Photolysis Dynamics Laser Chemistry Lab

Abstract The nanohybrids of noble metal (M=Ag, Au, Pd, Pt, and Ru) nanoparticle-decorated rhenium disulfide nanosheets (ReS2 NSs) were demonstrated as excellent catalysts towards the reduction of aromatic nitro compounds. The M/ReS2 nanohybrids were synthesized by facile hydrothermal method and characterization results proved that each metal nanoparticle was anchored on the ReS2 NSs. These nanohybrids exhibited superior catalytic performance towards the reduction of aromatic nitro compounds including 4-nitrophenol, 2-nitroaniline, and nitrobenzene. Interestingly, the Ru/ReS2 and Pd/ReS2 showed enhanced catalytic reduction compared to Ag/ReS2, Au/ReS2, and Pt/ReS2 and also showed significant catalytic stability due to metal nanoparticles anchored strongly on the surface of ReS2 NSs. Moreover, these M/ReS2 nanohybrids turned out to have much better catalytic performance compared to noble metal nanoparticle-based catalysts. A plausible reduction mechanism was proposed for each nitro compound. It was verified that the metal-nanoparticle-mediated hydrogen transfer was involved in the reduction of nitro compounds to amines. This report demonstrates the catalytic activities for metal nanoparticle-decorated ReS2 nanohybrids, which can serve as a paradigm to open up a future trend in the design of transition metal dichalcogenides nanohybrids as superior catalysts.

Palladium nanoparticles encapsulated in the carbon dots (Pd/C-dots) are demonstrated to play a role of multifunctional nanohybrid in the synergetic applications of sensor and catalysis. The photochemical method is applied to synthesize Pd/C-dots in which Pd nanoparticles (NPs) are dispersedly encapsulated by C-dots layer. The nanohybrid can function as a fluorescent sensor and reductive catalyst, due to the inherent properties of C-dots and Pd NPs, respectively. The Pd/C-dots exhibit a highly selective and sensitive detection toward the nickel (Ni2+) ion with a detection limit of 7.26 × 10−9 m. Moreover, the Ni2+ is detected in MCF-7 live cells signifying the applicability of nanohybrid as a promising sensor. On the other hand, the Pd/C-dots show an excellent catalytic performance in the reduction of 4-nitrophenol and eosin yellow. A plausible mechanism for sensing and catalysis behavior is proposed. The sensor system is designed on the basis of the fluorescence turn-on when Ni2+ interacts with functional groups of the C-dots layer. The activities of catalytic reduction are mainly governed by the Pd NPs and further enhanced when the C-dots layer is incorporated. The Pd/C-dots can serve as a new paradigm for opening a potential trend in the design of multifunctional materials to diverse applications. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Steady-state and time-resolved fluorescence spectroscopy techniques were used to probe multifluorescence resulting from citric-acid-derived carbon dots (C-dots). Commonly, both carboxyl-/amine-functionalized C-dots exhibit three distinct emissive states corresponding to the carbon-core and surface domain. The shorter-wavelength fluorescence (below 400 nm) originates from the carbon-core absorption band at ∼290 nm, whereas the fluorescence (above 400 nm) is caused by two surface states at ∼350 and 385 nm. In addition to three emissive states, a molecular state was also found in amine-functionalized C-dots. Time-resolved emission spectra (TRES) and time-resolved area normalized emission spectra (TRANES) were analyzed to confirm the origin of excitation wavelength-dependent fluorescence of C-dots. The surface functional groups on the C-dots are capable of regulating the electron transfer to affect the multifluorescence behavior. The electron transfer takes place from the carbon-core to surface domain by the presence of -COOH on the surface and vice versa for the case of -NH2 present on the surface. To the best of our knowledge, this is the first report that the multiemissive states are probed in C-dots systems using TRES and TRANES analyses, and related fluorescence mechanisms are verified clearly. © 2015 American Chemical Society.

Multiple sensor systems are designed by varying aza-crown ether moiety in silicon quantum dots (SiQDs) for detecting individual Mg2+, Ca2+, and Mn2+ metal ions with significant selectivity and sensitivity. The detection limit of Mg2+, Ca2+, and Mn2+ can reach 1.81, 3.15, and 0.47 μM, respectively. Upon excitation of the SiQDs which are coordinated with aza-crown ethers, the photoinduced electron transfer (PET) takes place from aza-crown ether moiety to the valence band of SiQDs core such that the reduced probability of electron-hole recombination may diminish the subsequent fluorescence. The fluorescence suppression caused by such PET effect will be relieved after selective metal ion is added. The charge-electron binding force between the metal ion and aza-crown ether hinders the PET and thereby restores the fluorescence of SiQDs. The design of sensor system is based on the fluorescence "turn-on" of SiQDs while in search of the appropriate metal ion. For practical application, the sensing capabilities of metal ions in the live cells are performed and the confocal image results reveal their promising applicability as an effective and nontoxic metal ion sensor. © 2016 American Chemical Society.

The multiple sensing capabilities of molybdenum disulfide quantum dots (MoS2 QDs) towards metal ions were scrutinized by tuning their surface functional groups. The MoS2 QDs surface was individually modified with thiol-containing capping agents to form carboxylic-, amine- and thiol-functionalized MoS2 QDs (MoS2/COOH, MoS2/NH2 and MoS2/SH) by the facile hydrothermal method. Each as-prepared QDs exhibits strong excitation wavelength dependent fluorescence behavior. The design of MoS2 QDs based metal ion sensor was implemented based on the fluorescence turn-on mechanism. These MoS2/COOH, MoS2/NH2 and MoS2/SH QDs sensors exhibit superior performance towards the highly selective detection of Co2+, Cd2+ and Pb2+ ions, respectively, due to the varied association of each functional group towards metal ions. The resultant detection limit of Co2+, Cd2+ and Pb2+ was evaluated to be 54.5, 99.6 and 0.84 nM, respectively, and the related fluorescence turn-on mechanism is verified unambiguously. The binding energies were calculated for QDs with metal ions pairs and the results lent support to the determined sensitivity. The as-prepared QDs were also successfully demonstrated to detect the above metal ions in real water samples. While becoming potential candidates in the chemosensors based on the fluorescence probe, these surface modified MoS2 QDs can offer an excellent sensing capability for specific metal ions with extremely high selectivity.

Carbon mesoporous materials (CPMs) have great potential in the field of heterogeneous catalysis. Highly dispersed ruthenium nanoparticles (RuNPs) embedded in three dimensional (3D) CPMs as catalysts with a high surface area (1474 m2 g-1) were prepared by microwave-thermal reduction processes. Characterization technologies including X-ray diffraction (XRD), N2 adsorption/desorption isotherm measurements, field emission transmission electron microscopy (FE-TEM), thermogravimetric analysis (TGA), hydrogen temperature-programmed reduction (H2-TPR), Raman spectroscopy and 13C solid state cross polarization and magic angle spinning (13C CP/MAS) NMR spectroscopy were utilized to scrutinize the catalysts. It was revealed that the Ru/CPM catalysts exhibited a highly ordered 3D mesoporous structure and a large surface area and were widely used as catalysts for reduction reactions. Reduction of p-nitroaniline (p-NA) and crystal violet (CV) using NaBH4 with the use of this catalyst was studied by means of UV-vis spectroscopy. Here, NaBH4 acts as a hydrogen donor. This catalyst shows an excellent catalytic activity towards reduction of p-NA and CV dye at room temperature. Due to the promising properties of CPMs, they can be utilized to fabricate 3D carbon-based materials for a variety of novel applications. © The Royal Society of Chemistry 2015.

Herein, we report ultra-sensitive sensing of a prostate-specific antigen (PSA), which is used as a biomarker to detect prostate cancer, using a molybdenum series (MoO3, MoS2, and MoSe2) of two-dimensional nanosheets (2D NSs). Moreover, the design of a 2D NS-based PSA aptamer sensor system was demonstrated based on a fluorescence turn-on mechanism in the presence of a target. The 2D NSs acted as an excellent sensing platform in which the PSA aptamer was adsorbed on the NSs and subsequent energy transfer between them led to fluorescence quenching of the aptamer. The detection limit of PSA was achieved to be 13 pM for MoO3 NSs, whereas the MoS2 and MoSe2 systems exhibited a detection limit of 72 and 157 pM, respectively. To the best of our knowledge, this is the first report on the ultra-sensitive detection of a 2D NS-based aptamer sensor. The in vitro bioimaging measurements were performed using confocal fluorescence microscopy. Herein, PSA detection was successfully demonstrated in human embryonic kidney 293T (HEK) live cells. Moreover, the MoO3, MoS2, and MoSe2 NSs exhibit excellent biocompatibility and low toxicity; thus, these 2D NSs can be used as a promising sensor platform to detect prostate cancer. This journal is © The Royal Society of Chemistry.