The investigation of the fluorescence mechanism of carbon dots (CDs) has attracted significant attention, particularly the role of the oxygen-containing groups. Dual-CDs exhibiting blue and green emissions are synthesized from glucose via a simple ultrasonic treatment, and the oxidation degree of the CDs is softly modified through a slow natural oxidation approach, which is in stark contrast to that aggressively altering CDs’ surface configurations through chemical oxidation methods. It is interesting to find that the intensity of the blue fluorescence gradually increases, eventually becoming the dominant emission after prolonging the oxidation periods, with the quantum yield (QY) of the CDs being enhanced from ~0.61% to ~4.26%. Combining the microstructure characterizations, optical measurements, and ultrafiltration experiments, we hypothesize that the blue emission could be ascribed to the surface states induced by the C–O and C=O groups, while the green luminescence may originate from the deep energy levels associated with the O–C=O groups. The distinct emission states and energy distributions could result in the blue and the green luminescence exhibiting distinct excitation and emission behaviors. Our findings could provide new insights into the fluorescence mechanism of CDs.

Solid-state phosphorescent materials with stimulus-responsive properties have been widely developed for diverse applications. However, the task of generating excited states with long lifetimes in aqueous solution remains challenging due to the ultrafast deactivation of the triplet excitons and the difficulty in regulating stimulation sites in an aqueous environment. Additionally, most existing materials are primarily responsive to limited stimuli, such as light, oxygen, or temperature. Here, we present a microscale rigid framework engineering strategy that can be used to modulate the phosphorescence properties of carbon nanodots (CNDs), by brightening triplet excitons through ultrasound-enhanced rigidity in CNDs. Ultrasound-responsive phosphorescent CNDs with a lifetime of 1.25 seconds in an aqueous solution were achieved. The CNDs exhibit high sensitivity to surrounding ultrasound, showing a linear response to ultrasound exposure during the treatment period. The ultrasound-responsive phosphorescent CNDs demonstrate potential applications as sensing units in ultrasound radar detection and in vivo afterglow imaging.

To realize the safe transmission of images, a chaotic image encryption algorithm based on Latin square and random shift is proposed. The algorithm consists of four parts: key generation, pixel scrambling, pixel replacement, and bit scrambling. Firstly, the key is generated from the plain image to improve the sensitivity of the encryption method. Secondly, each pixel in each row of the image matrix is moved cyclically to the right, in turn, to change the position of the image pixel and realize pixel position scrambling. Then, a 256‐order Latin square matrix composed of a chaotic sequence is used as a lookup table, and the replacement coordinates are calculated based on the image pixel value and the chaotic sequence value, replacing the corresponding coordinate elements in the image matrix. Finally, decompose the bitplane of the image matrix and combine it into two‐bit matrices, scramble the two bit matrices, respectively, with the Latin square matrix, recombine the scrambled two‐bit matrices, and convert them into decimal to obtain the ciphertext image. In the proposed encryption method, all the Latin square matrices used are generated by chaotic sequences, further enhancing the complexity of the generated Latin square matrix and improving the algorithm’s security. Experimental results and security analysis show that the proposed algorithm has good security performance and is suitable for image encryption.

A high-Q magnetoelectric (ME) gyrator consisting of a trilayer laminate of nickel-iron-based constant elasticity alloy (Ni–Fe–Cr) and lead zirconate titanate with a coil wound around it has been developed and systematically characterized. Highly efficient magneto-mechanical-electric conversion can be achieved by means of the combination contributions of high quality factors from individuals, and much energy can be transferred through the gyration device. Under an electromechanical resonance frequency of 54.04 kHz, experimental results show that maximum efficiency reaches as high as 88.5% under an extremely low input density of 3.31 µW/cm³ with an optimum load resistance of 9.6 kΩ and a magnetic bias of 66 Oe. Such a highly efficient ME gyrator with a high Q factor can be beneficial or degrade the design goals that are likely to be achievable for practical applications in compact power transfer electronic devices.