Traceable Optical Physical Unclonable Functions Based on Germanium Vacancy in Diamonds.

Physical unclonable functions (PUFs) have emerged as an unprecedented solution for modern information security and anticounterfeiting by virtue of their inherent unclonable nature derived from distinctive, randomly generated physical patterns that defy replication. However, the creation of traceable optical PUF tags remains a formidable challenge. Here, we demonstrate a traceable PUF system whose unclonability arises from the random distribution of diamonds and the random intensity of the narrow emission from germanium vacancies (GeV) within the diamonds. Tamper-resistant PUF labels can be manufactured on diverse and intricate structural surfaces by blending diamond particles into polydimethylsiloxane (PDMS) and strategically depositing them onto the surface of objects. The resulting PUF codes exhibit essentially perfect uniformity, uniqueness, reproducibility, and substantial encoding capacity, making them applicable as a private key to fulfill the customization demands of circulating commodities. Through integration of a digitized "challenge-response" protocol, a traceable and highly secure PUF system can be established, which is seamlessly compatible with contemporary digital information technology. Thus, the GeV-PUF system holds significant promise for applications in data security and blockchain anticounterfeiting, providing robust and adaptive solutions to address the dynamic demands of these domains.

Entropy-Dominated Triplet Exciton Emission in Carbon Dots.

Phosphorescence in carbon dots (CDs) from triplet exciton radiative recombination at room temperature has achieved significant advancement. Confinement and nanoconfinement, serving as valuable techniques, are commonly utilized to brighten triplet exciton in CDs, thereby enhancing their phosphorescence. However, a comprehensive and universally applicable physical description of confinement-enhanced phosphorescence is still lacking, despite efforts to understand its underlying nature. In this study, the dominance of entropy is revealed in triplet exciton emission from CDs through the establishment of a microscopic vibration state model. CDs with varying entropy levels are studied, indicating that in a low entropy system, the multi-energy triplet exciton emission in CDs exhibits enhanced brightness, accompanied by a corresponding increase in their lifetimes. The product of lifetime and intensity in CDs serves as a descriptor for their phosphorescence properties. Moreover, an entropy-dependent information variation system based on the CDs is demonstrated. Specifically, in a low-entropy system, information is retained, whereas the corresponding information is erased in a high-entropy system. This work elucidates the underlying physical nature of confinement-enhanced triplet exciton emission, offering a deeper understanding of achieving ultralong phosphorescence in the future.

Broadband Negative Photoconductive Response in Carbon Nanodots.

Due to the broadband response and low selectivity of external light, negative photoconductivity (NPC) effect holds great potential applications in photoelectric devices. Herein, different photoresponsive carbon nanodots (CDs) are prepared from diverse precursors and the broadband response from the NPC CDs are utilized to achieve the optoelectronic logic gates and optical imaging for the first time. In detail, the mcu-CDs which are prepared by the microwave-assisted polymerization of citric acid and urea possess the large specific surface area and abundant hydrophilic groups as sites for the adsorption of H2O molecules and thereby present a high conductivity in dark. Meanwhile, the low affinity of mcu-CDs to H2O molecules permits the light-induced desorption of H2O molecules by heat effect and thus endow the mcu-CDs with a low conductivity under illumination. The easy absorption and desorption of H2O molecules contribute to the extraordinary NPC of mcu-CDs. With the broadband NPC response in CDs, the optoelectronic logic gates and flexible optical imaging system are established, achieving the applications of "NOR" or "NAND" logic operations and high-quality optical images. These findings unveil the unique optoelectronic properties of CDs, and have the potential to advance the applications of CDs in optoelectronic devices.

Thermally Enhanced Phosphorescent Carbon Nanodots for Monitoring Cold-Chain Logistics.

Room-temperature phosphorescent materials, renowned for their long luminescence lifetimes, have garnered significant attention in the field of optical materials. However, the challenges posed by thermally induced quenching have significantly hindered the advancement of luminescence efficiency and stability. In this study, thermally enhanced phosphorescent carbon nanodots (CND) are developed by incorporating them into fiber matrices. Remarkably, the phosphorescence lifetime of the thermally enhanced CND exhibits a twofold enhancement, increasing from 326 to 753 ms, while the phosphorescence intensity experienced a tenfold enhancement, increasing from 25 to 245 as the temperature increased to 373 K. Rigid fiber matrices can effectively suppress the non-radiative transition rate of triplet excitons, while high temperatures can desorb oxygen adsorbed on the surface of the CND, disrupting the interaction between the CND and oxygen. Consequently, a thermally enhanced phosphorescence is obtained. In addition, benefiting from the thermally enhanced phosphorescence property of CND, a warning indicator with an anti-counterfeiting function for monitoring cold-chain logistics is demonstrated based on CND.

Visualizing Motion Trail via Phosphorescence Carbon Nanodots-Based Delay Display Array.

A scene that contains both old and instant events with a clear motion trail is visually intriguing and dynamic, which can convey a sense of change, transition, or evolution. Developing an eco-friendly delay display system offers a powerful tool for fusing old and instant events, which can be used for visualizing motion trails. Herein, we brighten triplet excitons of carbon nanodots (CNDs) and increase their emission yield by a multidimensional confinement strategy, and the CND-based delay display array is demonstrated. The intense confinement effects via multidimensional confinement strategy suppress nonradiative transitions, and 240% enhancement in the phosphorescence efficiency and 260% enhancement in the lifetime of the CNDs are thus realized. Considering their distinctive phosphorescence performances, a delay display array containing a 4 × 4 CND-based delay lighting device is demonstrated, which can provide ultralong phosphorescence over 7 s, and the motion that occurred in different timelines is recorded clearly. This finding will motivate the investigation of phosphorescent CNDs in motion trail recognition.

Efficient Deep-Blue Light-Emitting Diodes from Highly Luminescent Eu2+-Doped Alkali Metal Halide Nanocrystals via Lattice Field Modulation.

Lead-halide perovskite nanocrystals (NCs) are promising for fabricating deep-blue (<460 nm) light-emitting diodes (LEDs), but their development is plagued by low electroluminescent performance and lead toxicity. Herein, the synthesis of 12 kinds of highly luminescent and eco-friendly deep-blue europium (Eu2+)-doped alkali-metal halides (AX:Eu2+; A = Na+, K+, Rb+, Cs+; X = Cl-, Br-, I-) NCs is reported. Through adjustment of the coordination environment, efficient deep-blue emission from Eu-5d → Eu-4f transitions is realized. The representative CsBr:Eu2+ NCs exhibit a high photoluminescence quantum yield of 91.1% at 441 nm with a color coordinate at (0.158, 0.023) matching with the Rec. 2020 blue specification. Electrically driven deep-blue LEDs from CsBr:Eu2+ NCs are demonstrated, achieving a record external quantum efficiency of 3.15% and half-lifetime of ∼1 h, surpassing the reported metal-halide deep-blue NCs-based LEDs. Importantly, large-area LEDs with an emitting area of 12.25 cm2 are realized with uniform emission, representing a milestone toward commercial display applications.

Silicon Vacancies Diamond/Silk/PVA Hierarchical Physical Unclonable Functions for Multi-Level Encryption.

Physical unclonable functions (PUFs) have emerged as a promising encryption technology, utilizing intrinsic physical identifiers that offer enhanced security and tamper resistance. Multi-level PUFs boost system complexity, thereby improving system reliability and fault tolerance. However, crosstalk-free multi-level PUFs remain a persistent challenge. In this study, a hierarchical PUF system that harnesses the spontaneous phase separation of silk fibroin /PVA blend and the random distribution of silicon-vacancy diamonds within the blend is presented. The thermodynamic instability of phase separation and inherent unpredictability of diamond dispersion gives rise to intricate random patterns at two distinct scales, enabling time-efficient hierarchical authentication for cryptographic keys. These patterns are complementary yet independent, inherently resistant to replication and damage thus affording robust security and reliability to the proposed system. Furthermore, customized authentication algorithms are constructed: visual PUFs authentication utilizes neural network combined structural similarity index measure, while spectral PUFs authentication employs Hamming distance and cross-correlation bit operation. This hierarchical PUF system attains a high recognition rate without interscale crosstalk. Additionally, the coding capacity is exponentially enhanced using M-ary encoding to reinforce multi-level encryption. Hierarchical PUFs hold significant potential for immediate application, offering unprecedented data protection and cryptographic key authentication capabilities.

Solar-Blind Photodetector Arrays Fabricated by Weaving Strategy.

The quest for solar-blind photodetectors (SBPDs) with exceptional optoelectronic properties for imaging applications has prompted the investigation of SBPD arrays. Ga2O3, characterized by its ultrawide bandgap and low growth cost, has emerged as a promising material for solar-blind detection. In this study, SBPD arrays were fabricated by weaving Sn-doped ß-Ga2O3 microbelts (MBs). These MBs, which have a conductive core surrounded by a high-resistivity depletion surface layer resulting from the segregation of Sn and oxygen, are woven into a grid structure. Each intersection of the MBs functions as a photodetector pixel, with the intersecting MBs serving as the output electrodes of the pixel. This design simplifies the readout circuit for the photodetector array. The solar-blind photodetector array demonstrates superior solar-blind detection performance, including a dark current of 0.5 pA, a response time of 38.8 µs, a light/dark current ratio of 108, and a responsivity of 300 A/W. This research may provide a feasible strategy for the fabrication of photodetector arrays, thus pushing forward the application of photodetectors in imaging.

Photooxidation triggered ultralong afterglow in carbon nanodots.

It remains a challenge to obtain biocompatible afterglow materials with long emission wavelengths, durable lifetimes, and good water solubility. Herein we develop a photooxidation strategy to construct near-infrared afterglow carbon nanodots with an extra-long lifetime of up to 5.9 h, comparable to that of the well-known rare-earth or organic long-persistent luminescent materials. Intriguingly, size-dependent afterglow lifetime evolution from 3.4 to 5.9 h has been observed from the carbon nanodots systems in aqueous solution. With structural/ultrafast dynamics analysis and density functional theory simulations, we reveal that the persistent luminescence in carbon nanodots is activated by a photooxidation-induced dioxetane intermediate, which can slowly release and convert energy into luminous emission via the steric hindrance effect of nanoparticles. With the persistent near-infrared luminescence, tissue penetration depth of 20 mm can be achieved. Thanks to the high signal-to-background ratio, biological safety and cancer-specific targeting ability of carbon nanodots, ultralong-afterglow guided surgery has been successfully performed on mice model to remove tumor tissues accurately, demonstrating potential clinical applications. These results may facilitate the development of long-lasting luminescent materials for precision tumor resection.

Engineering Sizable and Broad-Spectrum Antibacterial Fabrics through Hydrogen Bonding Interaction and Electrostatic Interaction.

Long-lasting and highly efficient antibacterial fabrics play a key role in public health occurrences caused by bacterial and viral infections. However, the production of antibacterial fabrics with a large size, highly efficient, and broad-spectrum antibacterial performance remains a great challenge due to the complex processes. Herein, we demonstrate sizable and highly efficient antibacterial fabrics through hydrogen bonding interaction and electrostatic interaction between surface groups of ZnO nanoparticles and fabric fibers. The production process can be carried out at room temperature and achieve a production rate of 300 × 1 m2 within 1 h. Under both visible light and dark conditions, the bactericidal rate against Gram-positive (S. aureus), Gram-negative (E. coli), and multidrug-resistant (MRSA) bacteria can reach an impressive 99.99%. Furthermore, the fabricated ZnO nanoparticle-decorated antibacterial fabrics (ZnO@fabric) show high stability and long-lasting antibacterial performance, making them easy to develop into variable antibacterial blocks for protection suits.

Supramolecular Aggregation of Carbon Nanodots.

Supramolecular aggregation has provided the archetype concept to understand the variants in an emerging systems property. Herein, we have achieved the supramolecular assembly of carbon nanodots (CDs) for the first time and employ supramolecular aggregation to understand their alteration in photophysical properties. In detail, we have employed the CDs as a block to construct the supramolecular assembly of aggregates in the CDs' antisolvent of ethanol. The CD-based aggregates exhibit complex and organized morphologies with another long-wavelength excitation-dependent emission band. The experimental results and density functional theoretical calculations reveal that the supramolecular assembly of CDs can decrease the energy gap between the ground and excited states, contributing to the new long-wavelength excitation-dependent emission. The supramolecular aggregation can be employed as one universal strategy to manipulate and understand the luminescence of CDs. These findings cast new light to build the emerging systems and understand the light emission of CDs through supramolecular chemistry.

Highly Antibacterial and Antioxidative Carbon Nanodots/Silk Fibroin Films for Fruit Preservation.

The issues of fruit waste and safety resulting from rot have spurred a demand for improved packaging systems. Herein, we present highly antibacterial and antioxidative carbon nanodot/silk fibroin (CD/SF) films for fruit preservation. The films are composed of CDs and SF together with a small amount of glycerol via hydrogen bonding, exhibiting outstanding biosafety, transparency, and stretchability. The films effectively integrate key functionalities (atmosphere control, resistance to food-borne pathogens, and antioxidation properties) and can be manufactured in large sizes (about 20 × 30 cm), boasting a transmission rate of 13 183 cm3/m2·day for oxygen and 2860 g/m2·day for water vapor, favoring the preservation of fresh fruits. A convenient dip-coating method enables in situ fabrication of films with a thickness of approximately 14 µm directly on the fruits' surface providing comprehensive protection. Importantly, the films are washable and biodegradable. This work presents a promising technology to produce multifunctional and eco-friendly antibacterial packaging systems.

Uncooled Mid-Infrared Sensing Enabled by Chip-Integrated Low-Temperature-Grown 2D PdTe2 Dirac Semimetal.

Next-generation mid-infrared (MIR) imaging chips demand free-cooling capability and high-level integration. The rising two-dimensional (2D) semimetals with excellent infrared (IR) photoresponses are compliant with these requirements. However, challenges remain in scalable growth and substrate-dependence for on-chip integration. Here, we demonstrate the inch-level 2D palladium ditelluride (PdTe2) Dirac semimetal using a low-temperature self-stitched epitaxy (SSE) approach. The low formation energy between two precursors facilitates low-temperature multiple-point nucleation (∼300 °C), growing up, and merging, resulting in self-stitching of PdTe2 domains into a continuous film, which is highly compatible with back-end-of-line (BEOL) technology. The uncooled on-chip PdTe2/Si Schottky junction-based photodetector exhibits an ultrabroadband photoresponse of up to 10.6 µm with a large specific detectivity. Furthermore, the highly integrated device array demonstrates high-resolution room-temperature imaging capability, and the device can serve as an optical data receiver for IR optical communication. This study paves the way toward low-temperature growth of 2D semimetals for uncooled MIR sensing.

Enhanced Phosphorescence of Carbon Nanodots via Double Confinement for 3D Artworks with Long Emission Lifetimes.

Phosphorescent materials as block elements to build artwork incorporating the time and emission, enable them with spectacular lighting effects. In this work, enhanced phosphorescence of carbon nanodots (CNDs) is demonstrated via double confinement strategy, which silica and epoxy resin are used as the first and the second order confinement layer. The multi-confined CNDs show an enhanced phosphorescence quantum yield up to 16.4%, with enduring emission lifetime up to 1.44 s. Delicately, the plasticity of the epoxy resin enables them easily to be designed for 3D artworks with long emission lifetimes in different shapes. The efficient and eco-friendly phosphorescent CNDs may arouse intense interest both in the academic community and markets.

Chemiluminescent carbon nanodots for dynamic and guided antibacteria.

Advanced antibacterial technologies are needed to counter the rapid emergence of drug-resistant bacteria. Image-guided 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%.

Antibacterial Carbon Dots: Mechanisms, Design, and Applications.

The increase in antibiotic resistance promotes the situation of developing new antibiotics at the forefront, while the development of non-antibiotic pharmaceuticals is equally significant. In the post-antibiotic era, nanomaterials with high antibacterial efficiency and no drug resistance make them attractive candidates for antibacterial materials. Carbon dots (CDs), as a kind of carbon-based zero-dimensional nanomaterial, are attracting much attention for their multifunctional properties. The abundant surface states, tunable photoexcited states, and excellent photo-electron transfer properties make sterilization of CDs feasible and are gradually emerging in the antibacterial field. This review provides comprehensive insights into the recent development of CDs in the antibacterial field. The topics include mechanisms, design, and optimization processes, and their potential practical applications are also highlighted, such as treatment of bacterial infections, against bacterial biofilms, antibacterial surfaces, food preservation, and bacteria imaging and detection. Meanwhile, the challenges and outlook of CDs in the antibacterial field are discussed and proposed.

Paper-Fiber-Activated Triplet Excitons of Carbon Nanodots for Time-Resolved Anti-counterfeiting Signature with Artificial Intelligence Authentication.

The easy-to-imitate character of a personal signature may cause significant economy loss due to the lack of speed and strength information. In this work, we report a time-resolved anti-counterfeiting signature strategy with artificial intelligence (AI) authentication based on the designed luminescent carbon nanodot (CND) ink, whose triplet excitons can be activated by the bonding between the paper fibers and the CNDs. Paper fibers can bond with the CNDs through multiple hydrogen bonds, and the activated triplet excitons release photons for about 13 s; thus, the speed and strength of the signature are recorded through recording the changes in luminescence intensity over time. The background noise from commercial paper fluorescence is completely suppressed, benefiting from the long phosphorescence lifetime of the CNDs. In addition, a reliable AI authentication method with quick response based on a convolutional neural network is developed, and 100% identification accuracy of the signature based on the CND ink is achieved, which is higher than that of the signature with commercial ink (78%). This strategy can also be expanded for painting, calligraphy identification.

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.

Thermally Enhanced and Long Lifetime Red TADF Carbon Dots via Multi-Confinement and Phosphorescence Assisted Energy Transfer.

Thermally activated delayed fluorescence (TADF) materials, which can harvest both singlet and triplet excitons for high-efficiency emission, have attracted widespread concern for their enormous applications. Nevertheless, luminescence thermal quenching severely limits the efficiency and operating stability in TADF materials and devices at high temperature. Herein, a surface engineering strategy is adopted to obtain unique carbon dots (CDs)-based thermally enhanced TADF materials with ≈250% enhancement from 273 to 343 K via incorporating seed CDs into ionic crystal network. The rigid crystal network can simultaneously boost reverse intersystem crossing process via enhancing spin-orbit coupling between singlet and triplet states and suppressing non-radiative transition rate, contributing to the thermally enhanced TADF character. Benefiting from efficient energy transfer from triplet states of phosphorescence center to singlet states of CDs, TADF emission at ≈600 nm in CDs displays a long lifetime up to 109.6 ms, outperforming other red organic TADF materials. Thanks to variable decay rates of the delayed emission centers, time and temperature-dependent delayed emission color has been first realized in CDs-based delayed emission materials. The CDs with thermally enhanced and time-/temperature-dependent emission in one material system can offer new opportunities in information protection and processing.