Cathepsin B Responsive Peptide–Purpurin Conjugates Assembly-Initiated in Situ Self-Aggregation for Cancer Sonotheranostics

Sonodynamic therapy (SDT) was hampered by the sonosensitizers with low bioavailability, tumor accumulation, and therapeutic efficiency. In situ responsive sonosensitizer self-assembly strategy may provide a promising route for cancer sonotheranositics. Herein, an intelligent sonotheranostic peptide–purpurin conjugate (P18-P) is developed that can self-assemble into supramolecular structures via self-aggregation triggered by rich enzyme cathepsin B (CTSB). After intravenous injection, the versatile probe could achieve deep tissue penetration because of the penetration sequence of P18-P. More importantly, CTSB-triggered self-assembly strongly prolonged retention time, amplified photoacoustic imaging signal for sensitive CTSB detection, and boosted reactive oxygen species for advanced SDT, evoking specific CTSB responsive sonotheranostics. This peptide–purpurin conjugate may serve as an efficient sonotheranostic platform for the early diagnosis of CTSB activity and effective cancer therapy

Effect of Trace Water on the Growth of Indium Phosphide Quantum Dots

We report that trace amounts of water impurities in indium myristate precursors can negatively impact indium phosphide nanoparticle growth by limiting its size tunability. Without water, the growth can be effectively tuned by growth temperature and time with the first absorption peak reaching 620 nm; with water, the growth presents a “focused” behavior with the first absorption peak remaining around 550 nm. The results imply that water impurities, either from indium acetate derived indium precursors or generated in situ during nanoparticle growth, may be the cause of the currently observed inhibited growth behavior of indium phosphide quantum dots. We use multistage microfluidic reactors to show that this inhibiting effect occurs at the late stage of particle growth, following precursor depletion. We extend our study by showing that trace amounts of free hydroxide can also inhibit nanoparticle growth. We attribute the inhibited growth behavior to the hydroxylation effect of water or free hydroxide

Effect of Trace Water on the Growth of Indium Phosphide Quantum Dots

We report that trace amounts of water impurities in indium myristate precursors can negatively impact indium phosphide nanoparticle growth by limiting its size tunability. Without water, the growth can be effectively tuned by growth temperature and time with the first absorption peak reaching 620 nm; with water, the growth presents a “focused” behavior with the first absorption peak remaining around 550 nm. The results imply that water impurities, either from indium acetate derived indium precursors or generated in situ during nanoparticle growth, may be the cause of the currently observed inhibited growth behavior of indium phosphide quantum dots. We use multistage microfluidic reactors to show that this inhibiting effect occurs at the late stage of particle growth, following precursor depletion. We extend our study by showing that trace amounts of free hydroxide can also inhibit nanoparticle growth. We attribute the inhibited growth behavior to the hydroxylation effect of water or free hydroxide

Highly Efficient Bi₄Ti₃O₁₂/g‑C₃N₄/BiOBr Dual Z-Scheme Heterojunction Photocatalysts with Enhanced Visible Light-Responsive Activity for the Degradation of Antibiotics

A novel Bi4Ti3O12/g-C3N4/BiOBr­(BTO/CN/BOB) composite was synthesized by a solvothermal–mechanical mixed thermal method. The composition, structure, and micromorphology of the samples were analyzed. The BTO/CN/BOB composite photocatalyst shows better photocatalytic performance for tetracycline hydrochloride (TC) degradation compared to Bi4Ti3O12 and binary composite photocatalysts. The highest degradation rate of TC can reach 89.84% using the BTO/CN/BOB photocatalyst under the optimal conditions, and BTO/CN/BOB still exhibits good photocatalytic properties after recycling. Moreover, it also shows good photodegradation activity for different kinds of antibiotics, implying its wide application prospect. The photocatalytic performance and reuse stability of BTO/CN/BOB were significantly improved, which may be because of the enhanced spectral absorption range and efficient electron transfer capability by the synergistic effect and interaction among Bi4Ti3O12, BiOBr, and g-C3N4. Finally, the possible degradation pathway and electron transfer mechanism of the dual Z-scheme heterojunction are proposed

Metalloporphyrins as Catalytic Models for Studying Hydrogen and Oxygen Evolution and Oxygen Reduction Reactions

ConspectusThe hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) are involved in biological and artificial energy conversions. H–H and O–O bond formation/cleavage are essential steps in these reactions. In nature, intermediates involved in the H–H and O–O bond formation/cleavage are highly reactive and short-lived, making their identification and investigation difficult. In artificial catalysis, the realization of these reactions at considerable rates and close to their thermodynamic reaction equilibria remains a challenge. Therefore, the elucidation of the reaction mechanisms and structure–function relationships is of fundamental significance to understand these reactions and to develop catalysts.This Account describes our recent investigations on catalytic HER, OER, and ORR with metalloporphyrins and derivatives. Metalloporphyrins are used in nature for light harvesting, energy conversion, electron transfer, O2 activation, and peroxide degradation. Synthetic metal porphyrin complexes are shown to be active for these reactions. We focused on exploring metalloporphyrins to study reaction mechanisms and structure–function relationships because they have stable and tunable structures and characteristic spectroscopic properties.For HER, we identified three H–H bond formation mechanisms and established the correlation between these processes and metal hydride electronic structures. Importantly, we provided direct experimental evidence for the bimetallic homolytic H–H bond formation mechanism by using sterically bulky porphyrins. Homolytic HER has been long proposed but rarely verified because the coupling of active hydride intermediates occurs spontaneously and quickly, making their detection challenging. By blocking the bimolecular mechanism through steric effects, we stabilized and characterized the NiIII–H intermediate and verified homolytic HER by comparing the reaction behaviors of Ni porphyrins with and without steric effects. We therefore provided an unprecedented example to control homolytic versus heterolytic HER mechanisms through tuning steric effects of molecular catalysts.For the OER, the water nucleophilic attack (WNA) on high-valent terminal Mn-oxo has been proposed for the O–O bond formation in natural and artificial water oxidation. By using Mn tris­(pentafluorophenyl)­corrole, we identified MnV(O) and MnIV-peroxo intermediates in chemical and electrochemical OER and provided direct experimental evidence for the Mn-based WNA mechanism. Moreover, we demonstrated several catalyst design strategies to enhance the WNA rate, including the pioneering use of protective axial ligands. By studying Cu porphyrins, we proposed a bimolecular coupling mechanism between two metal-hydroxide radicals to form O–O bonds. Note that late-transition metals do not likely form terminal metal-oxo/oxyl.For the ORR, we presented several strategies to improve activity and selectivity, including providing rapid electron transfer, using electron-donating axial ligands, introducing hydrogen-bonding interactions, constructing dinuclear cooperation, and employing porphyrin-support domino catalysis. Importantly, we used Co porphyrin atropisomers to realize both two-electron and four-electron ORR, representing an unparalleled example to control ORR selectivity by tuning only steric effects without modifying molecular and/or electronic structures.Lastly, we developed several strategies to graft metalloporphyrins on various electrode materials through different covalent bonds. The molecular-engineered materials exhibit boosted electrocatalytic performance, highlighting promising applications of molecular electrocatalysis. Taken together, this Account demonstrates the benefits of exploring metalloporphyrins for the HER, OER, and ORR. The knowledge learned herein is valuable for the development of porphyrin-based catalysts and also other molecular and material catalysts for small molecule activation reactions

Characterization of Indium Phosphide Quantum Dot Growth Intermediates Using MALDI-TOF Mass Spectrometry

Clusters have been identified as important growth intermediates during group III–V quantum dot (QD) formation. Here we report a one-solvent protocol that integrates synthesis, purification, and mass characterization of indium phosphide (InP) QD growth mixtures. The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) successfully tracks the evolution of clusters and the formation of QDs throughout the synthesis. Similar clusters are observed during the formation of large particles, suggesting that these clusters serve as a reservoir for QD formation. Combining MALDI and NMR techniques further enables us to extract extinction coefficients and construct sizing curves for cluster-free InP QDs. The use of MALDI MS opens new opportunities for characterization and mechanistic studies of small-sized air-sensitive clusters or QDs

Oscillatory Microprocessor for Growth and in Situ Characterization of Semiconductor Nanocrystals

An automated two-phase small scale platform based on controlled oscillatory motion of a droplet within a 12 cm long tubular Teflon reactor is designed and developed for high-throughput in situ studies of a solution-phase preparation of semiconductor nanocrystals. The unique oscillatory motion of the droplet within the heated region of the reactor enables temporal single-point spectral characterization of the same nanocrystals with a time resolution of 3 s over the course of the synthesis time without sampling while removing the residence time limitation associated with continuous flow-based strategies. The developed oscillatory microprocessor allows for direct comparison of the high temperature and room temperature spectral characteristics of nanocrystals. Utilizing this automated experimental strategy, we study the effect of temperature on the nucleation and growth of II–VI and III–V semiconductor nanocrystals. The automated droplet preparation and injection of the precursors combined with the oscillatory flow technique allows 7500 spectral data within a parameter space of 10 min reaction time at ten different temperatures and five different precursor ratios to be obtained automatically using only 250 μL of each precursor solution. The oscillatory microprocessor platform provides real-time in situ spectral information at the synthesis temperature, vital for fundamental studies of different mechanisms involved during the nucleation and growth stages of different types of nanomaterials

Electrochemical Reduction of Nitrate to Ammonia on an In Situ-Derived Co₃O₄@CoBi Core–Shell Nanoarray

Room-temperature nitrate electroreduction can simultaneously synthesize ammonia and eliminate N-contaminants, which has attracted a lot of interest but still needs efficient electrocatalysts. Here, we report the in situ derivation of an amorphous cobalt borate (CoBi) film on a Co3O4 nanoarray on carbon cloth (Co3O4@CoBi/CC) for efficient ammonia generation via selective electroreduction of nitrate at room temperature and atmospheric pressure. In a neutral phosphate-buffered electrolyte containing 0.1 M NaNO3, such a catalyst exhibits a maximum ammonia yield rate of 6.80 mg/h/cm2 (−1.0 V vs RHE) and a high Faradaic efficiency of up to 97% (−0.7 V vs RHE). Besides, its catalytic activity remains stable in recycling tests and long-term electrolysis. An aqueous Zn nitrate battery with Co3O4@CoBi/CC as the cathode shows a high battery performance as well

Visible Light Response Photocatalytic Performance of Z‑Scheme Ag₃PO₄/GO/UiO–66–NH₂ Photocatalysts for the Levofloxacin Hydrochloride

A Ag3PO4/GO/UiO–66–NH2(AGU) composite photocatalyst was prepared by an ultrasonic-assisted in situ precipitation method. The optical property, structure, composition, and morphology of photocatalysts were investigated using UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, electrochemical impedance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive spectrometry, transmission electron microscopy, Fourier transform infrared spectroscopy, and charge flow tracking by photodeposition of Pt and PbO2 nanoparticles. In comparison with Ag3PO4 and Ag3PO4/UiO–66–NH2(AU), the AGU composite photocatalyst showed heightened photocatalytic performance for the degradation of levofloxacin hydrochloride (LVF). The AGU photocatalyst (dosage: 0.8 g/L) with 1% mass content of graphene oxide (GO), the mass ratio of Ag3PO4 and UiO–66–NH2(U66N) reached 2:1, showed the highest photodegradation rate of 94.97% for 25 mg/L LVF after 60 min of visible light irradiation at pH = 6. The formation of a heterojunction and the addition of GO synergistically promote faster separation of electron–hole pairs, retain more active substances, and enhance the performance of the photocatalyst. Furthermore, the mechanism of the Z-scheme of the AGU composite photocatalytic is proposed

Oscillatory Microprocessor for Growth and in Situ Characterization of Semiconductor Nanocrystals

An automated two-phase small scale platform based on controlled oscillatory motion of a droplet within a 12 cm long tubular Teflon reactor is designed and developed for high-throughput in situ studies of a solution-phase preparation of semiconductor nanocrystals. The unique oscillatory motion of the droplet within the heated region of the reactor enables temporal single-point spectral characterization of the same nanocrystals with a time resolution of 3 s over the course of the synthesis time without sampling while removing the residence time limitation associated with continuous flow-based strategies. The developed oscillatory microprocessor allows for direct comparison of the high temperature and room temperature spectral characteristics of nanocrystals. Utilizing this automated experimental strategy, we study the effect of temperature on the nucleation and growth of II–VI and III–V semiconductor nanocrystals. The automated droplet preparation and injection of the precursors combined with the oscillatory flow technique allows 7500 spectral data within a parameter space of 10 min reaction time at ten different temperatures and five different precursor ratios to be obtained automatically using only 250 μL of each precursor solution. The oscillatory microprocessor platform provides real-time in situ spectral information at the synthesis temperature, vital for fundamental studies of different mechanisms involved during the nucleation and growth stages of different types of nanomaterials