Directly Self-Assembly of Aligned Ag NWs Films at the Air-Water Interface for the Detection of Pathogens in Artificial Breath Aerosols

Exhaled aerosols from humans, containing various pathogens, are crucial for early disease diagnosis. However, the traditional pathogen detection methods, such as polymerase chain reaction, are often slow and cumbersome due to complex sampling and procedures. This study introduces a novel, direct, and label-free detection method for pathogens in respiratory aerosols, utilizing a highly aligned silver nanowire (Ag NW) film combined with a filter membrane (Ag NWs@filter) as a surface-enhanced Raman spectroscopy-active substrate. A large-scale, ordered silver nanowire film was developed through a simplified self-assembly process. This process eliminates the need for an organic phase and complex surface modifications of Ag NWs, which are common in other preparation methods. Subsequently, the fabricated Ag NWs@filter demonstrated its capability to continuously capture and efficiently preconcentrate pathogens from aerosols, achieving a remarkable detection limit of 3 × 103 CFU/mL, demonstrated using Escherichia coli (E. coli) as a model pathogen. Moreover, the classification between E. coli and Pseudomonas aeruginosa achieved an overall accuracy of 96.5% by the principal component analysis with linear discriminant analysis models. The success of this sensing strategy illustrates its potential in detecting and identifying a variety of biomarkers present in respiratory aerosols, marking a significant step forward in the field of pathogen detection.

A simple colorimetric method based on "on-off-on" mode for detection of H2S and Hg2+ in water

It is of great significance to develop efficient platforms for the detection of hypertoxic Hg²⁺ and H₂S. Colorimetric have received much attention for the detection of H₂S and Hg²⁺ in the last decades. In this work, an "on-off-on" mode colorimetric method based on MnO₂/multi-wall carbon nanotubes (MnO₂/MWCNTs) composite was constructed. MnO₂/MWCNTs composite can oxidize TMB directly to form blue product (ox TMB) with a good simulated oxidase activity. In the presence of H₂S, it can decompose the MnO₂/MWCNTs composite causing the absorbance of the chromogenic system to decrease. When Hg²⁺ is introduced, the formation of Hg-S bond between Hg²⁺ and H₂S inhibited the decomposition ability of H₂S toward MnO₂ composite, thus resulting in a color change from colorless to blue. Based on this phenomenon, the proposed "on-off-on" colorimetric sensor can be used for detection of H₂S (off) and Hg²⁺ (on). Under optimized experimental conditions, this sensor showed a satisfactory linear relationship of H₂S and Hg²⁺ with pleasant repeatability, acceptable method accuracy and stability. More importantly, the proposed colorimetric sensor has been successfully applied to the detection of H₂S and Hg²⁺ in real samples, which not only provides a simple and cost-effective method to detect H₂S and Hg²⁺ but also hopefully makes a certain contribution to environmental protection.

Nanomaterial-enhanced chemiluminescence reactions and their applications

Chemiluminescence (CL) analysis is a trace analytical method that possesses advantages including high sensitivity, wide linear range, easy operation, and simple instruments. With the development of nanotechnology, many nanomaterial (NM)-enhanced CL systems have been established in recent years and applied for the CL detection of metal ions, anions, small molecules, tumor markers, sequence-specific DNA, and RNA. This review summarizes the research progress of the nanomaterial-enhanced CL systems the past five years. These CL reactions include luminol, peroxyoxalate, lucigenin, ultraweak CL reactions, and so on. The CL mechanisms of the nanomaterial-enhanced CL systems are discussed in the first section. Nanomaterials take part in the CL reactions as the catalyst, CL emitter, energy acceptor, and reductant. Their applications are summarized in the second section. Finally, the challenges and opportunities are discussed.

Gold Nanocluster-catalyzed Luminol Chemiluminescent Sensing Method for Sensitive and Selective Detection of Alkaline Phosphatase

A sensitive sensing method was developed for the determination of alkaline phosphatase (ALP) activity based on gold nanocluster (Au NC)-catalyzed luminol-H2O2 chemiluminescent (CL) reaction. The CL signal of luminol-H2O2-Au NCs can be quenched by ascorbic acid, which was the product of magnesium ascorbyl phosphate (MAP) hydrolysis reaction catalyzed by ALP. The proposed sensing platform showed convenient, sensitive and selective detection of ALP in the range of 0.0027 - 1.3890 U L-1, with the detection limit of 0.0026 U L-1. The broad detection linear range and ultra-high sensitivity were inherited from the efficient free radical scavenging capability of ascorbic acid on the luminol-H2O2-Au NCs CL reaction. The CL sensing platform was applied to the detection of ALP activity in serum samples. We believe that this sensing platform is a universal CL strategy for ALP detection because ascorbic acid is an efficient CL quencher for many CL reactions.

Core-shell Au@Pt Nanoparticles Catalyzed Luminol Chemiluminescence for Sensitive Detection of Thiocyanate

In this study, core-shell Au@Pt nanoparticles (Au@Pt NPs) with peroxidase catalytic activity were synthesized by the seed-mediated method, and were used to catalyze the reaction of luminol-H₂O₂ to enhance the chemiluminescence (CL) intensity. It was found that thiocyanate (SCN^-) can effectively inhibit the catalytic activity of Au@Pt NPs. Based on this phenomenon, a method to detect SCN^- by using the Au@Pt NPs-catalytic luminol-H₂O₂ CL system was established, which has an ultra-low detection limit and an ultra-wide linear range, as well as the advantages of being simple and having low-cost and convenient operation. The research mechanism indicated that SCN^- could be adsorbed on the surface of Au@Pt NPs and occupies the active sites of Pt nanostructures, which led to a decrease in the amount of Pt⁰ and a loss of the excellent catalytic activity of Au@Pt NPs. After optimizing the experimental conditions, this assay for detecting SCN^- exhibited a good linear range from 5 to 180 nM, and the low detection limit was 2.9 nM. In addition, this approach has been successfully applied to the detection of SCN^- in tap-water samples, which has practical application value and embodies good development prospects.

In Situ Generation of Prussian Blue with Potassium Ferrocyanide to Improve the Sensitivity of Chemiluminescence Immunoassay Using Magnetic Nanoparticles as Label

Using magnetic nanoparticles (MNPs) as a label in immunoassay (IA) possesses advantages such as high specific surface area, simple modification process. However, the catalytic activity of MNPs is low, which limits their applications in IA. The present study found it interesting that potassium ferrocyanide reacts with MNPs, leading to the in situ generation of Prussian blue. The produced Prussian blue shows high catalytic activity on a luminol chemiluminescent (CL) reaction. Therefore, a simple and sensitive immunoassay for rabbit IgG (rIgG) as model analyte using MNPs as label was developed. The CL intensity had a linear increase with the concentration of rIgG that ranged from 0.625 to 20 ng mL^-1. The limit of detection was calculated to be 0.59 ng mL^-1. In addition, the applicability of this method was evaluated using the standard addition method. The recovery ranged from 80.0% to 115.0%. What's more, the proposed CLIA method based on in situ generation of Prussian blue with MNPs was also applied to the detection of carcinoembryonic antigen (CEA) and hepatitis B virus (HBV)-related sequence-specific DNA. The LOD for the detection of CEA and sequence-specific DNA was estimated to be 0.28 ng mL^-1 and 0.044 pmol, respectively.