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The controllable construction of complex metal-organic coordination polymers (CPs) merits untold scientific and technological potential, yet remains a grand challenge of one-step construction and modulating simultaneously valence states of metals and topological morphology. Here, a thiocyanuric acid (TCA)-triggered strategy is presented to one-step rapid synthesis a double-crystalline Prussian blue analogue hetero-superstructure (PBA-hs) that comprises a Co3[Fe(CN)6]2 cube overcoated with a KCo[Fe(CN)6] shell, followed by eight self-assembled small cubes on vertices. Unlike common directing surfactants, TCA not only acts as a trigger for the fast growth of KCo[Fe(CN)6] on the Co3[Fe(CN)6]2 phase resulting in a PBA-on-PBA hetero-superstructure, but also serves as a flange-like bridge between them. By combining experiments with simulations, a deprotonation-induced electron transfer (DIET) mechanism is proposed for formation of second phase in PBA-hs, differing from thermally and photo-induced electron transfer processes. To prove utility, the calcined PBA-hs exhibits enhanced oxygen evolution reaction performance. This work provides a new method to design of novel CPs for enriching chemistry and material science. This work offers a practical approach to design novel CPs for enriching chemistry and material science.
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The hollow sandwich core-shell micro-nanomaterials are widely used in materials, chemistry, and medicine, but their fabrication, particularly for transition metal phosphides (TMPs), remains a great challenge. Herein, a general synthesis strategy is presented for binary TMPs hollow sandwich heterostructures with vertically interconnected nanosheets on the inside and outside surfaces of polyhedron FeCoPx /C, demonstrated by a variety of transition metals (including Co, Fe, Cd, Mn, Cu, Cr, and Ni). Density functional theory (DFT) calculation reveals the process and universal mechanism of layered double hydroxide (LDH) growth on Prussian blue analog (PBA) surface in detail for the first time, which provides the theoretical foundations for feasibility and rationality of the synthesis strategy. This unique structure exhibits a vertical nanosheet-shell-vertical nanosheet configuration combining the advantages of sandwich, hollow and vertical heterostructures, effectively achieving their synergistic effect. As a proof-of-concept of their applications, the CoNiPx @FeCoPx /C@CoNiPx hollow sandwich polyhedron architectures (representative samples) show excellent catalytic performance for the oxygen evolution reaction (OER) in alkaline electrolytes. This work provides a general method for constructing hollow-sandwich micro-nanostructures, which provides more ideas and directions for design of micro-nano materials with special geometric topology.
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A recently synthesized novel molecule (named CAT-1) exhibits intriguing near-infrared (NIR) thermally activated delayed fluorescence (TADF) close to 1000 nm wavelength; however, the mechanism behind these intrinsic properties is not fully understood. Herein, we unravel that the fluorescence emission spectrum with a broad wavelength range (770-950 nm) of CAT-1 is primarily induced by hydrogen bond steric hindrance based on density functional theory and Marcus theory. It is found that the hydrogen bond steric hindrance plays a critical role in inhibiting the twist of the configuration of different excited states, which leads to the minor driving force for fast electron trapping between the excited states, as well as small internal reorganization energy caused by less changed geometric configuration. Furthermore, such steric hindrance will cause a more distorted plane, resulting in a less favorable electron delocalization. A faster reverse intersystem crossing (RISC) rate is then obtained due to the nearly unchanged conformation between excited states caused by steric hindrance, although the spin-orbit coupling is small. Consequently, the NIR TADF with a longer wavelength can be emitted in CAT-1. This work shows that the hydrogen bond steric hindrance can fine-tune the electronic interactions of the donor and acceptor units to control the TADF.
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The energetic alignment of band edges at the interface plays a central role in determining the properties and applications of two-dimensional (2D) van der Waals (vdW) heterostructures. Generally, three conventional heterojunction types (type-I, type-II, and type-III) have widely been investigated and used in diverse fields. Unconventional band alignments (type-IV, type-V, and type-VI) are, however, hitherto unreported in the vdW heterostructures. We find that 2D binary semiconductors composed of group IV-V elements manifest a similar electronic structure, offering in principle the possibility of designing heterostructures with novel band alignments due to the hybridization of band-edge states. We first show here that a 2D SiAs/GeP heterostructure exhibits a type-VI band alignment, which is induced by the interlayer pz orbital hybridization, and a transition of band alignment from type-VI to type-V occurs when strain or electric field is applied over a critical value. The unconventional band alignments and their transition natures enable broad application of these vdW heterostructures in special opto-electronic devices and energy conversion.
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A high light-absorption coefficient and long-range hot-carrier transport of hybrid organic-inorganic perovskites give huge potential to their composites in solar energy conversion and environmental protection. Understanding interfacial interactions and their effects are paramount for designing perovskite-based heterostructures with desirable properties. Herein, we systematically investigated the interfacial interactions in monolayer and few-layer SnS/CH3 NH3 PbI3 heterostructures and their effects on the electronic and optical properties of these structures by density functional theory. It was found that the interfacial interactions in SnS/CH3 NH3 PbI3 heterostructures were van der Waals (vdW) interactions, and they were found to be insensitive to the layer number of 2D SnS sheets. Interestingly, although their band gap decreased upon increasing the layer number of SnS, the near-gap electronic states and optical absorption spectra of these heterostructures were found to be strikingly similar. This feature was determined to be critical for the design of 2D layered SnS-based heterostructures. Strong absorption in the ultraviolet and visible-light regions, typeâ II staggered band alignment at the interface, and few-layer SnS as an active co-catalyst make 2D SnS/CH3 NH3 PbI3 heterostructures promising candidates for photocatalysis, photodetectors, and solar energy harvesting and conversion. These results provide first insight into the nature of interfacial interactions and are useful for designing hybrid organic-inorganic perovskite-based devices with novel properties.
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Elimination of pollutants from water is one of the greatest challenges in resolving global environmental issues. Herein, we report a high-surface-area mesoporous g-C3N4 nanosheet with remarkable high adsorption capacity and photocatalytic performance, which is prepared through directly polycondensation of urea followed by a consecutive one-step thermal exfoliation strategy. This one-pot method to prepare mesoporous g-C3N4 nanosheet is facile and rapid in comparison with others. The superior adsorption capacity of the fabricated mesoporous g-C3N4 nanostructures is demonstrated by a model organic pollutant-methylene blue (MB), which is up to 72.2 mg/g, about 6 times as that of the largest value of various g-C3N4 adsorbents reported so far. Moreover, this kind of porous g-C3N4 nanosheet exhibits high photocatalytic activity to MB and phenol degradation. Particularly, the regenerated samples show excellent performance of pollutant removal after consecutive adsorption/degradation cycles. Therefore, this mesoporous g-C3N4 nanosheet may be an attractive robust metal-free material with great promise for organic pollutant elimination.
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Understanding the interfacial interaction is of paramount importance for rationally designing carbon nanomaterial-based hybrids with optimal performance for electronics, optoelectronics, sensing, advanced energy conversion and storage. Here, we firstly reveal that both covalent and noncovalent interactions simultaneously exist in carbon nanotube (CNT)/Ag3PO4 hybrids by studying systematically the electronic and optical properties to elucidate the mechanism of their enhanced photocatalytic performance. Metallic CNT(9,0) may chemically or physically interact with the Ag3PO4(100) surface depending on its relative orientations, whereas semiconducting CNT(10,0) can only noncovalently functionalize Ag3PO4. The C-Ag bond in the covalently bonded hybrid and type-II, staggered, band alignment in noncovalent hybrids lead to a robust separation of photoexcited charge carriers between two constituents, thus enhancing the photocatalytic activity. The small band gap makes the CNT/Ag3PO4 hybrids absorb sunlight from the ultraviolet to infrared region. Moreover, CNTs are not only effective sensitizers, but also highly active co-catalysts in hybrids. The results can be rationalized by the available experiments, thereby partly resolving a debate on the interpretation of the experimental results, and paving the way for developing highly efficient carbon-based nanophotocatalysts.
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Recent experiments have shown that the photocatalytic activity of g-C3N4 can be greatly enhanced by C60 modification, however, a fundamental understanding of its mechanistic operation is still lacking. Using first-principles calculations, the interfacial effects of C60/g-C3N4 nanocomposites on the electronic properties, charge transfer and optical response have been explored in detail. For different stacking patterns, the two constituents are always linked by van der Waals (vdW) forces without any exception, and form type-II heterojunctions in most cases. The valence band maximum and conduction band minimum of these heterostructures are dominated by the unsaturated nitrogen (N2) atoms and C60 molecule, respectively, which strongly interact with each other, resulting in strong charge transfer between the two involved constituents and an obvious bending of the g-C3N4 sheets. The unsaturated N2 atoms included in the interfaces have a significant influence on promoting the photocatalytic performance, while the existence of saturated nitrogen (N1 and N3) atoms lying in the interfaces will weaken the interfacial interactions between C60 molecules and the g-C3N4 monolayers. Moreover, the sensitive optical response and satisfactory type-II band alignment clearly show that the C60/g-C3N4 heterostructure is an outstanding photocatalyst for hydrogen production. We proposed a deep insight (the role of nitrogen) into understanding the improved photocatalytic ability of the C60/g-C3N4 nanocomposites, which may contribute to the rational design of both C60/g-C3N4 and g-C3N4-based nanocomposite photocatalysts.
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The coupling of carbon nanomaterials with semiconductor photocatalysts is a promising route to improve their photocatalytic performance. Herein, density functional theory was used to investigate the electronic structure, charge transfer, photocatalytic activity, and stability in a series of hybrid fullerene (C20, Li@C20, C26, Li@C26)/Ag3PO4(100) composites. When a Li atom is incorporated in fullerene, the adsorption energies significantly increase, although the change of interface distance is negligibly small due to the weak interface interaction. The charge transfer between constituents decreases with the C atom number of fullerene. Compared to pure Ag3PO4, the band gap of the composites is smaller, which enhances the visible-light absorption and photoinduced electron transfer. Most importantly, a type-II, staggered band alignment could be obtained in the C26-Ag3PO4(Li@C26-Ag3PO4) interface, leading to significantly reduced charge recombination and thus enhanced photocatalytic activity. These results reveal that fullerene modification would be an effective strategy to improve the photocatalytic performance of Ag3PO4 semiconductor photocatalysts.
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The construction of high-asymmetrical structures demonstrates significant potential in improving the functionality and distinctness of nanomaterials, but remains a considerable challenge. Herein, we develop a one-pot method to fabricate regioselective super-assembly of Prussian blue analogue (PBA) -- a PBA anisotropic structure (PBA-AS) decorated with epitaxial modules--using a step-by-step epitaxial growth on a rapidly self-assembled cubic substrate guided by thiocyanuric acid (TCA) molecules. The epitaxial growth units manifest as diverse geometric shapes, which are predominantly concentrated on the {100}, {111}, or {100}+{111} crystal plane of the cubic substrate. The crystal plane and morphology of epitaxial module can be regulated by changing the TCA concentration and reaction temperature, enabling a high level of controllability over specific assembly sites and structures. To illustrate the advantage of the asymmetrical structure, phosphated PBA-AS demonstrates improved performance in the oxygen evolution reaction compared to simple phosphated PBA nanocube. This method offers valuable insights for designing asymmetrical nanomaterials with intricate architectures and versatile functionalities.
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The rational design of electrocatalysts with well-designed compositions and structures for the oxygen evolution reaction (OER) is promising and challenging. Herein, we developed a novel strategy - a one-step double-cation etching sedimentation equilibrium strategy - to synthesize amorphous hollow Fe-Co-Ni layered double hydroxide nanocages with an outer surface of vertically interconnected ultrathin nanosheets (Fe-Co-Ni-LDH), which primarily depends on the in situ etching sedimentation equilibrium of the template interface. This unique vertical nanosheet-shell hierarchical nanostructure possesses enhanced charge transfer, increased active sites, and favorable kinetics during electrolysis, resulting in superb electrocatalytic performance for the oxygen evolution reaction (OER). Specifically, the Fe-Co-Ni-LDH nanocages exhibited remarkable OER activity in alkaline electrolytes and achieved a current density of 100 mA cm-2 at a low overpotential of 272 mV with excellent stability. This powerful strategy provides a profound molecular-level insight into the control of the morphology and composition of 2D layered materials.
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Catalytic performance of single-atom catalysts (SACs) relies fundamentally on the electronic nature and local coordination environment of the active site. Here, based on a machine-learning (ML)-aided density functional theory (DFT) method, we reveal that the intrinsic dipole in Janus materials has a significant impact on the catalytic activity of SACs, using 2D γ-phosphorus carbide (γ-PC) as a model system. Specifically, a local dipole around the active site is a key degree to tune the catalytic activity and can be used as an important descriptor with a high feature importance of 17.1% in predicting the difference of adsorption free energy (ΔGO* - ΔGOH*) to assess the activity of the oxygen evolution reaction. As a result, the catalytic performance of SACs can be tuned by an intrinsic dipole, in stark contrast to those external stimuli strategies previously used. These results suggest that dipole engineering and the revolutionary DFT-ML hybrid scheme are novel approaches for designing high-performance catalysts.
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Background and aims: Vitamin C, as an antioxidant, may play a role in the treatment of NAFLD. This research aimed to investigate the association of serum vitamin C levels with the risk of NAFLD and to further examine the causal relationship by Mendelian randomization (MR) method. Methods: The cross-sectional study selected 5,578 participants of the National Health and Nutrition Examination Survey (NHANES), 2005-2006 and 2017-2018. The association of serum vitamin C levels with NAFLD risk was evaluated under a multivariable logistic regression model. A two-sample MR study, using genetic data from large-scale genome-wide association studies (GWAS) of serum vitamin C levels (52,014 individuals) and NAFLD (primary analysis: 1,483 cases /17,781 controls; secondary analysis: 1,908 cases/340,591 controls), was conducted to infer causality between them. The inverse-variance-weighted (IVW) was applied as the main method of MR analysis. A series of sensitivity analyzes were used to evaluate the pleiotropy. Results: In the cross-sectional study, results showed that Tertile 3 group (Tertile 3: ≥1.06 mg/dl) had a significantly lower risk (OR = 0.59, 95% CI: 0.48 ~ 0.74, p < 0.001) of NAFLD than Tertile 1 group (Tertile 1: ≤0.69 mg/dl) after full adjustments. In regard to gender, serum vitamin C was protective against NAFLD in both women (OR = 0.63, 95% CI: 0.49 ~ 0.80, p < 0.001) and men (OR = 0.73, 95% CI: 0.55 ~ 0.97, p = 0.029) but was stronger among women. However, in the IVW of MR analyzes, no causal relationship between serum vitamin C levels and NAFLD risk was observed in the primary analysis (OR = 0.82, 95% CI: 0.47 ~ 1.45, p = 0.502) and secondary analysis (OR = 0.80, 95% CI: 0.53 ~ 1.22, p = 0.308). MR sensitivity analyzes yielded consistent results. Conclusion: Our MR study did not support a causal association between serum vitamin C levels and NAFLD risk. Further studies with greater cases are warranted to confirm our findings.
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The oxygen evolution reaction (OER) activity of transition metal (TM)-based (oxy)hydroxide is dominated by the number and nature of surface active sites, which are generally considered to be TM atoms occupying less than half of surface sites, with most being inactive oxygen atoms. Herein, based on an in situ competing growth strategy of bimetallic ions and OH- ions, a facile one-step method is proposed to modulate oxygen defects in NiFe-layered double hydroxide (NiFe-LDH)/FeOOH heterostructure, which may trigger the single lattice oxygen mechanism (sLOM). Interestingly, by only varying the addition of H2 O2 , one can simultaneously regulate the concentration of oxygen defects, the valence of metal sites, and the ratio of components. The proper oxygen defects promote synergy between the adsorbate evolution mechanism (AEM, metal redox chemistry) and sLOM (oxygen redox chemistry) of OER in NiFe-based (oxy)hydroxide, practically maximizing the use of surface TM and oxygen atoms as active sites. Consequently, the optimal NiFe-LDH/FeOOH heterostructure outperforms the reported non-noble OER catalysts in electrocatalytic activity, with an overpotential of 177 mV to deliver a current density of 20 mA cm-2 and high stability. The novel strategy exemplifies a facile and versatile approach to designing highly active TM-LDH-based OER electrocatalysts for energy and environmental applications.
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Heteroatom incorporation can effectively suppress the phase transition of layered sodium-ion battery cathode, but heteroatom behaviors during operating conditions are not completely understood at the atomic scale. Here, density functional theory calculations are combined with experiments to explore the mitigation behavior of Mg dopant and its mechanisms under operating conditions in P2-Na0.67Ni0.33Mn0.67O2. The void formed by Na extraction will pump some Mg dopants into Na layers from TM layers, and the collective diffusion of more than one Mg ion most likely occurs when the Mg content is relatively high in the TM layer, finally aggregating to form Mg-enrich regions (i.e., Mg segregation) apart from Ni vacancies. The void-pump-effect-induced Mg segregation effectively suppresses the P2-O2 phase transition owing to the stronger Mg-O electrostatic attraction that enhances the integrate of two adjacent oxygen layers and prevents the crack growth by mitigating the lattice volume variation under high-voltage cycling. Our work provides a fundamental understanding of heteroatom mitigation behavior in layered cathodes at the atomic level for next-generation energy storage technologies.
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BACKGROUND: Wound healing impairment is a dysfunction induced by hyperglycemia and its effect on endothelial precursor cells (EPCs) in type 2 diabetes mellitus. There is increasing evidence showing that exosomes (Exos) derived from adipose-derived mesenchymal stem cells (ADSCs) exhibit the potential to improve endothelial cell function along with wound healing. However, the potential therapeutic mechanism by which ADSC Exos contribute to wound healing in diabetic mice remains unclear. AIM: To reveal the potential therapeutic mechanism of ADSC Exos in wound healing in diabetic mice. METHODS: Exos from ADSCs and fibroblasts were used for high-throughput RNA sequencing (RNA-Seq). ADSC-Exo-mediated healing of full-thickness skin wounds in a diabetic mouse model was investigated. We employed EPCs to investigate the therapeutic function of Exos in cell damage and dysfunction caused by high glucose (HG). We utilized a luciferase reporter (LR) assay to analyze interactions among circular RNA astrotactin 1 (circ-Astn1), sirtuin (SIRT) and miR-138-5p. A diabetic mouse model was used to verify the therapeutic effect of circ-Astn1 on Exo-mediated wound healing. RESULTS: High-throughput RNA-Seq analysis showed that circ-Astn1 expression was increased in ADSC Exos compared with Exos from fibroblasts. Exos containing high concentrations of circ-Astn1 had enhanced therapeutic effects in restoring EPC function under HG conditions by promoting SIRT1 expression. Circ-Astn1 expression enhanced SIRT1 expression through miR-138-5p adsorption, which was validated by the LR assay along with bioinformatics analyses. Exos containing high concentrations of circ-Astn1 had better therapeutic effects on wound healing in vivo compared to wild-type ADSC Exos. Immunofluorescence and immunohistochemical investigations suggested that circ-Astn1 enhanced angiopoiesis through Exo treatment of wounded skin as well as by suppressing apoptosis through promotion of SIRT1 and decreased forkhead box O1 expression. CONCLUSION: Circ-Astn1 promotes the therapeutic effect of ADSC-Exos and thus improves wound healing in diabetes via miR-138-5p absorption and SIRT1 upregulation. Based on our data, we advocate targeting the circ-Astn1/miR-138-5p/SIRT1 axis as a potential therapeutic option for the treatment of diabetic ulcers.
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Photoelectrocatalytic performance of a system is fundamentally determined by the full absorption of sunlight and high utilization of photoexcited carriers, but efficiency of the latter is largely limited by inefficient charge transfer from the absorber to reactive sites. Here, we propose to construct directional charge transfer channels in a monolithically integrated electrode, taking carbon dots/carbon nitride (CCN) nanotubes and FeOOH/FeCo layered double hydroxide (FFC) nanosheets as a representative, to boost the photoassisted overall water splitting performance. Detailed experimental investigations and DFT calculations demonstrate that the interfacial C-O-Fe bonds between CCN and FFC act as charge transfer channels, facilitating the directional migration of the photogenerated carriers between CCN and FFC surfaces. Moreover, the in situ oxidized Fe/Co species by photogenerated holes trigger lattice oxygen activation, realizing the construction of the Fe-Co dual-site as the catalytic center and efficiently lowering the barrier energy for water oxidation. As a result, the CCN@FFC electrode shows multiple functionalities in photoelectrocatalysis: only a low overpotential of 68 mV, 182 mV, and 1.435 V is required to deliver 10 mA cm-2 current densities for the photoassisted HER, OER, and overall water splitting, respectively. This directional charge transfer modulation strategy may facilitate the design of highly active and cost-effective multifunctional catalysts for energy conversion and storage.
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We present a procedure to generate slow light with a large group index, wideband, and low dispersion in our suggested photonic crystal waveguide. By modulation of the declinations in the first two rows of air holes, the group index, the bandwidth, and the dispersion can be tuned effectively. Utilizing the two-dimensional plane wave expansion method (PWE) and the finite-difference time-domain method (FDTD), we demonstrate slow light with the group indices of 23, 35, and 45, respectively, while restricting the group-index variation within a 10% range. We accordingly attain an available bandwidth of 40.7, 23.7, and 5.1 nm, respectively. Meanwhile, the normalized delay-bandwidth product stays around 0.45, with minimal dispersion less than 0.2 (ps2/m) for all the cases.
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The novel Bi2O2Se, produced by the oxidation of the layered Bi2Se3, has been considered as one of the most promising candidates for the next-generation electronics owing to its high carrier mobility and air-stability. In this work, by using crystal structure prediction and first-principles calculations, we report the phase transformations from the hexagonal Bi2Se3to the monoclinic Bi2OSe2, and then to the tetragonal Bi2O2Se with the gradual oxidization. Owing to the difference in electronegativity between selenium (Se) and oxygen (O), the oxidation process is accompanied by an increase in bond ionicity. Our results shed light on the phenomena occurring in the interaction between the precursors Bi2Se3and O2and have a potential contribution to the application of optoelectronic devices. The intermediate Bi2OSe2with calculated band gap of 1.01 eV, may be a candidate for photovoltaic application in future.
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Microbial infections cause significant morbidity and mortality in neonates. Metagenomic next-generation sequencing is a hypothesis-free and culture-free test that enables broad identification of pathogens and antimicrobial resistance genes directly from clinical samples within 24 h. In this study, we used mNGS for etiological diagnosis and monitoring the efficacy of antibiotic treatment in a cohort of neonatal patients with severe infections. The median age was 19.5 (3-52) days, median gestational age was 37.96 (31-40+3) weeks, and the median birth weight was 3,261 (1,300-4,300) g. The types of infectious diseases included pneumonia, sepsis, and meningitis. mNGS reported microbial findings in all cases, which led to changes in antibiotic treatment. These included cases of Mycobacterium tuberculosis, Legionella pneumophila, and Bacillus cereus. Eight of ten infants recovered after antibiotic adjustment and showed normal development during follow-up. On the other hand, neurological retardation was seen in two infants with meningitis. mNGS enabled etiological diagnosis and guided antibiotic therapy when all conventional methods failed to discover the culprit. It has the potential to cut down the overall cost and burden of disease management in neonatal infections.