Search

In recent years, research on human umbilical cord mesenchymal stem cells (hUCMSCs) derived from human umbilical cord tissue has accelerated and entered clinical application research. Compared with mesenchymal stem cells (MSCs) from other sources, hUCMSCs can be extracted from different parts of umbilical cord or from the whole umbilical cord. It has the characteristics of less ethical controversy, high differentiation potential, strong proliferation ability, efficient expansion in vitro, avoiding immune rejection and immune privilege, and avoids the limitations of lack of embryonic stem cells, heterogeneity, ethical and moral constraints. hUCMSCs avoid the need for embryonic stem cell sources, heterogeneity, and ethical and moral constraints. Bone defects are very common in clinical practice, but completely effective bone tissue regeneration treatment is challenging. Currently, autologous bone transplantation and allogeneic bone transplantation are main treatment approaches in clinical work, but each has different shortcomings, such as limited sources, invasiveness, immune rejection and insufficient osteogenic ability. Therefore, to solve the bottleneck of bone tissue regeneration and repair, a great amount of research has been carried out to explore the clinical advantages of hUCMSCs as seed cells to promote osteogenesis. However, the regulation of osteogenic differentiation of hUCMSCs is an extremely complex process. Although a large number of studies have demonstrated that the role of hUCMSCs in enhancing local bone regeneration and repair through osteogenic differentiation and transplantation into the body involves multiple signaling pathways, there is no relevant article that summarize the findings. This article discusses the osteogenesis-related regulatory mechanisms of hUCMSCs, summarizes the currently known related mechanisms, and speculates on the possible signals. [ABSTRACT FROM AUTHOR]

A new Fe metal–organic framework-loaded liquid crystal 4-octoxybenzoic acid (FeMOF@OCTB) nanosol was synthesized using 1,3,5-phthalic acid, ferrous sulfate, and OCTB as precursors. The FeMOF@OCTB exhibits good stability and strong catalytic effect for the polyethylene glycol 400-Ag (I) indicator reaction, which was evaluated rapidly by the slope procedure. The generated silver nanoparticles have a strong surface-enhanced Raman scattering (SERS) effect and a surface plasmon resonance absorption (Abs) peak at 420 nm. This new bimodal nanosilver indicator reaction was coupled with the isocarbophos (IPS)-aptamer (Apt) reaction. A FeMOF@OCTB nanocatalytic amplified-SERS/Abs bimodal Apt assay for IPS was established. The SERS assay can detect IPS in the concentration range 0.02–1.2 nM, with a detection limit of 0.010 nM. It has been applied to the determination of IPS in rice samples. The relative standard deviation was 4.4–5.8%, and the recovery was 97.7–104%. An Ag nanosol plasmon SERS/Abs dimode aptamer assay was fabricated for trace isocarbophos, based on highly catalysis MOF@OCTB nanoenzyme. [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]

At temperature of 75 °C, the ethanol-HAuCl4 reaction to generate gold nanoparticles is relatively slow (AuNPs), and the noble metal nanoparticles can catalyze this nanoreaction. Sulfite can reduce PdCl2-H2PtCl6 to generate PtPd nanoalloy (PtPd) and strong catalysis to generate red AuNPs, which has a strong RRS peak at 370 nm. When Victoria blue 4R (VB4R) is added, it produced a strong SERS peak at 1617 cm−1. We use SERS, RRS, absorption spectroscopy, electron microscopy, and other techniques to study the catalytic reaction of PtPd nanoalloy and propose a new mechanism for the nanoalloy catalytic reactions. When the SO32−concentration in the system gradually increases, the AuNPs produced by the catalytic reaction gradually increase and the RRS/SERS peak intensity increases linearly. Based on the nanoalloy catalytic amplification strategy, a new and sensitive RRS/SERS coupled dual-mode detection method for SO32− was constructed, with linear range of 0.13–12.1 μg·L−1 and a DL of 0.02 μg·L−1. [ABSTRACT FROM AUTHOR]

The stable silver nanotriangle (AgNT) sol was prepared by reduction of silver ions with sodium borohydride in the presence of HO and sodium citrate. Under the action of NaCl, AgNTs were aggregated to a highly surface-enhanced Raman scattering (SERS) active substrate. In pH 6.0 NaHPO-NaHPO buffer solution (PBS) at 80 °C water bath, ninhydrin reacted with amino acids to form blue-violet complex Ruhemann's purple (RP), and the RP molecules adsorbed on the aggregated AgNT surfaces that exhibited a strong SERS peak at 657 cm. The peak was linear to amino acid concentration in the range of 0.7-99.8 μmol/L, with a detection limit (DL) of 0.5 μmol/L. This SERS method was applied to detect amino acid in samples, with satisfactory results. In addition, the analytical system was also investigated by resonance Rayleigh scattering (RRS), absorption, and electron microscope techniques. [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]

The reduced graphene oxide/silver nanotriangle (rGO/AgNT) composite sol was prepared by the reduction of silver ions with sodium borohydride in the presence of HO and sodium citrate. In the nanosol substrate, the molecular probe of acridine red (AR) exhibited a weak surface-enhanced Raman scattering (SERS) peak at 1506 cm due to its interaction with the rGO of rGO/AgNT. Upon addition of dopamine (DA), the competitive adsorption between DA and AR with the rGO took place, and the AR molecules were adsorbed on the AgNT aggregates with a strong SERS peak at 1506 cm that caused the SERS peak increase. The increased SERS intensity is linear to the DA concentration in the range of 2.5-500 μmol/L. This new analytical system was investigated by SERS, fluorescence, absorption, transmission electron microscope (TEM), and scanning electron microscope (SEM) techniques, and a SERS quantitative analysis method for DA was established, using AR as a label-free molecular probe. [ABSTRACT FROM AUTHOR]

Using the chemical-microwave reduced procedure with HO, NaBH, and citrate as reducer, a silver nanorod (AgNR)/reduced graphene oxide (rGO) nanosheet composite (AgNR/rGO) was prepared in a solution with good stability. Upon addition of NaCl and molecular probe of rhodamine 6G (Rh6G), a stable and sensitive AgNR/rGO-aggregation (AgNR/rGOA) surface-enhanced Raman scattering (SERS) nanosensor was fabricated for Rh6G that exhibited a strongest SERS peak at about 1505 cm. The SERS peak intensity is linear to Rh6G concentration in the range of 1.0-600 nmol/L, with a detection limit of 0.2 nmol/L. Combined with the iodide SERS quenching effect on the molecular probe, a 8-1500 nmol/L iodine in solution was detected by this SERS nanosensor analytical platform, with satisfactory results. [ABSTRACT FROM AUTHOR]

TiO thin films deposited by magnetron sputtering possess excellent optical transmittance, high refractive index, good adhesion and chemical stability. In this manuscript, TiO thin films deposited by magnetron sputtering was used for the first time as an electron extraction layer in inverted polymer solar cells (IPSCs), and the effect of the TiO thickness on the photovoltaic performance of P3HT:PCBM IPSCs was investigated. The highest PCE value of 3.75% was obtained when the thickness of TiO thin films was in the range between 42 nm and 73 nm. The absorption properties, morphology and structure of the TiO films were characterized by UV-Vis spectroscopy, SEM and Raman spectroscopy, and were related to the device performance of P3HT:PCBM IPSCs. The results indicate that TiO films deposited by magnetron sputtering are an excellent electron extraction layer for IPSCs. [ABSTRACT FROM AUTHOR]

In pH 5.5 2-( N-morpholino)-ethanosulfonic acid buffer solution containing 0.25 M NaCl at 80 °C, the single-stranded substrate DNA hybridizes with the enzyme DNA to form double-stranded DNA (dsDNA). The substrate chain of dsDNA could be cracked catalytically by UO to produce a short single-stranded DNA (ssDNA) that adsorbed on the nanogold (NG) surface to form a stable nanogold-ssDNA conjugate and then further combine with rhodamine 6G (RhG) to form a NG-ssDNA-RhG conjugate that can be monitored by the surface-enhanced resonance Raman scattering (SERRS) spectral technique at 1,360 cm. Under the selected conditions, the increased SERRS intensity Δ I was linear to UO concentration in the range of 5-125 nmol/L, with a detection limit of 1.6 nmol/L. Using a 0.5-μmol/L Hg as enhancer, a 2.5-100-nmol/L UO can be determined. [ABSTRACT FROM AUTHOR]

In pH 8.4 Tris-HCl buffer solutions, alcohol dehydrogenase catalyzed the reaction between ethanol and nicotinamide adenine dinucleotide to produce acetaldehyde. In the medium of HCl, acetaldehyde reduced HAuCl to form gold particles that exhibited a strong resonance scattering (RS) peak at 600 nm. The RS peak increased with ethanol concentration. The increased RS intensity at 600 nm (Δ I) was proportional to the ethanol concentration ( C) from 0.068 to 10.2 mmol/L, with a regression equation of Δ I = 35.59 C + 16.1, and a detection limit (3 σ) of 3.2 μmol/L. This proposed method was applied to detect ethanol in saliva and plant cell culture medium 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 2.72 HCl-NaAc buffer solution at room temperature and in the presence of a nanocatalyst of FeO nanoparticles, potassium persulfate rapidly oxidized folic acid (FA) to form a product with strong fluorescence at 446 nm. The analytical conditions were considered, and a simple, rapid, and accurate fluorescence method was proposed for the determination of 0.007-8.0 mg/L FA, with a detection limit of 2.0 ng/mL FA. This method was applied to the analysis of FA in a real sample with satisfactory results that agree with the HPLC results. [ABSTRACT FROM AUTHOR]

In pH 6.0 NaHPO-NaHPO buffer solution and in the presence of cetyltrimethyl ammonium bromide, nanosilver particles were aggregated to a stable suspension. Therein, rhodamine 6G (Rh6G) exhibited three strong surface-enhanced Raman scattering (SERS) peaks at 613, 1,363, and 1,510 cm, and their SERS intensities were enhanced when the concentration of Rh6G increased. In the presence of Hg, the SERS intensity decreased greatly owing to formation of stable Rh6G-HgBr ternary association complex molecules as well as its particles. In the optimal condition, the decreased SERS intensity at 613 cm responds linearly with the concentration of Hg over 25-2,000 nmol/L. Thus, a new sensitive SERS method has been proposed for the determination of trace Hg in the water sample, with satisfactory results. [ABSTRACT FROM AUTHOR]

In pH 5.5 2-( N-morpholino)-ethanosulfonic acid buffer solution containing 0.0125 M NaCl at 80 °C, the single-stranded substrate DNA hybrid with enzyme DNA to form double-stranded DNA (dDNA). The substrate chain of dDNA could be cracked catalytically by UO to produce a short single-stranded DNA (ssDNA) that adsorbed on the nanogold (NG) surface to form stable NGssDNA conjugate, and the unadsorbed NG take place aggregation to produce the NG aggregations in blue color. Both NG and NGssDNA exhibited strong catalytic activity on the gold particle reaction between HAuCl and ascorbic acid that can be monitored by resonance scattering (RS) spectral technique at 620 nm. However, the catalytic effect of NG aggregation was very weak and it cannot be separated from the cracked reaction solution. When the UO concentration increased, the ssDNA increased, the NGssDNA increased, the formed gold particles increased, and the RS intensity at 620 nm increased. The increased RS intensity Δ I was linear to UO concentration in the range of 3.35-23.45 pM, with a regression equation of Δ I = 27.6 C + 29.1, and detection limit of 0.1 pM. This new RS assay was applied to analysis of UO in water sample with satisfactory results. [ABSTRACT FROM AUTHOR]

In pH 8.9 Tris-HCl buffer solutions, alkaline phosphatase (ALP) catalyzed the hydrolysis of ascorbic acid 2-phosphate (AAP) substrate to form ascorbic acid. Then HPO was added to stop the enzymatic reaction and HAuCl was used to react with ascorbic acid to generate gold nanoparticles that exhibited a resonance scattering (RS) peak at 600 nm. Under the selected conditions, when the activity of ALP increased, the formed ascorbic acid and gold nanoparticles also increased. Thus, the RS intensity at 600 nm enhanced linearly. The linear range was 0.06-22 U/L, with a detection limit of 0.03 U/L. The ALP in serum was analyzed, and the results were in agreement with those of the fluorescence method. [ABSTRACT FROM AUTHOR]

In pH 1.99 sodium acetate-HCl buffer solutions at 60 °C, Rhodamine B exhibited a strong fluorescence peak at 584 nm using an excitation wavelength of 548 nm. The fluorescence quenching occurred when FeO nanoparticles catalyzed HO oxidation of Rhodamine B. Under the chosen conditions, the fluorescence intensity at 584 nm decreased when the concentration of HO increased. The fluorescence quenching intensity is linear with the concentration of HO in the range of 10-200 nmol/L. Thus, a new and simple and sensitive nanocatalytic fluorescence method was proposed for the determination of HO in synthetic sample, 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]

The resonance scattering spectral probe for Pb was obtained using aptamer-modified AuPd Nanoalloy. In the pH 7.0 NaHPO-NaHPO buffer solution, the aptamer interacted with AuPd nanoalloy particles to form stable aptamer-AuPd nanoalloy probe for Pb that is stable in high concentration of salt. The probe combined with Pb ions to form a G-quadruplex and to release AuPd nanoalloy particles that aggregate to form big particles which led the resonance scattering (RS) intensity enhancing. The reaction solution was filtered by 0.15 μm membrane to obtain the filtration containing aptamer-AuPd nanoalloy probe that has strong catalytic effect on the electrodeless nickel particle plating reaction between Ni(II) and PO that exhibited a strong RS peak at 508 nm. The RS intensity at 508 nm decreased when the Pb concentration increased. The decreased intensity (Δ I) is linear to the concentration of 0.08-42 nM Pb, with regress equation of $$ \Delta {I_{{5}0{\rm{8nm}}}} = {16}.{3}\,c + {1}.{5} $$, correlation coefficient of 0.9965, and detection limit of 0.04 nM Pb. The RS assay was applied to the analysis of Pb in wastewater, with satisfactory results. [ABSTRACT FROM AUTHOR]

The gold-rhenium (AuRe) composite nanoparticle was prepared by NaBH reduction procedure, and was modified by the aptamer to obtain an AuRe nanoprobe (AuRessDNA) for thrombin. In pH 7.0 Tris-HCl buffer solution and in the presence of salt, the nanoprobe specifically combined with thrombin to form AuRe-aptamer-thrombin cluster that resulted in the resonance scattering intensity ( I) increasing at 560 nm. The increased intensity Δ I was linear to the thrombin concentration in the range of 0.115-6.93 nmol/L, with a regression equation of Δ I = 53.0 C + 2.5, a correlation coefficient of 0.9989, and a detection limit of 13 pmol/L. This method was applied to detect thrombin in human plasma samples, with satisfactory results. [ABSTRACT FROM AUTHOR]

The resonance scattering spectral technique has been established using the synchronous scanning technique on spectrofluorometry. Because of its advantages of simplicity, rapidity and sensitivity, it has been widely applied to analyses of proteins, nucleic acids and inorganic ions. This paper summarizes the application of immunonanogold and aptamer modified nanogold (AptAu) catalytic resonance scattering spectral technique in combination with the work of our group, citing 53 references. [ABSTRACT FROM AUTHOR]

Single-strand deoxyribonucleic acid (ssDNA) were used to modified nanogold particle to obtain a aptamer-nanogold probe (NGssDNA) for Hg(II). The probe is not aggregated in high concentration of NaCl. In the pH 7.0 Na2HPO4-NaH2PO4 buffer solution and in the presence of high concentration of NaCl, NGssDNA interact with Hg(II) to form stable double-strand T-Hg(II)-T mismatches and to release nanogold particles from the probe. The released nanogold particles aggregated to form bigger clusters which leaded the resonance scattering (RS) intensity at 540 nm enhanced linearly with the concentration of Hg2+ in the range of 0.39–1666.7 nM, with detection of 0.1 nM. This simple, rapid, and sensitive aptamer-nanogold RS assay was applied to determination of Hg2+ in wastewater, with satisfactory results. [ABSTRACT FROM AUTHOR]

In the medium of H2SO4 and in the presence of TiO2+, gold nanoparticles in size of 10 nm exhibited a weak surface plasmon resonance scattering (SPRS) peak at 775 nm. Upon addition of trace H2O2, the yellow complex [TiO(H2O2)]2+ formed that cause the gold nanoparticles aggregations to form bigger gold nanoparticle clusters in size of about 900 nm, and the SPRS intensity at 775 nm ( I) enhanced greatly. The enhanced intensity Δ I was linear to the H2O2 concentration in the range of 0.025–48.7 μg/mL, with a detection limit of 0.014 μg/mL H2O2. This SPRS method was applied to determining H2O2 in water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Nanogold particles of 10 nm were used to label goat anti-human IgG (GIgG) to obtain nanogold-labeled GIgG (AuGIgG). In a citrate-HCI buffer solution of pH 2.27, AuGIgG showed a strong catalytic effect on the reaction between HAuCl4 and NH2OH to form big gold particles that exhibited a resonance scattering (RS) peak at 796 nm. Under the chosen conditions, AuGIgG combined with IgG to form immunocomplex AuGIgG-IgG that can be removed by centrifuging at 16000 r/min. AuGIgG in the centrifuging solution also showed catalytic effect on the reaction. On those grounds, an immunonanogold catalytic RS assay for IgG was designed. With addition of IgG, the amount of AuGIgG in the centrifuging solution decreased; the RS intensity at 796 nm ( I 796 nm) decreased linearly. The decreased intensity Δ I 796 nm was linear with respect to the IgG concentration in the range of 0.08–16.0 ng · mL−1 with a detection limit of 0.02 ng · mL−1. This assay was applied to analysis of IgG in sera with satisfactory sensitivity, selectivity and rapidity. [ABSTRACT FROM AUTHOR]

Silver nanoparticles were prepared under a microwave high-pressure condition using citric acid sodium as a reducer while the excess citrate was removed under high speed centrifugation. There is a resonance scattering (RS) peak at 470 nm for silver nanoparticles. In a pH 4.0 HAc-NaAc buffer solution, hydroxyl radicals from the Fenton reaction can oxidize silver nanoparticles to Ag+, resulting in the RS intensity decreasing. The decreased RS intensity at 470 nm (Δ I 470 nm) is linear with respect to the concentration of H2O2 ( C) in the range of 0.27–7.56 μmol/L with a detection limit of 0.23 μmol/L. Its regression equation is Δ I 470 nm = 24.3 C + 13.8 with a correlation coefficient of 0.9959. This method was applied to screening the antioxidants with satisfactory results. [ABSTRACT FROM AUTHOR]

Silver nanoparticles in size of 8.0 nm was prepared by the trisodium citrate and used to label goat anti-human fibrinogen. In the pH 5.8 Na2HPO4-NaH2O4 buffer solution (PBS) and in the presence of polyethylene glycol (PEG) and KCl, the immune reaction between silver-labeled goat anti-human fibrinogen and fibrinogen took place and led the resonance scattering intensity at 465 nm ( I 465) to decreasing. The I 465 decreased intensity was linear to the fibrinogen concentration in the range from 0.067 to 1.67 μg/mL, with a detection limit of 0.024 μg/mL. This method was applied to determination of fibrinogen in human plasma, with satisfactory results. [ABSTRACT FROM AUTHOR]

The gold nanoparticles in diameter of 10–95 nm have been prepared by Frens procedure, all of which exhibit a resonance scattering peak at 580 nm. The mechanism of resonance scattering for gold nanoparticle has been considered according to the wave motion theory of nanoparticle in liquid. The principle of superamolecular interface energy band(SIEB) has been set up and utilized to explain the relationship between the diameter and colors for gold nanoparticle in liquid. A novel spectrophotometric ruler for the determination of the diameter has been proposed according to the relationship of the maximum absorption wavelength and diameter. [ABSTRACT FROM AUTHOR]

The binding equilibrium between l− and human serum albumin (HSA) or bovine serum albumin (BSA) has been studied by means of the resonance Rayleigh scattering (RRS) and equilibrium dialysis. It has been found for the first time that RRS and multiple frequency scattering (MFS) are enhanced as the l− binding to the HSA and BSA, but fluorescence quenches. The equilibrium dialysis results suggest that the binding of l− to HSA and BSA fits a phase-distribution model other than Scatchard model, and that the order of magnitude of its phase-distribution constant was found to be 104. It is most probable that Cl− or other anion ions influence the binding of l− by changing the ionic strength in the solution. The dialysis at different pH indicates that the binding mechanism is due to the electrostatic forces between the l− and protonated basic amino-acid residues. [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]

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

A fluorometric clenbuterol immunoassay is described that uses S- and N-co-doped carbon quantum dots as the fluorescent probe. Strongly fluorescent S/N-doped carbon quantum dots (S/N-CDs) were synthesized by hydrothermal method using fructose as the carbon precursor and L-cysteine as S/N sources. The S/N-CDs were characterized by transmission electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy (FTIR). Under 350 nm photoexcitation, they display strong purple fluorescence with an emission peak at 405 nm. In pH 4.0 solution, the amino groups (confirmed by FTIR) on the carbon quantum dots were coupled to clenbuterol antibody (Ab) by amine–amine coupling reaction to quench the fluorescence. If clenbuterol (Clen) is added, it binds to the Ab to generate a stable Ab-Clen immunocomplex and free S/N-CD. This causes the fluorescence of nanoprobe to be restored. The fluorescence of the system increases linearly in the 0.07–1.7 ng·mL−1 Clen concentration range. The probe of type S/N4-CD displays the best sensitivity. The detection limit is 23 pg·mL−1. [ABSTRACT FROM AUTHOR]

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