A FRET-based carbon nanodot (CDot) drug delivery platform has been developed. These CDots offer excellent biocompatibility, stable fluorescence, and efficient FRET between CDots and the attached fluorescent drug molecules, such as doxorubicin, enabling enhanced drug delivery, convenient cell imaging, and real-time monitoring of drug release. Moreover, the FRET-based two-photon imaging and drug tracking in deep tissues are also demonstrated.

The fast development of nanoscience and nanotechnology has significantly advanced the fabrication of nanocatalysts and the in-depth study of the structural-activity characteristics of materials at the atomic level. Vacancies, as typical atomic defects or imperfections that widely exist in solid materials, are demonstrated to effectively modulate the physicochemical, electronic, and catalytic properties of nanomaterials, which is a key concept and hot research topic in nanochemistry and nanocatalysis. The recent experimental and theoretical progresses achieved in the preparation and application of vacancy-rich nanocatalysts for electrochemical water splitting are explored. Engineering of vacancies has shown to open up a new avenue beyond the traditional morphology, size, and composition modifications for the development of nonprecious electrocatalysts toward efficient energy conversion. First, an introduction followed by discussions of different types of vacancies, the approaches to create vacancies, and the advanced techniques widely used to characterize these vacancies are presented. Importantly, the correlations between the vacancies and activities of the vacancy-rich electrocatalysts via tuning the electronic states, active sites, and kinetic energy barriers are reviewed. Finally, perspectives on the existing challenges along with some opportunities for the further development of vacancy-rich noble metal-free electrocatalysts with high performance are discussed.

Conductive 2D metal–organic frameworks (MOFs) have merits beyond traditional MOFs for electrochemical applications, but reports on using MOFs as electrodes for electrochemical microsupercapacitors (MSCs) are practically non‐existent. In this work, a Ni‐catecholate‐based MOF (Ni‐CAT MOF) having good conductivity and exhibiting redox chemistry in the positive and negative voltage windows is developed. A novel process is developed to selectively grow the conductive Ni‐CAT MOF on 3D laser scribed graphene (LSG). The LSG with its superior wettability serves as a functional matrix‐current collector for the hybridization of conductive Ni‐CAT MOF nanocrystals. Impressively, MSCs fabricated using the hybrid LSG/Ni‐CAT MOF show significant improvement compared with MOF‐free LSG electrodes. Specifically, the LSG/Ni‐CAT MOF electrodes can deliver MSCs with a wide operating voltage (1.4 V), high areal capacitance (15.2 mF cm−2), energy density (4.1 µWh cm−2), power density (7 mW cm−2), good rate performance, and decent cycling stability. This work opens up an avenue for developing electrochemical microsupercapacitors using conductive MOF electrodes.

Semiconducting silicon nanowires (SiNWs) represent one of the most interesting research directions in nanoscience and nanotechnology, with capabilities of realizing structural and functional complexity through rational design and synthesis. The exquisite control of chemical composition, structure, morphology, doping, and assembly of SiNWs, in both individual and array format, as well as incorporation with other materials, offers a nanoscale building block with unique electronic, optoelectronic, and catalytic properties, thus allowing for a variety of exciting opportunities in the fields of life sciences and renewable energy. This review provides a brief summary of SiNW research in the past decade, from the SiNW synthesis by both the top-down approaches and the bottom-up approaches, to several important biological and energy applications including biomolecule sensing, interfacing with cells and tissues, lithium-ion batteries, solar cells, and photoelectrochemical conversion.

We have developed sensitive detection of glutathione using the IrO2-hemin-TiO2 nanowire arrays. Single-crystalline TiO2 nanowires are synthesized by a hydrothermal reaction, followed by surface functionalization of ~3 nm thick hemin and ~1-2 nm diameter IrO2 nanoparticles. The IrO2-hemin-TiO2 nanowire arrays offer much enhanced photocurrent with ∼100% increase compared to the pristine TiO2 nanowires and allow for label-free, real-time, sensitive photoelectrochemical detection of glutathione. The sensitivity achieved is ~10 nM in buffer, comparable to or better than most of the existing glutathione detection methods. Furthermore, cell extracts containing glutathione are robustly detected, with ~8000 cells/mL for HeLa cells and ~5000 cells/mL for human embryonic kidney 293T cells. This nanowire PEC sensor assay exhibits excellent selectivity and stability, suggesting a potential detection platform for analyzing the glutathione level in biosamples.

Furthermore, the electronic and catalytic property modulation are mostly achieved by extrinsic doping of heteroatoms. [20][21][22] However, the capability of solely utilizing the intrinsic composition of biomass for catalysts has not been demonstrated.On the other hand, mesoporous materials represent another large category of materials for catalysis [21][22][23] and energy applications, [ 15 ] due to their high surface areas, ordered mesostructures, and tunable pore sizes. A variety of mesoporous materials have been synthesized and loaded with different metal, [ 22 ] nonmetal, [ 23 ] or even biomaterial components [ 17 ] toward high catalytic activity. Nonetheless, the development of mesoporous materialbased bifunctional OER and ORR electrocatalysts, especially from ecofriendly biomass, has seldom been reported. [ 18 ] Eggs, as one of natural living organisms, contain abundant proteins, cholesterols, and lecithins that can be utilized as a unique precursor for carbon frameworks. More importantly, the resourceful metal and nonmetal elements (e.g., N, P, O, and Fe) in egg organisms may enable intrinsic, homogeneous doping of carbon framework to achieve catalytic activity, waiving the need to adding extrinsic doping sources. Herein, we report an ecofriendly and facile way to synthesize homogeneously N, P, and Fe codoped mesoporous carbon microspheres (egg-CMS) from eggs, using a high-throughput spray-drying technique without the extrinsic doping sources. Tetraethyl orthosilicate (TEOS) was fi rst mixed and spray dried with eggs, and subsequently etched to obtain mesostructures. Remarkably, the as-obtained codoped egg-CMS possesses a large specifi c surface area with high pore volume and shows excellent electrocatalytic performances, including low onset potentials, Tafel slopes, large current densities, and superior stabilities for both ORR and OER. Furthermore, rechargeable Zn-air batteries fabricated with this bifunctional egg-CMS electrocatalyst show an initial cell voltage of 1.28 V, which can be well maintained at ≈1 V after 30 charge-discharge cycles. Results and DiscussionThe main components in eggs include amino acids, cholesterols, and lipids, [ 24 ] whose structural formula is displayed A bifunctional evolution reaction (OER) and oxygen reduction reaction (ORR) electrocatalysts are developed, based on codoped mesoporous carbon microspheres from ecofriendly biomass of eggs without the introduction of extrinsic dopants, via a facile and high-throughput spray-drying process. The obtained egg-derived mesoporous carbon microspheres (egg-CMS) present large specifi c surface area and high pore volume, as well as abundant dopant types including nitrogen, phosphorous, and iron that are originated from the innate protein and small organic molecule contents. When fabricated as OER or ORR catalysts, these egg-CMS exhibit low onset potentials, high current densities, small Tafel slopes, and excellent stabilities. As a proof-of-concept, a rechargeable Zn-air battery is demonstrated using the high-active egg-CMS as a bifu...

Supercapacitors (SCs) are important energy storage devices that are increasingly playing an important role in various applications. [1-6] Though SCs can offer high power density, they have lower energy density in comparison to batteries. [1] The high power density makes them suitable for applications such as uninterruptible power supply (UPS), portable tools, rubber-tired gantry crane, and emergency doors on airplanes. [1,2] However, in order to deploy SCs in automotive and grid storage applications, their energy density needs to be significantly uplifted. [7,8] To enhance the energy density of SCs, which is calculated using this equation (E = 0.5 C V 2), either the specific capacitance (C) or cell voltage (V) needs to be improved. [2,9] The C values of the SC device can be improved by tuning the intrinsic properties of the electrode material. [10] For example, employing pseudocapacitive electrode materials is an effective strategy to enhance the specific capacitance (C) of the SC. [8] Pseudocapacitive materials, in general, show high capacitance values in comparison to electrical double layer capacitor (EDLC) based materials due to their fast reversible electron transfer redox reactions. [8] On the other hand, the cell voltage (V), the second major factor which influences the energy density, is greatly controlled by device engineering. [8,11] Organic electrolyte based SC devices usually offer a higher voltage window in comparison to aqueous devices. [8,11] However, the former suffers from some disadvantages such as low ionic mobility, high cost, toxicity, and not being environmentally benign. [12] On the other hand, aqueous electrolyte based SCs go without the aforementioned disadvantages, but the conventional symmetric SCs with aqueous electrolyte are hampered by low voltage windows. [12] In case of aqueous electrolyte SCs, the voltage window can be significantly improved by constructing asymmetric supercapacitors (ASCs). [12,13] In ASCs, two different electrode materials are used separately for the negative and positive electrodes. [12,13] The complementary potential windows of the individual electrodes enable the ASC device to cross the thermodynamic break New covalent organic frameworks (COFs), encompassing redox-functionalized moieties and an aza-fused π-conjugated system, are designed, synthesized, and deployed as negative electrodes in asymmetric supercapacitors (ASC), for the first time. The Hex-Aza-COFs are synthesized based on the solvothermal condensation reaction of cyclohexanehexone and redox-functionalized aromatic tetramines with benzoquinone (Hex-Aza-COF-2) or phenazine (Hex-Aza-COF-3). The redox-functionalized Hex-Aza-COFs show a specific capacitance of 585 F g −1 for Hex-Aza-COF-2 and 663 F g −1 for Hex-Aza-COF-3 in a three-electrode configuration. These values are the highest among reported COF materials and are comparable with state-of-the-art pseudocapacitive electrodes. The Hex-Aza-COFs exhibit a wide voltage window (0 to −1.0 V), which allow the construction of a two-electrode ASC device b...

Fabrication of ultrathin 2D nonlayered nanomaterials remains challenging, yet significant due to the new promises in electrochemical functionalities. However, current strategies are largely restricted to intrinsically layered materials. Herein, a combinatorial self‐regulating acid etching and topotactic transformation strategy is developed to unprecedentedly prepare vertically stacked ultrathin 2D nonlayered nickel selenide nanosheets. Due to the inhibited hydrolyzation under acidic conditions, the self‐regulating acid etching results in ultrathin layered nickel hydroxides (two layers). The ultrathin structure allows limited epitaxial extension during selenization, i.e., the nondestructive topotactic transformation, enabling facile artificial engineering of hydroxide foundation frameworks into ultrathin nonlayered selenides. Consequently, the exquisite nonlayered nickel selenide affords high turnover frequencies, electrochemical surface areas, exchange current densities, and low Tafel slopes, as well as facilitating charge transfer toward both oxygen and hydrogen evolution reactions. Thus, the kinetically favorable bifunctional electrocatalyst delivers advanced and robust overall water splitting activities in alkaline intermediates. The integrated methodology may open up a new pathway for designing other highly active 2D nonlayered electrocatalysts.