Plasmonic Ag Core-Satellite Nanostructures with a Tunable Silica-Spaced Nanogap for Surface-Enhanced Raman Scattering

Development of Au Nanoparticle Two-Dimensional Assemblies Dispersed with Au Nanoparticle-Nanostar Complexes and Surface-Enhanced Raman Scattering Activity

We recently found that polyvinylpyrrolidone (PVP)-protected metal nanoparticles dispersed in water/butanol mixture spontaneously float to the air/water interface and form two-dimensional assemblies due to classical surface excess theory and Rayleigh-Bénard-Marangoni convection induced by butanol evaporation. In this study, we found that by leveraging this principle, a unique structure is formed where hetero gold nanospheres (AuNPs)/gold nanostars (AuNSs) complexes are dispersed within AuNP two-dimensional assemblies, obtained from a mixture of polyvinylpyrrolidone-protected AuNPs and AuNSs that interact electrostatically with the AuNPs. These structures were believed to form as a result of AuNPs/AuNSs complexes formed in the water/butanol mixture floating to the air/water interface and being incorporated into the growth of AuNP two-dimensional assemblies. These structures were obtained by optimizing the amount of mixed AuNSs, with excessive addition resulting in the formation of random three-dimensional network structures. The AuNP assemblies dispersed with AuNPs/AuNSs complexes exhibited significantly higher Raman (surface-enhanced resonance Raman scattering: SERRS) activity compared to simple AuNP assemblies, while the three-dimensional network structure did not show significant SERRS activity enhancement. These results demonstrate the excellent SERRS activity of AuNP two-dimensional assemblies dispersed with hetero AuNPs/AuNSs complexes.

An anisotropic nanobox based core-shell-satellite nanoassembly of multiple SERS enhancement with heterogeneous interface for stroke marker determination

Herein, A novel gold-silver alloy nanobox (AuAgNB)@SiO₂-gold nanosphere (AuNP) nanoassembly based on core-shell-satellite structure is fabricated and applied to the surface-enhanced Raman scattering (SERS) detection of S100 calcium-binding protein B protein (S100B). It contains an anisotropic hollow porous AuAgNB core with rough surface, an ultrathin silica interlayer labeled with reporter molecules, and AuNP satellites. The nanoassemblies were systematically optimized by tuning the reporter molecules concentration, silica layer thickness, AuAgNB size, and the size and number of AuNP satellite size. Remarkably, AuNP satellites are adjacent to AuAgNB@SiO₂, developing AuAg-SiO₂-Au heterogeneous interface. With the strong plasmon coupling between AuAgNB and AuNP satellites, chemical enhancement from heterogeneous interface, and the tip "hot spots" of AuAgNB, the SERS activity of the nanoassemblies was multiply enhanced. Additionally, the stability of nanostructure and Raman signal was significantly improved by the silica interlayer and AuNP satellites. Eventually, the nanoassemblies were applied for S100B detection. It demonstrated satisfactory sensitivity and reproducibility with a wide detection range of 10 fg/mL-10 ng/mL and a limit of detection (LOD) of 1.7 fg/mL. This work based on the AuAgNB@SiO₂-AuNP nanoassemblies with multiple SERS enhancements and favorable stability demonstrates the promising application in stroke diagnosis.

Microfluidic SERS devices: brightening the future of bioanalysis

A new avenue has opened up for applications of surface-enhanced Raman spectroscopy (SERS) in the biomedical field, mainly due to the striking advantages offered by SERS tags. SERS tags provide indirect identification of analytes with rich and highly specific spectral fingerprint information, high sensitivity, and outstanding multiplexing potential, making them very useful in in vitro and in vivo assays. The recent and innovative advances in nanomaterial science, novel Raman reporters, and emerging bioconjugation protocols have helped develop ultra-bright SERS tags as powerful tools for multiplex SERS-based detection and diagnosis applications. Nevertheless, to translate SERS platforms to real-world problems, some challenges, especially for clinical applications, must be addressed. This review presents the current understanding of the factors influencing the quality of SERS tags and the strategies commonly employed to improve not only spectral quality but the specificity and reproducibility of the interaction of the analyte with the target ligand. It further explores some of the most common approaches which have emerged for coupling SERS with microfluidic technologies, for biomedical applications. The importance of understanding microfluidic production and characterisation to yield excellent device quality while ensuring high throughput production are emphasised and explored, after which, the challenges and approaches developed to fulfil the potential that SERS-based microfluidics have to offer are described.

Assembling of anisotropic plasmonic sheet-core-satellites for simultaneous ultrasensitive detection of MC-LR toxin

An anisotropic plasmonic sheet-core-satellite (PSCS) superstructure can be controlled via competitive binding between aptamer/MC-LR conjugation and aptamer-ssDNA hybridization. SERS nanotags can be incorporated into anisotropic plasmonic sheet-cores, e.g., pGO/nanorods, or pGO/hollow AgCl : Au nanoplates so as to fabricate an aptasensor for "ON-OFF" detection of MC-LR toxin. Preparing a PSCS superstructure and detection of toxin can be simultaneously completed so as to simplify the detection procedure of MC-LR toxin. Detection sensitivity of MC-LR toxin can be optimized by controlling aspect ratios or hollow interiors of plasmonic core nanoparticles. Herein, a limit of detection (0.635 pM) with a wide linear range from 1 pM to 10 nM can be obtained via optimized PSCS of pGO/nanorod/dotnanotags. When the aptasensor was tested in real samples, the PSCS shows excellent recoveries from 96.6% to 104.5% with relative standard deviation (RSD) lower than 2.89% in spiked reservoir samples. It can be predicted that a one-step facile nanofabrication/aptasensing approach would be extensively applied for rapid detection of some other environmental contaminants.

Revealing the Hemispherical Shielding Effect of SiO2@Ag Composite Nanospheres to Improve the Surface Enhanced Raman Scattering Performance

Many studies widely used SiO₂@Ag composite nanospheres for surface enhanced Raman scattering (SERS), which mainly contributes to electromagnetic enhancement. In addition to experiments, previous simulations mostly adopted a two-dimensional model in SERS research, resulting in the three-dimensional information being folded and masked. In this paper, we adopted the three-dimensional model to simulate the electric field distribution of SiO₂@Ag composite nanospheres. It is found that when the Ag nanoparticles are distributed densely on the surface of SiO₂ nanospheres, light cannot pass through the upper hemisphere due to the local surface plasmon resonance (LSPR) of the Ag nanoparticles, resulting in the upper hemisphere shielding effect; and if there are no Ag nanoparticles distributed densely on the surface of SiO₂ nanospheres, the strong LSPR cannot be formed, so the incident light will be guided downward through the whispering gallery mode of the spherical structure. At the same time, we designed relevant experiments to synthesize SiO₂@Ag composite nanosphere as SERS substrate and used Rhodamine 6G as a probe molecule to study its SERS performance. This design achieved a significant SERS effect, and is very consistent with our simulation results.

Recent Progress of SERS Nanoprobe for pH Detecting and Its Application in Biological Imaging

As pH value almost affects the function of cells and organisms in all aspects, in biology, biochemical and many other research fields, it is necessary to apply simple, intuitive, sensitive, stable detection of pH and base characteristics inside and outside the cell. Therefore, many research groups have explored the design and application of pH probes based on surface enhanced Raman scattering (SERS). In this review article, we discussed the basic theoretical background of explaining the working mechanism of pH SERS sensors, and also briefly described the significance of cell pH measurement, and simply classified and summarized the factors that affected the performance of pH SERS probes. Some applications of pH probes based on surface enhanced Raman scattering in intracellular and extracellular pH imaging and the combination of other analytical detection techniques are described. Finally, the development prospect of this field is presented.

Biomacromolecular-Assembled Nanoclusters: Key Aspects for Robust Colloidal SERS Sensing

Superstructures of gold nanospheres offer augmented surface-enhanced Raman scattering (SERS) activities beyond the limits of their individual building blocks. However, for application as reliable and quantitative colloidal SERS probes, some key aspects need to be considered to combine efficiency and robustness with respect to hotspot excitation, analyte adsorption, signal stability, and colloidal stability. For this purpose, we studied core/satellite superstructures with spherical cores as a simple optically isotropic model system. Superstructures of different core sizes were assembled using bovine serum albumin (BSA), which serves as a non-specific biomacromolecular linker and provides electrosteric stabilization. We show that the "noisy" spectral footprint of the protein coating may serve as an internal standard, which allows accurate monitoring of the adsorption kinetics of analytes. The SERS activity was quantified using 4-mercaptobenzoic acid (MBA) as an aromatic low-molecular-weight model analyte. The molar SERS efficiency was studied by variation of the particle (Au⁰) and analyte concentrations with a limit of detection of 10^-7 M MBA. The practical importance of colloidal stability for robust measurement conditions was demonstrated by comparing the superstructures with their citrate-stabilized or protein-coated building blocks. We explain the theoretical background of hotspot formation by a leader/follower relationship of asymmetric control between the core and the satellites and give practical guidelines for robust colloidal SERS sensing probes.

Gold Nanorod Array-Bridged Internal-Standard SERS Tags: From Ultrasensitivity to Multifunctionality

Bimetallic gold core-silver shell (Au@Ag) surface-enhanced Raman scattering (SERS) tags draw broad interest in the fields of biological and environmental analysis. In reported tags, silver coating tended to smooth the surface and merge the original hotspot of Au cores, which was disadvantageous to signal enhancement from the aspect of surface topography. Herein, we developed gold nanorod (AuNR)-bridged Au@Ag SERS tags with uniform three-dimensional (3D) topography for the first time. This unique structure was achieved by selecting waxberry-like Au nanoparticles (NPs) as cores, which were capped by vertically oriented AuNR arrays. Upon selective surface blocking with thiol-ligands, Ag NPs were controlled to anisotropically grow on the tips of the AuNRs, producing high-density homo- (Ag-Ag) and hetero- (Au-Ag) hotspots in a single NP. The 3D hotspots rendered this NP extraordinary SERS enhancement ability (an analytical enhancement factor of 3.4 × 10⁶) 30 times higher than the counterpart with a smooth surface, realizing signal detection from a single NP. More importantly, multiplexing signals ("blank" or multiplex "internal standard") can be achieved by simply changing thiol-ligands, as exemplified in the synthesis of NPs with 8 signatures. Furthermore, the multifunctionality has been demonstrated in living cell/in vivo imaging, photothermal therapy, and SERS substrates for ratiometric quantitative analysis, relying on the inherent internal standard signal. The prepared Au@Ag NPs have great potential as standard tools in many SERS-related fields.

Growth of Spherical Gold Satellites on the Surface of Au@Ag@SiO2 Core-Shell Nanostructures Used for an Ultrasensitive SERS Immunoassay of Alpha-Fetoprotein

The identification and detection of cancer biomarkers in early stages is an important issue for the therapy of cancer. However, most methods are time-consuming and have limited sensing sensitivity and specificity. In this work, we prepared a novel plasmonic multilayered core-shell-satellite nanostructure (Au@Ag@SiO₂-AuNP) consisting of a gold nanosphere with a silver coating core (Au@Ag), an ultrathin continuous silica (SiO₂) shell, and a high coverage of gold nanosphere (AuNP) satellites. The Au@Ag core is a prominent surface enhanced Raman scattering (SERS) platform, and the thin SiO₂ layer exhibits a long-range plasmon coupling between the Au@Ag core to the AuNP satellites, further leading to enhanced Raman scattering. Meanwhile, the outer AuNP satellites have a high biocompatibility and long-term stability. Combining the above advantages, the well-designed metallic nanoassemblies would be a promising candidate for SERS-based applications in biochemistry. For specific detection of alpha-fetoprotein (AFP), we utilized the SERS-active core-shell-satellite nanostructures modified with AFP antibody as immune probes and nitrocellulose membrane (NC) stabilized captured anti-AFP antibodies as solid substrate. To improve the detection performance, we further systematically optimized the parameters, including the silver coating thickness of the Au@Ag core and the density and size of the satellite AuNPs. Under the optimized conditions, AFP could be detected by the SERS-based sandwich immunoassay with an ultralow detection limit of 0.3 fg/mL, and the method exhibited a wide linear response from 1 fg/mL to 1 ng/mL. The limit of detection (LOD) was considerably lower than conventional methods in the literature. This work relies on the unique Au@Ag@SiO₂-AuNP nanostructures as the immune probe develops a new outlook for the application of multilayered nanoassemblies and demonstrates the great potential in early tumor marker detection.

Modular assembly of plasmonic core-satellite structures as highly brilliant SERS-encoded nanoparticles

Herein, we present a fabrication approach that produces homogeneous core-satellite SERS encoded particles with minimal interparticle gaps (<2-3 nm) and maximum particle loading, while positioning the encoding agents at the gaps. Integration of plasmonic building blocks of different sizes, shapes, compositions, surface chemistries or encoding agents is achieved in a modular fashion with minimal modification of the general synthetic protocol. These materials present an outstanding optical performance with homogeneous enhancement factors over 4 orders of magnitude as compared with classical SERS encoded particles, which allows their use as single particle labels.

Au-Protected Ag Core/Satellite Nanoassemblies for Excellent Extra-/Intracellular Surface-Enhanced Raman Scattering Activity

Silver nanoparticles (AgNPs) and their assembled nanostructures such as core/satellite nanoassemblies are quite attractive in plasmonic-based applications. However, one biggest drawback of the AgNPs is the poor chemical stability which also greatly limits their applications. We report fine Au coating on synthesized quasi-spherical silver nanoparticles (AgNSs) with few atomic layers to several nanometers by stoichiometric method. The fine Au coating layer was confirmed by energy-dispersive X-ray spectroscopy elemental mapping and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy. The optimized minimal thickness of Au coating layer on different sized AgNSs (22 nm Ag@0.9 nm Au, 44 nm Ag@1.8 nm Au, 75 nm Ag@2.9 nm Au, and 103 nm Ag@0.9 nm Au) was determined by extreme chemical stability tests using H₂O₂, NaSH, and H₂S gas. The thin Au coating layer on AgNSs did not affect their plasmonic-based applications. The core/satellite assemblies based on Ag@Au NPs showed the comparable SERS intensity and uniformity three times higher than that of noncoated Ag core/satellites. The Ag@Au core/satellites also showed high stability in intracellular SERS imaging for at least two days, while the SERS of the noncoated Ag core/satellites decayed significantly. These spherical Ag@Au NPs can be widely used and have great advantages in plasmon-based applications, intracellular SERS probes, and other biological and analytical studies.

Three-Dimensional SERS Substrates Formed with Plasmonic Core-Satellite Nanostructures

We demonstrate three-dimensional surface-enhanced Raman spectroscopy (SERS) substrates formed by accumulating plasmonic nanostructures that are synthesized using a DNA-assisted assembly method. We densely immobilize Au nanoparticles (AuNPs) on polymer beads to form core-satellite nanostructures for detecting molecules by SERS. The experimental parameters affecting the AuNP immobilization, including salt concentration and the number ratio of the AuNPs to the polymer beads, are tested to achieve a high density of the immobilized AuNPs. To create electromagnetic hot spots for sensitive SERS sensing, we add a Ag shell to the AuNPs to reduce the interparticle distance further, and we carefully adjust the thickness of the shell to optimize the SERS effects. In addition, to obtain sensitive and reproducible SERS results, instead of using the core-satellite nanostructures dispersed in solution directly, we prepare SERS substrates consisting of closely packed nanostructures by drying nanostructure-containing droplets on hydrophobic surfaces. The densely distributed small and well-controlled nanogaps on the accumulated nanostructures function as three-dimensional SERS hot spots. Our results show that the SERS spectra obtained using the substrates are much stronger and more reproducible than that obtained using the nanostructures dispersed in solution. Sensitive detection of melamine and sodium thiocyanate (NaSCN) are achieved using the SERS substrates.

Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents

Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe3O4@SiO2@Ag microflowers) were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe3O4@SiO2@Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe3O4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe3O4@SiO2@Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus, with minimum inhibitory concentrations of 10 and 20 μg mL-1, respectively. The microflowers also showed enhanced effect compared with bare Fe3O4@SiO2@Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the two components. Moreover, the antimicrobial effect was maintained at more than 90% after five cycling assays, indicating the high stability of the product. These findings reveal that Van/Fe3O4@SiO2@Ag microflowers exhibit promising applications in the antibacterial fields.

Sonochemical synthesis of highly branched flower-like Fe3O4@SiO2@Ag microcomposites and their application as versatile SERS substrates

We report a novel strategy for the synthesis of magnetic-based flower-like silver composite microspheres (Fe₃O₄@SiO₂@Ag microflowers) with a highly branched shell structure through a sonochemical-assisted method. The obtained Fe₃O₄@SiO₂@Ag microflowers possess good dispersity, high magnetic responsiveness, and highly reproducible structures. The size and morphology of the silver petal shell of these microflowers can be easily controlled by varying the experimental parameters. The silver petal provides an effectively large surface area for forming sufficient plasmonic hot spots and capturing target molecules. The microscale magnetic core endows microflowers with superior magnetic nature to enrich targeted analytes and create abundant interparticle hot spots through magnetism-induced aggregation. Hence, Fe₃O₄@SiO₂@Ag microflowers could be a versatile SERS substrate, as verified by the detection of the non-adsorbed R6G molecules and the adsorbed pesticide thiram, with a detection limit as low as 1 × 10^-14 M and 1 × 10^-11 M, respectively. We further demonstrate that aptamer-functionalized microflowers can easily capture S. aureus in tap water and significantly enhance their SERS signal. Moreover, the microflowers can be easily recycled because of the intrinsic magnetism of the Fe₃O₄ cores, which indicate a new route in eliminating the "single-use" problem of traditional SERS substrates. These advantages make the microflowers powerful SERS probes for chemical and biological analyses.

Facile Synthesis of Au-Coated Magnetic Nanoparticles and Their Application in Bacteria Detection via a SERS Method

This study proposes a facile method for synthesis of Au-coated magnetic nanoparticles (AuMNPs) core/shell nanocomposites with nanoscale rough surfaces. MnFe2O4 nanoparticles (NPs) were first modified with a uniform polyethylenimine layer (2 nm) through self-assembly under sonication. The negatively charged Au seeds were then adsorbed on the surface of the MnFe2O4 NPs through electrostatic interaction for Au shell formation. Our newly developed sonochemically assisted hydroxylamine seeding growth method was used to grow the adsorbed gold seeds into large Au nanoparticles (AuNPs) to form a nanoscale rough Au shell. Au-coated magnetic nanoparticles (AuMNPs) were obtained from the intermediate product (Au seeds decorated magnetic core) under sonication within 5 min. The AuMNPs were highly uniform in size and shape and exhibited satisfactory surface-enhanced Raman scattering (SERS) activity and strong magnetic responsivity. PATP was used as a probe molecule to evaluate the SERS performance of the synthesized AuMNPs with a detection limit of 10(-9) M. The synthesized AuMNPs were conjugated with Staphylococcus aureus (S. aureus) antibody for bacteria capture and separation. The synthesized plasmonic AuNR-DTNB NPs, whose LSPR wavelength was adjusted to the given laser excitation wavelength (785 nm), were conjugated with S. aureus antibody to form a SERS tag for specific recognition and report of the target bacteria. S. aureus was indirectly detected through SERS based on sandwich-structured immunoassay, with a detection limit of 10 cells/mL. Moreover, the SERS intensity at Raman peak of 1331 cm(-1) exhibited a linear relationship to the logarithm of bacteria concentrations ranging from 10(1) cells/mL to 10(5) cells/mL.

Stimuli-Responsive Extraction and Ambidextrous Redispersion of Zwitterionic Amphiphile-Capped Silver Nanoparticles

Citrate-stabilized silver nanoparticles (AgNPs) were functionalized with a pH-responsive amphiphile, 3-[(2-carboxy-ethyl)-hexadecyl-amino]-propionic acid (C16CA). At pH ∼ 4, the zwitterionic C16CA assembled into lamellar structures due to the protonation of the amine groups of the amphiphile that neutralized the anionic charge of the carboxylate groups. The lamellar supramolecules incorporated the AgNPs into their 3D network and extracted them from water. C16CA supramolecules dissolved into water (at pH > 6) and organic solvents; consequently, the recovered C16CA-AgNPs were redispersed not only to water but also to chloroform and tetrahydrofuran without any additional functionalization. C16CA acted as a pH-responsive stabilizer of AgNPs and formed a solvent-switchable molecular layer such as a bilayered structure in water and densely packed monolayer in chloroform and tetrahydrofuran. Redispersion of the AgNPs was achieved in different solvents by changing the solvent affinity of the adsorbed C16CA molecular layer based on the protonation of the amine groups of the pH-responsive amphiphile. The morphology of redispersed AgNPs did not change during the recovery and redispersion procedure, due to the high steric effect of the network structure of C16CA supramolecules. These observations can lead to a novel solvent-exchange method for nanocrystals without aggregation and loss of nanocrystals, and they enable effective preparations of stimuli-responsive plasmonic nanomaterials.

Sensitive Glycoprotein Sandwich Assays by the Synergistic Effect of In Situ Generation of Raman Probes and Plasmonic Coupling of Ag Core-Au Satellite Nanostructures

Sensitive surface-enhanced Raman scattering (SERS) assays of glycoproteins have been proposed using p-aminothiophenol (PATP)-embedded Ag core-Au satellite nanostructures modified with p-mercaptophenylboronic acid (PMBA) and the self-assembled monolayer of PMBA on a smooth gold-coated wafer. The apparent Raman probe PATP on the surfaces of the Ag cores underwent a photodimerization to generate 4,4'-dimercaptoazobenzene (DMAB) in situ upon excitation of laser, and the in situ generated DMAB acted as the actual Raman probe with considerably strong SERS signals, which was further enhanced by the plasmonic coupling of the Ag core-Au satellite nanostructures due to the synergistic effect. The sandwich assays of glycoproteins showed high sensitivity and excellent selectivity against nonglycoproteins. The Ag core-Au satellite SERS nanostructures can be used for highly sensitive SERS assays of other analytes.

Surface- and Tip-Enhanced Raman Spectroscopy in Catalysis

Surface- and tip-enhanced Raman spectroscopy (SERS and TERS) techniques exhibit highly localized chemical sensitivity, making them ideal for studying chemical reactions, including processes at catalytic surfaces. Catalyst structures, adsorbates, and reaction intermediates can be observed in low quantities at hot spots where electromagnetic fields are the strongest, providing ample opportunities to elucidate reaction mechanisms. Moreover, under ideal measurement conditions, it can even be used to trigger chemical reactions. However, factors such as substrate instability and insufficient signal enhancement still limit the applicability of SERS and TERS in the field of catalysis. By the use of sophisticated colloidal synthesis methods and advanced techniques, such as shell-isolated nanoparticle-enhanced Raman spectroscopy, these challenges could be overcome.

SERS-based immunoassay using a core–shell SiO2@Ag immune probe and Ag-decorated NiCo2O4 nanorods immune substrate

A novel sandwich structure consisting of the SiO₂@Ag immune probe and the Ag-decorated NNRs substrate was used to detect AFP and a detection limit is as low as 2.1 fg mL⁻¹.

Iron-Carbonyl Aqueous Vesicles (MCsomes) by Hydration of [Fe(CO){CO(CH2)5CH3}(Cp)(PPh3)] (FpC6): Highly Integrated Colloids with Aggregation-Induced Self-Enhanced IR Absorption (AI-SEIRA)

Self-assembly of hydrophobic molecules into aqueous colloids contradicts common chemical intuition, but has been achieved through hydration of [Fe(CO){CO(CH2)5CH3}(Cp)(PPh3)] (FpC6). FpC6 has no surface activity, no NMR signals in D2O and no critical aggregation concentration (CAC) in H2O. The molecule, however, contains both acyl and terminal CO groups that are prone to being hydrated. By adding water to a solution in THF, self-assembly of FpC6 can be initiated through water-carbonyl interactions (WCIs) with the highly polarized acyl CO groups. This aggregation subsequently enhances the hydration of the acyl CO groups and also induces the WCI of otherwise unhydrated terminal CO groups. The resultant metal-carbonyl aggregates have been proved to be bilayer vesicles with iron complexes exposed towards water and alkyl chains forming inner walls (MCsomes). These MCsomes show high structure integration upon dilution due to the hydrophobic nature of the building blocks. The highly polarized CO groups on the surface of the MCsomes result in a negative zeta potential (-65 mV) and create a local electric field, which significantly enhances the IR absorption of CO groups by more than 100-fold. This is the first discovery of aggregation-induced self-enhanced IR absorption (AI-SRIRA) without the assistant of external dielectric substrates. Highly integrated MCsomes are, therefore, promising as a novel group of materials, for example, for IR-based sensing and imaging.