Localized surface plasmon resonance: nanostructures, bioassays and biosensing--a review

Localized surface plasmon resonance (LSPR) is an optical phenomena generated by light when it interacts with conductive nanoparticles (NPs) that are smaller than the incident wavelength. As in surface plasmon resonance, the electric field of incident light can be deposited to collectively excite electrons of a conduction band, with the result being coherent localized plasmon oscillations with a resonant frequency that strongly depends on the composition, size, geometry, dielectric environment and separation distance of NPs. This review serves to describe the physical theory of LSPR formation at the surface of nanostructures, and the potential for this optical technology to serve as a basis for the development bioassays and biosensing of high sensitivity. The benefits and challenges associated with various experimental designs of nanoparticles and detection systems, as well as creative approaches that have been developed to improve sensitivity and limits of detection are highlighted using examples from the literature.     

金属纳米材料中的晶格应变及其在催化中的应用

纳米结构中的晶格应变作为基础研究课题的势头日益增强.可以设计纳米颗粒的表面晶格以产生应变或者其他结构变化,使其原子位置偏离正常的晶格点,进而影响纳米颗粒的电子结构和催化性能.本文首先介绍了金属纳米粒子的不同应变源,重点介绍了不同应变基本结构的合成.讨论了晶格应变的表征手段及其在催化领域应用的研究进展.最后介绍了应变金属...     

Synthesis and electrochemical applications of gold nanoparticles

This review covers recent advances in synthesis and electrochemical applications of gold nanoparticles (AuNPs). Described approaches include the synthesis of AuNPs via designing and choosing new protecting ligands; and applications in electrochemistry of AuNPs including AuNPs-based bioelectrochemical sensors, such as direct electrochemistry of redox-proteins, genosensors and immunosensors, and AuNPs as enhancing platform for electrocatalysis and electrochemical sensors.     

Nanoparticle-based electrochemical detection in conventional and miniaturized systems and their bioanalytical applications: a review

With recent advances in nanotechnology making more easily available the novel chemical and physical properties of metal nanoparticles (NPs), these have become extremely suitable for creating new sensing assays. Many kinds of NPs, including metal, metal-oxide, semiconductor and even composite-metal NPs, have been used for constructing electrochemical sensors. This article reviews the progress of NP-based electrochemical detection in recent applications, especially in bioanalysis, and summarizes the main functions of NPs in conventional and miniaturized systems. All references cited here generally show one or more of the following characteristics: a low detection limit, good signal amplification and simultaneous-detection capabilities.     

Discrete DNA three-dimensional nanostructures: the synthesis and applications

Structural DNA nanotechnology, an emerging technique that utilizes the nucleic acid molecule as generic polymer to programmably assemble well-defined and nano-sized architectures, holds great promise for new material synthesis and constructing functional nanodevices for different purposes. In the past three decades, rapid development of this technique has enabled the syntheses of hundreds and thousands of DNA nanostructures with various morphologies at different scales and dimensions. Among them, discrete three-dimensional (3D) DNA nanostructures not only represent the most advances in new material design, but also can serve as an excellent platform for many important applications. With precise spatial addressability and capability of arbitrary control over size, shape, and function, these nanostructures have drawn particular interests to scientists in different research fields. In this review article, we will briefly summarize the development regarding the synthesis of discrete DNA 3D nanostructures with various size, shape, geometry, and topology, including our previous work and recent progress by other groups. In detail, three methods majorly used to synthesize the DNA 3D objects will be introduced accordingly. Additionally, the principle, design rule, as well as pros and cons of each method will be highlighted. As functions of these discrete 3D nanostructures have drawn great interests to researchers, we will further discuss their cutting-edge applications in different areas, ranging from novel material synthesis, new device fabrication, and biomedical applications, etc. Lastly, challenges and outlook of these promising nanostructures will be given based on our point of view.     

Analytical and bioanalytical applications of carbon dots

Carbon dots (CDs) comprise a recently discovered class of strongly fluorescent, emission-color-tuning and non-blinking nanoparticles with great analytical and bioanalytical potential. Raw CDs can be obtained by laser ablation or electrochemical exfoliation of graphite, from soot, or thermal carbonization, acid dehydration or ultrasonic treatment of molecular precursors. Passivation of raw CDs makes them fluorescent and their functionalization confers reactivity towards selected targets. CDs can be excited by single-photon (ultraviolet or near-ultraviolet) and multi-photon (red or near-infrared) excitation, and their luminescence properties are due to surface defects. CDs are being proposed as bioimaging probes because they comprise non-toxic elements and are biocompatible. Passivated and functionalized CDs can be made to sense pH, metal ions and molecular substances.     

Nanomaterial-based electrochemical biosensors for medical applications

With recent advances in nanotechnology, great progress has been made in biosensors based on nanomaterials, but there are still numerous challenges to overcome. We describe nanomaterial-based biosensors for researchers new to the field, paying particular attention to metal nanoparticles and carbon nanotube (CNT)-based label-free approaches. Label-free monitoring of biorecognition events provides a promising platform, which is simple, cost-effective, and requires no external modification to biomolecules. Using examples from recent reports, we illustrate the diversity of biological recognition events and the range of experimental techniques employed for metal-nanoparticle-based and label-free characterization.     

Silicon nanowire biosensor and its applications in disease diagnostics: A review

Over the past decade, silicon nanowire (SiNW) biosensors have been studied for the detection of biological molecules as highly sensitive, label-free, and electrical tools. Herein we present a comprehensive review about the fabrication of SiNW biosensors and their applications in disease diagnostics. We discuss the detection of important biomarkers related to diseases including cancer, cardiovascular diseases, and infectious diseases. SiNW biosensors hold great promise to realize point-of-care (POC) devices for disease diagnostics with potential for miniaturization and integration.     

Recent advances in ZnO nanostructures and thin films for biosensor applications: Review

Biosensors have shown great potential for health care and environmental monitoring. The performance of biosensors depends on their components, among which the matrix material, i.e., the layer between the recognition layer of biomolecule and transducer, plays a crucial role in defining the stability, sensitivity and shelf-life of a biosensor. Recently, zinc oxide (ZnO) nanostructures and thin films have attracted much interest as materials for biosensors due to their biocompatibility, chemical stability, high isoelectric point, electrochemical activity, high electron mobility, ease of synthesis by diverse methods and high surface-to-volume ratio. ZnO nanostructures have shown the binding of biomolecules in desired orientations with improved conformation and high biological activity, resulting in enhanced sensing characteristics. Furthermore, compatibility with complementary metal oxide semiconductor technology for constructing integrated circuits makes ZnO nanostructures suitable candidate for future small integrated biosensor devices. This review highlights recent advances in various approaches towards synthesis of ZnO nanostructures and thin films and their applications in biosensor technology.     

Synthesis and nanostructures of 5,10,15,20-tetrakis(4-piperidyl)porphyrin

A new water-soluble porphyrin, 5,10,15,20-tetrakis(4-piperidyl)porphyrin (T(4-Pip)P), has been synthesized. T(4-Pip)P is related to the extensively studied water-soluble porphyrin 5,10,15,20-tetrakis(4-pyridyl)porphyrin (T(4-Py)P) but has substituents with different electronic and hydrogen-bonding properties and is soluble over a much larger pH range due to the higher pK_a of its conjugate acid T(4-H-Pip)P⁴⁺. Investigations of the ionic self-assembly reactions of T(4-H-Pip)P⁴⁺ with anionic water-soluble porphyrins reveal that it forms nanoscale materials.     

Nanomaterial-amplified chemiluminescence systems and their applications in bioassays

Nanomaterial-amplified chemiluminescence (CL) has become a growing area of interest in recent years. We review the development of nanomaterial-amplified CL systems and their applications in bioassays. We mainly focus on nanoparticles (gold, platinum, silver, bimetallic, semiconductor and magnetic). Furthermore, we discuss some critical challenges in this field and possible solutions to overcome these challenges.     

Synthesis and characterization of flowerlike ZnO nanostructures via an ethylenediamine-meditated solution route

Flowerlike ZnO nanostructures were deposited on Si substrate by choosing hexamethylenetetramine as the nucleation control reagent and ethylenediamine as the chelating and capping reagent. Structural and optical measurements reveal that obtained ZnO exhibits well-defined flowerlike morphology, hexagonal wurtzite structure, uniform distribution on substrate, and strong photoluminescence in ultraviolet band. The well-arrayed pedals of each ZnO flower possess the typical tapering feature, and are built up by many well-aligned ZnO nanorods. Moreover, each single nanorod building up the pedal exhibits the single crystal nature and the growth direction along c-axis. Effects of the precursor composition on the morphology of ZnO were discussed.     

Novel organotin-containing diblock copolymer with tunable nanostructures: Synthesis, self-assembly and morphological change

Interesting self-assembly behavior and morphological change of a novel organotin-containing diblock copolymer were firstly reported. The organotin-containing diblock copolymer, poly(methyl methacrylate)-block-poly(acetoxydibutyltin methacrylate) (PMMA-b-PADBTMA), was prepared via RAFT polymerization of ADBTMA with PMMA as the macroCTA and AIBN as the initiator in toluene. Both the FT-IR and TG analysis revealed an incorporation of both co-monomers in the resulted polymer backbone. The ratio of two segments was determined indirectly by TG analysis, gravimetric method and derivative process. All results from the different methods were well matched. And it was found that the morphology of the diblock copolymer could be changed easily from vesicles to nano-particle or cross-linked nano-composite under the ultrasonication or additional Ph₂SnCl₂, respectively. All the morphologies were analyzed by SEM, TEM and DLS. The self-assembly and the morphological change attributed to the strong coordination action between tin atoms and the carbonyl groups among PADBTMA segments.     

Synthesis of metallic copper nanoparticles coated with polypyrrole

This paper describes a method for polypyrrole (PPy) coating of metallic Cu nanoparticles in aqueous solution in atmosphere. Colloid solution of Cu nanoparticles was prepared by reducing Cu ions with the use of hydrazine in an aqueous solution dissolving citric acid and cetyltrimethylammonium bromide as stabilizers. The PPy coating was performed by polymerizing pyrrole with the use of hydrogen peroxide as an initiator in an aqueous colloid solution of the Cu nanoparticles. Ultraviolet–visible extinction measurements, transmission electron microscopy observation, and X-ray diffraction measurements revealed that the metallic Cu nanoparticles with a size of 27.6 ± 11.1 nm were coated with PPy. The obtained PPy-coated Cu particles were chemically stable even in atmosphere.     

Environmental and bioanalytical applications of hollow fiber membrane liquid-phase microextraction: a review

In hollow fiber membrane liquid-phase microextraction (LPME), target analytes are extracted from aqueous samples and into a supported liquid membrane (SLM) sustained in the pores in the wall of a small porous hollow fiber, and further into an acceptor phase present inside the lumen of the hollow fiber. The acceptor phase can be organic, providing a two-phase extraction system compatible with capillary gas chromatography, or the acceptor phase can be aqueous resulting in a three-phase system compatible with high-performance liquid chromatography or capillary electrophoresis. Due to high enrichment, efficient sample clean-up, and the low consumption of organic solvent, substantial interest has been devoted to LPME in recent years. This paper reviews important applications of LPME with special focus on bioanalytical and environmental chemistry, and also covers a new possible direction for LPME namely electromembrane extraction, where analytes are extracted through the SLM and into the acceptor phase by the application of electrical potentials.     

Preparation of Nanogapped Gold Nanoparticle Array for DNA Detection

A novel DNA detection technique using a gold nanoparticle array film electrode has been reported here. The gold nanoparticles molecularly linked with binder molecule (1,10‐decanedithiol) were separated 1.3 nm from each other, and the DNA conductivity change from single to double strand was measured by monitoring a voltage drop across the particles, between which a probe of a 12‐mer oligonucleotide was immobilized. In adding a complementary oligonucleotide on the nanoparticle film chip, an immediate decrease in the film resistance (ca. 1.4 Ω) due to a hybridization event occurred in a reproducible manner with this simple setup. In the paper, we have an interest in the primary sensing properties; effect of the film resistance on the sensor response, dependence of the resistance change on the DNA concentration, and the performance of the system for DNA detection including single nucleotide polymorphisms were described.     

Heavy metal-induced inhibition of Aspergillus niger nitrate reductase: applications for rapid contaminant detection in aqueous samples

Enzyme inhibition assays have the potential to rapidly screen and identify heavy metals in environmental samples. Inhibition of nitrate reductase (NR) was examined as a method for detecting toxic metals. The activity of NR (EC 1.6.6.2) from Aspergillus niger was assayed as a function of metal concentration in the presence of Cd²⁺, Cr³⁺, Cr⁶⁺, Cu²⁺, Ni²⁺, Pb²⁺, and Zn²⁺. NR exhibited sensitivity to these metals at concentrations below 10 μM. Various buffers were screened for their ability to protect NR activity from metal inhibition, and 3-(N-morpholino) propanesulfonic acid (MOPS) was selected as the buffering system for the NR assays as it exhibited the least interference with metal inhibition, thus providing increased assay sensitivity. The hypothesis that chelating agents could prevent the inhibition of NR activity by metal ions was also tested. Results indicated that 10 mM ethylenediaminetetraacetic acid (EDTA) could protect NR activity from inhibition by Cr³⁺, Cu²⁺, Cd²⁺, Ni²⁺, and Zn²⁺ at concentrations below 100 μM, but that the EDTA had no effect on NR inhibition by Cr⁶⁺. An amount of 10 mM nitrilotriacetic acid (NTA) prevented NR inhibition by Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ at metal concentrations below 100 μM. However, 10 mM NTA was unable to protect the enzyme from inhibition by either Cr³⁺ or Cr⁶⁺. These results indicated that through specific metal chelation, a NR-based method for individually quantifying Cr³⁺ and Cr⁶⁺ species in aqueous solutions could be developed. The ability to restore activity to NR which been previously inhibited by exposure to 100 μM Pb²⁺, Cd²⁺, Zn²⁺, Cu²⁺, and Cr³⁺ was explored to determine whether NR activity could be recovered by EDTA additions for use in consecutive metal inhibition assays. The results showed NR activity could not be regained after exposure to Cr³⁺ or Cu²⁺, but did partially recover activity after Cd²⁺, Pb²⁺, and Zn²⁺ exposure.     

Applications of diatoms and silica nanotechnology in biosensing, drug and gene delivery, and formation of complex metal nanostructures

Diatoms, single-cell eukaryotic microalgae, are present in nearly every water habitat and their silicon-dioxide (silica)-based cell walls of tens to hundreds of micrometers in size are the most interesting feature to be used in nanotechnology, including biosensing, drug delivery, molecular separation, molecular biology, biomimetics, frustule formation, and electronic, photonic, optical and structural materials. In this review, we present recent progress in applications of diatoms and silica nanomaterials in biosensing, drug and gene delivery, and formation of complex metal nanostructures.