Unraveling the Structure Transition and Peroxidase Mimic Activity of Copper Sites over Atomically Dispersed Copper-Doped Carbonized Polymer Dots

Highly Crystalline Copper Aluminum-Layered Double Hydroxides with Intrinsic Fenton-Like Catalytic Activity for Robust Oral Health Management

As the main challenge of dental healthcare, oral infectious diseases are highly associated with the colonization of pathogenic microbes. However, current antibacterial treatments in the field of stomatology still lack a facile, safe, and universal approach. Herein, we report the controllable synthesis of copper aluminum-layered double hydroxides (CuAl-LDHs) with high Fenton-like catalytic activity, which can be utilized in the treatment of oral infectious diseases with negligible side effects. Our strategy can efficiently avoid the unwanted doping of other divalent metal ions in the synthesis of Cu-contained LDHs and result in the formation of binary CuAl-LDHs with high crystallinity and purity. Evidenced by experimental and theoretical results, CuAl-LDHs exhibit excellent catalytic ability toward the ·OH generation in the presence of H2O2 and hold strong affinity toward bacteria, endowing them with great catalytic sterilization against both Gram-positive and Gram-negative bacteria. As expected, these CuAl-LDHs provide outstanding treatments for mucosal infection and periodontitis by promoting wound healing and remodeling of the periodontal microenvironment. Moreover, toxicity investigation demonstrates the overall safety. Accordingly, the current study not only provides a convenient and economic strategy for treating oral infectious diseases but also extends the development of novel LDH-based Fenton or Fenton-like antibacterial reagents for further biomedical applications.

Precise Modulation of the Coordination Environment of Single Cu Site Catalysts to Regulate the Peroxymonosulfate Activation Pathway for Water Remediation

Single atom site catalysts (SACs) with atomically dispersed active sites can be expected to be potential ideal catalysts for accurately modulating the persulfate activation pathway during the water remediation process because of their well-defined structure and the maximum metallic atom utilization. In this paper, a series of Cu SACs with different coordination environments were synthesized to elaborately regulate the peroxymonosulfate activation pathway in AOPs to clarify active species generation and transformation in water remediation. The degradation rate constants (kobs) of Cu-N2, Cu-N3, and Cu-N4 were 0.028, 0.021, and 0.015 min-1, respectively. Cu-N2 SACs exhibited a noticeable enhanced performance for bisphenol A (BPA) removal from water compared to that of the Cu-Nx SACs (x = 3, 4), accompanied by peroxymonosulfate (PMS) activation pathway variation. As shown by experimental and theoretical results, the PMS activation pathway was transformed from ROS to electron transfer with nitrogen coordination numbers decreasing from 4 to 2, which can be ascribed to the uneven charge distribution of Cu sites as well as upshifts in the d-band center, and thereby optimized electron transfer for PMS activation. Furthermore, the increasing nitrogen vacancies of single Cu site catalysts can also result in more unoccupied 3d orbitals of Cu atoms in SACs, thereby improving the intermediates' (PMS and BPA) adsorption-desorption process and BPA removal performance. These findings provided a beneficial approach for the coordination number regulation of SACs in water remediation.

Facilitation of Fenton-Like Reaction of Copper-Nitrogen-Doped Carbon-Based Nanocatalysts by Enhancing Hydroxyl Adsorption on Single-Atom Cu-NxC4- x Sites

Copper-nitrogen-doped carbon-based nanocatalysts (Cu-NCs), containing atomically dispersed Cu-NxC4- x sites, are efficient in boosting the Fenton-like reaction. However, the mechanisms of the Fenton-like reaction, including the pH effect on the products and the effect of the coordination environment on catalytic activity, remain controversial, restricting the development of Cu-NCs. Cu-NCs are experimentally synthesized with Cu-N4 sites and prove that the Fenton-like reaction generates mainly hydroxyl radicals (·OH) in the acidic but ·OH and superoxide radicals (·O2 -) in the neutral. The density functional theory (DFT) calculations reveal that the catalytic activity of Cu-NCs in the Fenton-like reaction is associated with the adsorption strength of ·OH at the Cu site. Further investigation of the effect of the coordination environment of Cu-NCs indicates that the Cu-N2C2 site, which can enhance the ·OH adsorption strength, is an ideal catalyst site for the Fenton-like reaction. These results open the way to facilitating the catalytic activity of Cu-NCs in the Fenton-like reaction.

Product Peroxidation Inhibition in Methane Photooxidation into Methanol

Methane photooxidation into methanol offers a practical approach for the generation of high-value chemicals and the efficient storage of solar energy. However, the propensity for C─H bonds in the desired products to cleave more easily than those in methane molecules results in a continuous dehydrogenation process, inevitably leading to methanol peroxidation. Consequently, inhibiting methanol peroxidation is perceived as one of the most formidable challenges in the field of direct conversion of methane to methanol. This review offers a thorough overview of the typical mechanisms involved radical mechanism and active site mechanism and the regulatory methods employed to inhibit product peroxidation in methane photooxidation. Additionally, several perspectives on the future research direction of this crucial field are proposed.

Machine-Learning-Assisted Nanozyme Design: Lessons from Materials and Engineered Enzymes

Nanozymes are nanomaterials that exhibit enzyme-like biomimicry. In combination with intrinsic characteristics of nanomaterials, nanozymes have broad applicability in materials science, chemical engineering, bioengineering, biochemistry, and disease theranostics. Recently, the heterogeneity of published results has highlighted the complexity and diversity of nanozymes in terms of consistency of catalytic capacity. Machine learning (ML) shows promising potential for discovering new materials, yet it remains challenging for the design of new nanozymes based on ML approaches. Alternatively, ML is employed to promote optimization of intelligent design and application of catalytic materials and engineered enzymes. Incorporation of the successful ML algorithms used in the intelligent design of catalytic materials and engineered enzymes can concomitantly facilitate the guided development of next-generation nanozymes with desirable properties. Here, recent progress in ML, its utilization in the design of catalytic materials and enzymes, and how emergent ML applications serve as promising strategies to circumvent challenges associated with time-expensive and laborious testing in nanozyme research and development are summarized. The potential applications of successful examples of ML-aided catalytic materials and engineered enzymes in nanozyme design are also highlighted, with special focus on the unified aims in enhancing design and recapitulation of substrate selectivity and catalytic activity.

Iron-Doped Polymer Dots with Enhanced Fluorescence and Dual Enzyme Activity for Versatile Bioassays

Nanozymes with multiple functionalities endow biochemical sensing with more sensitive and efficient analytical performance by widening the sensing modes. Meanwhile, the target-oriented design of multifunctional nanozymes for certain biosensing remains challenging. Herein, a constructive strategy of doping iron into polymer dots (PDs) to achieve nanozymes with excellent oxidase-mimicking and peroxidase-mimicking activity is proposed. Compared with the Fe-free PDs prepared under the same mild condition, the Fe-doped PDs (Fe-PDs) exhibit greatly boosted fluorescence at 500 nm. While applying 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate, the fluorescence of the Fe-PDs can be further quenched by oxTMB due to the inner filter effect (IFE). Inspired by this, a simple but efficient colorimetric and fluorometric dual-mode sensing platform is developed for monitoring the reducing substances ascorbic acid (AA), α-glucosidase (α-Glu), and its inhibitors (AGIs). We believe that such multifunctional enzyme-mimic materials will provoke the exploration of multimode sensing strategy with strong practicality to serve as a versatile tool in biochemical sensing.

A Versatile Strategy for the Generation of Air-stable Radical-functionalized Materials

The exploration of a facile approach to create structurally versatile substances carrying air-stable radicals is highly desired, but still a huge challenge in chemistry and materials science. Herein, a non-contact method to generate air-stable radicals by exposing pyridine/imidazole ring-bearing substances to volatile cyanuric chloride vapor, harnessed as a chemical fuel is reported. This remarkable feat is accomplished through a nucleophilic substitution reaction, wherein an intrinsic electron transfer event transpires spontaneously, originating from the chloride anion (Cl- ) to the cationic nitrogen (N+ ) atom, ultimately giving rise to pyridinium/imidazolium radicals. Impressively, the generated radicals exhibit noteworthy stability in the air over one month owing to the delocalization of the unpaired electron through the extended and highly fused π-conjugated pyridinium/imidazolium-triazine unit. Such an approach is universal to diverse substances, including organic molecules, metal-organic complexes, hydrogels, polymers, and organic cage materials. Capitalizing on this versatile technique, surface radical functionalization can be readily achieved across diverse substrates. Moreover, the generated radical species showcase a myriad of high-performance applications, including mimicking natural peroxidase to accelerate oxidation reactions and achieving high-efficiency near-infrared photothermal conversion and photothermal bacterial inhibition.

Lignocellulosic Biomass-Based Carbon Dots: Synthesis Processes, Properties, and Applications

Carbon dots (CDs), a new type of carbon-based fluorescent nanomaterial, have attracted widespread attention because of their numerous excellent properties. Lignocellulosic biomass is the most abundant renewable natural resource and possesses broad potential to manufacture different composite and smart materials. Numerous studies have explored the potential of using the components (such as cellulose, hemicellulose, and lignin) in lignocellulosic biomass to produce CDs. There are few papers systemically aiming in the review of the state-of-the-art works related to lignocellulosic biomass-derived CDs. In this review, the significant advances in synthesis processes, formation mechanisms, structural characteristics, optical properties, and applications of lignocellulosic biomass-based CDs such as cellulose-based CDs, hemicellulose-based CDs and lignin-based CDs in latest research are reviewed. In addition, future research directions on the improvement of the synthesis technology of CDs using lignocellulosic biomass as raw materials to enhance the properties of CDs are proposed. This review will serve as a road map for scientists engaged in research and exploring more applications of CDs in different science fields to achieve the highest material performance goals of CDs.

Plasmonic nanobipyramids with photo-enhanced catalytic activity under near-infrared II window for effective treatment of breast cancer

Nanozyme-based catalytic therapy is an effective method for cancer treatment, but insufficient catalytic activity presents a challenge in achieving optimal therapeutic outcomes. External light can provide an innovative approach to modulate nanozyme catalytic activity. Herein, we report on plasmonic gold nanobipyramid@cuprous oxide (Au NBP@Cu2O) nanozyme for the effective phototherapy of breast cancer. In the tumor microenvironment, Cu+-mediated Fenton-like reaction catalyzes the generation of toxic hydroxyl radicals (•OH) from endogenous hydrogen peroxide to induce apoptosis. Additionally, the Au NBP@Cu2O nanostructure improves the absorption performance of Au NBPs in the near-infrared II region through near-field enhancement of equipartite exciters and achieves a high photothermal conversion efficiency value of 58%. Remarkably, the Au NBP@Cu2O nanoheterostructure can capture hot electrons induced by equipartition excitations and promote electron-hole separation under 1064 nm laser irradiation, facilitating the production of more reactive oxygen species (ROS). The mechanism behind this enhanced catalytic activity was unraveled using femtosecond transient absorption spectroscopy. Both in vitro and in vivo investigations have demonstrated the efficacious tumor therapeutic potential of Au NBP@Cu2O nanozyme, particularly under 1064 nm laser irradiation. Furthermore, the proposed therapeutic approach has been proved to effectively block tumor metastasis, providing a promising strategy for the development of multifunctional nanotherapeutics to tackle metastatic tumors. STATEMENT OF SIGNIFICANCE: A highly effective plasmonic nanozyme has been developed to improve catalytic therapy for breast cancer. When exposed to 1064 nm laser irradiation, Au NBP@Cu2O nanozyme can promote the separation of hot electrons and holes thereby facilitating the production of reactive oxygen species. Hot electrons transfer behavior is unveiled by femtosecond transient absorption spectroscopy technique. This enhanced catalytic activity, along with the intrinsic photothermal effect, effectively kills tumor cells.

Functional Tailoring of Multi-Dimensional Pure MXene Nanostructures for Significantly Accelerated Electromagnetic Wave Absorption

Transition metal carbide (Ti3 C2 Tx MXene), with a large specific surface area and abundant surface functional groups, is a promising candidate in the family of electromagnetic wave (EMW) absorption. However, the high conductivity of MXene limits its EMW absorption ability, so it remains a challenge to obtain outstanding EMW attenuation ability in pure MXene. Herein, by integrating HF etching, KOH shearing, and high-temperature molten salt strategies, layered MXene (L-MXene), network-like MXene nanoribbons (N-MXene NRs), porous MXene monolayer (P-MXene ML), and porous MXene layer (P-MXene L) are rationally constructed with favorable microstructures and surface states for EMW absorption. HF, KOH, and KCl/LiCl are used to functionalize MXene to tune its microstructure and surface state (F- , OH- , and Cl- terminals), thereby improving the EMW absorption capacity of MXene-based nanostructures. Impressively, with the unique structure, proper electrical conductivity, large specific surface area, and abundant porous defects, MXene-based nanostructures achieve good impedance matching, dipole polarization, and conduction loss, thus inheriting excellent EMW absorption performance. Consequently, L-MXene, N-MXene NRs, P-MXene ML, and P-MXene L enable a reflection loss (RL ) value of -43.14, -63.01, -60.45, and -56.50 dB with a matching thickness of 0.95, 1.51, 3.83, and 4.65 mm, respectively.

Dual enzyme-mimicking carbon dots for enhanced antibacterial activity

Carbon dot (CD)-based nanozymes have great potential in antibacterial applications. In order to achieve enhanced broad-spectrum antibacterial capacity, we synthesized Co-doped drug-based CDs (Co-Lvx-CDs) using levofloxacin and vitamin B12 as precursors by mimicking the catalysis of antibacterial activity of natural enzymes. The Co-Lvx-CDs retained not only the effective functional groups of the traditional antibiotic levofloxacin but also achieved oxidase-like and peroxidase-like activities to generate reactive oxygen species (ROS) through Co doping. Additionally, the Co-Lvx-CDs had superb fluorescence properties and could be applied in information encryption. The CDs were validated to have a broad-spectrum bactericidal effect against Gram-positive and -negative bacteria, compensating for the limitations of levofloxacin while also having enhanced sterilization ability. Importantly, the proposed Co-Lvx-CDs provide a new idea for the design of multifunctional CD-based nanozymes with preconceived outcomes.

Nickel-Atom Doping as a Potential Means to Enhance the Photoluminescence Performance of Carbon Dots

Heteroatom doping, particularly with nonmetallic atoms such as N, P, and S, has proven to be an effective strategy for modulating the fluorescent properties of carbon dots (CDs). However, there are few reports on the regulation of the photoluminescence of CDs by transition-metal doping. In this work, nickel-doped CDs (Ni-CDs) were fabricated using the hydrothermal approach. Ni atoms were incorporated into the sp² domains of the CDs through Ni-N bonds, resulting in an increased degree of graphitization of the Ni-CDs. Additionally, Ni-atom doping served to shorten the electron transition and recombination lifetimes, and suppress the nonradiative recombination process, resulting in an absolute fluorescence quantum yield of 54.7% for the Ni-CDs. Meanwhile, the as-prepared Ni-CDs exhibited excellent biocompatibility and were utilized for fluorescent bioimaging of HeLa cells. Subsequently, the Ni-CDs were employed as fluorescent anticounterfeiting inks for the successful encryption of two-dimensional barcodes. Our work demonstrates a novel heteroatom doping strategy for the synthesis of highly fluorescence-emitting CDs.