Ultrathin BP QDs with a uniform size of ∼3.4 nm were prepared via small molecule-assisted liquid phase exfoliation and they exhibited superior broadband nonlinear saturable absorption promising for nonlinear optical applications. Laser photolysis measurement implied that the nonlinear response origin was related to the long-lived electron–hole pairs delocalized within the BP QDs.

Graphitic carbon nitrides have appeared as a new type of photocatalyst for water splitting, but their broader and more practical applications are oftentimes hindered by the insolubility or difficult dispersion of the material in solvents. We herein prepared novel two-dimensional (2D) carbon nitride-type polymers doped by iron under a mild one-pot method through preorganizing formamide and citric acid precursors into supramolecular structures, which eventually polycondensed into a homogeneous organocatalyst for highly efficient visible light-driven hydrogen evolution with a rate of ∼16.2 mmol g–1 h–1 and a quantum efficiency of 0.8%. Laser photolysis and electrochemical impedance spectroscopic measurements suggested that iron-doping enabled strong electron coupling between the metal and the carbon nitride and formed unique electronic structures favoring electron mobilization along the 2D nanomaterial plane, which might facilitate the electron transfer process in the photocatalytic system and lead to efficient H2 evolution. In combination with electrochemical measurements, the electron transfer dynamics during water reduction were depicted, and the earth-abundant Fe-based catalyst may open a sustainable strategy for conversion of sunlight into hydrogen energy and cope with current challenging energy issues worldwide.Keywords: carbon nitride; hydrogen evolution; laser photolysis; two-dimensional; visible light-driven photocatalysis

Ultrathin uniform BP nanosheets with lateral dimensions of up to several tens of micrometers were prepared via a small molecule–assisted liquid phase exfoliation method, which exhibited attractive electron accepting abilities from photosensitizers and was thus promising in diverse applications such as photocatalysis and photovoltaics.

MOFs (Metal–Organic Frameworks) have emerged as novel photocatalysts for water reduction but are frequently plagued by their instability when exposed to moist and strongly acidic or alkaline reaction environments. Herein we employed a volatile Fe-based MOF in alkaline solution as precursor to evolve into a magnetic carbonaceous photocatalyst in situ, which demonstrated highly efficient visible-light-driven hydrogen evolution (∼125 μmol H2 produced within 6 h using 5 mg of MOF precursor) with a quantum efficiency of 1.8% even in the absence of noble metal cocatalyst, indicative of a possible photocatalytic system containing only earth-abundant elements for long-term conversion of solar light into hydrogen energy. The catalyst exhibited an apparent stoichiometric formula of FeO3.3C0.2H1.0 and was determined to be essentially a carbon–metal oxides/oxyhydroxides composite. Laser photolysis and electrochemical measurements were performed to visualize the fundamental multistep electron transfer processes during water reduction, which opens a strategy for the rational design of MOF-derived catalysts to dramatically increase H2 evolution efficiency.

One novel cobalt-coordinated graphitic carbon nitride-type polymer (Co-g-CN) integrating the advantages of both molecular catalytic efficiency and nano semiconductor stability was fabricated, which served as homogeneous photocatalyst exhibiting superior hydrogen evolution efficiency (ca. ∼ 12.3 mmol g–1 h–1) under visible light irradiation in the absence of noble metal cocatalyst. Various techniques including laser photolysis and electron paramagnetic resonance were combined to disentangle the underlying photocatalytic mechanism, which suggested that, unlike nano semiconducting catalysis, the multivalent Co metal center of the polymer mediated the electron transfer process, directly got involved in the proton reduction by sequentially exchanging electrons in a way similar to those molecular coordinated catalysts. These findings provide useful insight into the photocatalytic mechanism of the metal center-mediated water splitting process, and the employment of an economical non-noble metal-coordinated polymer as highly efficient catalyst may open a new avenue for long-term conversion of sunlight into sustainable hydrogen energy.

Fluorescent carbon dots have attracted great attention, but their application in photocatalysis has not been well explored. Herein we report a facile layer-by-layer method to fabricate uniform C dot/CdS heterojunction films via an electrophoretic and sequential chemical bath deposition method. Because no ligands are used, this strategy facilitates the formation of intimate interfacial contact beneficial for charge separation and transfer, which can lead to a high photocurrent density of 2.6 mA cm−2. In addition, the electron donor–acceptor heterojunction can expedite charge separation and effectively suppress electron–hole pair recombination, eventually contributing to enhanced photoelectrochemical and/or photocatalytic efficiency of the system. As a proof-of-concept, the hybrid films manifested themselves as an efficient visible-light-driven photocatalyst when applied for the reduction of nitro-benzene derivatives in the aqueous phase under low power irradiation. Our findings thus establish a new frontier on the rational design and fabrication of well-controlled hybrid films with built-in heterojunctions for solar light conversion.

Graphene-based materials have shown promising nonlinear optical properties in the visible range. To extend their nonlinear optical response to the near infrared (NIR) region, we prepared a new nanohybrid consisting of uniform PbS quantum dots (QDs) attached on the reduced graphene oxide, named rGO–PbS, via a facile, low-cost, and phosphine-free method. The rGO–PbS nanohybrid exhibited superior optical limiting properties to either graphene oxide or PbS QDs upon both 532 nm and 1064 nm excitation in the nanosecond laser pulse regime, which is attributed to the synergetic effects stemming from charge transfer between the two components. Meanwhile, the thin films containing the rGO–PbS nanohybrid dispersed in polymethylmethacrylate (PMMA) also showed excellent optical limiting properties with high transparency, implying the potential applications of this hybrid material in broadband nonlinear optical devices.

Direct solvent exfoliation of bulk MoS2 with the assistance of poly(3-hexylthiophene) (P3HT) produces a novel two-dimensional organic/inorganic semiconductor hetero-junction. The obtained P3HT–MoS2 nanohybrid exhibits unexpected optical limiting properties in contrast to the saturated absorption behavior of both P3HT and MoS2, showing potential in future photoelectric applications.

The accurate description of the energy and/or charge transfer mechanism involving Localized Surface Plasmon Resonance (LSPR) is crucial for the research field of plasmonics. The investigation is however frequently hampered by the inaccurate definition of separation distance between the energy and/or charge donor–acceptor pair. Herein we designed and constructed core–shell plasmonic nanostructures to realize precise, long separation distance control between the gold core (energy acceptor) and fluorophores (energy donor). Both steady-state and time-resolved fluorescence measurements were employed to investigate radiative properties of the as-prepared nanosystem. The observed overall fluorescence quenching of the core–shell plasmonic nanocomposites with the decrease of shell thickness is attributed to a concurrent increase of nonradiative rates and decrease of radiative rates with the separation distance decrease. However, neither fluorescence resonance energy transfer (FRET) nor nanometal surface energy transfer (NSET) model is suitable for describing the fluorescence quenching efficiency as a function of separation distance reported in this article. Remarkably, a long-range fluorescence quenching distance of over 34 nm is observed, possibly arising from the coincidence of fluorophore emission wavelength with the plasmon resonance of the gold nanoparticles. This study not only gains insight for designing novel plasmonic devices, but also provides new thoughts for investigation on molecular ruler on a larger measurement scale, molecular beacons and new generation photovoltaics.Highlights► Au@SiO2@FITC core–shell plasmonic nanostructures are designed and constructed. ► Precise, long separation distance control between Au core and FITC is realized. ► A long-range fluorescence quenching distance of over 34 nm is observed.

Fluorescent carbon dots have attracted great attention, but their application in photocatalysis has not been well explored. Herein we report a facile layer-by-layer method to fabricate uniform C dot/CdS heterojunction films via an electrophoretic and sequential chemical bath deposition method. Because no ligands are used, this strategy facilitates the formation of intimate interfacial contact beneficial for charge separation and transfer, which can lead to a high photocurrent density of 2.6 mA cm−2. In addition, the electron donor–acceptor heterojunction can expedite charge separation and effectively suppress electron–hole pair recombination, eventually contributing to enhanced photoelectrochemical and/or photocatalytic efficiency of the system. As a proof-of-concept, the hybrid films manifested themselves as an efficient visible-light-driven photocatalyst when applied for the reduction of nitro-benzene derivatives in the aqueous phase under low power irradiation. Our findings thus establish a new frontier on the rational design and fabrication of well-controlled hybrid films with built-in heterojunctions for solar light conversion.

Ultrathin uniform BP nanosheets with lateral dimensions of up to several tens of micrometers were prepared via a small molecule–assisted liquid phase exfoliation method, which exhibited attractive electron accepting abilities from photosensitizers and was thus promising in diverse applications such as photocatalysis and photovoltaics.

Direct solvent exfoliation of bulk MoS2 with the assistance of poly(3-hexylthiophene) (P3HT) produces a novel two-dimensional organic/inorganic semiconductor hetero-junction. The obtained P3HT–MoS2 nanohybrid exhibits unexpected optical limiting properties in contrast to the saturated absorption behavior of both P3HT and MoS2, showing potential in future photoelectric applications.