Photoswitching of Lipid Vesicles In-Liquid
In this study researchers used transient infrared nanoscopy and a microfluidic liquid cell to observe azobenzene-based lipid vesicles in their native environment. This novel setup achieved lable-free observation of photoswitching dynamics with 50 ms temporal and few 10 nm spatial resolution.The findings demonstrate s-SNOM’s effectiveness in nanoscale studies of soft matter and its potential applications in nanomedicine and drug delivery, highlighting the microfluidic cell’s crucial role in real-time, native environment analysis of nanocarriers.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
T. Gölz et al., Arxiv 2406.02513 (2024)
Imaging Live Bacteria In-Liquid
The study demonstrates the imaging of living bacteria in a liquid environment using s-SNOM through a silicon nitride (SiN) membrane, where bacteria from a culture were incubated in a nutrient medium, drop-casted onto the membrane, and observed in their native state. The s-SNOM images captured the dynamic behavior of the bacteria as they adhered to the membrane, moved, and divided over a period of 0 to 74 minutes. The bacteria appeared brighter in the infrared images compared to the surrounding water, with cells oriented mostly parallel to the membrane and showing widths of about 400 nm. The images documented the cells’ movement and adhesion changes, with numerous relocations occurring within minutes. Despite these movements, the images remained unblurred during the typical acquisition time of 30 sec to 1 min.
This imaging technique provided valuable insights into the real-time dynamics of living bacteria in a liquid environment. The ability to capture such detailed movements and interactions at the nanoscale enhances our understanding of bacterial behavior and their interactions with surfaces.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Kaltenecker et al., Scientific Reports 11, 21860 (2021)
Chemotherapy Impact on a Single Cell
Osteosarcoma, a common and aggressive bone cancer mainly affecting children and young adults, was analyzed on a single-cell level using synchrotron-based nano-FTIR spectroscopy to assess the impact of cisplatin treatment. Significant shifts in protein, lipid, and DNA peaks were observed: the Amide I band moved from 1657 cm-1 to 1633 cm-1, and the Amide II band from 1546 cm-1 to 1539 cm-1, indicating structural and conformational changes in proteins. Lipid d(CH2) bands shifted from 1465 cm-1 to 1446 cm-1, suggesting alterations in lipid structures and dynamics, and DNA ?(CC) and ?(CO) bands shifted from 967 cm-1 to 977 cm-1 and 1171 cm-1 to 1166 cm-1, showing changes in the DNA backbone and phosphate groups. These findings provide nanoscale insights into cisplatin's mechanism of action, aiding in anticancer therapy development. Read the full article for detailed nanoscale insights into cisplatin's mechanism of action, highlighting the drug's impact on cellular components.
nano-FTIR reveals the subcellular impact of cisplatin at the nanoscale, aiding targeted drug development and personalized cancer treatments through its high-resolution chemical and morphological insights.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Carvalho et al., Scientific Reports 14, 17166 (2024)
Enhancing Gas Flow in Copolymer Membranes
This study examines the gas permeability and nanoscale morphology of bio-based polyether-block-amide copolymer PEBAX® RNEW membranes, known for high gas separation and eco-friendliness, by comparing solvent casting and extrusion methods. Nano-FTIR spectroscopy provided key insights into local polymer composition and structure, identifying nanoscale features overlooked by traditional techniques. By analyzing sub-micrometer cross-sections with nano-FTIR in the range of 1000 to 1800 cm-1, the authors detected a 50 nm thick crystalline PEO surface layer on extruded membranes. This layer led to up to 50% lower gas permeability compared to solvent-cast membranes. Using nano-FTIR as a standard tool could allow precise control over membrane properties, enhancing applications like carbon capture, natural gas processing, and hydrogen production.
IR-neaSCOPE advances gas separation technology by revealing polymer crystalline status, enhancing understanding of membrane morphology and gas permeability, and promoting efficient, eco-friendly solutions for gas purification, environmental protection, and sustainable materials industries.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
David et al., J. Membr. Sci. 708, 123001 (2024)
Plasmons in Kagome Metals
This study explores infrared nano-imaging of thin flakes of the Kagome metal CsV3Sb5, focusing on plasmon polaritons. The frequency-momentum dispersion data enabled the inference of the out-of-plane dielectric function, which is challenging to measure with conventional optics. Using s-SNOM, researchers observed tunable propagating plasmon waves, with wavelengths adjustable by flake thickness. The study found that correlation effects might alter the real part of the dielectric function from negative to positive over mid-IR frequencies, transforming surface plasmons into hyperbolic bulk plasmons and reducing dissipation. Findings showed that CsV3Sb5 hosts tunable plasmons across IR wavelengths of 860-1700 cm-1. Furthermore, experiments on different flake thicknesses confirmed high-quality factors for plasmons and higher-order hyperbolic branches with enhanced confinement. This research advances understanding of hyperbolic plasmons driven by electronic correlations, promising applications in mid-IR to far-IR plasmonic devices.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Shiravi et al., Nature Communications 15, 5389 (2024)
Enhanced Perovskite Phonon Polaritons
This research focuses on strontium titanate (SrTiO3) perovskite membranes, crucial for their potential to enhance infrared photonics through their ability to support highly confined surface phonon polaritons. Key findings include the experimental observation of mode splitting in 100 nm thick membranes, demonstrating epsilon-near-zero modes and significant phonon polariton confinement. The near-field amplitude and phase variations of surface phonon polaritons in SrTiO3 perovskite membranes illustrate their spatial dynamics and enhanced propagation characteristics, with a focused analysis on confinement and dispersion properties at specific frequencies like 590 cm-1. Measuring down to 400 cm-1 was crucial to capture the full spectral response of the SrTiO3 membranes.
The s-SNOM findings on these perovskite materials have broad applications in sensing, optical switching, and nonlinear optics. The ability to manipulate light on nanoscales using SrTiO3 perovskite membranes enables the development of efficient nanoscale optical devices.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Xu et al., Nature Communications 15, 4743 (2024)
Advances in Dental Materials
The degradation of dental fillings poses a significant challenge, incurring high costs for repeated treatments and impacting millions globally; this underscores the urgent need for more durable materials. The authors use nano-FTIR to analyze dental materials at the molecular level providing detailed insights into the chemical composition of dental composites and adhesives. It enables precise maps of the interfaces between different components in fillings, crucial for assessing bonding effectiveness and mechanical properties. The study also applies FTIR imaging spectroscopy to various adhesives, capturing high-resolution reflectance images at different wavenumbers and detailing molecular resonances. Through detailed spectral analysis, researchers can identify specific chemical vibrations that reveal material composition and integrity, which are essential for enhancing the clinical performance and durability of dental restorations.nano-FTIR insights will guide the development of dental materials tailored to resist shrinkage and microleakage, enhancing restoration longevity.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Beddoe et al., Acta Biomaterialia 168, 309-322, (2023)
Single Protein IR Nanospectroscopy
The article from the Institute for Molecular Science discusses a breakthrough in observing single proteins using nano-FTIR, enabling the detection of infrared vibrational spectra of a single protein. This advancement allows for analyzing extremely small samples, which was previously challenging with conventional methods. The research is significant for understanding protein functions and interactions, and it opens new possibilities in nanoscale infrared spectroscopy applications across various fields. The study represents a major step in ultra-sensitive and high-resolution imaging using mid-infrared light.nano-FTIR, as demonstrated in the study, opens up diverse applications in fields like molecular biology for precise protein analysis, materials science for nanomaterial characterization, and medical diagnostics for identifying molecular markers in diseases.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Nishida et al., Nano Lett. 2024
nano-Vesicle Tumor Diagnostic
Cells communicate by releasing tiny, membrane-bound vesicles, pivotal in transmitting bioactive molecules. These vesicles are not just cellular messengers; they play a crucial role in the development and spread of tumors. One intriguing aspect of these vesicles is their protein composition, which changes in correlation with the severity of malignancy. This study dives into this world of microscopic communication using nano-FTIR to examine the subtle differences in individual small extracellular vesicles related to cancer.Xue et al. discovered that as a tumor becomes more malignant, the ratio of amide I/II absorption in these vesicles increases. Ratio which corelates directly with the decrease in a-helix and random coil structures and increase of ß-sheet and ß-turn structures. The use of nano-FTIR spectroscopy is proving to be invaluable in detecting these small but critical variations. This research paves the way for a novel, noninvasive approach to understanding cancer's progression. It holds the promise of uncovering new biomarkers for cancer, potentially revolutionizing early detection methods.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Xue et al., J. Am. Chem. 144, 20278 (2022)
Nano-to-Micro Silk Fiber Morphing
Silk is a uniquely strong biomaterial, remarkable for its simple protein components. Despite numerous attempts, replicating silk synthetically remains a challenge. A groundbreaking discovery in silk fiber production was the formation of nanoscale compartments. These compartments facilitate a reversible transformation of silk proteins. They transition from their native structure into crystalline ß-sheets, a process that can be reversed. This reversibility is key to modifying the final mechanical properties of silk, opening doors to custom-tailored silk products. This customization is achieved by controlling the silk proteins' structural changes and their self-assembly into larger molecular formations.nano-FTIR spectroscopy has enabled researchers to closely examine protein structures at the nanometer level. This technique is especially beneficial for analyzing protein complexes and the stages of protein aggregation into fibers. It combines the morphological insights from AFM with the detailed structural information from FTIR spectroscopy. The team conducted qualitative tests with nano-FTIR spectra on different protein structures - from individual monomers to nanocompartments and fibrils - confirming the effectiveness of their method.This synergy of nano-FTIR spectroscopy and atomic force microscopy has been pivotal in deciphering the reversible transitions of silk proteins. It's a cornerstone in the journey towards developing more sophisticated and versatile silk-based materials.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Eliaz et al., Nature Communications 13, 7856 (2022)
Polaritons Defy Symmetry
Nanoscale polaritons are crucial for nanophotonic devices. Hyperbolic polaritons (HPs) in high-symmetry crystals often lack directionality. In a recent eLight publication, scientists led by Profs. Zhang, Li, and Dai introduced a technique for anisotropic HP excitation and propagation. They discovered hyperbolic shear polaritons in low-symmetry crystals with enhanced directional propagation. This approach allows control of HPs' mirror symmetry without needing low crystalline symmetry. It enables tunable asymmetric polariton propagation, expanding possibilities for nanoscale light control and reconfigurable polaritonic devices.Introduced method breaks mirror symmetry in crystal polaritons, enabling control of asymmetry in HP responses. Offers nanoscale light manipulation and potential applications in nanoimaging, photonics, and quantum physics.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Hu et al, eLight 3, 14 (2023)
SciTechDaily Article
Optical Surface Waves
Infrared near-field microscopy allows to study the propagation of surface waves in the infrared spectral regime. Amplitude and phase resolved near-field images reveal local interference effects or enable the determination of the complex wave vector of surface waves. Surface waves can be excited in the mid-infrared spectral regime by e.g. metal structures on Silicon Carbide (SiC) crystals (propagating Surface Phonon Polaritons, SPhP). The topography image shows a circular structure used to excite SPhPs. The SPhPs propagate normal to the edge of the metal film and the curved structure leads to a focusing effect of the waves. The near-field amplitude image clearly reveals a locally enhanced signal about 40 µm away from the structure. Note that the metal structure is illuminated by a plane wave (used to excite the SPhPs) which interferes with the field of the surface waves. The images demonstrate that infrared near-field microscopy can be used for amplitude and phase resolved studies of e.g. spoof plasmons with tailored optical properties in detail.
This measurement was realized with the IR-neaSCOPE+s.
Coating Protects Ancient Pottery
Neolithic Cucuteni ceramic pottery is a valuable artifact that requires proper protection to ensure its preservation for future generations. In this study, polymer nanostructured material is used as protective coatings for the conservation of such ancient artefacts against UV ageing. In the context of comparative evaluation of the protective efficiency, this article reports the use of a functional coating that operates via specific photochemical transformations at the coating-air interface as a UV resistant protection coating for cultural heritage artefacts. An important finding was related to the decrease of the carbonyl band from 1739 cm-1 and to the appearance of other two additional bands located at 1718 (saturated aliphatic ketone) and 1712 cm-1 (carboxylic acid dimer). In addition, the loss of ester groups may be considered the main degradation process, as illustrated by the decrease of the intensity and area of the 1739 cm-1 main carbonyl stretching band.
This study reports the first investigation of the photodegradation behaviour of protective coatings through nano-FTIR technique.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Oancea et al., Materials Degradation 7, 21 (2023)
Nanoscale Negative Refraction
Refraction is a familiar effect in which a light beam alters direction as it propagates from one medium to another. Negative refraction is a nonintuitive but well-established effect in which the light beam is bent in the “wrong” direction. Two groups now independently demonstrate negative refraction at the interface of two-dimensional van der Waal materials. Hu et al. used molybdenum trioxide with a graphene MoO3 / Graphene overlayer to show that in-plane negative refraction of mid-infrared (mid-IR) polaritons occurs at the interface and is gate tunable. Sternbach et al. used molybdenum trioxide/hexagonal boron nitride MoO3 / hBN bicrystals to show that negative refraction of mid-IR polaritons occurs for propagation normal to the interface.
Polaritonic negative refraction in the mid-IR provides opportunities for optical and thermal applications such as IR super-resolution imaging, nanoscale thermal manipulation, and chemical sensing devices with enhanced sensitivity.
This measurement was realized with the IR-neaSCOPE+s.
Non-Aqueous Lithium–Air Cells
Metal–air batteries, such as Li–air, may be the key for large-scale energy storage as they have the highest energy density among all electrochemical devices. However, these devices suffer from irreversible side reactions leading to battery failure, especially when ambient air is used as the O2 source. This study uses nano-FTIR to track the chemical composition changes at the nanoscale of electrode surface during cell discharge. The results obtained here open an instructive operando chemical analysis of the Li–Air battery development. The authors observed a high sensitivity to humidity and CO2 in atmospheric conditions, and that the interaction between DMSO and carbon nanotubes (CNT) generates formate species. From 140 s of operation, the DMSO presented a low decomposition rate that remained the same until the end of the discharge.
nano-FTIR is an important tool to study complex discharge processes typically found in conversion batteries, as the case studied here for Lithium–Air.
This measurement was realized with the IR-neaSCOPE+s.
Molecular Identity of Catalytic Agent
Unambiguous identification of catalytic poisoning species requires experimental methods simultaneously delivering accurate information regarding adsorption sites and adsorption geometries of adsorbates with nanometer-scale spatial resolution, as well as their detailed chemical structure and surface functional groups. However, to date, it has not been possible to study catalytic sulfur poisoning of metal/metal-oxide interfaces at the nanometer scale without sacrificing chemical identity. In this study, nano-FTIR & s-SNOM identify the chemical nature, adsorption sites, and adsorption geometries of sulfur-based catalytic poisons on a Pd(nanodisk)/Al2O3 (thin-film) planar model catalyst surface at the nanometer scale. In addition, this study reveals striking variations between sulfate species from one nanoparticle to another and even vast alterations of sulfur poisoning on a single Pd nanoparticle.
s-SNOM & nano-FTIR provide critical molecular-level insights crucial for the development of high-performance heterogeneous catalysts with extended lifetimes.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Say et al., JACS April 29 (2022)
Luttinger-liquid Plasmons
1D Luttinger-liquid plasmons formed inside carbon nanotubes (CNTs) are long-lived excitations with extreme electromagnetic field confinement. In the past, s-SNOM amplitude studies were limited to semiconducting CNTs which require additional doping. This s-SNOM phase study, allows investigation of metallic carbon nanotubes as they support strong tip-launched Luttinger-liquid plasmons at ambient conditions. The Authors extracted the dispersion relation of the hybrid Luttinger-liquid plasmon–phonon polaritons. The dispersion shows pronounced mode splitting, and an ultrastrong coupling regime with phonons of both investigated substrates, i.e., native silica and hBN. Such strong coupling of quasiparticles allows now applications like induced transparency, polariton lasing, changing of the rate of chemical reactions, or enhanced sensitivity in infrared and Raman spectroscopy
s-SNOM studies of Luttinger-liquid plasmons is an essential application to develop novel low-loss plasmonic circuits for the sub-wavelength manipulation of light.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Németh et al., Nano Lett. 22, 3495 (2022)
Solid-State Battery
Solid-state batteries possess the potential to significantly impact energy storage industries by enabling diverse benefits, such as increased safety and energy density. However, challenges persist with physicochemical properties and processes at electrode/electrolyte interfaces. Thus, there is great need to characterize such interfaces in situ and unveil scientific understanding that catalyzes engineering solutions. In this study, the authors conduct multiscale in situ microscopies (optical, atomic force, and infrared near-field) and nano-FTIR of intact and electrochemically operational graphene/solid polymer electrolyte interfaces. They find nanoscale structural and chemical heterogeneities intrinsic to the solid polymer electrolyte initiate a cascade of additional interfacial nanoscale heterogeneities during Li plating and stripping; including Li-ion conductivity, electrolyte decomposition, and interphase formation.
nano-FTIR applies to buried interfaces and interphases in their native environment and readily adaptable to a number of other electrochemical systems and battery chemistries.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
He et al., Nature Communications 13, 1398 (2022)
Plasmon in Suspended Graphene
Plasmons in 2D graphene have been invariably studied in supported samples so far. The substrate provides stability for graphene but often causes undesired interactions (such as dielectric losses, phonon hybridization, and impurity scattering) that compromise the quality and limit the intrinsic flexibility of graphene plasmons. This s-SNOM study demonstrate the visualization of plasmons in suspended graphene and introduces the graphene suspension height as an effective plasmonic tuning knob that enables in situ change of the dielectric environment and substantially modulates the plasmon wavelength, propagation length, and group velocity. Such active control of micrometer plasmon propagation facilitates near-unity-order modulation of nanoscale energy flow that serves as a plasmonic switch with an on-off ratio above 14.
The suspended graphene plasmons possess long propagation length, high tunability, and controllable energy transmission simultaneously, opening up broad horizons for application in nano-photonic devices.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Hu et al., Nature Communications 13, 1465 (2022)
Organic Semiconductors
Semiconductors based on organic polymers have several advantages over their conventional, mostly silicon-based cousins. They are simpler and cheaper to manufacture, and can be produced in the form of thin, flexible layers, which allows them to be attached to diverse substrates and surfaces. Their electrical conductivity and energy efficiency are a function of the properties of the materials of which they are made. This degree of molecular order affects the mobility and transport of the charge carriers within them. Up until now, it has been very difficult to access these structures experimentally. s-SNOM and nano-FTIR make a valuable contribution to our understanding of these layered systems and to organic electronics in general.
s-SNOM & nano-FTIR is ideally suited for monitoring and optimize growth parameters to get highly ordered organic films and thus faster devices with crucial impact in development of optoelectronic devices such as OLED technology, or organic solar cells.
This measurement was realized with the IR-neaSCOPE+s.
Enzymatical Biocatalytic Reactions
Biocatalytic transformations in living organisms, such as multi-enzyme catalytic cascades, proceed in different cellular membrane-compartmentalized organelles with high efficiency. Nevertheless, it remains challenging to mimic biocatalytic cascade processes of natural systems. One method to mimic natural enzymes is the use of multi-shelled metal-organic frameworks (MOFs). Such MOFs can be used as a hierarchical scaffold to spatially organize enzymes on nanoscale to enhance cascade catalytic efficiency. In this study, the authors employed s-SNOM and nano-FTIR technology, which resolves nanoscale heterogeneity of vibrational activity associated to enzymes encapsulated in multi-shelled MOFs. This work provides important insights into developing complex multi-spatial compartmental systems for multi-enzyme catalytic cascades that hold great promise in many industrial processes.
Infrared nanoscale analysis reveals molecular identity of nm-small materials. Method which can be applied in many chemical and pharmaceutical industrial processes.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Man et al., Nature Communications 13, 305 (2022)
Phonon Polaritons & Organic Molecules
Light plays an essential role in modern science and technology, with applications ranging from fast optical communication to medical diagnosis and laser surgery. In many of these applications, the interaction of light with matter is of fundamental importance. The images obtained in this work reveal that the interaction between infrared light and molecular vibrations can be so strong that eventually the material properties are modified, such as conductivity and chemical reactivity. This effect, called vibrational strong coupling, could be used in the future for development of ultrasensitive spectroscopy devices or to study quantum aspects of strong vibrational coupling that have been not accessible so far.
Infrared s-SNOM imaging reveals vibrational strong coupling between propagating phonon polaritons and small organic molecules. A phenomenon with high potential to control fundamental physical and chemical material properties.
This measurement was realized with the IR-neaSCOPE+s.
Secondary Structure of Single Proteins
The secondary structure of a proteins is highly relevant in the pathogenous mechanism leading to Alzheimer, Parkinson, and other neuro-degenerative diseases. Although a variety of methods have been developed to study the protein chemistry and structure, recognizing and mapping the secondary structure on the nanometer scale, or even with single protein sensitivity, is still a major challenge. nano-FTIR technology is used in this study to enabled nanoscale chemical imaging and probing of protein’s secondary structure with enormous sensitivity. In short, a sharp metalized tip is illuminated with a broadband infrared laser beam, and the backscattered light is analyzed with a specially designed Fourier transform spectrometer.
nano-FTIR probes the infrared spectroscopy and resolves the secondary structure of proteins complexes with diameter of 12 nm, 6 nm protein monolayer and even of 3 nm thin fibrils.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Amenabar et al., Nature Communications 4, 2890 (2013)
Nanoscale phase transitions in V2O3
The high spatial resolution of infrared near-field microscopy allows for detailed studies of phase transitions in materials like the insulator-to-metal transition of vanadium dioxide (VO2) thin films. Infrared near-field microscopy provides novel insights into the temperature-induced phase transition of VO2. Near-field images directly confirm the percolative nature of the VO2 thin film phase transition where insulating and metallic phases coexist in the temperature range where the transition occurs. Images of a VO2 film (wavelength 10.75µm) recorded for a controlled temperature change between ca. 340K to 343K reveal how nanoscale metallic puddles are formed, exhibiting a higher amplitude signal for metallic sample regions compared to insulating. Analysis of the metallic puddles extension/geometry at the onset of the phase transition allows in combination with effective medium theory calculations to extract a divergent effective carrier mass.The images recorded for the VO2 thin film phase transitions demonstrate that IR near-field microscopy allows detailed studies of nanoscale phase transitions in materials. The technique cannot be only applied to VO2-related phase transitions, but to all phase changes where a dielectric/metallic or amorphous/crystalline transition (like in GeSbTe alloys) occurs.
This measurement was realized with the IR-neaSCOPE+s.
Infrared nanofocusing on transmission lines
Transmission lines are specialized cables for carrying for example radio frequency signals where electromagnetic radiation is guided in form of a tightly bound surface wave. Infrared near-field microscopy verifies that the concepts of radiofrequency can be scaled down to optical frequencies and that the concept of classic transmission lines can be adapted to the infrared frequency range.Near-field images taken at a wavelength of 9.3µm show how an optical antenna captures infrared light and converts it into a propagating surface wave traveling along the transmission line. By gradually reducing the width of the transmission line (“tapering”), the infrared surface wave is compressed to a tiny spot at the taper apex with a diameter of only 60 nm. This tiny spot is 150 times smaller than the free-space wavelength. Phase-resolved infrared near-field microscopy can applied to map the different electrical field components of the infrared focus with nanoscale resolution.The near-field images demonstrate the potential of neaSCOPE to resolve the vectorial character of local optical fields and to verify novel fundamental predictions and technological concepts in nanophotonics, plasmonics and metamaterials research. Offering wavelength-independent resolution, it can be used at visible, infrared and terahertz frequencies.
This measurement was realized with the IR-neaSCOPE+s.
Further reading:
Schnell, P. AlonsSchnell et al., Nature Photonics 5, 283 (2011)
Studying superlensing and meta-materials
The studies focus on achieving sub-diffraction optical imaging and pushing the limits of resolution using advanced superlensing and metamaterial concepts paired with near-field microscopy techniques, such as s-SNOM.
SiC-Based Superlens for Near-Field Imaging
The study by Taubner et al. explores superlensing in the infrared range using a thin SiC slab with negative permittivity, enabling near-field microscopy beyond the diffraction limit. A SiC superlens, 440 nm thick, resolves buried objects—gold patterns—located 880 nm below the surface at a resolution of λ/20 (sub-540 nm at λ = 11 μm). The study confirms that superlensing resonance conditions are necessary for enhanced resolution, as control experiments at non-resonant wavelengths failed to resolve subsurface structures?.
Quantum Metamaterial Superlenses
In Harnessing a Quantum Design Approach, Bak et al. introduce a novel Quantum Metamaterial (QM) superlens to reduce optical losses and achieve superior resolution. Using intersubband transitions in III-V semiconductor quantum wells, the QM superlens demonstrates diffraction-beating resolution of λ/10 (at λ = 10.7 μm). The design minimizes losses by separating in-plane and out-of-plane dielectric responses, achieving a loss figure of merit (FOM) of ~80, which is a tenfold improvement over traditional superlenses. The study combines numerical FDTD simulations and experimental imaging with s-SNOM to demonstrate high-quality imaging through the QM superlens?.
Subsurface Imaging Limits and Superlens Effects
In Exploring Detection Limits of Infrared Near-Field Microscopy, Jung et al. examine subsurface imaging with s-SNOM through dielectric membranes, such as Si3N4. Gold nanoparticles buried under Si3N4 layers are resolved up to a depth of 50 nm, with imaging performance influenced by the thickness and dielectric function of the capping layer. At specific wavelengths within the Reststrahlenband, where Si3N4 exhibits negative permittivity, surface phonon polariton (SPhP) effects enhance near-field signals, enabling superlensing-like behavior with sub-50 nm resolution?.
Outlook
These studies collectively demonstrate how superlenses and metamaterials paired with near-field microscopy techniques like s-SNOM push the resolution limits of optical imaging. Applications span nanoelectronics, subsurface material characterization, and advanced imaging technologies. The advent of quantum metamaterials promises low-loss super-resolution devices, enabling practical use cases in nanophotonics, biomedical imaging, and beyond.
This measurement was realized with the IR-neaSCOPE+s.
Mapping local conductivity in semiconductor devices
The studies by Huber et al. showcase groundbreaking advancements in nanoscale characterization of semiconductor materials using near-field microscopy techniques at infrared (IR) and terahertz (THz) frequencies. These techniques reveal crucial spatial and conductivity details of single semiconductor devices with resolutions far below the diffraction limit.
THz Near-Field Nanoscopy
In Terahertz Near-Field Nanoscopy of Mobile Carriers, THz scattering-type near-field optical microscopy (s-SNOM) achieves a resolution of 40 nm, far beyond the diffraction limit. Using a 2.54 THz laser, this method maps mobile carrier concentrations ranging from 1016 to 1019 cm-3. The nanoscale THz contrast reveals plasmon-assisted carrier excitations in semiconductors, enabling quantitative carrier profiling and sensitivity to less than 100 electrons in a 40 nm³ volume.
IR s-SNOM Conductivity Mapping
The Simultaneous IR Material Recognition and Conductivity Mapping study applies mid-infrared (IR) s-SNOM to distinguish materials like Si, SiO2, TiN, and Al. Using a CO2 laser with a wavelength of 10.7 μm, the technique resolves amplitude and phase contrasts of materials and maps mobile carrier concentrations in the range of 1019–1020 cm-3 with a resolution of 30–40 nm. It highlights doping gradients and conductivity variations critical for device failure analysis.
Outlook
Combining THz and IR near-field microscopy enables unprecedented nanoscale insights into materials and conductivity. These advancements are pivotal for nanoelectronics, semiconductor failure analysis, and photonic device optimization. Future developments like broadband THz spectroscopy and enhanced carrier mobility models will expand these tools' applications in emerging technologies.
This measurement was realized with the IR-neaSCOPE+s.
Tracking slow nanolight in natural hyperbolic metamaterial slabs
Recent studies highlight significant advancements in controlling polaritons and plasmons in van-der-Waals (vdW) materials and heterostructures, enabling ultrafast manipulation of light-matter interactions at deep subwavelength scales.
In WSe2 waveguides, femtosecond exciton dynamics reveal coherent optical Stark shifts and exciton bleaching using time-resolved SNOM techniques. Meanwhile, hBN-based systems demonstrate polariton acceleration through substrate engineering and reduced losses by enriching 11B isotopes.
In a-V2O5, sodium intercalation enables broad spectral tuning of phonon polaritons without compromising their ultra-low losses (~4 ps lifetimes), showcasing their potential for mid-infrared tunable devices.
Furthermore, graphene-MoS2 vdW heterostructures achieve highly efficient all-optical plasmon modulation. The system operates with LED intensities as low as 0.15 mW/cm2, featuring ultrafast carrier transfer (~600 fs) and recombination (~7 ps), enabling rapid optical switching.
Collectively, these results open new pathways for ultrafast optical modulation, polariton acceleration, and tunable nanophotonic devices, paving the way for energy-efficient and high-speed applications in infrared optics and integrated photonics.
This measurement was realized with the IR-neaSCOPE+s.