P-doped Co3S4/NiS2 heterostructures embedded in N-doped carbon nanoboxes: Synergistical electronic structure regulation for overall water splitting.

Water splitting using transition metal sulfides as electrocatalysts has gained considerable attention in the field of renewable energy. However, their electrocatalytic activity is often hindered by unfavorable free energies of adsorbed hydrogen and oxygen-containing intermediates. Herein, phosphorus (P)-doped Co3S4/NiS2 heterostructures embedded in N-doped carbon nanoboxes were rationally synthesized via a pyrolysis-sulfidation-phosphorization strategy. The hollow structure of the carbon matrix and the nanoparticles contained within it not only result in a high specific surface area, but also protects them from corrosion and acts as a conductive pathway for efficient electron transfer. Density functional theory (DFT) calculations indicate that the introduction of P dopants improves the conductivity of NiS2 and Co3S4, promotes the charge transfer process, and creates new electrocatalytic sites. Additionally, the NiS2-Co3S4 heterojunctions can enhance the adsorption efficiency of hydrogen intermediates (H*) and lower the energy barrier of water splitting via a synergistic effect with P-doping. These characteristics collectively enable the titled catalyst to exhibit excellent electrocatalytic activity for water splitting in alkaline medium, requiring only small overpotentials of 150 and 257 mV to achieve a current density of 10 mA cm-2 for hydrogen and oxygen evolution reactions, respectively. This work sheds light on the design and optimization of efficient electrocatalysts for water splitting, with potential implications for renewable energy production.

MIL-88B(Fe)-reduced graphene oxide as an artificial enzyme for gold nanorod etching and its application to develop the prostate-specific antigen immunosensor.

An immunosensor based on gold nanorods (AuNRs) etchant activity of a metal-organic framework (MOF): MIL-88B(Fe)-reduced graphene oxide (rGMOF) was developed for the determination of prostate-specific antigen (PSA). Several techniques, including FTIR, UV-Vis spectrophotometry, XRD, and electron microscopy, were employed to characterize the MOFs containing iron-oxygen clusters on the surface of reduced graphene oxide. Enzyme mimetic activity of rGMOF before and after bioconjugation with antibodies was calculated as 8.4 and 2.5 U mg-1, respectively. The primary anti-PSA was conjugated to a magnetic bead and used as PSA-specific capturing. Then, the secondary anti-PSA was grafted to the rGMOF. In the presence of antigen, an immuno-sandwich was formed between the conjugations mentioned above. Afterward, AuNRs were etched by rGMOF, and the related spectrum was recorded in the wavelength range 350 to 900 nm. By progressing the etching procedure, the longitudinal LSPR peak of AuNRs was gradually blue-shifted with a linear correlation with the PSA concentration from 0.1 pg mL-1 to 100 ng mL-1. The detection limit was 0.09 pg mL-1. The proposed immunosensor was successfully employed to determine PSA levels in real samples. Since the obtained results showed an excellent correlation with those acquired by the chemiluminescence gold standard method, it has the potential for PSA determination in clinical assays.

Shape-Controlled Photochemical Synthesis of Noble Metal Nanocrystals Based on Reduced Graphene Oxide.

The fabrication of supported noble metal nanocrystals (NCs) with well-controlled morphologies have been attracted considerable interests due to their merits in a wide variety of applications. Photodeposition is a facile and effective method to load metals over semiconductors in a simple slurry reactor under irradiation. By optimizing the photodeposition process, the size, chemical states, and the geometrical distribution of metal NCs have been successfully tuned. However, metal NCs with well-controlled shapes through the photodeposition process have not been reported until now. Here, we report our important advances in the controlled photodeposition process to load regular noble metal NCs. Reduced graphene oxide (rGO) is introduced as a reservoir for the fast transfer of photoelectrons to avoid the fast accumulation of photogenerated electrons on the noble metals which makes the growth process uncontrollable. Meanwhile, rGO also provides stable surface for the controlled nucleation and oriented growth. Noble metal NCs with regular morphologies are then evenly deposited on rGO. This strategy has been demonstrated feasible for different precious metals (Pd, Au, and Pt) and semiconductors (TiO2, ZnO, ZrO2, CeO2, and g-C3N4). In the prototype application of electrochemical hydrogen evolution reaction, regular Pd NCs with enclosed {111} facets showed much better performance compared with that of irregular Pd NCs.

Analyte-restrained silver coating of gold nanostructures: an efficient strategy to advance multicolorimetric probes.

Visual detection based on gold nanorods (AuNRs) has gained tremendous attention in sensing applications owing to the potential for simple, inexpensive, instrument-free, and on-site detection. The proper selection of the mechanism involved in the interaction between the analyte and the nanostructure plays a significant role in designing a selective and multicolorimetric probe for visual purposes. A winning mechanism to develop multicolorimetric probes is the silver metalization of AuNRs. Herein, an unprecedented idea is presented to expand the variety of multicolorimetric sensors relying on the mechanism of silver deposition. We introduce the anti-silver deposition mechanism in which the analyte directly or indirectly restrains the silver coating of AuNRs. To ascertain the anti-silver deposition mechanism, we have exploited the proposed idea for the direct detection of nitrate. The presence of nitrate (as restrainer agent), which was firstly treated with ascorbic acid (as reducing agent), induced a decrease in the spectral blueshift of AuNRs along with diverse sharp color transitions from reddish-orange (blank) to maroon, wine, berry/purple, dark blue, teal, green, seafoam, and mint. The difference in the spectrum area of the probe in the absent (So) and presence (S) of nitrate were linearly proportional to nitrate concentration in the range of 0.5-5.5 mmol l-1and the limit of detection was calculated to be 465µmol l-1. Furthermore, the practicability of the multicolor probe was assessed by the determination of nitrate in complex environmental samples.