Energy-Resolved Ion Mobility Spectrometry: Composite Breakdown Curves for Distinguishing Isomeric Product Ions

Identification of lipopeptides (LpAA) synthesized from bacteria involves the study of structural characterization. Twenty LpAA have been characterized using commercial tandem high-resolution mass spectrometers in negative electrospray, employing nonresonant excitation in “RF only” collision cells and generally behave identically. However, [LpAA-H]− (AA = Asp or Glu) shows surprising fragmentation pathways, yielding a complementary fatty acid carboxylate and dehydrated amino acid fragment anions. In this study, the dissociation mechanisms of [C12Glu-H]− were determinate using energy-resolved mass spectrometry (ERMS). Product ion breakdown profiles are, generally, unimodal with full width at half-maximum (fwhm) increasing as product ion m/z ratios decrease, except for the two product ions of interest (fatty acid carboxylate and dehydrated glutamate) characterized by broad and composite profiles. Such behavior was already shown for other ions using a custom-built guided ion beam mass spectrometer. In this study, we investigate the meaning of these particular profiles from an ERMS breakdown, using fragmentation mechanisms depending on the collision energy. ERMS on line with ion mobility spectrometry (IMS), here called ER-IMS, provides a way to probe such questions. Broad or composite profiles imply that the corresponding product ions may be generated by two (or more) pathways, resulting in common or isomeric product ion structures. ER-IMS analysis indicates that the fatty acid carboxylate product ion is produced with a common structure through different pathways, while dehydrated glutamate has two isomeric forms depending on the mechanism involved. Drift time values correlate with the calculated collision cross section that confirms the product ion structures and fragmentation mechanisms

Low-Temperature Plasma-Enhanced Atomic Layer Deposition of ZnMgO for Efficient CZTS Solar Cells

Cu2ZnSnS4 (CZTS) solar cells are an emerging photovoltaic technology owing to their earth abundance, all-dry processability, and environmental friendliness. Further power conversion efficiency enhancement of the Cd-free CZTS device necessitates the substitution of traditionally used intrinsic ZnO by an alternative wide-band-gap window layer. Here, we demonstrate deposition of a ZnMgO window layer of controlled thickness, composition, and electro-optical properties by atomic layer deposition (ALD). The amorphous ZnMgO deposited at low temperature down to 100 °C using plasma-enhanced ALD showed smoothness superior to that of high-temperature plasma-enhanced ALD and doping density comparable to that of high-temperature thermal ALD but with a much lower electron affinity. The overall charge carrier recombination at the CZTS/ZnSnO/ZnMgO region was reduced due to the optimized ZnMgO conduction band minimum, thus reducing the VOC value and fill factor loss for a CZTS solar cell. In addition, the thinner- and larger-band-gap ZnMgO was believed to reduce the parasitic absorption, improving the JSC value and boosting the efficiency to 10%

Self-assembled Nanometer-Scale ZnS Structure at the CZTS/ZnCdS Heterointerface for High-Efficiency Wide Band Gap Cu₂ZnSnS₄ Solar Cells

Despite remarkable progress in the performance of kesterite Cu2ZnSnS4 (CZTS)-based photovoltaic technology has been achieved, the interface recombination and associated open-circuit voltage (Voc) deficit still dominate the loss mechanism in this technology. To alleviate heterojunction interface recombination in pure sulfide thin film solar cells, passivation structure at the interface is required. In this work, we developed an ultrathin nanometer-scale ZnS dielectric passivation layer which is readily formed in situ at the CZTS/ZnCdS heterointerface during the ZnCdS buffer deposition process via Zn diffusion from the ZnCdS bulk to the interface. With this nanoscale structure, a remarkable open-circuit voltage and fill factor improvement is illustrated, and a total area efficiency of 9.25% is obtained. The formation and features of the nanoscale ZnS layer are investigated by high-resolution scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy. This self-assembled ZnS layer with dielectric properties passivates defects at the interface while still enabling the electrons to transport across the buffer layer because of the ultrathin thickness, which satisfies the requirement of dielectric passivation layer but requiring no complicated regular patterning. The correlation between the effects of passivation and device performance is investigated by device simulation, presenting a reasonable understanding of the experimental results. The results open a new aspect to passivate the interface recombination and expand the potential of upscaling CZTS technology

Energy Resolved Mass Spectrometry for Interoperable Non-resonant Collisional Spectra in Metabolomics

In untargeted metabolomics, the unambiguous identification of metabolites remains a major challenge. This requires high-quality spectral libraries for reliable metabolite identification, which is essential for translating metabolomics data into meaningful biological information. Several attempts have been made to generate reproducible product ion spectra (PIS) under a low collision energy (ELab) regime and nonresonant collisional conditions but have not fully succeeded. We examined the ERMS (energy-resolved mass spectrometry) breakdown curves of two lipo-amino acids and showed the possibility to highlight “singular points”, called descriptors hereafter (linked to respective ELab depending on the instrument), for each of the monomodal product ion profiles. Using several instruments based on different technologies, the PIS recorded at these specific ELab sites shows remarkable similarities. The descriptors appeared as being independent of the fragmentation mechanisms and can be used to overcome the main instrumental effects that limit the interoperability of spectral libraries. This proof-of-concept study, performed on two particular lipo-amino acids, demonstrates the high potential of ERMS-derived information to determine the instrument-specific ELab at which PIS recorded in nonresonant conditions become highly similar and instrument-independent, thus comparable across platforms. This innovative but straightforward approach could help remove some of the obstacles to metabolite identification in nontargeted metabolomics, putting an end to a challenging chimera

Protocol for VIVALDI social care: Pilot study to reduce infections, outbreaks and antimicrobial resistance in care homes for older adults

Care home residents are vulnerable to severe outcomes from infections such as COVID-19 and influenza. However, measures to control outbreaks, such as care home closures to visitors and new admissions, have a detrimental impact on their quality of life. Many infections and outbreaks could be prevented but the first step is to measure them reliably. This is challenging in care homes due to the lack of data and research infrastructure. During the pandemic, the VIVALDI study measured COVID-19 infections in residents and staff by partnering with care providers and using routinely collected data. This study aims to establish sentinel surveillance and a research database to enable observational and future interventional studies in care homes. The project has been co-produced with care providers, staff, residents, relatives, and researchers. The study (October 2023 to March 2025) will explore the feasibility of establishing a network of 500-1500 care homes for older adults in England that is underpinned by a linked data platform. No data will be collected from staff. The cohort will be created by regularly extracting resident identifiers from Digital Social Care Records (DSCR), followed by pseudonymisation and linkage to routinely collected datasets. Following extensive consultation, we decided not to seek informed consent from residents for data collection, but they can 'opt out' of the study. Our goal is to be inclusive, and it is challenging to give every resident the opportunity to 'opt in' due to cognitive impairment and the requirement for consultees. The project, and all requests to use the data will be overseen by relatives, residents, staff, and care providers. The study has been approved by the Health Research Authority Confidentiality Advisory Group (23/CAG/0134&0135) and the South-West Frenchay Research Ethics Committee (23/SW/0105). It is funded by the UK Health Security Agency.</p

Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites

The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA+/MA+/Cs+, X=I -/Br -) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI 3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials