits strong catalysis of the new nanoreaction to form AgNPs. • The in situ generated AgNPs are of strong SERS, RRS and Abs effects. • A new, simple, selective and sensitive trimode method for Gly was established. [ABSTRACT FROM AUTHOR]

A new gold nanosol SERS method for ultratrace atrazine by a difunctional surface molecular imprinted polymethacrylate probe. [Display omitted] • A new AuNP@MIP nanoprobe was prepared. • The nanoprobe not only has recognition function but also has catalytic function. • The new nano indicator reaction of glyoxal-HAuCl 4 is in situ generated AuNP. • A new SESR sensor platform was created for ultratrace ATZ. A new type of bifunctional nanosurface molecularly imprinted polymer nanoprobe (Au@MIP) was prepared using methacrylic acid as functional monomers respectively, gold nanoparticles (AuNP) as nanosubstrate. The Au@MIP nanoprobe not only has recognition function but also has catalytic function. The findings demonstrate that the AuNP@MIP nanoprobes, prepared with methacrylic acid as the functional monomer, very strongly catalyzed the new nano indicator reaction of glyoxal (GO)-HAuCl 4. In situ generated AuNP sol exhibits strong surface-enhanced Raman scattering (SESR) effects. After adding atrazine (ATZ), the signals were significantly boosted. As a result, a new SESR trimode sensor platform was created for ultratrace ATZ. The linear ranges for ATZ was 0.005–0.0625 nmol/L, with detection limits of 0.0012 nmol/L. Moreover, the SERS method was used to determine the content of ATZ in corn samples, achieving relative standard deviations (RSDs) of 6.53–9.57 % and recoveries of 96.4 %–108.2 %. [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]

[Display omitted] • Highly catalytic and stable CD N was prepared by microwave hydrothermal method. • A new dual-mode SERS/RRS method was developed for Pb2+. • The detection limit of Pb2+ is as low as 0.11 nmol/L. Nitrogen-doped carbon dots (CD N) were prepared by microwave hydrothermal method using ammonium citrate (AC) and ethylenediaminetetraacetic acid (EDTA) as precursor. It was characterized by transmission electron microscopy (TEM) and infrared spectroscopy (IR). The CD N was found to catalyze the reduction of HAuCl 4 to produce gold nanoparticles (AuNP), among which fructose was an effective reducing agent. Using malachite green (MG) as a molecular probe, the surface enhanced Raman scattering (SERS) intensity at 1617 cm−1 and the resonance Rayleigh scattering (RRS) intensity at 375 nm increased linearly with increasing CD N concentration, respectively. The catalytic activity of CD N is inhibited because the aptamer (Apt) can be adsorbed on the surface of the catalyst CD N. The aptamer (Apt)-Pb2+ reaction and CD N -Apt adsorbing reaction were competitive reaction. When there is Pb2+ that binds more tightly to Apt, Apt is desorbed, and the catalytic ability of CD N is restored. Accordingly, an Apt-mediated nanocatalytic amplification SERS/RRS platform for quantitative detection of lead ions was constructed. For the SERS method, the linear range was 0.5–120 nmol/L with DL of 0.11 nmol/L. For the RRS method, the Pb2+ concentration was linear in the range of 50–400 nmol/L with the RRS intensity, and the DL was 15.32 nmol/L. The analysis platform uses CD N catalyzed nanoreactions to generate AuNP products with SERS activity as a substrate, thus overcoming the shortcomings of Pb2+ without scattering activity, and realizing the possibility of SERS and RRS detection of metal ions. It was used for the determination of Pb2+ in real samples with relative standard deviations were 0.94–2.71 % and recovery was 99.00–103.70 %, respectively. In addition, the mechanism of CD N nanoenzyme heterogeneous catalysis of nano-gold reactions was discussed. [ABSTRACT FROM AUTHOR]

Highlights • CD Ca exhibited strong catalysis of nanogold reaction between HAuCl 4 and H 2 O 2. • PA binds with CD Ca to inhibit its nanocatalysis. • The intensity of the SERS peak at 1615 cm−1 is increased linearly with Na+ concentration increasing. • The SERS quantitative analysis method for Na+ has high sensitivity. Abstract The Ca-doped carbon dots (CD Ca) exhibited strong catalysis of HAuCl 4 -H 2 O 2 reaction to produce gold nanoparticle (AuNP), using Vitoria blue 4R (VB4r) as molecular probe, it appeared a strong surface enhanced Raman scattering (SERS) peak at 1615 cm−1 in the AuNP nanosol substrate. When catalyst CD Ca increased, the SERS peak enhanced linearly owing to AuNPs increasing, that is, the AuNP concentration is linear to SERS signal. Potassium pyroantimonate (PA) ligand can adsorb on CD Ca surface to inhibit the catalysis and cause the SERS peak decreasing. The analyte of Na+ reacts with PA to produce the stable precipitate of [Na 2 (PA)] and free CD Ca catalyst. The more Na+, the more CD Ca released, and the stronger SERS signal due to more AuNP substrate. Accordingly, a SERS quantitative analysis method for Na+ was developed based on CD Ca catalytic SERS reaction, with a linear range of 0.004–0.043 μmol/L, and a detection limit of 0.0019 μmol/L Na. [ABSTRACT FROM AUTHOR]

Abstract Highly stable, SERS active and catalytic nanosilver sol (AgNP) was synthesized under the exposure of light wave, using AgNO 3 as precursor and sodium citrate as reducer. Under the conditions of pH 7.0 NaH 2 PO 4 -Na 2 HPO 4 buffer solution (PBS), the glucose can be catalyzed by glucose oxidase to produce H 2 O 2 specifically. Based on the nanocatalyst and SERS substrate of AgNP, H 2 O 2 can oxidize the 3,3′,5,5′-tetramethylbenzidine (TMB) quickly to form a blue oxidation product (TMB ox) that induced the AgNPs aggregation, which exhibited a strong SERS signal at 1606 cm−1. As the concentration of glucose increases, the TMB ox molecular probes and AgNPs aggregation increase, and the intensity of SERS peak at 1606 cm−1 increase linearly. Thus, a new SERS strategy for quantitative analysis of 0.33–6.67 μmol/L glucose was developed, with a detection limit of 0.035 μmol/L, coupled the catalysis of nanosilver with glucose oxidase, and label-free molecular probe of TMB ox. Graphical abstract The increased SERS intensity was linear to glucose concentration in the range of 0.33–6.67 μmol/L. Unlabelled Image Highlights • Glucose oxidase catalysis can be coupled with the H 2 O 2 -TMB-AgNP nanocatalytic reaction. • TMB ox can induce the aggregation of AgNP. • The SERS peak intensity is linear with glucose concentration. [ABSTRACT FROM AUTHOR]

Abstract The highly catalytic Ca-doped carbon dots (CD Ca) were prepared by microwave procedure, that exhibit strong catalytic effect on HAuCl 4 -glucose (GLC) reaction to form gold nanoparticles (AuNPs) with high SERS activity, using Victoria blue B (VBB) as a molecular probe. The SERS intensity at 1615 cm−1 increased linearly with CD Ca increasing, due to formation of more AuNPs nanosol substrate as indicator. When thrombin aptamer (Apt) was added in this system, Apt adsorbed on the CD Ca surface to inhibit theirs catalytic activity, and the SERS intensity decreased. However, when thrombin (TB) was present, it can bind to Apt to form stable G-duplex of Apt-TB and free CD Ca catalyst in the system, and the SERS signal increased linearly. Thus a free-label Apt-SERS quantitative analysis method was developed for ultratrace TB, with a linear range of 0.0058–0.115 nmol/L and a detection limit of 0.0018 nmol/L TB. Highlights • The highly catalytic Ca-doped carbon dots (CDCa) were prepared by microwave procedure. • CD Ca exhibits strong catalysis of the SERS active gold nanoparticle reaction. • The catalytic reaction was used to amplify SERS signal. • A free-label Apt-SERS quantitative analysis method was developed for ultratrace TB. [ABSTRACT FROM AUTHOR]

Highlights • Highly SERS active silver nanosol (AgNP) was prepared by light wave irradiation. • Urea reacted with dimethylglyoxime to produce SERS molecular probes. • A sensitive SERS quantitative analysis method was developed for urea. Abstract Under the light wave irradiation, the stable and highly surface enhanced Raman scattering (SERS) active silver nanosol (AgNP) was prepared by reduction of AgNO 3 , using sodium citrate as reducer. Urea reacted with dimethylglyoxime to produce 4,5-dimethyl-2-imidazole ketone that exhibited a strong SERS peak at 1320 cm−1 in the as-prepared AgNPs substrate. Under the selected conditions, the increased SERS intensity Δ I was linear to urea concentration in the range of 8.25–825 nM, with a detection limit of 4.92 nM. Accordingly, a new, simple SERS quantitative analysis method for trace urea in foods was established, with relative standard deviation of 0.92–4.8% and recovery of 97.4–101%. [ABSTRACT FROM AUTHOR]

In 50 °C conditions, the gold nanoreaction of HAuCl 4 -H 2 O 2 is very slow, graphene oxide (GO) exhibited strong catalysis on the nanoreaction to form gold nanoparticles (AuNPs) with strong surface-enhanced Raman scattering (SERS) activity at 1614 cm −1 in the presence of molecular probes of Victoria Blue (VB4r). The SERS intensity increased with the GO increasing due to formation of more AuNPs. The ferritin antibody (Ab) can bind to GO surface to form Ab-GO that can inhibit the nanocatalysis. When ferritin (Ag) existed, the produced immunocomplexes of Ab-Ag are separated from the GO surface, which led to the recovery of GO catalysis. The enhanced SERS signal △I 1614cm-1 is linear to ferritin concentration in the range of 0.017–1.02 ng/mL. Accordingly, a new SERS quantitative analysis method was established for detection of ferritin, based on the regulating GO nanocatalysis. [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]

Gold nanosol with good stability and high SERS activity was prepared under the light wave irradiation, with triethanolamine as reducing agent. In the acid medium, the oxidized product of scorbic acid (SA) by H 2 O 2 , malondialdehyde, react with thiobarbituric acid (TBA) to produce 3,5,5-trimethyloxazole-2,4-dione (trimethadione, TMD) that exhibited strong surface-enhanced Raman scattering (SERS) effect at 1280 cm −1 in the as-prepared gold nanosol substrate containing enhancement reagent of AlCl 3 . Under the chosen conditions, the SERS intensity at 1280 cm −1 was linear to the SA concentration in the linear range of 0.0066–1.59 μg/mL, with a detection limit of 3.2 ng/mL. This SERS method has been applied to the quantitative analysis of SA in real samples with advantages of high sensitivity, good selectivity and simple operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new solvothermal procedure was used to prepare COFloaded gold nanocluster (AuCOF). • The AuCOF catalysis and stability were improved by loaded gold nanoclusters onto the COF. • The AuCOF catalyzed strongly the new nanogold indicator reaction of Au(III)-SO 3 2− with SERS and RRS effects. • A new Apt SERS quantitative method for the rapid determination of estradiol. A new covalent organic framework loaded gold nanocluster (AuCOF) was prepared by solvothermal procedure, using 1,3,5-benzenetricarboxaldehydeand p-phenylenediamine and chloroauric acid as precursor. It was found that the AuCOF exhibits strong catalysis of sulfite reduction of HAuCl 4 to form gold nanoparticles (AuNP) with surface enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) effects. The aptamer (Apt) of estradiol (E2) can be electrostatically adsorbed on the AuCOF surface to suppress its catalytic performance. While the Apt E2 can selectively bind to target molecule E 2 and desorb from the AuCOF surface to recover its catalysis. The SERS and RRS signals increased linearly with E 2 concentration increasing due to produce more AuNP indicator. The highly sensitive SERS method shows good linearity with E2 concentration in the range of 0.333–5.33nmol/L, and the detection limit was 0.150 nmol/L E2. This SERS method has been used for the determination of E2 in actual samples. In addition, the nanocatalytic mechanism and SERS quantitative analysis formula were studied. [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]

With development of economy and society, there is an urgent need to develop convenient and sensitive methods for detection of Cu 2+ pollution in water. In this article, a simple and sensitive SERS sensor was proposed to quantitative analysis of trace Cu 2+ in water. The SERS sensor platform was prepared a common gold nanoparticle (AuNP)-SiO 2 sol substrate platform by adsorbing HSA, coupling with the catalytic reaction of Cu 2+ -ascorbic acid (H 2 A)-dissolved oxygen, and using label-free Victoria blue B (VBB) as SERS molecular probes. The SERS sensor platform response to the AuNP aggregations by hydroxyl radicals (•OH) oxidizing from the Cu 2+ catalytic reaction, which caused the SERS signal enhancement. Therefore, by monitoring the increase of SERS signal, Cu 2+ in water can be determined accurately. The results show that the SERS sensor platforms owns a linear response with a range from 0.025 to 25 μmol/L Cu 2+ , and with a detection limit of 0.008 μmol/L. In addition, the SERS method demonstrated good specificity for Cu 2+ , which can determined accurately trace Cu 2+ in water samples, and good recovery and accuracy are obtained for the water samples. With its high selectivity and good accuracy, the sensitive SERS quantitative analysis method is expected to be a promising candidate for determining copper ions in environmental monitoring and food safety. [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]

In pH 7.4 Na 2 HPO 4 -NaH 2 PO 4 buffer solution containing the peptide probes for human chorionic gonadotropin (hCG), silver nanoparticles (AgNPs) were aggregated to big AgNPs clusters that exhibited very weak catalytic effect on the gold nanoparticle reaction of H 2 O 2 -HAuCl 4 . When hCG was present in the peptide probe solution, the AgNPs did not aggregate and it had strong catalytic effect on the gold nanoparticle reaction with a strong resonance Rayleigh scattering (RRS) peak at 370 nm and a strong surface enhanced Raman scattering (SERS) peak at 1615 cm −1 in the presence of molecular probe of Victoria blue 4R (VB4R). With the increase of the hCG concentration, the catalysis enhanced due to the nanocatalyst of AgNPs increasing, and the RRS intensity increased at 370 nm. The increased RRS intensity was linear to the hCG concentration in 0.05–10 ng/mL, with a linear regression equation of Δ I 370 nm =409.8 C +294. And the SERS intensity at 1615 cm −1 increased linearly with the hCG concentration in the range of 0.05–20 ng/mL, with a linear regression equation of ΔI 1615 cm-1 =142 C+134. Based on this, two new methods of nanocatalytic SERS and RRS were proposed for the determination of trace hCG. [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]

Abstract: A stable nanosilver solution was prepared, using PEG10000 as stabilizer and NaBH4 as reducer. In pH 6.6 Na2HPO4–NaH2PO4 buffer solution containing PEG10000 and NaCl, the nanosilvers (AgNPs) were aggregated to form the stable nanosilver-aggregation (AgNPA) that could conjugate with 4-mercaptopyridine (MPy) to obtain an AgNPA-MPy surface-enhanced Raman scattering (SERS) probe with a strong SERS peak at 1097cm−1. When Hg2+ concentration increased, the SERS intensity at 1097cm−1 decreased linearly as the stable complex of [Hg(MPy)2]2+ was formed and the AgNPA particles precipitate to the bottom. The decreased SERS intensity was linear to Hg2+ concentration in the range of 50–3000nmol/L. Based on this, a new sensitive SERS method has been proposed for the determination of trace Hg2+ in the water sample, with satisfactory results. [Copyright &y& Elsevier]

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]

• Highly catalytic and stable CD Fe was prepared by water hydrothermal procedure. • The new SERS/Flu/Abs catalytic indicator reaction was utilized to amplify signal. • A trimode molecular spectral method was developed for H 2 O 2. • The detection limit of H 2 O 2 is as low as 2.52 × 10−10 mol/L. A stable Fe-doped carbon dot (CD Fe) nanosol with high catalytic activity was prepared by water hydrothermal procedure using ferrocene as precursor. In Tris-HCl buffer solution, 3,3′,5,5′-tetramethylbenzidine (TMB) was oxidized slowly by H 2 O 2 that catalyzed quickly by CD Fe. The oxidation product (TMBox) molecular probes exhibit surface-enhanced Raman scattering (SERS) peak at 1606 cm−1 in the silver nanosol substrate, fluorescence (Flu) peak at 400 nm and absorption (Abs) peak at 560 nm. With the increase of H 2 O 2 concentration, the produced TMBox increased, and the SERS/Flu/Abs peaks were enhanced linearly. Based on this, a new SERS/Flu/Abs trimode molecular spectral method was established for the determination of trace H 2 O 2 based on CD Fe catalytic amplification. The results show that the SERS linear range for H 2 O 2 concentration is 5.0 × 10−10–2.5 × 10−8 mol/L, and the detection limit is 2.52 × 10−10 mol/L. The H 2 O 2 contents in food samples were analyzed by this SERS quantitative method, with relative standard deviations of 2.1–4.3 % and recovery of 94.5−103.8 %. [ABSTRACT FROM AUTHOR]

• A COF of MaBd was prepared by melamine (Ma) and p -benzaldehyde (Bd). • MaBd can strongly catalyze the GC-HAuCl 4 nanoreaction. • A SERS quantitative method was constructed coupled aptamer with nanoreaction. • The method has high sensitivity and selectivity, and low blank. A highly catalytic and stable covalent organic frameworks (COFs) of MaBd were prepared by the polycondensation of melamine (Ma) and p -benzaldehyde (Bd), and characterized by molecular spectra and electron microscopy. MaBd strongly catalyze the new indicator reaction between glycol (GC) and chloroauric acid to generate gold nanoparticles (AuNP) with strong RRS effect at 370 nm and surface enhanced Raman scattering (SERS) effect at 1617 cm−1 using Vitoria blue B (VBB) as molecular probes. Combining the MaBd nanocatalytic amplification reaction with highly selective aptamer (Apt) of glyphosate (GLY), a new, simple and highly sensitive SERS method was developed with a linear range of 0.003−0.07 nmol/L, and the detection limit of 0.002 nmol/L GLY. GLY in soil samples were analyzed by this SERS method, with relative standard deviation of 4.78–5.71 % and recovery of 92.3–105.3 %. [ABSTRACT FROM AUTHOR]

• Highly catalytic N-doped carbon dots (N-CDs) were prepared by microwave irradiation. • The N-CDs catalytic nano-reaction was utilized to amplify SERS signal. • The N-CDs nanocatalytic reaction was coupled with the affinity reaction. • A highly sensitive and selective SERS quantitative method was developed for biotin. Highly catalytic and stable N-doped carbon dots (N-CDs) were prepared rapidly by microwave procedure using glucose as precursor and ammonium sulfite as N-dopant. The reduction of AgNO 3 by trisodium citrate (TCA) was slow to form nanosilver (AgNP), and the N-CDs exhibited strong catalysis of the AgNP reaction. The formed AgNPs were used as indicator in the presence of Vitoria blue B (VBB) molecule probe with a SERS peak at 1615 cm−1. With the increase of nancatalyst N-CDs concentration, the AgNP reaction speed up, and the SERS peak of VBB enhanced linearly due to formation of more AgNPs as substrate. In the presence of avidin (Ad), the SERS peak weakened. Upon addition of biotin, the SERS peak enhanced due to turn on the indicator nanoreaction. The enhanced SERS signal had a good linear relationship with the biotin concentration in range of 0.0006–0.021 ng/mL, with a detection limit of 0.3 pg/mL. [ABSTRACT FROM AUTHOR]

• Fe3+ catalyzed the oxidization of TMB to form TMB OX. • F− inhibit the catalysis. • TMB OX can be used as SERS and fluorescence probes. • Two methods were developed for detection of F−. • The two methods were sensitive. Fluoride constitutes an essential component for the formation of hard bones and teeth. However long-term excessive intake of fluoride causes chronic poisoning changes in the body. Therefore, the determination of its content is of great significance. Herein, a sensitive SERS quantitative analysis method was proposed to detect F−. Trace Fe3+ exhibited strong catalysis of H 2 O 2 oxidizing 3, 3′, 5, 5′-tetramethylbenzidine (TMB) under the ultrasonic irradiation, and the reaction product called TMB diimine (TMB OX) not only had strong fluorescence, but also had SERS activity in the silver nanosol substrate. Upon addition of fluoride ion (F−), the stable complex of [FeF 6 3− formed, and could inhibit the catalytic action of Fe3+, resulting in the SERS and fluorescence signal decreasing due to the TMB OX concentration decreasing. In the range of 2–1000 nmol/L F−, the SERS intensity Δ I decreased line with the concentration increased, with a detection limit of 0.7 nmol/L. Based on the catalytic amplifying strategy and the TMB OX molecular probes, ultratrace Fe3+ could be also detected by SERS and fluorescence methods. [ABSTRACT FROM AUTHOR]

• The aptamer combined with K+ and hemin to form DNAzyme. • The DNAzyme catalyzed H2O2 oxidization of 3,3′,5,5′-tetramethylbenzidine (TMB). • The oxidized product of TMB (TMBOX) was used as fluorescence and SERS probes. • Trace hemin and K+ can be determined by the two fluorescence and SERS methods. • The SERS method was highly sensitive and accurate. The aptamer of K+ (Apt) was a guanine G-rich nucleotide sequence, Apt can bind K+ and hemin (HM) to form a stable G-quadruplex/HM DNAzyme with strong catalytic activity. Under ultrasonic irradiation, DNAzyme catalyzed the oxidation of tetramethylbenzidine (TMB) by H 2 O 2 to form oxidation product TMB OX with fluorescence effect and SERS activity. Under the optimized analytical conditions, the linear range of catalyzed SERS determination of HM and K+ were 0.01–75 nmol/L and 2–1000 nmol/L, with the detection limits of 0.004 nmol/L and 1.6 nmol/L, respectively. The fluorescence linear ranges of HM and K+ were 1–100 nmol/L and 10–300 nmol/L, with the detection limits of 0.88 nmol/L and 9.4 nmol/L, respectively. Thus, a SERS and fluorescence dual-mode platform was developed for determination of trace HM and K+. [ABSTRACT FROM AUTHOR]