The electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance owing to preferential catalyst–H formation and the ...consequential hydrogen evolution reaction (HER). Now, the Pt/Au electrocatalyst d‐band structure is electronically modified using zeolitic imidazole framework (ZIF) to achieve a Faradaic efficiency (FE) of >44 % with high ammonia yield rate of >161 μg mgcat−1 h−1 under ambient conditions. The strategy lowers electrocatalyst d‐band position to weaken H adsorption and concurrently creates electron‐deficient sites to kinetically drive NRR by promoting catalyst–N2 interaction. The ZIF coating on the electrocatalyst doubles as a hydrophobic layer to suppress HER, further improving FE by >44‐fold compared to without ZIF (ca. 1 %). The Pt/Au‐NZIF interaction is key to enable strong N2 adsorption over H atom.
A kinetically driven ambient nitrogen reduction reaction has a Faradaic efficiency of over 44 % and an ammonia yield rate of over 161 μg mgcat−1 h−1. It employs a zeolitic imidazole framework to induce electron‐deficient sites on the catalyst and a lower d‐band to weaken catalyst–H interactions whilst promoting the catalyst–N2 interaction.
Photothermal materials are crucial for diverse heating applications, but it remains challenging to achieve high energy conversion efficiency due to the difficulty to concurrently improve light ...absorbance and suppress heat loss. Herein, a zeolitic imidazolate framework‐isolated graphene (G@ZIF) nanohybrid is demonstrated that utilizes ultrathin, heat‐insulating ZIF layers, and G@ZIF interfacial nanocavity to synergistically intensify light absorbance and heat localization. Under artificial sunlight illumination (≈1 kW m−2), the G@ZIF film attains a maximum temperature of 120 °C in an open environment with a 98% solar‐to‐thermal conversion efficiency. Importantly, the porous ZIF layer allows small molecules/media to enter and access the embedded hot graphene surface for targeted heat transfer in practical applications. As a proof‐of‐concept, the G@ZIF‐based steam generator realizes 96% energy conversion from light to vapor with near‐perfect desalination and water purification efficiencies (>99.9%). This design is generic and can be extended to other photothermal systems for advanced solar‐thermal applications, including catalysis, water treatments, sterilization, and mechanical actuation.
MOF‐isolated graphene (G@ZIF) nanohybrids demonstrate strong solar light absorbance and a 98% solar‐to‐thermal conversion efficiency, owing to its ultrathin, heat‐insulating ZIF layers, and G@ZIF interfacial nanocavity to synergistically intensify light absorbance and minimize heat loss. The maximum surface temperature reaches 120 °C under simulated one‐sun illumination, enabling efficient interfacial water evaporation for desalination.
Population-wide surveillance of COVID-19 requires tests to be quick and accurate to minimize community transmissions. The detection of breath volatile organic compounds presents a promising option ...for COVID-19 surveillance but is currently limited by bulky instrumentation and inflexible analysis protocol. Here, we design a hand-held surface-enhanced Raman scattering-based breathalyzer to identify COVID-19 infected individuals in under 5 min, achieving >95% sensitivity and specificity across 501 participants regardless of their displayed symptoms. Our SERS-based breathalyzer harnesses key variations in vibrational fingerprints arising from interactions between breath metabolites and multiple molecular receptors to establish a robust partial least-squares discriminant analysis model for high throughput classifications. Crucially, spectral regions influencing classification show strong corroboration with reported potential COVID-19 breath biomarkers, both through experiment and in silico. Our strategy strives to spur the development of next-generation, noninvasive human breath diagnostic toolkits tailored for mass screening purposes.
Gas–liquid reactions form the basis of our everyday lives, yet they still suffer poor reaction efficiency and are difficult to monitor in situ, especially at ambient conditions. Now, an inert ...gas–liquid reaction between aniline and CO2 is driven at 1 atm and 298 K by selectively concentrating these immiscible reactants at the interface between metal–organic framework and solid nanoparticles (solid@MOF). Real‐time reaction SERS monitoring and simulations affirm the formation of phenylcarbamic acid, which was previously undetectable because they are unstable for post‐reaction treatments. The solid@MOF ensemble gives rise to a more than 28‐fold improvement to reaction efficiency as compared to ZIF‐only and solid‐only platforms, emphasizing that the interfacial nanocavities in solid@MOF are the key to enhance the gas–liquid reaction. Our strategy can be integrated with other functional materials, thus opening up new opportunities for ambient‐operated gas–liquid applications.
Gas–liquid reactions form the basis of our lives, yet they suffer from poor reaction efficiency and are difficult to monitor in situ, especially at ambient conditions. An inert gas–liquid reaction between aniline and CO2 is driven at 1 atm and 298 K. Real‐time reaction monitoring was performed by selectively concentrating these immiscible reactants at the interface between metal–organic framework and solid nanoparticles.
Conspectus Surface-enhanced Raman scattering (SERS) is a molecular-specific spectroscopic technique that provides up to 1010-fold enhancement of signature Raman fingerprints using nanometer-scale 0D ...to 2D platforms. Over the past decades, 3D SERS platforms with additional plasmonic materials in the z-axis have been fabricated at sub-micrometer to centimeter scale, achieving higher hotspot density in all x, y, and z spatial directions and higher tolerance to laser misalignment. Moreover, the flexibility to construct platforms in arbitrary sizes and 3D shapes creates attractive applications besides traditional SERS sensing. In this Account, we introduce our library of substrate-based and substrate-less 3D plasmonic platforms, with an emphasis on their non-sensing applications as microlaboratories and data storage labels. We aim to provide a scientific synopsis on these high-potential yet currently overlooked applications of SERS and ignite new scientific discoveries and technology development in 3D SERS platforms to tackle real-world issues. One highlight of our substrate-based SERS platforms is multilayered platforms built from micrometer-thick assemblies of plasmonic particles, which can achieve up to 1011 enhancement factor. As an alternative, constructing 3D hotspots on non-plasmonic supports significantly reduces waste of plasmonic materials while allowing high flexibility in structural design. We then introduce our emerging substrate-less plasmonic capsules including liquid marbles and colloidosomes, which we further incorporate the latter within an aerosol to form centimeter-scale SERS-active plasmonic cloud, the world’s largest 3D SERS platform to date. We then discuss the various emerging applications arising only from these 3D platforms, in the fields of sensing, microreactions, and data storage. An important novel sensing application is the stand-off detection of airborne analytes that are several meters away, made feasible with aerosolized plasmonic clouds. We also describe plasmonic capsules as excellent miniature lab-in-droplets that can simultaneously provide in situ monitoring at the molecular level during reaction, owing to their ultrasensitive 3D plasmonic shells. We highlight the emergence of 3D SERS-based data storage platforms with 10–100-fold higher storage density than 2D platforms, featuring a new approach in the development of level 3 security (L3S) anti-counterfeiting labels. Ultimately, we recognize that 3D SERS research can only be developed further when its sensing capabilities are concurrently strengthened. With this vision, we foresee the creation of highly applicable 3D SERS platforms that excel in both sensing and non-sensing areas, providing modern solutions in the ongoing Fourth Industrial Revolution.
Electrochemical nitrogen reduction reaction (NRR) offers sustainable ammonia production but suffers from poor performance owing to favorable water electrolysis. Recent designs achieve better ...efficiency by eradicating water but do not leverage on water as a readily available NRR proton source. Herein, we design a hydrophobic oleylamine-functionalized zeolitic-imidazolate framework coated over the electrocatalyst to achieve >18% NRR efficiency in the presence of water, an approximately fourfold boost compared to that without water. Our strategy kinetically regulates water availability at the electrocatalyst surface, suppresses direct water adsorption/electrolysis, and promotes preferential nitrogen adsorption to achieve water-assisted NRR. Conversely, control systems without hydrophobic modification experience a drastic decrease in efficiencies (<3%) upon water addition. In situ surface-enhanced Raman scattering investigation reveals that our hydrophobic system’s ability in suppressing water accessibility to the electrocatalyst is the key to transform water from a hindrance to an NRR promotor. Our universal design is a paradigm shift from current approaches to achieve sustainable air-to-ammonia electrosynthesis.
Stand-off Raman spectroscopy combines the advantages of both Raman spectroscopy and remote detection to retrieve molecular vibrational fingerprints of chemicals at inaccessible sites. However, it is ...currently restricted to the detection of pure solids and liquids and not widely applicable for dispersed molecules in air. Herein, we realize real-time stand-off SERS spectroscopy for remote and multiplex detection of atmospheric airborne species by integrating a long-range optic system with a 3D analyte-sorbing metal–organic framework (MOF)-integrated SERS platform. Formed via the self-assembly of Ag@MOF core–shell nanoparticles, our 3D plasmonic architecture exhibits micrometer thick SERS hotspot to allow active sorption and rapid detection of aerosols, gas, and volatile organic compounds down to parts-per-billion levels, notably at a distance up to 10 m apart. The platform is highly sensitive to changes in atmospheric content, as demonstrated in the temporal monitoring of gaseous CO2 in several cycles. Importantly, we demonstrate the remote and multiplex quantification of polycyclic aromatic hydrocarbon mixtures in real time under outdoor daylight. By overcoming core challenges in current remote Raman spectroscopy, our strategy creates an opportunity in the long-distance and sensitive monitoring of air/gaseous environment at the molecular level, which is especially important in environmental conservation, disaster prevention, and homeland defense.
Gas‐phase surface‐enhanced Raman scattering (SERS) remains challenging due to poor analyte affinity to SERS substrates. The reported use of capturing probes suffers from concurrent inconsistent ...signals and long response time due to the formation of multiple potential probe–analyte interaction orientations. Here, we demonstrate the use of multiple non‐covalent interactions for ring complexation to boost the affinity of small gas molecules, SO2 and NO2, to our SERS platform, achieving rapid capture and multiplex detection down to 100 ppm. Experimental and in‐silico studies affirm stable ring complex formation, and kinetic investigations reveal a 4‐fold faster response time compared to probes without stable ring complexation capability. By synergizing spectral concatenation and support vector machine regression, we achieve 91.7 % accuracy for multiplex quantification of SO2 and NO2 in excess CO2, mimicking real‐life exhausts. Our platform shows immense potential for on‐site exhaust and air quality surveillance.
Practical applications of gas‐phase surface‐enhanced Raman scattering (SERS) suffer from poor analyte affinity to plasmonic substrates, low concentration, and inherently small Raman cross‐sections. Herein, ring complexation is leveraged via formation of multiple non‐covalent interactions with small gases to yield effective capture and distinct spectral changes for multiplex detection of SO2 and NO2 in excess of CO2 mimicking artificial exhaust.
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