The decomposition of HCOOH on Pd surfaces over a potential range of practical relevance to hydrogen production and fuel cell anode operation was probed by combining high-sensitivity in situ surface-enhanced IR spectroscopy with attenuated total reflection and thin-layer flow cell configurations. For the first time, concrete spectral evidence of CO(ad) formation has been obtained, and a new main pathway from HCOOH to CO(ad) involving the reduction of the dehydrogenation product of HCOOH (i.e., CO(2)) is proposed.

An improved approach composed of an oxidation reaction in acidic H2O2 solution and a sequential silanization reaction using neat silane reagents for surface modification of poly(dimethylsiloxane) (PDMS) substrates was developed. This solution-phase approach is simple and convenient for some routine analytical applications in chemistry and biology laboratories and is designed for intact PDMS-based microfluidic devices, with no device postassembly required. Using this improved approach, two different functional groups, poly(ethylene glycol) (PEG) and amine (NH2), were introduced onto PDMS surfaces for passivation of nonspecific protein absorption and attachment of biomolecules, respectively. X-ray electron spectroscopy and temporal contact angle experiments were employed to monitor functional group transformation and dynamic characteristics of the PEG-grafted PDMS substrates; fluorescent protein solutions were introduced into the PEG-grafted PDMS microchannels to test their protein repelling characteristics. These analytical data indicate that the PEG-grafted PDMS surfaces exhibit improved short-term surface dynamics and robust long-term stability. The amino-grafted PDMS microchannels are also relatively stable and can be further activated for modifications with peptide, DNA, and protein on the surfaces of microfluidic channels. The resulting biomolecule-grafted PDMS microchannels can be utilized for cell immobilization and incubation, semiquantitative DNA hybridization, and immunoassay.

Organic solid-state luminescence switching (SLS) materials with the ability to reversibly switch the luminescence by altering the mode of molecular packing without changing the chemical structures of their component molecules have attracted considerable interest in recent years. In this work, we design and synthesize a new class of 2,7diphenylfluorenone derivatives (compounds 1−6) that exhibit prominent aggregation-induced emission (AIE) properties with high solid-state fluorescence quantum yields (29−65%). Among them, 2,7-bis(4-methoxyphenyl)-9H-fluoren-9-one (2) and 2,7-bis(4-ethylphenyl)-9H-fluoren-9-one ( 6) display reversible stimuli-responsive solid-state luminescence switching. Compound 2 transforms between red and yellow crystals (the emission wavelength switches between 601 and 551 nm) under the stimuli of temperature, pressure, or solvent vapor. Similarly, compound 6 exhibits SLS behavior, with luminescence switching between orange (571 nm) and yellow (557 nm). Eight X-ray single-crystal structures, characterization of the photophysical properties, powder X-ray diffraction, and differential scanning calorimetry provide insight into the structure−property relationships of the solid-state fluorescence behavior. The results indicate that the variable solid-state luminescence of the fluorenone derivatives is attributed to the formation of different excimers in different solid phases. Additionally, the stimuli-responsive reversible phase transformations of compounds 2 and 6 involve a structural transition between π−π stacking-directed packing and hydrogen bond-directed packing. The results also demonstrate the feasibility of our design strategy for new solid-state luminescence switching materials: introduction of both π−π stacking and hydrogen bonding into an AIE structure to obtain a metastable solid/crystalline state luminescence system.

The development of an effective method for detecting heavy-metal ions remains a serious task because of their high toxicity to public health and environments. Herein, a new electrochemical method based on a graphene aerogel (GA) and metal–organic framework (MOF) composites was developed for simultaneous detection of multiple heavy-metal ions in aqueous solutions. The GA-MOF composites were synthesized via the in situ growth of the MOF UiO-66-NH2 crystal on the GA matrix. GA not only serves as the backbone for UiO-66-NH2 but also enhances the conductivity of the composites by accelerating the electron transfer in the matrix. UiO-66-NH2 worked as a binding site for heavy-metal ions because of the interaction between hydrophilic groups and metal cations. The detection performance of the GA-UiO-66-NH2 composite-modified electrodes was determined. The developed electrochemical method can be successfully applied for individual and simultaneous detection of heavy-metal ions, namely, Cd2+, Pb2+, Cu2+,and Hg2+, in aqueous solutions with high sensitivity and selectivity. The method can also be used for simultaneous detection of Cd2+, Pb2+, Cu2+, and Hg2+ in river water and the leaching solutions of soil and vegetable with high accuracy and reliability. This work provides a new approach for simultaneous detection of multiple heavy-metal ions in practical applications.

Inspired by the “third-body” effect and the d-band center theory, a series of carbon black-supported Pd x Pt1−x (denoted as Pd x Pt1-x /C, with atomic fraction x = 0.5−1) nanocatalysts were synthesized and screened in order to pinpoint the optimal composition targeted for the electrocatalytic oxidation of formic acid. The effective alloying of these two elements is better demonstrated by the compositional dependent synergetic electrocatalysis identified for the as-synthesized Pd x Pt1−x /C nanoparticles rather than by the XRD characterization. Preliminary screening indicates that Pd0.9Pt0.1/C is the optimum catalyst for the desired reaction among all tested Pd x Pt1−x /C samples. This high performance of the Pd0.9Pt0.1 nanoalloy can be ascribed to the effectively inhibited CO poisoning at largely separated Pt sites and appropriately lowered d-band center of Pd sites.