•Three-in-one role of our designed nanosensor.•Cancer cell discrimination based on expression of sialoglycans via SERS.•Monitoring dynamic sialoglycans expression under external stimuli by SERS.•New method for evaluating sialidase concentration and activity on cell.Sialoglycan expression is critical for assessing various diseases progression. Especially, its abnormal levels are commonly believed to be associated with tumor and metastatic cancer types. While, complicated structures, multiple types and dynamic distributions make it challenging for in situ investigating sialoglycans at the physiological status. Herein, we developed a 4-mercaptophenylboronic acid (MPBA)-based surface-enhanced Raman scattering (SERS) nanosensor to in situ study sialoglycan levels and dynamic expression processes of different cell types based on molecular recognition between phenylboronic acid and sialoglycans at physiological condition. This nanosensor is designed by the MPBA decorated silver nanoparticle (AgNP), which is unique and multifunctional because of its three-in-one role involving the Raman signal enhancer (AgNP), the sensing reporter of MPBA and the target receptor based on the recognition of phenylboronic acid and sialoglycans. When this nanosensor binds to sialoglycans, the molecular vibrational modes of MPBA will change, which can be traced by ultrasensitive SERS technique. The superiority of this study is that we built the relation between the spectral changes of MPBA (relative intensities) in molecular recognition with the sialoglycan dynamic expression of cells. We believe that our SERS strategy could be further extended to explore crucial physiological processes and significant biological system that glycans are involved in.

A supramolecular recognition and oriented assembly system was developed on chip for the highly selective surface-enhanced Raman scattering (SERS) detection of thrombin by means of the aptamer-based SERS tag method. A 15-base thrombin-binding aptamer (TBA15) with a thiol end was first immobilized on an Ag nanoprism array by the S–Ag bond. This aptamer has high binding affinity with thrombin when it folds into a G-quadruplex structure. After the recognition between the aptamer and thrombin, a bridge is built between the SERS tag (4-mercaptobenzoic acid marked Ag nanoparticle) and the fixed thrombin based on the activation of the carboxylic group of 4-mercaptobenzoic acid. Thus, the quantitative detection of thrombin can be achieved based on the SERS intensity of the immobilized SERS tags. The obvious advantages of this sensing method are as follows: (1) remarkable SERS enhancement due to the high electric field coupling effect via the gap structure formation, which improves the sensitivity of the SERS detection and the limit of detection of this method arrives in 1.6 × 10–11 M, (2) high selectivity based on the specific aptamer recognition toward thrombin, which can be extended to other enzymes easily by changing a proper sequence, (3) high repeatability of SERS signals according to a highly ordered structure, and (4) highly efficient oriented assembly of a sandwich structure over an Ag nanoprism array. The proposed method is expected to be a practical implement in medical diagnosis.

•We have proposed a simplified Ag+ sensor due to a dual role of GOD.•A biocompatible probe, applicable for intracellular and in vivo sensing.•Reusability due to the reversible binding of GOD to Ag+.•High selectivity to Ag+ and good sensitivity to 0.1 nM.A highly sensitive and recyclable surface-enhanced Raman scattering (SERS) chip sensor is designed for the determination of silver ions. It is based on the specific reversible binding between silver ions and glucose oxidase (GOD). The sensing chip is made by layer-by-layer assembling GOD on a metal nanoparticle-assembled, SERS-active chip with a positive charged polyelectrolyte as a linker. Iso-alloxazine, a chromophore in flavin adenine dinucleotide (FAD) in GOD, coordinates with silver ions, which causes significant variation in SERS spectra of GOD. The reaction shows high sensitivity and selectivity for silver ions with the detection limit of 1.0×10−10 M. Most significantly, the bonded Ag(I) in GOD can be reduced to Ag(0) by sodium borohydride and the GOD structure can be recovered then. Thus, the chip sensor is recyclable. Merits of using GOD as a novel SERS probe toward Ag+ are embodied in not only a simplified sensor structure based on its dual role of Ag+ accepter and SERS signal reporter, but also a nontoxic label to biological systems, indicating that it is promising for tracing Ag+ in vivo.Download high-res image (230KB)Download full-size image

Targeted delivery of chemotherapeutic agents to pathology areas can improve drug efficiency and reduce serious side effects on normal regions. However, their treatment mechanism on cells or cell nuclei is still mysterious due to the lack of in situ characterization methods. In this paper, the specific diagnosis and treatment processes of a targeted antitumor agent (doxorubicin, Dox) functionalized aptamer complex (TLS11a-GC–Dox) toward HepG2 cells, a human hepatocellular carcinoma cell line, were tracked in real time by the surface-enhanced Raman scattering (SERS) spectroscopic technique and dark-field imaging with the assistance of gold nanorod-based nuclear targeted probes, which possess remarkable SERS enhancement ability, specific targeting, and excellent biological compatibility. This is the first time to explore the acting mechanism of an aptamer-based targeted drug on cell nucleus based on the spectral information on components inside the cell nucleus. The results demonstrate that this aptamer/drug conjugate has targeting and sustained-release actions and its therapeutic effect is achieved by the gradual damage of relevant proteins and DNA in nuclei. Better understanding of the mechanism of aptamer–drug conjugates acting on cancer cells is conductive to increasing cancer therapy efficiency and is also helpful for the design of highly effective drug delivery methods.

A reversible diode-like resistive electrical switching composite material, an AgTCNQF4–AgNPs–TiO2 organic–metal–inorganic hetero-nanojunction array, has been successfully prepared on a fluorine-doped tin oxide (FTO) glass slide. These AgTCNQF4–AgNPs–TiO2 nanojunctions show obvious absorption bands in the visible to near-infrared region, which are attributed to interfacial charge transfer from TiO2 to AgTCNQF4. Moreover, the local electrical properties of these AgTCNQF4–AgNPs–TiO2 nanojunctions have been tested in a device configuration of Au-tip/AgTCNQF4–AgNPs–TiO2/FTO and the measured results reveal that these AgTCNQF4–AgNPs–TiO2 nanojunctions possess many applicable functions involving the switchable diode effect, reversible electrical switching and memory behavior.

A facile, highly sensitive “turn on” surface-enhanced Raman scattering (SERS) nanosensor for the detection of glucose has been developed based on the aggregation of 4-mercaptophenylboronic acid (4-MPBA)-decorated silver nanoparticles in specific bonding to glucose, which can be used for the clinical detection of glucose in urine.

A surface-enhanced Raman scattering (SERS) measurement of 3,3′,4,4′-tetrachlorobiphenyl (PCB77) with aptamer capturing in a microfluidic device was demonstrated. To construct the microfluidic chip, an ordered Ag nanocrown array was fabricated over a patterned polydimethylsiloxane (PDMS) that was achieved by replicating an anodic aluminum oxide (AAO) template. The patterned PDMS sheet was covered with another PDMS sheet having two input channel grooves to form a close chip. The Ag nanocrown array was used for the SERS enhancement area and the detection zone. PCB 77 aptamers were injected into one channel and the other allows for analytes (PCBs). The mercapto aptamers captured the targets in the mixed zone and were immobilized to the SERS detection zone via S–Ag bonds so as to further improve both the SERS sensitivity and selectivity of PCB77. Such an aptamer-based microfluidic chip realized a rapid SERS detection. The lowest detectable concentration of 1.0 × 10–8 M was achieved for PCB77. This work demonstrates that the aptamer-modified SERS microfluidic sensor can be utilized for selective detections of organic pollutants in the environment.

A highly ordered Ag nano-crown array with a hierarchical pattern is designed as a three-dimensional (3D) surface-enhanced Raman scattering (SERS) substrate. It was achieved by depositing Ag on a patterned polymethyl methacrylate (PMMA) film which precisely replicates the patterns of a honeycomb-like anodic aluminum oxide (AAO) template. We made a detailed analysis on the structure of Ag nano-crowns and place emphasis on the detection mode to optimize the excitation and collection of the SERS signals. Finite-different time-domain (FDTD) simulation was performed to confirm and compare electric field enhancement in the gaps between nano-crowns in two different detection ways. All the results exposed and confirmed that the unique detection way of the Ag nano-crown substrate which is different from the traditional mode is optimal. This hierarchical structural Ag nano-crown not only has satisfactory repeatability, but also provides high sensitivity which was supported by the high electric field enhancement in the proper detection way. As a practical application, the detection of pesticide thiram was achieved with a limit of detection down to 1.0 × 10−14 M. This hierarchical structural Ag nano-crown array on a polymer film is a promising candidate as a portable SERS chip.

In the studies of surface-enhanced Raman scattering (SERS), it is considered to be a key point to couple the surface plasmons of metallic nanomaterials and structures to resonate, which can assist higher SERS signal enhancement. This paper is to explore a strategy for plasmon resonating based on the leaky mode resonance (LMR) of a polyimide (PI) optical waveguide (OWG), for the purpose of achieving the highly sensitive evanescent field-excited SERS. PI was chosen to build the waveguide layer due to its merits of exhibiting small extinction coefficients in the natural light frequency, low cost, high flexibility, easy fabrication, and almost no Raman spectral interference. The OWG configuration guarantees a high harvesting efficiency for the incident light. Ag nanoparticles were assembled on top of the OWG layer as plasmonic antennas to provide a large scattering cross section based on the coupling of the LMR and metal plasmon resonance (MPR), which supports highly efficient SERS radiation and being conducive to the far-field collection. The LMR-MPR coupling can facilitate stronger local electromagnetic field around the side surfaces of the Ag nanoparticles, which is favorable to the adsorption of analytes. The PI OWG-coupled MPR structure can realize the integration of SERS excitation light paths and elements, which is not only a valuable SERS enhancement configuration but also a promising technique for the surface and thin film analysis.

Ag2–TCNQF4 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) was synthesized for the first time via a photo-induced charge transfer of the precursor of semiconductor Ag–TCNQF4 using Au nanoparticles (AuNPs) as a catalyst. We first prepared the one-dimensional Ag–TCNQF4 crystal wires on a solid-supported substrate via a solution process. Then, Ag–TCNQF4 was reacted with KAuCl4via the galvanic replacement reaction to form a metal–semiconductor complex, AuNPs decorated Ag–TCNQF4 (AuNPs@Ag–TCNQF4). The resulting Ag–TCNQF4 crystal wires and AuNPs@Ag–TCNQF4 complex were characterized by scanning electron microscopy (SEM), X-ray diffraction, ultraviolet-visible (UV-vis) and X-ray photoelectron spectroscopies. Under the plasmon-enhanced catalysis of AuNPs, a laser-induced charge transfer process occurred on Ag–TCNQF4, altering it to Ag2–TCNQF4. Time-resolved in situ Raman spectra were recorded to monitor the photo-induced charge transfer process. The Raman data show that this photo-induced charge transfer process is laser wavelength-dependant, power-dependant and irradiation time-dependant. It is also affected by the loading of AuNPs. The SEM images, UV-vis and infrared spectra of the AuNPs@Ag–TCNQF4 before and after laser irradiation further prove that the charge transfer product is Ag2–TCNQF4. The mechanism of the plasmon-enhanced catalysis of photo-induced charge transfer from TCNQF4− to TCNQF42− is suggested, which provides a good model to study the charge transfer process in metal–semiconductor systems. In addition, this material has significance for applications in memory storage and photoelectric devices.

A surface-enhanced Raman scattering (SERS)-active optical fiber sensor combining the optical fiber waveguide with various SERS substrates has been a powerful analytical tool for in situ and long-distance SERS detection with high sensitivity. The design and modification of a high-quality SERS-active sensing layer are important topics in the development of novel SERS-active optical fiber sensors. Here, we prepared a highly sensitive SERS-active optrode by in situ fabrication of a three-dimensional porous structure on the optical fiber end via a photoinduced polymerization reaction, followed by the growth of photochemical silver nanoparticles above the porous polymer material. The fabrication process is rapid (finished within 1 h) and can be on line under light control. The porous structure supports vast silver nanoparticles, which allows for strong electromagnetic enhancement of SERS. Interestingly, the preparation of this SERS optrode and its utilization for SERS detection can all be conducted in a microfluidic chip. The qualitative and quantitative on-chip SERS sensing of organic pollutants and pesticides has been achieved by this SERS optrode-integrated microfluidic chip, and its high detection sensitivity makes it a promising factor in the analysis of liquid systems.Keywords: microfluidic chip; on-chip detection; photoinduced growth; porous structure; SERS

We propose a highly sensitive and selective surface-enhanced Raman scattering (SERS) method for determining lead ions based on a DNAzyme-linked plasmonic nanomachine. A metallic nanoparticle-on-a-film structure was built through a rigid double-stranded bridge linker composed of a DNAzyme and its substrate. This DNAzyme could be activated by lead ions and catalyze a fracture action of the substrate. Thus, the double chain structure of DNA would turn into a flexible single strand, making the metal nanoparticles that connected to the terminal of DNAzyme fall to the surface of the metal film. Hereby, a narrow gap close to 2 nm generated between metal nanoparticles and the metal film, exhibiting a similar effect of a “hot spot” and remarkably enhancing the signal of randomly dispersed Raman-active molecules on the surface of metal film. By measuring the improvement of SERS intensity of the Raman-active molecules, we realized the lowest detection concentration of Pb2+ ions to 1.0 nM. This SERS analytical method is highly selective and can be extended universally to other targets via the accurate programming of corresponding DNA sequences.

We employed an electrospinning method to prepare metal nanoparticle (NP) doped polymer nanofiber mats, which can be easily cut to size and fixed on slides or in microfluidic channels for surface-enhanced Raman scattering (SERS) measurements. Metal NPs embedded in the composite nanofibers maintained their intrinsic shape and monodispersity, as well as their enhancement ability. In addition, they can be re-suspended in aqueous solution to recover a colloidal solution with persistent SERS activity. The SERS chips made from the metal NP-doped polymer nanofiber mats displayed high detection sensitivity and reproducibility. The microfluidic chips decorated with several metal NP-doped polymer nanofiber mats possess multi-SPR properties and can be widely used for different analytes. These composite polymer mats can be easily stored and transported, and also possess potential for use as antibacterial filters and paint for medical purposes.

A kind of functional noble metal nanoparticles and metal/organic semiconductor composite nanomaterials, Ag nanoparticles (AgNPs, 6–10 nm in diameter) decorated small-sized Ag-tetracyano-p-tetrafluoroquinodimethane (AgTCNQF4) nanorods (150–400 nm in length and 60–100 nm in diameter), have been successfully synthesized through a rapid microemulsion reaction between TCNQF4 molecules and an AgNP colloid under a soft template of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol). The morphology, chemical structure, and elemental composition of the prepared AgNPs–AgTCNQF4 composite nanorods were studied by transmission electron microscopy, selected-area electron diffraction, and X-ray photoelectron spectroscopy. The real-time ultraviolet–visible spectroscopy assisted with two-dimensional correlation spectroscopic analysis was employed to explore the growth of AgNPs–AgTCNQF4 composite nanorods in microemulsion. These composite nanorods display the photoinduced charge transfer (CT) property from the monoanion (TCNQF4–) to dianion (TCNQF42–) selectively under 532 nm light irradiation. The larger content of AgNPs on the surface of AgTCNQF4 led to the higher conversion of dianion due to the plasmon-assisted photocatalysis. This photoelectric composite material is promising for the applications of light-writing data storage and photocatalysis.

•Luminescent composite polymer nanofibers were fabricated.•Ag nanoclusters were in situ growth in the electrospun nanofiber membrane.•The prepared Ag nanoclusters have high chemical stability and antibacterial ability.The purpose of this study is to prepare multifunctional polymer fibers. We report a simple and controllable method for in situ synthesis of Ag nanoclusters (NCs) in electrospun polymer fibers via a photochemical reaction. The prepared composite polymer fibers emit pink luminescence and the luminescence property can be optimized by pH and Ag(I) precursor concentration. The as-prepared Ag NCs in electrospun polymer fibers were mainly Ag2–5 with a quantum yield of 6.81% and a lifetime of 2.29 ns. The in situ growth of Ag NCs avoids excessive surface modifications which may cause the aggregation of Ag NCs in many ex situ assembly methods. The combination of Ag NCs with polymer fibers greatly improves the stability of Ag NCs and broadens their applications. The storage of Ag NCs becomes facilitative due to the formation of bulky mat. Furthermore, these luminescence composite polymer fibers show strong antibacterial activity against Staphylococcus aureus (S. aureus).

The solvent effect on the luminescence properties of highly stable water-soluble silver nanoclusters is discussed in this study. The polymer nanosphere templates swollen by organic solvents lead to the changes in the surrounding environments of silver nanoclusters, thus resulting in a significant influence on their luminescence.

We describe a novel ‘switch-off’ biosensing strategy for the detection of chymotrypsin based on surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) spectroscopy. This approach analyzes the fingerprint spectrum of the chymotrypsin-catalyzed substrate. The lowest probed concentration is 0.4 nM for chymotrypsin.

Novel fluorescent silver nanoclusters prepared by core/shell polymer nanoparticles as templates were applied to detecting copper (Cu2+) ions in aqueous solution based on fluorescence quenching. Changes in fluorescence intensity allow a quick response and sensitive detection of Cu2+ ions at concentrations as low as 20.9 nM. Also, excellent selectivity of Cu2+ ions was observed in anti-interference experiments against other metal cations. These fluorescent silver nanoclusters embedded with the polymer nanoparticles have the advantage of long-term stability and good water solubility, which are suitable to be combined with microfluidic systems for real-time sensing of Cu2+ ions. Detection in real water samples by our method also presented good results in the experiments, showing the potential of silver nanoclusters embedded with polymer nanoparticles as a practical analytical tool.

We reported a highly efficient and low-cost way to synthesize silver nanosphere dimers on a poly(dimethylsiloxane) (PDMS) sheet by using a stepwise upright assembly method for the “hot spots” study of surface-enhanced Raman scattering (SERS). The first silver nanoparticle (NP) layer is almost entirely embedded in PDMS, and the second-layered silver NPs directionally position the tops of the embedded particles. The analysis of the localized electric field distributions of the silver nanosphere dimer presents that the strongest electric field coupling appears at the gap of two nanospheres when the incident angle is about 45° and its intensity achieves 400 times enhancement. The SERS enhancement activity on this novel substrate was determined, and the results showed that SERS intensities on nanodimers were much stronger than those on the silver NP monolayer due to the electromagnetic field coupling of upright NP-NP. By using this novel SERS substrate, the lowest detection concentration for 4-mercaptopyridine is 4.0 × 10–14 M.

A green and environment-friendly method for synthesis of water-soluble and fluorescent Ag nanoclusters was developed using carboxymethyl-β-cyclodextrin (CM-β-CD) as both reducing and stabilizing reagent. The optical properties of Ag nanoclusters were characterized using the photoluminescence, ultraviolet–visible absorption, and laser desorption time of flight mass spectroscopies. The role of carboxylic groups was discussed in the photoactivated synthesis of Ag nanoclusters. Increasing the substitute of carboxylic groups on CM-β-CD was propitious to the formation of Ag nanoclusters and the stability of the produced silver nanoclusters was greatly improved. The in vitro antimicrobial ability of the produced Ag nanoclusters was tested. Compared with a silver nitrate solution and a typical Ag colloid, Ag nanoclusters stabilized by CM-β-CD exhibited greatly strong antimicrobial ability.Highlights► Small molecule-carboxymethyl-β-cyclodextrin was used to prepare Ag nanoclusters. ► Ag nanoclusters — water-soluble fluorescent Ag nanoclusters were synthesized. ► Antibacterial — the prepared Ag nanoclusters possessed strong antibacterial ability.

A planar-film plasmonic antenna for surface-enhanced Raman scattering (SERS) with good emission directivity (divergence angle < 3°) was realized on a Kretschmann prism configuration with Raman-active analytes as emitters. The simulated results of finite-difference time-domain method show the emission efficiency, the directivity and the gain of the planar-film antenna were expected to be 50%, 300 and 22 dB, respectively. Angle-resolved spectroscopy was used to characterize its properties in SERS. The experimental results show that the SERS signal of analytes was remarkably enhanced when a laser excited this planar-film plasmonic antenna at the resonance angle. Meanwhile, the radiation of SERS was concentrated in a small region in space. The planar-film antenna with high gain coefficient can be a promising light harvesting and emitting device. The good emission directivity allows high collection efficiency. This advantage opens up interesting prospects in the applications for plasmon-enhanced spectroscopy and single-phonon detections.Highlights► Angle-resolved Surface-Enhanced Raman Scattering (SERS) from an Ag-film coated prism. ► The thin silver film can be considered as a planar plasmonic antenna model.. ► The efficiency, directivity and gain of the antennas reached 50%, 300 and 22 dB. ► High excitation and collection efficiencies of SERS were achieved in this model.

The purpose of this article is to improve the collection efficiency of surface-enhanced Raman scattering (SERS) further to increase SERS detection sensitivity in trace detection. To achieve this, a silver nanowell array substrate was designed based on its tunable propagating surface plasmons. This substrate supported directional surface plasmon coupling emission and could guide SERS to the vertical direction of the substrate. Silver nanoparticles were assembled on the shallow silver nanowell array to contribute localized surface plasmons for higher electromagnetic enhancement. Spatial SERS radiation patterns on the silver nanoparticle assembled nanowell array substrate were simulated by the finite-difference time-domain method and recorded by a self-made 3D angle-resolved Raman spectrometer. The results showed that SERS signals were strong and unidirectional in space. The half divergence angle of the SERS pattern was about 10°, which would facilitate SERS collection by using a conventional backscattering Raman spectrometer. This silver nanowell array is supposed to be an applicable configuration to many systems that require high collection efficiency like single-molecule SERS detection and tip-enhanced Raman spectroscopy.

The solvent effect on the luminescence properties of highly stable water-soluble silver nanoclusters is discussed in this study. The polymer nanosphere templates swollen by organic solvents lead to the changes in the surrounding environments of silver nanoclusters, thus resulting in a significant influence on their luminescence.

Ag2–TCNQF4 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) was synthesized for the first time via a photo-induced charge transfer of the precursor of semiconductor Ag–TCNQF4 using Au nanoparticles (AuNPs) as a catalyst. We first prepared the one-dimensional Ag–TCNQF4 crystal wires on a solid-supported substrate via a solution process. Then, Ag–TCNQF4 was reacted with KAuCl4via the galvanic replacement reaction to form a metal–semiconductor complex, AuNPs decorated Ag–TCNQF4 (AuNPs@Ag–TCNQF4). The resulting Ag–TCNQF4 crystal wires and AuNPs@Ag–TCNQF4 complex were characterized by scanning electron microscopy (SEM), X-ray diffraction, ultraviolet-visible (UV-vis) and X-ray photoelectron spectroscopies. Under the plasmon-enhanced catalysis of AuNPs, a laser-induced charge transfer process occurred on Ag–TCNQF4, altering it to Ag2–TCNQF4. Time-resolved in situ Raman spectra were recorded to monitor the photo-induced charge transfer process. The Raman data show that this photo-induced charge transfer process is laser wavelength-dependant, power-dependant and irradiation time-dependant. It is also affected by the loading of AuNPs. The SEM images, UV-vis and infrared spectra of the AuNPs@Ag–TCNQF4 before and after laser irradiation further prove that the charge transfer product is Ag2–TCNQF4. The mechanism of the plasmon-enhanced catalysis of photo-induced charge transfer from TCNQF4− to TCNQF42− is suggested, which provides a good model to study the charge transfer process in metal–semiconductor systems. In addition, this material has significance for applications in memory storage and photoelectric devices.

A reversible diode-like resistive electrical switching composite material, an AgTCNQF4–AgNPs–TiO2 organic–metal–inorganic hetero-nanojunction array, has been successfully prepared on a fluorine-doped tin oxide (FTO) glass slide. These AgTCNQF4–AgNPs–TiO2 nanojunctions show obvious absorption bands in the visible to near-infrared region, which are attributed to interfacial charge transfer from TiO2 to AgTCNQF4. Moreover, the local electrical properties of these AgTCNQF4–AgNPs–TiO2 nanojunctions have been tested in a device configuration of Au-tip/AgTCNQF4–AgNPs–TiO2/FTO and the measured results reveal that these AgTCNQF4–AgNPs–TiO2 nanojunctions possess many applicable functions involving the switchable diode effect, reversible electrical switching and memory behavior.

Novel fluorescent silver nanoclusters prepared by core/shell polymer nanoparticles as templates were applied to detecting copper (Cu2+) ions in aqueous solution based on fluorescence quenching. Changes in fluorescence intensity allow a quick response and sensitive detection of Cu2+ ions at concentrations as low as 20.9 nM. Also, excellent selectivity of Cu2+ ions was observed in anti-interference experiments against other metal cations. These fluorescent silver nanoclusters embedded with the polymer nanoparticles have the advantage of long-term stability and good water solubility, which are suitable to be combined with microfluidic systems for real-time sensing of Cu2+ ions. Detection in real water samples by our method also presented good results in the experiments, showing the potential of silver nanoclusters embedded with polymer nanoparticles as a practical analytical tool.

A highly ordered Ag nano-crown array with a hierarchical pattern is designed as a three-dimensional (3D) surface-enhanced Raman scattering (SERS) substrate. It was achieved by depositing Ag on a patterned polymethyl methacrylate (PMMA) film which precisely replicates the patterns of a honeycomb-like anodic aluminum oxide (AAO) template. We made a detailed analysis on the structure of Ag nano-crowns and place emphasis on the detection mode to optimize the excitation and collection of the SERS signals. Finite-different time-domain (FDTD) simulation was performed to confirm and compare electric field enhancement in the gaps between nano-crowns in two different detection ways. All the results exposed and confirmed that the unique detection way of the Ag nano-crown substrate which is different from the traditional mode is optimal. This hierarchical structural Ag nano-crown not only has satisfactory repeatability, but also provides high sensitivity which was supported by the high electric field enhancement in the proper detection way. As a practical application, the detection of pesticide thiram was achieved with a limit of detection down to 1.0 × 10−14 M. This hierarchical structural Ag nano-crown array on a polymer film is a promising candidate as a portable SERS chip.