Super-resolution and super-sensitivity of entangled squeezed vacuum state using optimal detection strategy

Interference metrology is a method for achieving high precision detection by phase estimation. The phase sensitivity of a traditional interferometer is subject to the standard quantum limit, while its resolution is constrained by the Rayleigh diffraction limit. The resolution and sensitivity of phase measurement can be enhanced by using quantum metrology. We propose a quantum interference metrology scheme using the entangled squeezed vacuum state, which is obtained using the magic beam splitter, expressed as ｜ψ〉=（｜ξ〉｜0〉＋｜0〉｜ξ〉）/√2＋2/coshr, such as the N00 N state. We derive the phase sensitivity and the resolution of the system with Z detection, project detection, and parity detection. By simulation and analysis, we determine that parity detection is an optimal detection method, which can break through the Rayleigh diffraction limit and the standard quantum limit.

Immune fluorescence test strips based on quantum dots for rapid and quantitative detection of carcino-embryonic antigen

At present,many researchers focused on the point-of-care testing（POCT）,a method of disease markers detection without large-scale instruments and specialized persons.However,most POCT diagnostic methods were suffered from poor detection sensitivity or inefficiency in quantitative detection.Herein,we developed a newly QD-immune fluorescence test strips（QD-IFTS） based on quantum dots（QDs） as the fluorescence nanocarrier to prepare the immune fluorescence probes in the classical immunochromatography detection system for sensing carcino-embryonic antigen（CEA）,a kind of glycoprotein produced by intestinal tissue and a broad spectrum of tumor marker for cancer diagnosis.And we designed a homemade strips fluorescence reader for detection of fluorescence intensity of QDs on the QD-IFTS.Under the optimized reaction conditions,chromatographic time of the newly QD-IFTS was only25 min,sample volume of the newly QD-IFTS was only 40 m L and the LOD of the newly QD-IFTS was 0.72 ng/m L.In addition,the efficiency and robustness of the newly QD-IFTS were confirmed by successfully application in 300 clinical serum samples,and the results revealed great potential in clinical POCT of other biomarkers.

Thiourea functionalized CdSe/CdS quantum dots as a fluorescent sensor for mercury ion detection

CdSe/CdS quantum dots （QDs） functionalized by thiourea （TU） were synthesized and used as a fluorescent sensor for mercury ion detection. The TU-functionalized QDs were prepared by bonding TU via electrostatic interaction to the core/shell CdSe/CdS QDs after capping with thioglycolic acid （TGA）. It was observed that the fluorescence of the functionalized QDs was quenched upon the addition of Hg^2＋. The quantitative detection of Hg^2＋ with this fluorescent sensor could be conducted based on the linear relationship between the extent of quenching and the concentration of Hg^2＋ added in the range of 1-300 μg.L^-1, A detection limit of 0.56 μg.L^-1 was achieved. The sensor showed superior selectivity for Hg^2＋ and was successfully applied to the determination of mercury in environmental samples with satisfactory results

Advances in single-particle detection for DNA sensing

Rapid, accurate and sensitive detection of particular DNA sequence is critical in fundamental biomedical research and clinical diagnostics. However, conventional approaches for DNA assay often suffer from cumbersome procedures, long analysis time and insufficient sensitivity. Recently, single-particle detection technology has emerged as a powerful tool in the biosensing area due to its significant advantages of ultrahigh sensitivity, low sample-consumption and rapid analysis time. Especially, the introduction of novel nanomaterials has greatly promoted the development of single-particle detection and its applications for DNA sensing. In this review, we summarize the recent advance in single-particle detection strategies for DNA sensing, and focus mainly on metallic nanoparticle-and semiconductor quantum dot-based single-particle detection. We highlight the emerging trends in this field as well.