Deep-red afterglow materials with high emission efficiency remain fundamentally limited by inefficient intersystem crossing (ISC) and significant nonradiative decay of triplet excitons under solid-state conditions. Herein, we establish a space-confined triplet-singlet energy transfer (ET) design to achieve efficient long-wavelength afterglow emission in metal-free carbon dot hybrids. Urea-induced heteroatom engineering introduces (n, π*) states that facilitate ISC and increase triplet population, while an (3-aminopropyl) triethoxysilane-derived siloxane network rigidifies the microenvironment and suppresses vibrational relaxation, thereby stabilizing triplet excitons. Meanwhile, surface-state modulation enables favorable triplet energy alignment between the carbon core and surface-associated emissive centers, facilitating efficient triplet-mediated ET. This cooperative regulation results in bright deep-red afterglow centered at 662 nm with a photoluminescence quantum yield of 45.2%. Comparative investigations with red-emissive counterparts reveal that surface-state modulation and molecular rigidification play complementary roles in wavelength tunability and emission efficiency. The resulting materials demonstrate potential in time-resolved optical encryption and persistent afterglow lighting. This work provides mechanistic insight into triplet regulation in confined carbon systems and suggests a viable strategy for improving long-wavelength metal-free afterglow performance.

As a novel solution-processable laser material with excellent optical properties, high biocompatibility, and low toxicity, the intrinsic value of carbon dots and their role in optimizing small-scale lasers as a gain medium have received extensive attention. In this review, we systematically summarize a series of properties of carbon dots themselves and the carbon dot (CD) lasers fabricated based on them. Specifically, we first summarize the photoluminescence principle of carbon dots as well as their synthesis and modification methods. Secondly, we organize the current types of CD lasers. Finally, we summarize the applications of carbon dots and CD lasers, the current challenges they face, and provide outlooks and speculations for their future. It is hoped that this review can help other researchers comprehensively and completely understand or review the overall picture of carbon dots and CD lasers in the shortest possible time.

Energy transfer between chemiluminescence (CL) donor and acceptor enables the tunable long-wavelength emission for multidisciplinary applications. In this work, the carbon nanodots (CDs) with sp³-hybrid carbon nitride framework exhibit a conspicuous tunable CL wavelength in luminol–H₂O₂ reaction with ultrahigh energy transfer efficiency. The density functional theorical calculations and experimental surveys reveal that the synergistic effect of singlet/triplet mixed electron exchange between the CD and luminol–H₂O₂ reaction enable the efficient energy transfer, and the concentration-dependent distance between the luminol donor and CD acceptor mutate the efficiency of singlet/triplet electron exchange, leading to the efficient concentration-dependent CL emission. With the novel CL emission, an advanced paper-based CL system is established with the CDs and luminol–H₂O₂ reaction, and the applications of information encryption and anti-counterfeiting are achieved. This work paves a new paradigm to understand the energy transfer mechanism in CL process, and may inspire the design of new CL architecture.

As one promising carbon-based material, sp³-hybrid carbon nitride has been predicted with various novel physicochemical properties. However, the synthesis of sp³-hybrid carbon nitride is still limited by the nanaoscale, low crystallinity, complex source, and expensive instruments. Herein, we have presented a facile approach to the sp³-hybrid carbon nitride nano/micro-crystals with microwave-assisted confining growth and liquid exfoliation. Actually, the carbon nitride nano/micro-crystals can spontaneously emerge and grow in the microwave-assisted polymerization of citric acid and urea, and the liquid exfoliation can break the bulk disorder polymer to retrieve the highly crystalline carbon nitride nano/micro-crystals. The obtained carbon nitride nano/micro-crystals present superior blue light absorption strength and surprising photoluminescence quantum yields of 57.96% in ethanol and 18.05% in solid state. The experimental characterizations and density functional theory calculations reveal that the interface-trapped localized exciton may contribute to the excellent intrinsic light emission capability of carbon nitride nano/micro-crystals and the interparticle staggered stacking will prevent the aggregation-caused-quenching partially. Finally, the carbon nitride nano/micro-crystals are demonstrated to be potentially useful as the phosphor medium in light-emitting-diode for interrupting blue light-induced eye damage. This work paves new light on the synthesis strategy of sp³-hybrid carbon nitride materials and thus may push forward the development of multiple carbon nitride research.

The emergence of novel self-powered humidity sensors has attracted considerable attention in the fields of smart electronic devices and personal healthcare. Herein, self-powered humidity sensors have been fabricated using a moisture-driven energy generation (MEG) device based on asymmetric tubular graphitic carbon nitride (g-CN) films prepared on anodized aluminum (AAO) template. At a relative humidity (RH) of 96%, the MEG device can provide an open-circuit voltage of 0.47 V and a short-circuit current of 3.51 μA, with a maximum output power of 0.08 μW. With inherent self-powered ability and humidity response via current variation, an extraordinary response of 1.78 × 10⁶% (41%–96% RH) can be gained from the MEG device. The possible power generation mechanism is that g-CN/AAO heterostructure can form ion gradient and diffusion under the action of moisture to convert chemical potential into electrical potential, evoking a connaturally sensitive response to humidity. Self-powered respiration monitoring device based on the sensor is designed to monitor human movement (sitting, warming up, and running) and sleep status (normal, snoring, and apnea), maintaining excellent stability during cumulative 12-h respiration monitoring. This self-powered humidity sensing technology has promising potential for extensive integration into smart electronic and round-the-clock health monitoring devices.

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.

Ultraviolet position-sensitive detectors (PSDs) are expected to undergo harsh environments, such as high temperatures, for a wide variety of applications in military, civilian, and aerospace. However, no report on relevant PSDs operating at high temperatures can be found up to now. Herein, we design a new 2D/3D graphitic carbon nitride (g-C₃N₄)/gallium nitride (GaN) hybrid heterojunction to construct the ultraviolet high-temperature-resistant PSD. The g-C₃N₄/GaN PSD exhibits a high position sensitivity of 355 mV mm⁻¹, a rise/fall response time of 1.7/2.3 ms, and a nonlinearity of 0.5% at room temperature. The ultralow formation energy of −0.917 eV atom⁻¹ has been obtained via the thermodynamic phase stability calculations, which endows g-C₃N₄ with robust stability against heat. By merits of the strong built-in electric field of the 2D/3D hybrid heterojunction and robust thermo-stability of g-C₃N₄, the g-C₃N₄/GaN PSD delivers an excellent position sensitivity and angle detection nonlinearity of 315 mV mm⁻¹ and 1.4%, respectively, with high repeatability at a high temperature up to 700 K, outperforming most of the other counterparts and even commercial silicon-based devices. This work unveils the high-temperature PSD, and pioneers a new path to constructing g-C₃N₄-based harsh-environment-tolerant optoelectronic devices.