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Metal chalcogenide quantum dots (QDs) are prized for their unique and functional properties, associated with both intrinsic (quantum confinement) and extrinsic (high surface area) effects, as dictated by their size, shape, and surface characteristics. Thus, they have considerable promise for diverse applications, including energy conversion (thermoelectrics and photovoltaics), photocatalysis, and sensing. QD gels are macroscopic porous structures consisting of interconnected QDs and pore networks in which the pores may be filled with solvent (i.e., wet gels) or air (i.e., aerogels). QD gels are unique because they can be prepared as macroscale objects while fully retaining the size-specific quantum-confined properties of the initial QD building blocks. The extensive porosity of the gels also ensures that each QD in the gel network is accessible to the ambient, leading to high performance in applications that require high surface areas, such as (photo)catalysis and sensing. Metal chalcogenide QD gels are conventionally prepared by chemical approaches. We recently expanded the toolbox for QD gel synthesis by developing electrochemical gelation methods. Relative to conventional chemical oxidation approaches, electrochemical assembly of QDs (1) enables the use of two additional levers for tuning the QD assembly process and gel structure: electrode material and potential, and (2) allows direct gel formation on device substrates to simplify device fabrication and improve reproducibility. We have discovered two distinct electrochemical gelation methods, each of which enables the direct writing of gels on an active electrode surface or the formation of free-standing monoliths. Oxidative electrogelation of QDs leads to assemblies bridged by dichalcogenide (covalent) linkers, whereas metal-mediated electrogelation proceeds via electrodissolution of active metal electrodes to produce free ions that link QDs by binding to pendant carboxylate functionalities on surface ligands (non-covalent linkers). We further demonstrated that the electrogel composition produced from the covalent assembly could be modified by controlled ion exchange to form single-ion decorated bimetallic QD gels, a new category of materials. The QD gels exhibit unprecedented performance for NO(2) gas sensing and unique photocatalytic reactivities (e.g., the “cyano dance” isomerization and the reductive ring-opening arylation). The chemistry unveiled during the development of electrochemical gelation pathways for QDs and their post-modification has broad implications for guiding the design of new nanoparticle assembly strategies and QD gel-based gas sensors and catalysts.

Slow response and recovery kinetics is a major challenge for practical room-temperature NO2 gas sensing. Here, we report the use of visible light illumination to significantly shorten the response and recovery times of a PbSe quantum dot (QD) gel sensor by 21% (to 27 s) and 63% (to 102 s), respectively. When combined with its high response (0.04%/ppb) and ultralow limit of detection (3 ppb), the reduction in response and recovery time makes the PbSe QD gel sensor among the best p-type room-temperature NO2 sensors reported to date. A combined experimental and theoretical investigation reveals that the accelerated response and recovery time is primarily due to photoexcitation of NO2 gaseous molecules and adsorbed NO2 on the gel surface, rather than the excitation of the semiconductor sensing material, as suggested by the currently prevailing light-activated gas-sensing theory. Furthermore, we find that the extent of improvement attained in the recovery speed also depends on the distribution of excited electrons in the adsorbed NO2/QD gel system. This work suggests that the design of light-activated sensor platforms may benefit from a careful assessment of the photophysics of the analyte in the gas phase and when adsorbed onto the semiconductor surface.

We have recently described a new potential use for Langmuir-Blodgett films of surfactants containing redox-inert metal ions in the inhibition of corrosion and have shown good qualitative results for both iron and aluminum surfaces. In this study we proceed to quantify electrochemically the viability of gallium(III)- and zinc(II)-containing metallosurfactants [GaIII(LN2O3)] (1) and [ZnII(LN2O2)H2O] (2) as mitigators for iron corrosion in saline and acidic media. We evaluate their charge transfer suppression and then focus on potentiodynamic polarization and impedance spectroscopy studies, including detailed SEM data to interrogate their metal dissolution/oxygen reduction rate mitigation abilities. Both complexes show some degree of mitigation, with a more pronounced activity in saline than in acidic medium.

This study reports the long-term storage stability of a formulation of the cyanide (CN) antidote dimethyl trisulfide (DMTS). The F3-formulated DMTS was stored in glass ampules at 4, 22, and 37 °C. Over a period of one year, nine ampules (n = 3 at each temperature) were analyzed by high-performance liquid chromatography (HPLC)–UV/vis at daily time intervals in the first week, weekly time intervals in the first month, and monthly thereafter for a period of one year to determine the DMTS content. No measurable loss of DMTS was found at 4 and 22 °C, and good stability was noted up to five months for samples stored at 37 °C. At 37 °C, a 10% (M/M) decrease of DMTS was discovered at the sixth month and only 30% (M/M) of DMTS remained by the end of the study; discoloration of the formulation and the growth of new peaks in the HPLC chromatogram were also observed. To identify the unknown peaks at 37 °C, controlled oxidation studies were performed on DMTS using two strong oxidizing agents: meta-chloroperoxybenzoic acid (mCPBA) and hydrogen peroxide (H2O2). Dimethyl tetrasulfide and dimethyl pentasulfide were observed as products using both of the oxidizing agents. Dimethyl disulfide was also observed as a product of degradation, which was further oxidized to S-methyl methanethiosulfonate only when mCPBA was used. HPLC–UV/vis and gas chromatography–mass spectrometry/solid phase microextraction analysis revealed good agreement between the degradation products of the stability study at 37 °C and those of disproportionation reactions. Furthermore, at 4 and 22 °C, chromatograms were remarkably stable over the one-year study period, indicating that the F3-formulated DMTS shows excellent long-term storage stability at T ≤ 22 °C.

Relative to conventional chemical approaches, electrochemical assembly of metal chalcogenide nanoparticles enables the use of two additional levers for tuning the assembly process: electrode material and potential. In our prior work, oxidative and metal-mediated pathways for electrochemical assembly of metal chalcogenide quantum dots (QDs) into three-dimensional gel architectures were investigated independently by employing a noble-metal (Pt) electrode at relatively high potentials and a non-noble metal electrode at relatively low potentials, respectively. In the present work, we reveal competition between the two electrogelation pathways under the condition of high oxidation potentials and non-noble metal electrodes (including Ni, Co, Zn, and Ag), where both pathways are active. We found that the electrogel structure formed under this condition is electrode material-dependent. For Ni, the major phase is oxidative electrogel, not a potential-dependent mixture of oxidative and metal-mediated electrogel that one would expect. A mechanistic study reveals that the metal-mediated electrogelation is suppressed by dithiolates, a side product from the oxidative electrogelation, which block the Ni electrode surface and terminate metal ion release. In contrast, for Co, Ag, and Zn, the electrode surface blockage by dithiolates is less effective than for Ni, such that metal-mediated electrogelation is the primary gelation pathway.

Slow response and recovery kinetics is a major challenge for practical room-temperature NO

Atmospheric NO2 is of great concern due to its adverse effects on human health and the environment, motivating research on NO2 detection and remediation. Existing low-cost room-temperature NO2 sensors often suffer from low sensitivity at the ppb level or long recovery times, reflecting the trade-off between sensor response and recovery time. Here, we report an atomically dispersed metal ion strategy to address it. We discover that bimetallic PbCdSe quantum dot (QD) gels containing atomically dispersed Pb ionic sites achieve the optimal combination of strong sensor response and fast recovery, leading to a high-performance room-temperature p-type semiconductor NO2 sensor as characterized by a combination of ultra–low limit of detection, high sensitivity and stability, fast response and recovery. With the help of theoretical calculations, we reveal the high performance of the PbCdSe QD gel arises from the unique tuning effects of Pb ionic sites on NO2 binding at their neighboring Cd sites. Quantum dot-based NO2 sensors often suffer from low sensitivity or long recovery times. Here, the authors report that bimetallic PbCdSe quantum dot gels containing atomically dispersed Pb ionic sites enable ultra-sensitive and fast NO2 sensing.

Background: Myocarditis is an inflammatory heart disease caused by viral infections that can lead to heart failure, and occurs more often in men than women. Since animal studies have shown that myocarditis is influenced by sex hormones, we hypothesized that endocrine disruptors, which interfere with natural hormones, may play a role in the progression of the disease. The human population is exposed to the endocrine disruptor bisphenol A (BPA) from plastics, such as water bottles and plastic food containers. Methods: Male and female adult BALB/c mice were housed in plastic versus glass caging, or exposed to BPA in drinking water versus control water. Myocarditis was induced with coxsackievirus B3 on day 0, and the endpoints were assessed on day 10 post infection. Results: We found that male BALB/c mice that were exposed to plastic caging had increased myocarditis due to complement activation and elevated numbers of macrophages and neutrophils, whereas females had elevated mast cell activation and fibrosis. Conclusions: These findings show that housing mice in traditional plastic caging increases viral myocarditis in males and females, but using sex-specific immune mechanisms.

The use of metallosurfactants to prevent pitting corrosion of aluminum surfaces is discussed based on the behavior of the metallosurfactants [ZnII (LN2O2 )H2 O] (1) and [GaIII (LN2O3 )] (2). These species were deposited as multilayer Langmuir-Blodgett films and characterized by IR reflection absorption spectroscopy and UV/Vis spectroscopy. Scanning electron microscopy images, potentiodynamic polarization experiments, and electrochemical impedance spectroscopy were used to assess corrosion mitigation. Both metallosurfactants demonstrate superior anticorrosion activity due to the presence of redox-inactive 3d10 metal ions that enhance the structural resistance of the ordered molecular films and limit chloride mobility and electron transfer.

The ability to dictate the assembly of quantum dots (QDs) is critical for their integration into solid-state electronic and optoelectronic devices. However, assembly methods that enable efficient electronic communication between QDs, facilitate access to the reactive surface, and retain the native quantum confinement characteristics of the QD are lacking. Here we introduce a universal and facile electrochemical gelation method for assembling metal chalcogenide QDs (as demonstrated for CdS, ZnS, and CdSe) into macroscale 3-D connected pore-matter nanoarchitectures that remain quantum confined and in which each QD is accessible to the ambient. Because of the redox-active nature of the bonding between QD building blocks in the gel network, the electrogelation process is reversible. We further demonstrate the application of this electrogelation method for a one-step fabrication of CdS gel gas sensors, producing devices with exceptional performance for NO2 gas sensing at room temperature, thereby enabling the development of low-cost, sensitive, and reliable devices for air quality monitoring.