Silica encapsulated ZnO quantum dot-phosphor nanocomposites:Sol-gel preparation and white light-emitting device application

ZnO quantum dots （QDs） as an eco-friendly and low-cost material has bright fluorescence, which makes it promising material for healthy lighting and displaying. However, the low fluorescence efficiency and poor stability of ZnO QDs impede their applications in lighting application. In this work, silica encapsulated ZnO QD-phosphors nanocomposites （ZSPN） have been prepared through a sol-gel synthesis process, where yellow-emitting ZnO QDs and blue-emitting BaMgAl10O17：Eu2＋ are employed as the luminescence cores and silica as link between two luminescence materials. Tunable photoluminescence of ZSPN and the white light emission have been achieved through changing mass ratio of both of ZnO QDs and commercial phosphors. The PLQY of the ZSPN can reach 63.7% and they can maintain high luminous in- tensity even the ambient temperature up to 110 ℃ and after 35 h of UV irradiation. In addition, they can keep stable for 40 days. By coating the ZSPN phosphors onto a ultraviolet chip, WLEDs with luminous efficiency of 73.6 lm/W and the color coordinate, correlated color temperature, and color rendering index can reach （0.32, 0.34）, 5580 K, and 87, respectively, indicating the bright prospect of the ZSPN phosphors used in healthy lighting.

Rational design multi-color-emissive chemiluminescent carbon nanodots in a single solvothermal reaction

Recently,the chemiluminescence(CL)induced by carbon nanodots(CDs)has intrigued researchers’extensive interests in various applications due to its special light emission principle.However,the difficulty of synthesizing chemiluminescent CDs with full-spectrum emission severely hinders the further regulation of the CL emission mechanism.Herein,the multi-color-emissive chemiluminescent CDs are rational designed and further synthesized by regulating the sp2-hybrid core and sp3-hybrid surface from the citrate-ammonia molecular in a single solvothermal reaction.More experimental characterizations and density functional theory calculations reveal that the higher temperature can promote the crosslinking polymerization/carbonization of carbon core and the higher protonation of solvent can determine the core size of final CDs,resulting in the variant CL emission from molecular-,crosslinking-and core-states.Thus,the CL emission of the CDs can be further synthesized by tuning the luminescence chromophores in the formation process via regulating the temperature and solvent,enabling the applications of the CL CDs in illumination and information encryption.This study paves a new technology to understand the luminescence of CDs and affords an industry translational potential over traditional chemiluminescent molecular.

Cationic engineered nanodiamonds for efficient antibacterial surface with strong wear resistance

The spread of diseases caused by bacterial adhesion and immobilization in public places constitutes a serious threat to public health.Prevention of bacteria spread by the construction of an antibacterial surface takes precedence over post-infection treatment.Herein,we demonstrate an effective antibacterial surface with strong wear resistance by constructing cationic engineered nanodiamonds(C-NDs).The C-NDs with positive surface potentials interact effectively with bacteria through electrostatic interactions,where the C-NDs act on the phospholipid bilayer and lead to bacterial membrane collapse and rupture through hydrogen bonding and residual surface oxygen-containing reactive groups.In this case,bactericidal rate of 99.99%and bacterial biofilm inhibition rate of more than 80%can be achieved with the C-NDs concentration of 1 mg/mL.In addition,the C-NDs show outstanding antibacterial stability,retaining over 87%of the antibacterial effect after stimulation by adverse environments of heat,acid,and external abrasion.Therefore,an antibacterial surface with high wear resistance obtained by integrating C-NDs with commercial plastics has been demonstrated.The antibacterial surface with a mass fraction of 1 wt.%C-NDs improved abrasion resistance by 3981 times,with 99%killing of adherent bacteria.This work provides an effective strategy for highly efficient antibacterial wear-resistant surface,showing great practical applications in public health environments.

Triggering triplet excitons of carbon nanodots through nanospace domain confinement for multicolor phosphorescence in aqueous solution

Easy non-radiative decay property of long-lived triplet excitons in aqueous solution obstructs their applications in aquatic surroundings.Recently reported phosphorescence phenomena in aqueous solution have excited researchers enormously but achieving full-color water-soluble phosphorescent carbon nanodots(CNDs)is still a challenging issue.Herein,full-color phosphorescence of water-soluble CNDs has been demonstrated by triggering their triplet excitons through nanospace domain confinement,and Förster energy resonance transfer is used for further tuning phosphorescence range.The phosphorescence spans across most of the visible spectrum,ranging from 400 to 700 nm.In an aqueous solution,the CNDs exhibits blue,green,and red phosphorescence,lasting for approximately 6,10,and 7 s,respectively.Correspondingly,the phosphorescence quantum yields are 11.85%,8.6%and 3.56%,making them readily discernible to the naked eyes and laying a solid foundation for practical application.Furthermore,phosphorescence flexible optical display and bioimaging have been demonstrated by using the multicolor CNDs-based nanomaterials,showing distinct superiority for accuracy and complete display and imaging in complex emission background.

Theoretical study of superradiant masing with solid-state spins at room temperature

Steady-state superradiance and superradiant lasing attract significant attentions in the field of optical lattice clocks,but have not been achieved yet due to the technical challenges and atom loss problem.In this article,we propose that their counter-part may be observed in the microwave domain with solid-state spins,i.e.,nitrogen-vacancy center spins and pentacene molecular spins,coupled to microwave resonator at room temperature with realistic technical restrictions.To validate our proposal,we investigate systematically the system dynamics and steady-state by solving quantum master equations for the multi-level and multi-process dynamics of trillions of spins.Our calculations show that the superradiant Rabi oscillations occur firstly due to transitions among different Dicke states,and the subsequent continuous-wave superradiant masing can achieve a linewidth well below millihertz.Our work may guide further exploration of transient and steady-state superradiant masing with the mentioned and other solid-state spins systems.The ultra-narrow linewidth may find applications in deep-space communications,radio astronomy and high-precision metrology.

Chemiluminescent carbon nanodots for dynamic and guided antibacteria

Advanced antibacterial technologies are needed to counter the rapid emergence of drug-resistant bacteria.Imageguided therapy is one of the most promising strategies for efficiently and accurately curing bacterial infections.Herein,a chemiluminescence(CL)-dynamic/guided antibacteria(CDGA)with multiple reactive oxygen species(ROS)generation capacity and chemiexcited near-infrared emission has been designed for the precise theranostics of bacterial infection by employing near-infrared emissive carbon nanodots(CDs)and peroxalate as CL fuels.Mechanistically,hydrogen peroxide generated in the bacterial microenvironment can trigger the chemically initiated electron exchange between CDs and energy-riched intermediate originated from the oxidized peroxalate,enabling bacterial induced inflammation imaging.Meanwhile,type Ⅰ/Ⅱ photochemical ROS production and type Ⅲ ultrafast charge transfer from CDs under the self-illumination can inhibit the bacteria proliferation efficiently.The potential clinical utility of CDGA is further demonstrated in bacteria infected mice trauma model.The self-illuminating CDGA exhibits an excellent in vivo imaging quality in early detecting wound infections and internal inflammation caused by bacteria,and further are proven as efficient broad-spectrum antibacterial nanomedicines without drug-resistance,whose sterilizing rate is up to 99.99%.

Viral inactivation by irradiation rays

Viral infection can lead to serious illness and death around the world,as exemplified by the spread of COVID-19.Using irradiation rays can inactive virions through ionizing and non-ionizing effect.The application of light in viral inactivation and the underlying mechanisms are reviewed by the research group of Dayong Jin from University of Technology Sydney.

Water-induced ultralong room temperature phosphorescence by constructing hydrogen-bonded networks

Room temperature phosphorescence(RTP)materials show potential applications in information security and optoelectronic devices,but it is still a challenge to achieve RTP in organic materials under water ambient due to the unstable property of triplet states.Herein,water-induced RTP has been demonstrated in the organic microrod(OMR).Noting that the RTP intensity of the as-prepared OMR is greatly enhanced when water is introduced,and the reason for the enhancement can be attributed to the formation of hydrogen-bonded networks inside the OMR.The hydrogen-bonded networks can confine the molecular motion effectively,leading to the stability of triplet states;thus the lifetime of the OMR can reach 1.64 s after introducing water.By virtue of the long lifetime of the OMR in the presence of water,multilevel data encryption based on the OMR has been demonstrated.

Self-exothermic reaction driven large-scale synthesis ofphosphorescent carbon nanodots

Phosphorescent carbon nanodots(CNDs)have various attractive properties and potential applications,but it remains a formidable challenge to achieve large-scale phosphorescent CNDs limited by current methods.Herein,a large-scale synthesis method for phosphorescent CNDs has been demonstrated via precursors’self-exothermic reaction at room temperature.The as-prepared CNDs show fluorescence and phosphorescence property,which are comparable with that synthesized by solvothermal and microwave method.Experimental and computational studies indicate that exotic atom doped sp^(2) hybridized carbon core works as an emissive center,which facilities the intersystem crossing from singlet state to triplet state.The CNDs show phosphorescence with tunable lifetimes from 193 ms to 1.13 s at different temperatures.The demonstration of large-scale synthesis of phosphorescent CNDs at room temperature opens up a new window for room temperature fabrication phosphorescent CNDs.

Near-infrared carbon nanodots for effective identification and inactivation of Gram-positive bacteria

An unacceptable increase in antibacterial resistance has arisen due to the abuse of multiple classes of broad-spectrum antibiotics.Therefore,it is significant to develop new antibacterial agents,especially those that can accurately identify and kill specific bacteria.Herein,we demonstrate a kind of perilla-derived carbon nanodots(CNDs),integrating intrinsic advantages of luminescence and photodynamic,providing the opportunity to accurately identify and kill specific bacteria.The CNDs have an exotic-doped andπ-conjugated core,vitalizing them near-infrared(NIR)absorption and emission properties with photoluminescence quantum yield of 21.1%;hydrophobic chains onto the surface of the CNDs make them to selectively stain Gram-positive bacteria by insertion into their membranes.Due to the strong absorption in NIR region,reactive oxygen species are in situ generated by the CNDs onto bacterial membranes under 660 nm irradiation,and 99.99%inactivation efficiency against Gram-positive bacteria within 5 min can be achieved.In vivo results demonstrate that the CNDs with photodynamic antibacterial property can eliminate the inflammation of the area affected by methicillin-resistant Staphylococcus aureus(MRSA),and enabling the wound to be cured quickly.

Water-induced MAPbBr_(3)@PbBr(OH) with enhanced luminescence and stability

Poor stability has long been one of the key issues that hinder the practical applications of lead-based halide perovskites.In this paper,the photoluminescence(PL)quantum yield(QY)of bromide-based perovskites can be increased from 2.5% to 71.54% by introducing water,and the PL QY of a sample in aqueous solution decreases minimally over 1 year.The enhanced stability and PL QY can be attributed to the water-induced methylamino lead bromide perovskite(MAPbBr_(3))@PbBr(OH).We note that this strategy is universal to MAPbBr_(3),formamidine lead bromide perovskite(FAPbBr_(3)),inorganic lead bromide perovskite(CsPbBr_(3)),etc.Light-emitting devices(LEDs)are fabricated by using the as-prepared perovskite as phosphors on a 365 nm UV chip.The luminance intensity of the LED is 9549 cd/m^(2) when the driven current is 200 mA,and blemishes on the surface of glass are clearly observed under the illumination of the LEDs.This work provides a new strategy for highly stable and efficient perovskites.

Towards efficient and stable multi-color carbon nanoparticle phosphors: synergy between inner polar groups and outer silica matrix

Nanocarbon as an eco-friendly and abundant material has strong multi-color fluorescence, which makes it a promising candidate for healthy lighting and display. However, the low fluorescence efficiency and poor stability of multi-color carbon nanoparticle（CNP） phosphors are main hurdles that hinder their applications. This work demonstrated efficient and stable multi-color CNP phosphors through synergy between inner polar groups and outer silica matrix. The polar groups in polyethylene glycol（PEG） 6,000 are favor of high fluorescence of the CNP phosphors, and the low melting point（64℃） of PEG 6,000 helps to improve the thermal stability of the phosphors, while the silica matrix provides protection to the phosphors. Based on this design,blue, green, yellow and red CNP phosphors with photoluminescence quantum yield of 53.1%, 47.4%, 43.8% and 42.3% have been achieved, all of which are the best values in ever reported multi-color CNP phosphors. Furthermore, the fluorescence of the CNP phosphors keeps almost unchanged at 100℃ and degrades little in one month, indicating their good thermal tolerance and temporal stability. In addition, multicolor devices including white light-emitting devices（LEDs）have been realized by coating the CNP phosphors onto UV chips. The luminous efficiency, correlated color temperature,Commission Internationale de L＇Eclairage and color rendering index of the white LED can reach 12 lm W^-1, 6,107 K,（0.32, 0.33） and 89, respectively, indicating the potential applications of the CNP phosphors in lighting and display.

Ultraviolet phosphorescent carbon nanodots

Phosphorescent carbon nanodots(CNDs)have generated enormous interest recently,and the CND phosphorescence is usually located in the visible region,while ultraviolet(UV)phosphorescent CNDs have not been reported thus far.Herein,the UV phosphorescence of CNDs was achieved by decreasing conjugation size and in-situ spatial confinement in a NaCNO crystal.The electron transition from the P_(x) to the sp^(2) orbit of the N atoms within the CNDs can generate one-unit orbital angular momentum,providing a driving force for the triplet excitons population of the CNDs.The confinement caused by the NaCNO crystal reduces the energy dissipation paths of the generated triplet excitons.By further tailoring the size of the CNDs,the phosphorescence wavelength can be tuned to 348 nm,and the room temperature lifetime of the CNDs can reach 15.8 ms.As a demonstration,the UV phosphorescent CNDs were used for inactivating gram-negative and gram-positive bacteria through the emission of their high-energy photons over a long duration,and the resulting antibacterial efficiency reached over 99.9%.This work provides a rational design strategy for UV phosphorescent CNDs and demonstrates their novel antibacterial applications.