Metal-enhanced Fluorescence Effect Research Articles

An NIR-driven biosensor based on the metal-enhanced fluorescence effect and a signal amplification strategy for miRNA detection.

Research has shown that the expression level of microRNA-155 (miRNA-155) is positively correlated with clinical stage and depth of invasion in patients with cervical cancer and cervical intraepithelial neoplasia and tends to be highly expressed. Therefore, it is very important to develop sensitive miRNA-155 analysis methods for the early diagnosis, treatment, and prognostic evaluation of cervical cancer. In this study, a near-infrared light-driven fluorescent biosensor based on the metal-enhanced fluorescence effect of polydopamine-coated upconversion nanoparticle (UP/Au) and two toehold-mediated strand displacement (TMSD) steps was constructed for the detection of miRNA-155. The target miRNA-155 can undergo a TMSD1 reaction with single-stranded DNA1 (ssDNA1) modified on wrinkled silica (WSNs) to form the ssDNA1/miRNA-155 complex and expose toehold 2. Through the TMSD2 reaction, ssDNA2 adsorbed on the UP/Au surface reacts with ssDNA1 to form the ssDNA1/ssDNA2 complex, which replaces miRNA-155 and enables the recovery of the UP/Au fluorescence signal. The target miRNA-155 was reacted with the new ssDNA1 to amplify the detection signal, with a detection range of 0.5-20 pM and a detection limit of 19.76 fM for miRNA-155. In addition, the fluorescent biosensor has been applied for the analysis of miRNA-155 in serum samples, indicating its good practicality.

Design of silver nanoparticle-embedded nano zirconium-based metal-organic frameworks for highly sensitive detection of chlorpyrifos in real samples.

Chlorpyrifos (CPS) is widely found in food and water sources due to agricultural use, posing health and environmental risks. Therefore, this work introduces a fluorescent sensor design of silver nanoparticle-embedded nano zirconium-based metal-organic frameworks (UiO-66-NH2@AgNPs) for accurate examination of CPS. Briefly, UiO-66-NH2 was synthesized hydrothermally, exhibiting weak luminescence owed to ligand-to-metal charge transfer (LMCT). Here, it limits its direct utility in fluorescence-based detection. To address this limitation, silver nanoparticles (AgNPs) were introduced into UiO-66-NH2, enhancing fluorescence via the metal-enhanced fluorescence (MEF) effect. Briefly, a comprehensive spectral analysis such as XPS, SEM, TEM, PXRD, etc., was performed to validate the synthesis of UiO-66-NH2@AgNPs. Subsequent evaluation revealed that CPS effectively quenched the luminescence intensity of UiO-66-NH2@AgNPs through a static quenching mechanism. The fluorescence intensity exhibited good linearity with CPS concentration in the span of 10 to 1,000 ng/mL, with a recognition limit of 191.5ng/mL(S/N = 3). The interaction involved Ag-S bond formation and electrostatic interactions, reducing fluorescence intensity. The method was confirmed through successful CPS detection in fruit samples. The UiO-66-NH2@AgNPs nanoprobe offers a simple, sensitive, and accurate platform for CPS sensing, with potential for future use in detecting CPS in fruits and vegetables.

Metal-enhanced fluorescence (MEF) effect based on silver nanoparticles with different UV spectra on a surface carbon dot-based novel dry platform

In this work, to enhance the fluorescence quantum yield of carbon dots (CDs), a novel metal-enhanced fluorescence (MEF) structure was designed by decorating CDs on silver nanoparticle (AgNPs) film. The glass slide-AgNPs (GS-AgNPs) structure was fabricated using the electrostatic adsorption method, and the AgNPs-CDs structures were prepared by the direct drying method, which then formed the GS-AgNPs-CDs composite structure. In this structure, the MEF effect was found to be size dependent by changing the 5 types of AgNPs with different sizes. And the MEF effect also decreased as the distance between the AgNPs and CDs increased by using polyvinylpyrrolidone (PVP) to separate the AgNPs and CDs. This hybrid structure can be used as a fluorescence detection platform and the recorded fluorescence intensity of GS-AgNPs 428 nm-CDs achieved a maximum enhancement factor (EF) of 31.72. Considering the high enhancement factor, this system may become promising to find potential applications in biochemical assay fields.

Temperature-sensitive metal-enhanced fluorescence and plasmon resonance energy transfer.

Experimental decoupling of the effects of plasmon resonance energy transfer (PRET) and metal-enhanced fluorescence (MEF) within the same nanometal-fluorophore pair is fascinating but challenging. In this study, we presented a possible solution for this by coating plasmonic Au nanoparticles (AuNPs) with temperature-sensitive poly(N-isopropylacrylamide) (pNIPAM) shells and R6G hybrids, termed the Au@p-R nanoplatform, which could reversibly adjust the separation between dyes and the AuNP surface, enabling an ON/OFF switch between MEF and PRET. In our optimization process, we discovered that 20 kDa of pNIPAM causes an MEF effect owing to an appropriate shrinking distance of 6.86 ± 0.85 nm. This dual-model nanoplatform exhibits great potential for tracking temperature-dependent transitions.

Competitive fluorescent immunoassay for the ultrasensitive determination of amyloid beta peptide1-42 based on Ag@SiO2@N, S-GQD nanocomposites.

A competitive fluorescent immunoassay is described for the ultrasensitive determination of amyloid beta peptide1-42 (Aβ1-42), a biomarker for early diagnosis of Alzheimer's disease. N, S-doped graphene quantum dots (N, S-GQDs) were freely assembled on the surface of Ag@SiO2 nanoparticles to obtain a composite (Ag@SiO2@N, S-GQD nanocomposite), which was successfully prepared and characterized. By theoretical study, the optical properties of nanocomposites are improved compared with GQDs, due to the advantages of combining N, S co-doping and metal-enhanced fluorescence (MEF) effect of Ag NPs. In addition, Aβ1-42 was modified by Ag@SiO2@N, S-GQDs to prepare a probe with high photoluminescence properties (Ag@SiO2@N, S-GQDs-Aβ1-42). In the presence of Aβ1-42, a competitive reaction towards anti-Aβ1-42 fixed on the ELISA plate was proceeded between Aβ1-42 and Ag@SiO2@N, S-GQDs-Aβ1-42 by specific capture of antigen-antibody. The emission peak of Ag@SiO2@N, S-GQDs-Aβ1-42 (400 nm emission) was used for the quantitative determination of Aβ1-42. Under the optimal conditions, the fluorescent immunoassay exhibited a linear range of 0.32 pg·mL-1-5 ng·mL-1 with a detection limit of 0.098 pg·mL-1. The results show that the immunoassay has good analytical ability and can provide a new method for the clinical determination of Aβ1-42.

Metal-Enhanced Fluorescent Carbon Quantum Dots via One-Pot Solid State Synthesis for Cell Imaging

In this study, a facile one-pot solid-state synthesis method is developed to shed light on the metal-enhanced fluorescence (MEF) effect in carbon quantum dots (CQDs) and gold nanoparticles (AuNPs) hybrid materials. This is one of the few studies on the solid-state synthesis of N-doped CQDs/gold hybrid nanomaterials. We have conducted various sets of experiments to reveal the role of individual reagents during the nucleation and growth of nanoparticles. We have demonstrated that the addition of a small amount of gold salt illustrates a paramount effect (103-fold) in photoluminescence intensity. This effect is ascribed to MEF, which is caused due to interactions between the excited-state fluorophores and the free surface electrons of metal nanoparticles. It is interesting to note that a further increase of gold yields fluorescence quenching due to a large number of formed AuNPs causing fluorescence resonance energy transfer. By adjusting the volume ratio of gold salt and CD precursors, it is possible to obtain the CQDs-AuNPs hybrid with the highest fluorescence, which produces extensive visible light under 460 nm excitation. Synthesized materials have been successfully used for imaging human dermal fibroblasts and A549 lung epithelial cells. The dose-dependent cytotoxicity studies reveal that the hybrid structures do not have cytotoxicity.

Ag/Periodic Mesoporous Organosilica Yolk–Shell Nanostructures for Ratiometric Cu2+ Fluorescent Sensors

The creation of yolk–shell nanoparticles (YS NPs) with a movable core and periodic mesoporous organosilica (PMO) shell has been simplified using a “ self-template” strategy. In this method, the knitting of the PMO shell and the formation of the interlayer cavity co-occur. This benefit contributes to the simplification of preparation processes and the realization of greater YS NP preparation efficiency with varied functional cores. By incorporating a silver nanocore into the YS NP (Ag-PMO-YS), a ratiometric Cu2+ fluorescence sensor is created by the “like dissolves like” principle driving the self-assembly of fluorescein derivatives and Cu2+ ligands within the surfactant micelles. Due to the coordination of Cu2+ and its ligands and their impact on the emission of fluorescein derivatives, which take part in the fluorescence resonance energy transfer (FRET) process with carbon dots (CDs), this sensor system demonstrates extraordinary detection sensitivity to Cu2+ (10–7 M). Additionally, the movable Ag nanocore’s metal-enhanced fluorescence (MEF) effect strengthens the high detection sensitivity and stability.

Ag–ZnO Nanocomposites as a 3D Metal-Enhanced Fluorescence Substrate for the Fluorescence Detection of DNA

Fluorescence enhancement, including metal-enhanced fluorescence (MEF), has been widely explored in the field of biosensor technology. Two- and three-dimensional (2D and 3D) MEF substrate approaches have been developed for biosensors to detect target biomarkers such as genes and proteins. However, several issues remain, not least poor reproducibility caused by limited recognition and diffusion of biomolecules among target molecules, biological probes, and MEF substrates in aqueous environments. Here, an Ag–ZnO nanocomplex as a 3D MEF substrate was developed in two steps: hydrothermal synthesis of ZnO nanowire (NW) as a building block of Ag nanoparticles (NPs), and photochemical deposition of AgNPs on the ZnO NW. Fluorescence enhancement on Ag–ZnO nanocomposites (NCs) compared with the glass substrate was 14.8-, 16.9-, 11.4-, and 14.2-fold in the presence of 10, 20, 40, and 60 base pair (bp) double-stranded (ds) DNA, respectively. The MEF effects on glass, ZnO NW, and Ag–ZnO NCs were analyzed by measuring the fluorescence lifetime of fluorescein (FAM)-labeled dsDNA, and the average lifetimes were 9.76, 9.34, and 7.86 ns, respectively. Ag–ZnO NCs showed a 50-fold higher sensitivity for the detection of dsDNA than Ag nanoisland film (AgNIF) as a 2D MEF substrate. Therefore, Ag–ZnO NCs may have potential as a 3D MEF substrate. The MEF phenomenon might involve broad-range interactions between the surface of the metal nanostructure on Ag–ZnO NCs and fluorophores in various scenarios. Our Ag–ZnO NCs could facilitate the development of sensitive MEF-based biosensors for DNA detection.

Multifunctional plasmonic micro/nanobeads for sensitive suspension array assay and mass spectrometry analysis

Plasmonic micro/nanobeads exhibit unique physicochemical properties attributed to their localized surface plasmon resonance (LSPR), enabling use in sensitive suspension array assays and matrix-assisted laser deposition/ionization mass spectrometry (MALDI-MS) analysis. Herein, we report a facile method for the preparation of magnetic plasmonic micro/nanobeads by the combination of Shirasu porous glass (SPG) membrane emulsification and polydopamine (PDA)-assisted in-situ reduction. The magnetic responsiveness properties endowed by doped Fe3O4 nanoparticles result in easy and complete separation of unwanted components during the preparation and bio-reaction processes. In addition, the coverage degree of the plasmonic shell can be flexibly controlled. As a result of the significant metal-enhanced fluorescence effect, as-prepared plasmonic microbeads enable the sensitive detection of alpha-fetoprotein (AFP) and deoxyribonucleotide (DNA) in suspension array with detection limits of 0.11 ng mL−1 and 1.65 fmol mL−1, respectively, 8.6 times and 2 orders of magnitude higher than unmodified microbeads. Furthermore, as-prepared plasmonic nanobeads can be used as a matrix for MALDI-MS to allow the detection of low molecular weight biological molecules. As little as 0.2 pmol of proline and serine can be detected in a sample as small as 0.5 μL. This work provides a general strategy for the design of multifunctional plasmonic micro/nanomaterials that will help promote further advancements in sample analysis.

Highly sensitive detection of dopamine based on gold nanoflowers enhanced-Tb(III) fluorescence

We developed a trace level detection method for dopamine (DA) based on the metal-enhanced fluorescence (MEF) effect of gold nanoflowers (AuNFs). AuNFs prepared were excellent enhancement fluorescence substrates due to their unique morphology with rich edges and sharp quoins. DA was the target analyte and also as a bridge reagent that could regulate the distance between AuNFs and Tb3+. The characteristic fluorescence of Tb3+ was enhanced significantly through the synergistic effect between the luminescence sensitized by DA and the MEF caused by AuNFs. Under the optimum experimental conditions, the fluorescence intensity of Tb3+ at 545 nm demonstrated very significant sensing ability against DA concentration and showed a good linear relationship in the range of 0.80–300 nM and the limit of detection was 0.21 nM (S/N = 3). The proposed method was also validated in serum samples and the dopamine hydrochloride injection samples with satisfactory results.

Multilayers of avidin–biotin complexes as spacers used in the study of the effect of metal‐enhanced fluorescence

AbstractThe effects of metal‐enhanced fluorescence (MEF) of rhodamine dye by gold sub‐micro hexagonal plates were studied. A multilayered avidin–biotin complex was designed and used as a spacer to connect the fluorophore and the sub‐microplate. Fluorescence lifetime image microscopy (FLIM) combined with time‐correlated single‐photon counting was used to obtain lifetime images and intensities of dye on single particles. Gold hexagon plates ~900 nm were synthesized, and the avidin–biotin complexes were placed layer‐by‐layer for up to 4 layers onto the sub‐microplates. All emission curves of fluorophore displayed biexponential decay with short lifetimes of 18–23 ps and long lifetimes of 249, 271, 304, and 348 ps for 1–4 layers on gold sub‐microplates, respectively. Using the kinetic model of energy transfer between fluorophore and nanoparticles to explain the coupling mechanism, we found that the excited fluorophore transferred energy mostly to the high‐order modes for the 1‐layered avidin–biotin complexes enclosing gold nanospheres, consequently resulting in a non‐emissive pathway. The 4‐layered samples had the highest emission intensity because, at those distances, the enhancement by the gold sub‐microplates during plasmonic excitation remained high and became comparable to the energy quenching rate. Using the composed complexes, the MEF effect achieved the maximal enhancement in this system.

Plasmon-Enhanced Fluorescence in Electrospun Nanofibers of Polydiacetylenes Infused with Silver Nanoparticles.

A hybrid computational and experimental approach was employed toward the rational design of a silver nanoparticle (AgNP)/polydiacetylene (PDA) metal-enhanced fluorophore (MEF) ensemble system contained within a poly(ethylene oxide) (PEO) electrospun nanofiber matrix for creation of high-performance sensors. Simulations based on Mie theory and finite-difference time domain (FDTD) algorithms were performed to understand and optimize spectral overlap between the AgNP localized surface plasmon resonance and the absorbance and emission spectra of PDA, a supramolecular polymer fluorophore. A series of AgNPs of varied sizes were investigated for fluorescence enhancement capability, and an optimal size of 134 nm in diameter was chosen for synthesis and incorporation into the electrospun nanofibers of a PDA/PEO composite for experimental characterization and confirmation. Results on individual nanofibers indicated a clear metal-enhanced fluorescence effect, and a 4.6-fold enhancement over neat PDA/PEO fluorescent nanofibers was observed. The nanofiber/nanoparticle/MEF ensemble system offers new avenues for generating effective sensing devices with polymeric fluorophores using a straightforward incorporation approach.

Development of metal enhanced fluorescent nanomaterials featuring gold nanocubes in proximity to carbon nanodots

In the present study, gold nanocube (AuNC) particles conjugated with a carbon nanodot (CND) layer and spaced with polyethylene glycol (PEG) were prepared to generate a metal-enhanced fluorescence (MEF) effect. This is the first report of MEF from gold nanoparticles in proximity to CNDs. Biocompatible materials (AuNCs, CNDs, and PEGs) were used to fabricate the proposed AuNC-CND complex, thus providing potential utilities of fluorescent materials in various nanobiotechnology fields. Additionally, the use of AuNCs played a critical role in controlling the size and shape of amorphous CNDs exhibiting a soft polymer cluster morphology stemming from bottom-up synthesis. We also attempted to explain the complex interplay between the quenching and enhancing processes through the energy transfer direction between the AuNCs and CNDs based on our experimental results for photoluminescence emission spectra, dark-field microscope imaging, and single-particle scattering measurements in relation to differences in the size of core metals, and the concentration of fluorophores.

Fluorescence turn-on immunosensing of HE4 biomarker and ovarian cancer cells based on target-triggered metal-enhanced fluorescence of carbon dots

Rapid and sensitive detection of tumor biomarkers and cancer cells is of crucial importance for the early diagnosis and prognosis prediction of cancer. The present report describes a target-induced fluorescence enhancement immunosensor that utilizes the optical property of carbon dots (CDs) and the metal-enhanced fluorescence effect (MEF) property of silver nanoparticles (AgNPs) for the sensitive detection of the cancer biomarker human epididymis protein 4 (HE4) and ovarian cancer cells. Nitrogen and sulfur co-doped CDs with a quantum yield of 85.6% were prepared and served as the fluorophore in MEF. The HE4 antibody (Ab) specific to the HE4 antigen was linked covalently to the surface of the synthesized CDs as the capture. The HE4 Ab-conjugated AgNPs (AgNPs-Ab) were prepared and utilized as signal amplification elements. In the presence of the target HE4, composite sandwich structures were formed between the labeled CDs-Ab and AgNPs-Ab, which brought the CDs and AgNPs into proximity, resulting in the fluorescence of CDs enhancement owing to MEF. The intensity of fluorescence enhancement was positively correlated with the HE4 concentration in the clinically important range of 0.01–200 nM with a limit detection of 2.3 pM. Moreover, the immunosensor was also successfully applied to specific fluorescence labeling and quantitative determination of HE4-positive ovarian cancer cells. The proposed target-triggered MEF sensor platform demonstrated high sensitivity, excellent anti-interference ability, along with successful validation in complex biological matrices, providing a new approach for HE4 detection in early diagnosis and therapeutic monitoring.

DNA precisely regulated Au nanorods/Ag2S quantum dots satellite structure for ultrasensitive detection of prostate cancer biomarker

Currently, metal-enhanced fluorescence (MEF) is an emerging effective technology for sensitive bio-detection. In this report, the distance between Au nanorods (Au NRs) and NIR Ag2S quantum dots (Ag2S QDs) is precisely regulated by DNA with different chain lengths. The experimental results show that the best MEF effect can be obtained when the distance is about 8 nm. Based on the result, Au NRs and Ag2S QDs were modified with DNA at specific distances, which were used for accurate detection of prostate cancer marker PCA3 with high sensitivity and selectivity. And the designed biosensor show a good linear relationship in the 5−500 pM and a low detection limit of 1.42 pM (S/N = 3) for PCA3. Importantly, the designed metal-enhanced NIR fluorescence satellite structure probe have been successfully applied for sensing PCA3 in human serum samples and lysates of prostate cancer cells (1, 5 and 10 cells), which has significant potential in the field of biosensing, biological analysis and clinical diagnosis.

Inflow nano-optics from the near-to the far-field detection based on Metal-Enhanced Fluorescence signaling

In this communication we evaluated the detection and tracking of Ultraluminescent gold core–shell nanoplatforms based on Metal-Enhanced Fluorescence (MEF) within colloidal dispersion by In-Flow Cytometry and Imaging Flow Cytometry (IFC). The enhanced properties were developed by the incorporation of Rhodamine B (RhB) as a laser dye reporter at variable controlled silica spacer lengths (Au@SiO2-RhB) from a gold core template. Thus, SiO2 was varied from 6 to 7 nm to 25 nm in order to place the laser dye sensitizer at different lengths of the higher electromagnetic fields surrounding the 45-nm gold core diameter. By Laser Fluorescence Microscopy, high intense emissions were shown at shorter SiO2 lengths, while lower emissions were found towards longer ones. These characteristics related to MEF were evaluated by in-flow cytometry with dual laser excitation and fluorescence detection, and by an IFC set-up. By In-flow cytometry, different scattered-light distributions were shown, depending on the nanoparticle concentrations in the colloidal dispersion and size of the Au@SiO2-RhB. Moreover, varied fluorescent event detections and counting were recorded according to the SiO2 lengths applied. A ratio of fluorescent event detection counting of core–shell/core-less of 40–42 was established for optimal MEF Enhancement Factors (MEFEF) of 41–43 determined by Laser Fluorescence Microscopy. Core-less nanoparticles showed a marked decrease of fluorescent event detection counting caused by higher photobleaching and absence of the MEF effect. Hence, an improved detection effect was shown within in-flow based on MEF from single nanoplatforms. Therefore, the Ultraluminescence emission of core–shell nanoarchitectures within in-flow techniques was shown and discussed. A non-classical light in real time within colloidal gold core–shell nanoparticles was generated by accurate control of their architectures.

Characterization of Plasmonic Scattering, Luminescent Down-Shifting, and Metal-Enhanced Fluorescence and Applications on Silicon Solar Cells.

This paper studied characterized the plasmonic effects of silver nanoparticles (Ag-NPs), the luminescent down-shifting of Eu-doped phosphor particles, and the metal-enhanced fluorescence (MEF) achieved by combining the two processes to enhance the conversion efficiency of silicon solar cells. We obtained measurements of photoluminescence (PL) and external quantum efficiency (EQE) at room temperature to determine whether the fluorescence emissions intensity of Eu-doped phosphor was enhanced or quenched by excitation induced via surface plasmon resonance (SPR). Overall, fluorescence intensity was enhanced when the fluorescence emission band was strongly coupled to the SPR band of Ag-NPs and the two particles were separated by a suitable distance. We observed a 1.125× increase in PL fluorescence intensity at a wavelength of 514 nm and a 7.05% improvement in EQE (from 57.96% to 62.05%) attributable to MEF effects. The combined effects led to a 26.02% increase in conversion efficiency (from 10.23% to 12.89%) in the cell with spacer/NPs/SOG-phosphors and a 22.09% increase (from 10.23% to 12.48%) in the cell with spacer/SOG-phosphors, compared to the bare solar cell. This corresponds to an impressive 0.85% increase in absolute efficiency (from 12.04% to 12.89%), compared to the cell with only spacer/SOG.

Fabrication of a Nanoplasmonic Chip to Enhance Neuron Membrane Potential Imaging by Metal-Enhanced Fluorescence Effect

Optical imaging is a useful tool to acquire neural activities because of its high spatial resolution, and various voltage indicators were developed to image membrane potential of neurons. Voltage sensitive dyes (VSDs) are one of them but their signal-to-noise ratio (SNR) is so low that enhancing SNR of VSD has become important. In this study, we investigated the metal-enhanced fluorescence (MEF) effect on VSD imaging by fabricating nanoplasmonic resonance chip using gold nanorods (GNRs). To amplify the fluorescence signal we used polyelectrolyte layers to control the distance between metal nanoparticles and fluorophore. Cultured rat hippocampal neurons and di-8-ANEPPS, a widely used VSD, were used to test the nanoplasmonic resonance chip, and the maximum level of fluorescence signal was obtained when nine layers of polyelectrolyte spacer were used. The nanoplasmonic resonance chip with GNR showed the possibility of the improvement in voltage imaging of neurons and is expected to enhance the availability of neuronal activity imaging in the future.

Application of Biomimetic Nanomaterials in Biological Detection and the Intelligent Recognition Method of Nanoparticle Images

New nanomaterials (metal nanoclusters, graphene, etc.) are favored by researchers due to their unique properties and are widely used in biomedical detection. The excellent fluorescence characteristics of gold nanoclusters are utilized to develop a fast and highly sensitive bionic nanomaterial with non-label and dual functions, which can detect silver ions and mercury ions and study the particularity of TEM nanoparticle images. The particle segmentation of TEM nanoparticle images is studied to compare the traditional watershed algorithm and watershed transformation algorithm. The experiment results show that silver ions can enhance the fluorescence of gold nanoclusters to form gold-silver nanoclusters with strong yellow fluorescence, and mercury ions can quickly weaken the fluorescence of gold-silver nanoclusters. Based on the biomimetic nanomaterials, a dual-function fluorescent probe is designed to detect silver ions and mercury ions in lake with detection accuracy of 8 nM and 33 nM respectively; the sensing excitation of the fluorescent probe is further analyzed. Because the metal-enhanced fluorescence (MEF) effect enables the silver element and Au nanoparticles to form fluorescence-enhancing effect, the high metalphilic interaction between mercury ions and silver ions quenches the fluorescence effect of gold nanocluster; the rapid watershed transformation/region fusion method can achieve better particle image segmentation combined with the image segmentation algorithms of different TEM nanoparticles, which can be better applied to the characterization analysis of the preparation of gold nanomaterials.

Metal-enhanced fluorescence detection and degradation of tetracycline by silver nanoparticle-encapsulated halloysite nano-lumen

The ultrasensitive detection and efficient degradation of tetracycline (TC) residues are important for improving food safety and protecting human health. In this paper, a smart silver-enhanced fluorescence platform for the ultrasensitive detection of TC was constructed via a simple and selective modification of the interior and external tubes of natural halloysite nanotubes. The thick pipe wall of this platform provides a natural defense and promotes metal-enhanced fluorescence effects, which subsequently accelerates the detection of TC. Moreover, the nanoplatform of the modified Ag nanoparticles can induce the separation of electrons and holes, thereby enhancing photocatalytic activity in TC degradation. This platform provides new opportunities for studying natural halloysite nanotubes and for simultaneously detecting and photodegrading other deleterious substances.