Colloidal assembly of magnetic nanoparticles and polyelectrolytes by arrested electrostatic interaction

Carbon Dot Emission Enhancement in Covalent Complexes with Plasmonic Metal Nanoparticles

Carbon dots can be used for the fabrication of colloidal multi-purpose complexes for sensing and bio-visualization due to their easy and scalable synthesis, control of their spectral responses over a wide spectral range, and possibility of surface functionalization to meet the application task. Here, we developed a chemical protocol of colloidal complex formation via covalent bonding between carbon dots and plasmonic metal nanoparticles in order to influence and improve their fluorescence. We demonstrate how interactions between carbon dots and metal nanoparticles in the formed complexes, and thus their optical responses, depend on the type of bonds between particles, the architecture of the complexes, and the degree of overlapping of absorption and emission of carbon dots with the plasmon resonance of metals. For the most optimized architecture, emission enhancement reaching up to 5.4- and 4.9-fold for complexes with silver and gold nanoparticles has been achieved, respectively. Our study expands the toolkit of functional materials based on carbon dots for applications in photonics and biomedicine to photonics.

Unclonable Photonic Crystal Hydrogels with Controllable Encoding Capacity for Anticounterfeiting

Inspired by the formation of random sparkling microcrystallines in naturally precious opals, we develop a new strategy to produce a class of unclonable photonic crystal hydrogels (UPCHs) induced by the electrostatic interaction effect, which further achieve unclonable encoding/decoding and random high-encrypted patterns along with an ultrahigh and controllable encoding capacity up to ca. 2 × 10¹⁶⁶⁰⁵⁵. Owing to the randomness of colloidal crystals in the self-assembly process, UPCHs with randomly distributed sparkling spots are endowed with unpredictable/unrepeatable characteristics. This, coupled with the water response of UPCHs with angle dependence and robustness, can upgrade the encryption level and address some limitations of easy fading, limited durability, and high cost in practical uses of existing unclonable materials. Interestingly, UPCHs can be readily patterned to exhibit reliable and rapid authentication by utilizing artificial intelligence (AI) deep learning, which can find broad applications in developing unbreakable and portable information storage/steganography systems not limited to anticounterfeiting.

Condensed Clustered Iron Oxides for Ultrahigh Photothermal Conversion and In Vivo Multimodal Imaging

Magnetic iron oxide nanocrystals (MIONs) are established as potent theranostic nanoplatforms due to their biocompatibility and the multifunctionality of their spin-active atomic framework. Recent insights have also unveiled their attractive near-infrared photothermal properties, which are, however, limited by their low near-infrared absorbance, resulting in noncompetitive photothermal conversion efficiencies (PCEs). Herein, we report on the dramatically improved photothermal conversion of condensed clustered MIONs, reaching an ultrahigh PCE of 71% at 808 nm, surpassing the so-far MION-based photothermal agents and even benchmark near-infrared photothermal nanomaterials. Moreover, their surface passivation is achieved through a simple self-assembly process, securing high colloidal stability and structural integrity in complex biological media. The bifunctional polymeric canopy simultaneously provided binding sites for anchoring additional cargo, such as a strong near-infrared-absorbing and fluorescent dye, enabling in vivo optical and photoacoustic imaging in deep tissues, while the iron oxide core ensures detection by magnetic resonance imaging. In vitro studies also highlighted a synergy-amplified photothermal effect that significantly reduces the viability of A549 cancer cells upon 808 nm laser irradiation. Integration of such-previously elusive-photophysical properties with simple and cost-effective nanoengineering through self-assembly represents a significant step toward sophisticated nanotheranostics, with great potential in the field of nanomedicine.

Self-organization and energy of superparamagnetic nets

Superparamagnetic filaments assemble, building one-layered aggregates due to the screening effect inherited from the dipole interaction potential in a colloidal blend. The magnetic energy of rectangular and irregular ribbons is computed to obtain their mean length at thermodynamic equilibrium, in good agreement with experimental measurements.