[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Nanoparticles containing magnetic materials, such as magnetite (Fe3O4), are particularly useful for imaging and separation techniques. As these nanoparticles are generally considered to be biologically and chemically inert, they are typically coated with metal catalysts, antibodies or enzymes to increase their functionality as separation agents. Here, we report that magnetite nanoparticles in fact possess an intrinsic enzyme mimetic activity similar to that found in natural peroxidases, which are widely used to oxidize organic substrates in the treatment of wastewater or as detection tools. Based on this finding, we have developed a novel immunoassay in which antibody-modified magnetite nanoparticles provide three functions: capture, separation and detection. The stability, ease of production and versatility of these nanoparticles makes them a powerful tool for a wide range of potential applications in medicine, biotechnology and environmental chemistry.

Intrinsic peroxidase-like activity of ferromagnetic nanoparticles

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

A review on g-C3N4-based photocatalysts

We presented a new aptamer biosensor for thrombin in this work, which was based on fluorescence resonance energy transfer (FRET) from upconverting phosphors (UCPs) to carbon nanoparticles (CNPs). The poly(acrylic acid) (PAA) functionalized UCPs were covalently tagged with a thrombin aptamer (5′-NH2- GGTTGGTGTGGTTGG-3′), which bound to the surface of CNPs through π–π stacking interaction. As a result, the energy donor and acceptor were taken into close proximity, leading to the quenching of fluorescence of UCPs. A maximum fluorescence quenching rate of 89% was acquired under optimized conditions. In the presence of thrombin, which induced the aptamer to form quadruplex structure, the π–π interaction was weakened, and thus, the acceptor was separated from the donor blocking the FRET process. The fluorescence of UCPs was therefore restored in a thrombin concentration-dependent manner, which built the foundation of thrombin quantification. The sensor provided a linear range from 0.5 to 20 nM for thrombin with...

Aptamer Biosensor Based on Fluorescence Resonance Energy Transfer from Upconverting Phosphors to Carbon Nanoparticles for Thrombin Detection in Human Plasma

Fluorescence resonance energy transfer (FRET) is recognized as a sensitive and reliable analytical technique and has been widely used in biological assays. To obtain improved FRET efficiency and analytical performance, it is of continuing interest to search for new energy donor–acceptor pairs. In the past few years, the use of anti-Stokes fluorophores including upconverting phosphors (UCP) and multiphotonexcited dyes as energy donors which can be excited in the near-infrared (NIR) region has successfully circumvented the problem of autofluorescence and scattering of light arising from biological substances. This has made it possible to directly conduct FRET-based assays in biological samples. More recently, graphene, the newly emerging two-dimensional and zero-bandgap carbon nanomaterial, has attracted considerable attention in bioassays because of its unique electronic, mechanical, and thermal properties. In the pioneering work of Swathi et al. , it was proposed through theoretical calculations that graphene could act as a superquencher of organic dyes, as a result of nonradiative transfer of electronic excitation energy from dye excited states to the p system of graphene. The rate of this long-range resonance energy transfer was suggested to have a d 4 dependence on distance d, in sharp contrast to traditional FRET, for which the rate has a d 6 dependence. Inspired by this property, graphene and graphene oxide (GO) have been used as FRET acceptors with organic dyes and quantum dots as energy donors, in which both graphene and GO exhibit high efficiency in quenching the donor emission and thus provide good sensitivity. Herein we reveal energy transfer from UCP to GO and thus construction of a new biosensing platform which could be used to detect glucose directly in serum samples and extended to detection of other biologically significant molecules. The previously reported FRETmodels based on graphene or graphene oxide all rely on the p–p stacking interaction between the carbon nanomaterial and nucleic acid chains, which bring the acceptor and donor (organic dyes or quantum dots) into close proximity. We hereby tried a different model in which donor and acceptor are brought into FRET proximity through specific molecular recognition (Figure 1).

Biosensing Platform Based on Fluorescence Resonance Energy Transfer from Upconverting Nanocrystals to Graphene Oxide

Layered WS2 nanosheet is a kind of two-dimensional (2D) covalent-network solid material with remarkable structural and electronic properties that has attracted increasing interest in recent years. In this work, we propose a one-step sonication-assisted exfoliation method to prepare water-soluble WS2 nanosheet and demonstrate its application as a biosensing platform. The synthesis route is simple and straightforward. We reveal that single-strand DNA (ssDNA) chains can readily be adsorbed on the nanosheet, leading to complete and fast quenching of a fluorescent dye tagged to the DNA chain. The adsorbed ssDNA is detachable from the nanosheet upon the interaction with other biomolecules, resulting in the restoration of the fluorescence. The 2D WS2 nanosheet thus acts as an efficient platform for assembling of bioprobes. Because of the extraordinarily high quenching efficiency, which is the synergic result of both excited-state energy transfer and static quenching, the WS2 platform affords minimal background a...

Establishing Water-Soluble Layered WS2 Nanosheet as a Platform for Biosensing

Matrix metalloproteinase-2 (MMP-2) is a very important biomarker in blood. Presently, sensitive and selective determination of MMP-2 directly in blood samples is still a challenging job because of the high complexity of the sample matrix. In this work, we reported a new homogeneous biosensor for MMP-2 based on fluorescence resonance energy transfer (FRET) from upconversion phosphors (UCPs) to carbon nanoparticles (CNPs). A polypeptide chain (NH2-GHHYYGPLGVRGC-COOH) comprising both the specific MMP-2 substrate domain (PLGVR) and a π-rich motif (HHYY) was designed and linked to the surface of UCPs at the C terminus. The FRET process was initiated by the π–π interaction between the peptide and CNPs, which thus quenched the fluorescence of the donor. Upon the cleavage of the substrate by the protease at the amide bond between Gly and Val, the donor was separated from the acceptor while the π-rich motif stayed on the acceptor. As a result, the fluorescence of the donor was restored. The fluorescence recovery w...

Upconversion fluorescence resonance energy transfer based biosensor for ultrasensitive detection of matrix metalloproteinase-2 in blood.

Upconversion nanoparticles (UCNPs) are promising energy donors for luminescence resonance energy transfer (LRET) and have widely been used to construct nanoprobes. To improve the LRET efficiency, which is currently a limiting factor for UCNPs-based bioassay, we herein propose a strategy to construct LRET-based nanoprobe using UCNPs with confined emitters and bared surface as the luminophore, with Ca2+ as the proof-of-concept target. The sandwich-structure upconversion nanoparticles (SWUCNPs) are designed with a core-inner shell-outer shell architecture, in which the emitting ions (Ln3+) are precisely located in the inner shell near the particle surface, which is close enough to external energy acceptors. The target receptor (Fluo-4) is directly tagged on bared surface of SWUCNPs, which further reduces the donor-to-acceptor distance. Our strategy contributes to significantly improved LRET efficiency and hence affords an ultrahigh sensitivity for Ca2+ detection. The as-constructed nanoprobe is structurally ...

Zhihong Liu

Papers

Aptamer Biosensor Based on Fluorescence Resonance Energy Transfer from Upconverting Phosphors to Carbon Nanoparticles for Thrombin Detection in Human Plasma

Biosensing Platform Based on Fluorescence Resonance Energy Transfer from Upconverting Nanocrystals to Graphene Oxide

Establishing Water-Soluble Layered WS2 Nanosheet as a Platform for Biosensing

Upconversion fluorescence resonance energy transfer based biosensor for ultrasensitive detection of matrix metalloproteinase-2 in blood.

Construction of LRET-based nanoprobe using upconversion nanoparticles with confined emitters and bared surface as luminophore.