With narrow luminescence peak width, reduced photobleaching, high physical and chemical stability, low toxicity, etc., [4-8] RE-doped UCNPs have been widely utilized in all sorts of fields, [9-17] especially in photoinduced therapies. [18-24] Among these UCNPs, activator (usually Er 3+ , Tm 3+ , Ho 3+) or sensitizer (usually Yb 3+) highly doped ones, provided with unique optical properties like exceptional brightness, single-band emission, lifetime tuning, and so on, [25] which are of great bioapplication potentials, have become a hot research focus recently. [25-33] However, progress has been severely limited as once the activator or sensitizer concentration goes beyond certain values, upconversion luminescence (UCL) intensities would be substantially weakened. [34-38] Take Tm 3+-activated UCL for example. As reported, the UCL intensity of blue emission fell straightly downward to less than 5% when Tm 3+ concentration rose from 2 to merely 10 mol%. [39] Energy loss pathways could easily occur under highly doped circumstances, mainly including acute cross-relaxation (CR) processes within activators, energy-back-transfer (EBT) processes between activators and sensitizers, as well as resonant energy transfer to lattice and surface defects. [40-44] Therefore, probing into these highly doped nanoparticles for the sake of effective methods to improve and finetune their luminescence performances would be urgently required for deeper theory study and wider application use. Holmium (Ho) is a commonly adopted RE element emitting both red and green characteristic upconversion peaks in visible waveband under 980 nm laser excitation, with crest values approximately located at 540 and 645 nm, respectively. [45-47] Similar to Er 3+ , an overall bright green UCL could be obtained in low activator and sensitizer doping concentration. [48-50] To reduce the green/red (G/R) ratio for purer red emission, Ce 3+ is normally employed for its CR processes with Ho 3+ , which could increase the population of excited states 5 I 7 and 5 F 5 of Ho 3+ to promote the red emission. [51-57] In addition to this, other techniques involving high excitation power [58,59] or unwonted types of laser with specific parameters [60,61] could also implement high purity of red UCL, which actually gets unsuitable or too complicated for biouse. In this sense, exploring more targeted strategies would bring out more flexibility for Hobased UCL materials to distinguish themselves. It is absolutely imperative for development of material science to adjust upconversion luminescence (UCL) properties of highly doped upconversion nanoparticles (UCNPs) with special optical properties and prominent application prospects. In this work, featuring NaHoF 4 @NaYbF 4 (Ho@Yb) structures, sub-30 nm core-multishell UCNPs are synthesized with a small NaHoF 4 core and varied Gd 3+ /Yb 3+ coexisting shells. X-ray diffraction, transmission electron microscopy, UCL spectrum, UCL lifetime, and pump power dependence are adhibited for characterization. Compared with the former work, exc...

Ameliorating upconversion luminescence (UCL) properties of rare-earth (RE)-doped upconvertion nanoparticles (UCNPs), specifically with high doping concentration, is extremely crucial in progressive scientific research. In this work, by high temperature pyrolysis, various NaHoF 4 :Yb 3+ core-only and NaHoF 4 @NaYbF 4 featured core−multishell UCNPs were synthesized using oleate chemicals. X-ray diffraction (XRD), transmission electron microscopy (TEM) scans and mapping, X-ray photoelectron spectroscopy (XPS), UCL spectrum, UCL lifetime, and pump power dependency were used to characterize the samples. CT and MR imaging, DPBF absorbance curves, in vitro cytotoxicity of Ce6 modified UCNPs were examined. By using the method of simple structure alteration of core size and shell thickness, dominant emission shift from green to red was successfully achieved for highly doped NaHoF 4 @NaYbF 4 UCNPs. Meanwhile, high-quality red-upconversion luminescence with low G/R (green/red) ratio and high intensity from Ho 3+ ions were obtained. An innovative theory of F c and F q , serving as a revised version of traditional concentration quenching and size effect, was introduced and proved that a large core and thick shell would both enhance UCL intensity, but acted conversely in terms of G/R ratio. An extra active or inert shell would effectively increase the UCL intensity under low-power laser excitation and enable UCL color to vary from green to yellow to red. Our study may broaden the application domain for NaHoF 4 material from MR imaging to photo-induced therapy.

Rapid and clinically sensitive detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) play an important role in the contact tracing and containment of the COVID-19 pandemic. A recently developed fielddeployable clustered regularly interspaced short palindromic repeats (CRISPR) detection assay with lateral flow strips shows promise for point-of-care detection of SARS-CoV-2. However, the limit of detection of paper stripbased assays (10-100 copies/lL) is much lower than that of fluorescence-based detection methods. In this study, we developed an easy-readout and sensitive enhanced (ERASE) strip to visualize the results of CRISPR detection and improve the sensitivity to 1 copy/lL with an unambiguous easy-read result. Using 649 clinical samples from blind specimens collected from patients in China, we validated our ERASE assay for SARS-CoV-2 RNA detection with 90.67% positive predictive agreement and 99.21% negative predictive agreement. In conclusion, our study provided a customized CRISPR strip for use in a simple, rapid, ultrasensitive, and highly specific assay for SARS-CoV-2 detection.

Chemodynamic therapy (CDT) based on the Fenton reaction is a promising strategy for nonlight cancer treatment. However, the traditional Fenton reaction is only efficient in strongly acidic conditions (pH = 2−4), resulting in the limited curative effect in a weakly acidic tumor microenvironment (TME). Herein, we first developed a simple in situ growth method to confine FeOCl nanosheets into hollow dendritic mesoporous organosilicon (H-DMOS) nanoparticles to obtain FeOCl@H-DMOS nanospheres. Ascorbic acid (AA) was then absorbed on the nanosystem as a H 2 O 2 prodrug and, meanwhile, was used for the regeneration of Fentons reagent for Fe 2+ . Finally, poly(ethylene glycol) (PEG)

The accumulation of soil-borne pathogens is the main driving factor of negative plant-soil feedbacks (NPSFs), which seriously restricts the sustainable development of agriculture. Using natural volatile organic compounds (VOCs) from plants or microorganisms as biofumigants is an emerging strategy to alleviate NPSFs in an environmentally-friendly way. Here, we identified α-terpineol from the VOCs of pine needles, confirmed the ability of α-terpineol fumigation in alleviating the NPSF of Panax notoginseng via significantly reducing seed decay rate, and also deciphered the underlying mechanism by which the soil microbial community is modified. α-Terpineol fumigation could suppress culturable fungi but enrich bacteria in a dose-dependent manner. Network analysis with high-throughput sequencing data revealed that α-terpineol could distinctly modify both fungal and bacterial communities. In detail, α-terpineol significantly suppressed the relative abundance of Ascomycota from 64.04 to 32.26%, but enriched the relative abundance of Proteobacteria, Acidobacteria and Actinobacteria. Subnetwork analysis further demonstrated that α-terpineol could directly or indirectly suppress fungal pathogens and enrich plant growth-promoting rhizobacteria (PGPRs). In vitro fumigation and co-culture experiments with culturable isolates validated these findings. The antagonism between beneficial bacteria and pathogens, and the synergistic growth promotion among α-terpineol-enriched bacteria might be involved in soil microbial community assembly. In summary, α-terpineol fumigation could directly or indirectly modify the soil microbial community to alleviate NPSFs, especially by suppressing fungal pathogens and enriching beneficial bacteria. This study suggests that VOCs from natural products are worth developing as biofumigants due to their multiple functions in modifying the soil microbial community.