Benefiting from near-infrared persistent luminescence, chromiumdoped zinc gallate nanoparticles have become appealing for background-free biomedical imaging applications, where autofluorescence from adjacent tissues no longer poses a problem. Nevertheless, the synthesis of persistent luminescent nanoparticles with controllable and biologically appropriate size, high luminescence intensity, and long persistent duration remains very challenging. Herein, we report a solvothermal synthetic route for preparing differently sized ZnGa 2 O 4 :Cr nanoparticles with a particle size tunable from 4 to 31 nm and afterglow duration longer than 20 h. The route involves lower reaction temperatures and involves no reworking of the particles postsynthesis, providing materials that have far fewer unwanted defects and much higher luminescence yields (up to 51%). It was found that methanol played a paramount role in obtaining the Cr 3+ -doped ZnGa 2 O 4 nanoparticles. The effects of methanol were discussed in combination with NMR spectroscopy studies and theoretical calculations, and the underlying alcoholmediated growth and doping mechanisms were elucidated, which will be beneficial for developing highly persistent luminescent nanoparticles.

The coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread into a global pandemic. Early and accurate diagnosis and quarantine remain the most effective mitigation strategy. Although reverse transcriptase polymerase chain reaction (RT-qPCR) is the gold standard for COVID-19 diagnosis, recent studies suggest that nucleic acids were undetectable in a significant number of cases with clinical features of COVID-19. Serologic assays that detect human antibodies to SARS-CoV-2 serve as a complementary method to diagnose these cases, as well as to identify asymptomatic cases and qualified convalescent serum donors. However, commercially available enzyme-linked immunosorbent assays (ELISA) are laborious and non-quantitative, while point-of-care assays suffer from low detection accuracy. To provide a serologic assay with high performance and portability for potential point-of-care applications, we developed DNA-assisted nanopore sensing for quantification of SARS-CoV-2 related antibodies in human serum. Different DNA structures were used as detection reporters for multiplex quantification of immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against the nucleocapsid protein of SARS-CoV-2 in serum specimens from patients with conformed or suspected infection. Comparing to a clinically used point-of-care assay and an ELISA assay, our technology can reliably quantify SARS-CoV-2 antibodies with higher accuracy, large dynamic range, and potential for assay automation.

Nanopore technology has been employed as a powerful tool for DNA sequencing and analysis. To extend this method to peptide sequencing, a necessary step is to profile individual amino acids (AAs) through their nanopore stochastic signals, which remains a great challenge because of the low signal-tonoise ratio and unpredictable conformational changes of AAs during their translocation through nanopores. We showed that the combination of an Nterminal derivatization strategy of AAs with nanopore technology could lead to effective in situ differentiation of AAs. Four different derivatization reactions have been tested with five selected AAs: Ala, Phe, Tyr, His, and Asp. Using an αhemolysin nanopore, we demonstrated the feasibility of derivatization-assisted identification of AAs regardless of their charge composition and polarity. The method was further applied to discriminate each individual AA in testing data sets using their established nanopore profiles from training data sets. We envision that this proof-of-concept study will not only pave a way for identification of individual AAs but also lead to future applications in protein/peptide sequencing using the nanopore technology.

A derivatization strategy was demonstrated for reliable identification of individual amino acids using an α-hemolysin nanopore.

High quality single-crystal CdS nanowire (NW) networks have been synthesized on Si(111) substrates via the chemical vapour deposition method. X-ray diffraction and selected area electron diffraction show that the NWs in the networks grow along the directions and their (0001) crystal planes are parallel to the Si(111) substrates. Room-temperature photoluminescence (PL) spectra of single CdS NWs in the networks are dominated by a near-band-edge emission and free from deep-level defect emissions. The PLs resulting from free-exciton and bound-exciton recombinations are detected at 77 K. The results of the electrical transport measurement on the CdS NW networks show that the current can flow through different NWs via the cross-junctions. The resistivity, electron concentration and electron mobility of single NWs in the networks are estimated by fitting the I–V curves measured on single NWs with the metal–semiconductor–metal model suggested by Zhang et al (2006 Appl. Phys. Lett. 88 073102; 2007 Adv. Funct. Mater. at press).

As bimodal magnetic-fluorescent imaging agents, the preparation of ZnS:Tb,Gd and ZnS:Er,Yb,Gd nanoparticles via a facile homogeneous precipitation method is reported. The results show that these nanoparticles are almost spherical in shape with a diameter of 100-200 nm approximately and a major phase of wurtzite-structured ZnS. The products can successfully label the human hepatocellular carcinoma (HepG2) cells and present low toxicity even at concentrations up to 5 mg mL(-1). Additionally, for the ZnS:Er,Yb,Gd nanoparticles calcinated above 950 °C, NIR-to-visible up-conversion fluorescence were obtained, which is believed to be superior to traditional ZnS-based bioimaging agents with down conversion. In MRI studies, they reveal a longitudinal relaxivity rate (r(1)) of 39.46 mM(-1) s(-1) and 57.8 mM(-1) s(-1), respectively, which are much larger than the conventional Gd-DTPA and currently reported Gd-base nanoparticles, suggesting great potential as MRI agents.

Off-stoichiometry effects on the near-infrared emission of the aqueous based biocompatible copper indium sulfide quantum dots are revealed.

In this paper, fluorescent and magnetic bifunctional ZnO:Er,Yb,Gd particles were synthesized via a simple homogeneous precipitation method. The morphology, size, fluorescent properties, and magnetic properties of the particles can be readily modified by doping with Er 3+ , Yb 3+ , and Gd 3+ . The results revealed that the ZnO:Er,Yb,Gd particles have both down-conversion and up-conversion fluorescence after calcination at high temperatures (>700 °C). The products successfully labled the human hepatocellular carcinoma (HepG2) cells and presented low toxicity even at a high concentration of 2 mg/ mL. Being upconverting nanoparticles (UCNPs), the prepared ZnO:Er,Yb,Gd particles exposed to 980 nm near-infrared (NIR) laser light emitted up-conversion fluorescence which could be absorbed by a photodynamic therapy (PDT) drug, methylene blue (MB), and then killed the HepG2 cells via PDT mechanism. In vitro therapeutic investigation evidenced the prominent PDT effects of MB-loaded ZnO:Er,Yb,Gd UCNPs upon NIR light irradiation. In magnetic resonance imaging (MRI) studies, ZnO:Er,Yb,Gd particles revealed a tunable longitudinal relaxivity rate (r 1 ) from 23.03 mM −1 s −1 to 36.84 mM −1 s −1 , which is much larger than the conventional Gd-DTPA and currently reported Gd-base nanoparticles, suggesting it would be a good candidate as an MRI agent. It is expected that these particles have applications in magnetic-fluorescent bimodal imaging and NIR light triggered photodynamic therapy.