Nanozymes have advantages over natural enzymes, such as facile production on large scale, long storage time, low costs, and high stability in harsh environments. Carbon nanomaterials (CNMs), including fullerenes, carbon nanotubes, graphene, carbon quantum dots, and graphene quantum dots, have become a star family in materials science. As a new class of nanozymes, the catalytic activity of CNMs and their hybrids has been extensively reported. In this Minireview, recent progress of CNMs based artificial enzymes, focusing on those with peroxidase-like activity, has been summarized. The enzymatic properties, catalytic mechanisms, and novel applications of CNM nanozymes in sensing, therapy, and environmental engineering are discussed in detail. Additionally, we also highlight the remaining challenges and unsolved problems. With the fast development of bionanotechnology, the unique enzymatic properties and advantages of CNM nanozymes have received much attention and will continue to be an active and challenging field for the years to come.

Carbon Nanozymes: Enzymatic Properties, Catalytic Mechanism, and Applications.

Plasmonic biosensing has been used for fast, real-time, and label-free probing of biologically relevant analytes, where the main challenges are to detect small molecules at ultralow concentrations and produce compact devices for point-of-care (PoC) analysis. This review discusses the most recent, or even emerging, trends in plasmonic biosensing, with novel platforms which exploit unique physicochemical properties and versatility of new materials. In addition to the well-established use of localized surface plasmon resonance (LSPR), three major areas have been identified in these new trends: chiral plasmonics, magnetoplasmonics, and quantum plasmonics. In describing the recent advances, emphasis is placed on the design and manufacture of portable devices working with low loss in different frequency ranges, from the infrared to the visible.

Plasmonic Biosensing Focus Review

Energy transfer from photoexcited zero-dimensional systems to metallic systems plays a prominent role in modern day materials science. A situation of particular interest concerns the interaction between a photoexcited dipole and an atomically thin metal. The recent discovery of graphene layers permits investigation of this phenomenon. Here we report a study of fluorescence from individual CdSe/ZnS nanocrystals in contact with single- and few-layer graphene sheets. The rate of energy transfer is determined from the strong quenching of the nanocrystal fluorescence. For single-layer graphene, we find a rate of approximately 4 ns(-1), in agreement with a model based on the dipole approximation and a tight-binding description of graphene. This rate increases significantly with the number of graphene layers, before approaching the bulk limit. Our study quantifies energy transfer to and fluorescence quenching by graphene, critical properties for novel applications in photovoltaic devices and as a molecular ruler.

http://absimage.aps.org/image/MAR10/MWS_MAR10-2009-006247.pdf

Resonant Energy Transfer from Individual Semiconductor Nanocrystals to Graphene

ZnO-based nanostructured electrodes for electrochemical sensors and biosensors in biomedical applications

Plasmonic colorimetric sensors based on etching and growth of noble metal nanoparticles: Strategies and applications.

Early and accurate diagnosis is considered the key issue to prevent the further spread of viruses and facilitate influenza therapy. Herein, we report a colorimetric immunosensor for influenza A virus (IAV) based on gold nanoparticles (AuNPs) modified with monoclonal anti-hemagglutinin antibody (mAb). The immunosensor allows for a fast, simple, and selective detection of IAV. In this assay, influenza-specific antibodies are conjugated to AuNPs to create mAb–AuNP probes. Since IAV has multiple recognition sites for probes on the surface, the mAb–AuNP probes can be specifically arranged on the virus surface due to their very specific antigen recognition. In this case, this aggregation of the mAb–AuNP probes produces a red shift in the absorption spectrum due to plasmon coupling between adjacent AuNPs, and it can be detected with the naked eye as a color change from red to purple and quantified with the absorption spectral measurements. The aggregate formation is also confirmed with transmission electron microscopy (TEM) imaging and dynamic light scattering (DLS). Under the optimal conditions, the present immunoassay can sensitively measure H3N2 IAV (A/Brisbane/10/2007) with a detection limit of 7.8 hemagglutination units (HAU). This proposed immunosensor revealed high specificity, accuracy, and good stability. Notably, it is a single-step detection using AuNP probes and UV-vis spectrophotometer for readout, and no additional amplification, e.g., enzymatic, is needed to read the result. This assay depends on an ordered AuNP structure covering the virus surface and can be applied to any virus pathogen by incorporating the appropriate pathogen-specific antibody.

Colorimetric detection of influenza A virus using antibody-functionalized gold nanoparticles

Early diagnosis and life-long surveillance are clinically important to improve the long-term survival of cancer patients. Telomerase activity is a valuable biomarker for cancer diagnosis, but its measurement often used complex label procedures. Herein, we designed a novel, simple, visual and label-free method for telomerase detection by using enzymatic etching of gold nanorods (GNRs). First, repeating (TTAGGG)x sequences were extented on telomerase substrate (TS) primer. It formed G-quadruplex under the help of Hemin and K+. Second, the obtained horseradish peroxidase mimicking hemin/G-quadruplex catalyzed the H2O2-mediated etching of GNRs to the short GNRs, even to gold nanoparticles (GNPs), generating a series of distinct color changes due to their plasmon-related optical response. Thus, this enzymatic reaction can be easily coupled to telomerase activity, allowing for the detection of telomerase activity based on vivid colors. This can be differentiated sensitively by naked eyes because human eyes are ...

Visual, Label-Free Telomerase Activity Monitor via Enzymatic Etching of Gold Nanorods

A simple, fast, label-free colorimetric method for detection of telomerase activity in urine by using hemin-graphene conjugates.

Glucose and cholesterol in human fluids are clinically important analytes and their sensitive detection is significant in diagnosis. In this study, Au@Ag core–shell nanoparticles (Au@Ag NPs) prepared by in situ growth of silver nanoparticles (AgNPs) on the surface of thiol-PEG-capped gold nanoparticles (AuNPs, 13 nm) have been successfully applied to fabricate a colorimetric biosensing platform for glucose and cholesterol. Au@Ag NPs showed an obvious absorbance peak at 375 nm due to the surface plasmon resonance (SPR) absorption of AgNPs. In the presence of cholesterol and glucose, H2O2 was produced under the catalytic action of their corresponding enzymes such as glucose oxidase (GOx) or cholesterol oxidase (ChOx), which etched the AgNPs shell of Au@Ag NPs. As a result, their characteristic absorbance at 375 nm decreased, accompanied with a perceptible color change from orange to red, which could be used to detect glucose and cholesterol by the naked eye. Under optimum conditions, the linear ranges for the detection of glucose and cholesterol by UV-vis spectroscopy were from 0.5 to 400 μM and 0.3 to 300 μM, respectively. The detection limit of the biosensors for glucose and cholesterol were 0.24 μM and 0.15 μM, respectively. The practical applications of this method in urine or human serum have been realized with satisfactory results. This work provides a simple and sensitive approach for glucose and cholesterol detection, which has broad application prospects in clinical diagnosis.

Sensitive colorimetric detection of glucose and cholesterol by using Au@Ag core–shell nanoparticles

Telomerase is closely related to cancers, which makes it one of the most widely known tumor marker. Recently, many methods have been reported for telomerase activity measurement in which complex label procedures were commonly used. In this paper, a label-free method for detection of telomerase activity in urine based on steric hindrance changes induced by confinement geometry in the porous anodic alumina (PAA) nanochannels was proposed. Telomerase substrate (TS) primer was first assembled on the inside wall of PAA nanochannels by Schiff reaction under mild conditions. Then, under the action of telomerase, TS primer was amplified and extended to repeating G-rich sequences (TTAGGG)x, which formed multiplex G-quadruplex in the presence of potassium ions (K+). This configurational change led to the increment of steric hindrance in the nanochannels, resulting in the decrement of anodic current of potassium ferricyanide (K3[Fe(CN)6]). Compared with previously reported methods based on PAA nanochannels (usually ...

Yuanjian Liu

Papers

Colorimetric detection of influenza A virus using antibody-functionalized gold nanoparticles

Visual, Label-Free Telomerase Activity Monitor via Enzymatic Etching of Gold Nanorods

A simple, fast, label-free colorimetric method for detection of telomerase activity in urine by using hemin-graphene conjugates.

Sensitive colorimetric detection of glucose and cholesterol by using Au@Ag core–shell nanoparticles

Label-Free Detection of Telomerase Activity in Urine Using Telomerase-Responsive Porous Anodic Alumina Nanochannels.