Near-infrared Region Research Articles

Construction of a novel Au@Os mediated TMB-H2O2 platform with dual-signal output for rapid and accurate detection of ziram in food

The 3,3′,5,5′-tetramethylbenzidine-H2O2 (TMB-H2O2) platform has gained widespread use for rapid detection of various analytes in foods. However, the existing TMB-H2O2 platforms suffer from limited accuracy, as their signal output is confined to the visible region, which is prone to interference from various food colorants in real samples. To address this challenge, a novel Au@Os-mediated TMB-H2O2 platform is developed for both rapid and accurate detection of analytes in foods. The prepared Au@Os NPs exhibit remarkable peroxidase-like activity, making the platform display dual absorption peaks in visible and near-infrared (NIR) regions, respectively. This Au@Os-mediated TMB-H2O2 platform exhibited three linear ranges across different concentrations of ziram from 1–100, 150–600, and 800–2000 nM with limit of detection (LOD) 7.9 nM and limit of quantification (LOQ) 24.15 nM respectively. Further, the Au@Os-mediated TMB-H2O2 platform was also used for rapid and accurate detection of ziram in real food samples like apple, tomato, and black tea.

Deep near infrared light-excited stable synergistic photodynamic and photothermal therapies based on P-IR890 nano-photosensitizer constructed via a non-cyanine dye

The cyanine dyes represented by IR780 can achieve synergistic photodynamic therapy (PDT) and photothermal therapy (PTT) under the stimulation of near-infrared (NIR) light (commonly 808 nm). Unfortunately, the stability of NIR-excited cyanine dyes is not satisfactory. These cyanine dyes can be attacked by self-generated reactive oxygen species (ROS) during PDT processes, resulting in structural damage and rapid degradation, which is fatal for phototherapy. To address this issue, a novel non-cyanine dye (IR890) was elaborately designed and synthesized by our team. The maximum absorption wavelength of IR890 was located in the deep NIR region (ca. 890 nm), which was beneficial for further improving tissue penetration depth. Importantly, IR890 exhibited good stability when continuously illuminated by deep NIR light. To improve the hydrophilicity and biocompatibility, the hydrophobic IR890 dye was grafted onto the side chain of hydrophilic polymer (POEGMA-b-PGMA-g-CCH) via click chemistry. Then, the synthesized POEGMA-b-PGMA-g-IR890 amphiphilic polymer was utilized to prepare P-IR890 nano-photosensitizer via self-assembly method. Under irradiation with deep NIR light (850 nm, 0.5 W/cm2, 10 min), the dye degradation rate of P-IR890 was less than 5%. However, IR780 was almost completely degraded with the same light output power density and irradiation duration. In addition, P-IR890 could stably generate a large number of ROS and heat at the same time. It was rarely reported that the stable synergistic combination therapy of PDT and PTT could be efficiently performed by a single photosensitizer via irradiation with deep NIR light. P-IR890 exhibited favorable anti-tumor outcomes through apoptosis pathway. Therefore, the P-IR890 could provide a new insight into the design of photosensitizers and new opportunities for synergistic combination therapy of PDT and PTT.

Green Preparation of S, N Co-Doped Low-Dimensional C Nanoribbon/C Dot Composites and Their Optoelectronic Response Properties in the Visible and NIR Regions.

The green production of nanocomposites holds great potential for the development of new materials. Graphene is an important class of carbon-based materials. Despite its high carrier mobility, it has low light absorption and is a zero-bandgap material. In order to tune the bandgap and improve the light absorption, S, N co-doped low-dimensional C/C nanocomposites with polymer and graphene oxide nanoribbons (the graphene oxide nanoribbons were prepared by open zipping of carbon nanotubes in a previous study) were synthesized by one-pot carbonization through dimensional-interface and phase-interface tailoring of nanocomposites in this paper. The resulting C/C nanocomposites were coated on untreated A4 printing paper and the optoelectronic properties were investigated. The results showed that the S, N co-doped C/C nanoribbon/carbon dot hybrid exhibited enhanced photocurrent signals of the typical 650, 808, 980, and 1064 nm light sources and rapid interfacial charge transfer compared to the N-doped counterpart. These results can be attributed to the introduction of lone electron pairs of S, N elements, resulting in more transition energy and the defect passivation of carbon materials. In addition, the nanocomposite also exhibited some electrical switching response to the applied strain. The photophysical and doping mechanisms are discussed. This study provides a facile and green chemical approach to prepare hybrid materials with external stimuli response and multifunctionality. It provides some valuable information for the design of C/C functional nanocomposites through dimensional-interface and phase-interface tailoring and the interdisciplinary applications.

Structural modification of V1274 moiety to red-shift its light absorption for optical and photovoltaic properties: A DFT molecular insight

In this study, we propose a theoretical strategy to enrich the electronic populations at V1274 core to develop new hole-transporting insulators (1–7) to red shift its maximum absorption (λmax). All calculations are performed using Coulomb Attenuated Method- Becke three parameter Lee–Yang-Parr (CAM-B3LYP) method at the Density Functional Theory (DFT) level. The photovoltaic results vary across different parameters as Open Circuit Voltage (Voc) ranges from 0.87 to 0.98 V, Fill factor (FF) ranges from 0.190 to 0.863, Short Circuit (Jsc) ranges from 26.10 to 48.38 mA/cm2, and Maximum Power (Pmax) ranges from −9.38 to 31.85 W. The λmax varies from 372 to 658 nm. This enhanced absorption capability by the push-pull effect indicates their effectiveness of the chromophores in absorbing light in that specific wavelength range. The significant new density of states (DOS) after adsorbing the designed chromophores onto the TiO2 cluster indicates potential changes in the electronic structure and properties of the material. The significant shift of λmax towards the near-infrared region after nitrogen replacement is important because it indicates improved light absorption in that range, which could enhance its suitability for applications such as near-infrared photodetection or solar energy harvesting.

Triarylamine-based polyimide COFs for achieving high performance ambipolar multi-color electrochromic energy-storage films

Electrochromic energy storage materials that possess both electrochromic and electrochemical energy-storage properties have attracted significant attention for applications in visual energy-storage, energy-efficient windows, as well as displays. To fulfill their comprehensive applications, electrochromic energy-storage materials require specific characteristics, such as transparency, ambipolarity, multi-color capabilities, and high capacitance. Here, the polyimide covalent-organic framework based on triarylamine (PM-TPI and NT-TPI) COF films were grown successfully on FTO glass through solvothermal polycondensation, and exhibited crystallization, hierarchical porous structures, and ambipolar electrochemical redox activity. Notably, NT-TPI COF film displayed transparent bleached state, ambipolar electrochromism, multi-color (transparent, orange-red, cyan, gray), and high optical contrast. Due to their large specific surface area and efficient electron/ion transport ability, the NT-TPI COF film effectively controlled visible and near-infrared light, achieving optical contrasts of 49.8 % and 70.0 % at 420 and 850 nm, respectively. Moreover, the NT-TPI COF films showed promising electrochemical energy-storage properties and excellent charge–discharge rate performance, with a specific capacitance of 141.0 mAh/g. Additionally, NT-TPI COF/WO3-based ambipolar eclectrochromic energy-storage devices also exhibited high optical contrast from visible to near-infrared regions, and large capacitance. In summary, the NT-TPI COF film effectively combines the electrochromic and electrochemical energy-storage capabilities, making it a promising candidate for electrochromic energy-storage materials with transparency, ambipolarity, high optical contrast, multi-color functionality, and high specific capacitance.

Enhanced photodiode performance: Au/boron-dipyrromethene/n-Si/Ag structure unveiling high photosensitivity and efficiency

In this study, the classical boron-dipyrromethene (4,4- difuoro-4-borata-3a-azonia-4a-aza-s-indacene, BODIPY) unit (C1), its halogenated derivative (C2), and disytryl derivative (C3), which are known for their absorption properties in the near-infrared (NIR) region, were synthesized. Chemical and photophysical investigations were carried out to reveal the complex features of the molecules using a range of spectroscopic techniques and their energies were calculated by Density Functional Theory (DFT) with the same basis set. The BODIPY thin films were coated on n-Si substrates using a spin coater to examine the effect of interlayer on photodiode/photovoltaic properties and Au/BODIPY (C1, C2, C3)/n-Si/Ag photodiodes having rectifying behavior were fabricated. The thermionic emission theory (TET) and modified Norde’s functions were utilized to determine the rectification ratio, ideality factor, series resistance, and barrier height values of diodes. The values of barrier height, ideality factor, and rectification ratio at ± 2 V were calculated as 0.81 eV, 1.83 and 2.47x103 for the Au/C1/n-Si/Ag diode, 0.83 eV, 1.63, and 7.06 x103 for the Au/C2/n-Si/Ag diode and 0.84 eV, 1.51 and 2.14x104 for the Au/C3/n-Si/Ag diode in the dark from the TET, respectively. The values of FF (%) and efficiency were calculated as 38 and 1.51 for the Au/C1/n-Si/Ag diode, 47 and 2.03 for the Au/C2/n-Si/Ag diode, and 56 and 3.68 for the Au/C3/n-Si/Ag diode under 100 mW/cm2 illumination, respectively. With remarkable electrical properties, the Au/C3/n-Si/Ag photodiode stood out among the others, performing better in both dark and light conditions. Therefore, the produced diodes based on the BODIPY thin film can be employed as photodiodes/photovoltaics in optoelectronic applications.

Optically enhanced organic phototransistors for adaptive image processing under complex light conditions

Effectively handling massive information in complex lighting conditions is crucial for security-focused machine vision, as it relies on precise image feature detection and encryption/decryption to ensure integrity and confidentiality. Traditional hardware, primarily based on complementary metal-oxide-semiconductor (CMOS) technology, struggles with the complexity of processing tasks around the clock. To address this challenge, a ternary organic heterostructure visuomorphic phototransistor was tailored for adaptive critical image processing. The light coupling induced by the porous heterostructural layer enhances the light absorption efficiency by 2.5-fold. Our phototransistor exhibits bidirectional photoresponse across the visible and near-infrared (NIR) spectral regions, enabling adaptive edge detection in varying lighting conditions with precision above 85 %. The phototransistor array facilitates image encryption/decryption with a superior accuracy of 12 %/90 % compared to existing counterparts. This ternary organic hetero-integration combines multiple response modes, enabling compact and efficient critical feature processing.

Sub-picometer level all-solid-state narrow linewidth single-frequency Pr3+:LiYF4 laser in the near-infrared spectral region.

We report an all-solid-state near-infrared single-frequency (single longitudinal mode, SLM) Pr3+:LiYF4 (Pr:YLF) laser with the spectral linewidth at the sub-picometer level. The SLM lasers with center wavelengths of 868 and 907 nm are realized in Pr:YLF crystal for the first time to the best of our knowledge. The maximum output powers of SLM lasers at 868 and 907 nm are 102 and 213mW, corresponding to the narrowest spectral linewidths of 82 MHz (0.21 pm) and 94 MHz (0.26 pm), respectively. At the maximum output power, the beam quality factors in the x and y directions are measured as 1.25 and 1.16 at 868 nm and 1.21 and 1.13 at 907 nm, respectively. The output power stabilities of the 868 and 907 nm SLM lasers are calculated as 1.39% and 0.87%, respectively. The successful realization of 868 and 907 nm all-solid-state SLM lasers makes up for the gap that the Pr:YLF SLM lasers developed in the past are focused on the visible region, enriches the types of near-infrared (NIR) SLM lasers, and can provide practical applications in biomedicine, cold atom physics, and optical atom manipulation.

Bio-inspired Mechanically Responsive Smart Windows for Visible and Near-Infrared Multiwavelength Spectral Modulation.

Mechanochromic light control technology that can dynamically regulate solar irradiation is recognized as one of the leading candidates for energy-saving windows. However, the lack of spectrally selective modulation ability still hinders its application for different scenarios or individual needs. Here, inspired by the generation of structure color and color change of living organisms, a simple layer-by-layer assembly approach toward large-area fabricating mechanically responsive film for visible and near-infrared multiwavelength spectral modulation smart windows is reported here. The assembled SiO2 nanoparticlesand W18O49 nanowires enable the film with an optical modulation rate of up to 42.4% at the wavelength of 550nm and 18.4% for the near-infrared region, separately, and the typical composite film under 50% stretching shows ≈41.6% modulation rate at the wavelength of 550nm with NIR modulation rate less than 2.7%. More importantly, the introduction of the multilayer assembly structure not only optimizes the film's optical modulation but also enables the film with high stability during 100000 stretching cycles. A cooling effect of 21.3 and 6.9 °C for the blackbody and air inside a model house in the real environmental application is achieved. This approach provides theoretical and technical support for the new mechanochromic energy-saving windows.

Electrostatically self-assembled gold nanorods with sulfated hyaluronic acid for targeted photothermal therapy for CD44-positive tumors

Gold nanorods (GNR) produce heat upon irradiation with near-infrared light, enabling a tumor-targeted photothermal therapy. In this study, we prepared GNR coated with sulfated hyaluronic acid (sHA) with a binding affinity for CD44 via electrostatic interactions to deliver GNR to tumors efficiently and stably, and evaluated their usefulness for photothermal therapy. Cationic GNR modified with trimethylammonium groups electrostatically interacted with native HA or sHA with varying degrees of sulfation to form complexes. While GNR/HA was unstable in saline, GNR/sHA maintained the absorbance peak in the near-infrared region, particularly for GNR/sHA with higher degrees of sulfation. GNR/sHA exhibited an intense photothermal effect upon irradiation with near-infrared light. Furthermore, in vitro and in vivo studies revealed that GNR coated with sHA containing approximately 1.2 sulfated groups per HA unit could accumulate in CD44-positive tumors via an HA-specific pathway. These findings indicate the effectiveness of GNR/sHA as a tumor-targeted photothermal therapeutic agent.

Achieving ultrahigh electrochromic stability of triarylamine-based polymers by the design of five electroactive nitrogen centers

A shortage of long-term stability of electrochromic materials has been hindering their practical application. A series of novel polyamides (PAs) (4) with five electroactive nitrogen atoms within triphenylamine (TPA)-containing structures was synthesized via phosphorylation polyamidation. Polyamide 4b exhibited highly integrated electrochromic performances, including multiple color changes, high contrast of optical transmittance change, and the highest electrochromic stability (only 11.2 and 9.6 % decay of its coloration efficiency (CE) at 450 nm after 50000 and 16000 switching cycles, respectively) compared to all other triarylamine-based polymers to date. This record-high electrochromic cycling is attributed to the enhanced stability of polaron, which was studied through the electron-donating or electron-withdrawing effect of substituents and the resonance effect of electron delocalization over the electroactive nitrogen centers. Importantly, our core design of five electroactive nitrogen centers with electron-donating methoxy groups is the key factor to increase stability of polaron in the resulting polymers 4. More electroactive nitrogen centers are able to create a weaker electronic coupling due to a charge of cation radical dispersed by resonance successfully in-between the different redox states, which is evidenced clearly by the observed longer wavelength absorption in the NIR region. Our research confirms that the key to determining polaron stability is the resonance by the electrons delocalized over all the redox centers, rather than the electronic coupling between the different redox centers. And the resonance leads to increasing electrochromic stability of the polymer.

Structural, optical, and detailed photoluminescence characterization of solvothermal synthesized V2O5, ZrO2, and ZrV2O7 nanoparticles

It is indisputable that structural defects are pivotal in modulating the properties of materials. This study provides a comprehensive analysis of the structural, optical, and photoluminescence characteristics of V2O5, ZrO2, and ZrV2O7.These materials were chosen for their potential applications in various key technological domains. The XRD results revealed the formation of high-purity materials with no secondary phases. It was determined that ZrO2exhibits the most significant quantity of structural defects among the investigated materials. The variation in crystallite size as determined by XRD aligns with the variation in grain size observed through Scanning Electron Microscopy (SEM).The optical band gaps of V2O5, ZrO2, and ZrV2O7 were determined to be 2.27 eV, 5.19 eV, and 2.38 eV, respectively. X-ray Photoelectron Spectroscopy (XPS) analysis indicated the presence of constituent elements without any contaminants. A detailed examination of the photoluminescence (PL) emission characteristics in both UV–Vis and near-infrared (NIR) regions for all materials presented broad visible luminescence in the [450–650] nm range under UV excitation. Structural defects are crucial in determining the physico-chemical properties of materials. This is thoroughly examined for V2O5, ZrO2, and ZrV2O7.The infrared (IR) emission spectra, introduced for the first time in this study for V2O5, ZrO2, and ZrV2O7, are employed to elucidate the localization of structural defects within the band gap.

Lysosome-Targeted Polarity-Sensitive NIR Fluorescence Probe for Imaging Injured Lung and Liver in Diabetes.

Diabetes is a chronic disease marked by high blood glucose. With the progress of diabetes, complications gradually appear, and various organs may be affected. However, due to the lack of noninvasive in situ detection probes, the diagnosis of organ damage caused by diabetes is significantly delayed, which will cause many complications that cannot be treated in time. Here, we report a BODIPY-based fluorescent probe SNL, which can be used to detect lung and liver damage caused by diabetes. By introducing methylpiperazine and extending the conjugated system, SNL can locate lysosomes and exhibit absorption and emission both in the near-infrared (NIR) region. In addition, SNL is sensitive to polarity and can be used for sensitive detection of lysosomal polarity changes. Unexpectedly, SNL targets and images the lungs and liver of mice. Subsequently, hyperglycemia-stimulated cell models and diabetic mouse models were successfully established, and SNL was utilized to reveal that polarity can be used as a diagnostic signal of diabetic complications. Notably, SNL for the first time confirmed the lung injury and liver injury caused by diabetes using the fluorescent probes method, providing a new approach for the diagnosis of diabetes complications.

Tuning optical excitations of graphene quantum dots through selective nitrogen doping

Our research has revealed that the nitrogen doping configuration has a significant impact on the absorption properties and band gap of nitrogen doped graphene quantum dots (NGQDs). By analyzing the composition and character of optical transitions, we have observed that nitrogen doping causes a redistribution of oscillator strength between significant peaks and the emergence of new optical features. These changes lead to broken molecular orbital degeneracies, optical peak splitting, and activation of dark states in the visible to near-infrared (NIR) region. These findings shed light on the mechanisms that govern alterations in the spectral properties of NGQDs within the visible and near-infra red (NIR) absorption bands. Furthermore, selective manipulation of optoelectronic properties via distinct N-doping patterns could pave the way for the development of novel optoelectronic nanodevices and functional materials.

Graphene Intermediate Layer for Robust and Spectrum-Extended Cu Photocathode Activated with Cs and O.

Developing an effective method to stably enhance the quantum efficiency (QE) and extend the photoemission threshold of Cu photocathodes beyond the ultraviolet region could benefit the photoinjector for ultrafast electron source applications. The implementation of a 2D material protective layer is considered a promising approach to extending the operating lifetime of photocathodes. We propose that graphene can serve as an intermediate layer at the interface between photocathode material and low-work-function coating. The role of oxygen in the Cs/O activation process on the Cu surface is altered by the graphene interlayer. Besides, the few-layer graphene (FLG) surface could be more likely to induce the formation of Cs2O. Thus, the graphene-Cu composite photocathode can achieve an ultralow surface work function of down to 0.878 eV through Cs/O activation. The photoemission performance of the composite cathode with a FLG interlayer is significantly enhanced. The photocathode has an extended spectral response to the near-infrared region and a higher QE. At 350 nm, its QE is more than twice that of the cesiated bare Cu, reaching 0.247%. After degradation, the graphene-Cu cathode can be fully restored by reactivation, with remarkably enhanced stability. In addition, the composite cathode can be operated reliably under a poor vacuum pressure of over 4 × 10-6 Pa. This study validates a new method for incorporating 2D materials into photocathodes, offering novel approaches to explore robust and spectrum-extended photocathodes.

Single crystalline Holmium doped InSe for optical limiting operation in Near-IR region

Single crystals possessing nonlinear absorption (NA) character are favorable optical limiter in near infrared region (NIR). The NA features of pure and 0.005%, 0.05%, 0.1% Holmium (Ho) doped single crystals of InSe were analyzed at 1200 nm wavelength within 120 fs and 1 kHz repetition rate. The open-aperture Z-scan technique was employed to determine the NA performance and optical limiting-(OL) threshold. In an attempt to determine the NA coefficients, two types of theoretical models were used. The first model takes into account only the two photon absorption-(TPA), while the second model considers one photon absorption, TPA and free carrier absorption. Based on the experimental results, the main NA mechanism of the studied single crystals is determined as sequential TPA. TPA coefficient value of the pure InSe single crystal increased from 1.41 × 10−10 to 10.7 × 10−10 cm W−1 with increasing Ho doping concentration at 398.1 GW cm−2 input intensity. The NA coefficients increased from 0.84 × 10−9 to 1.62 × 10−9 cm W−1 at the same input intensity. On the other hand, the OL threshold values were found to be 0.027, 0.025, 0.022 and 0.020 J cm−2 at 1200 nm wavelength for pure InSe and the increasing Ho concentration, respectively. The robust NA characteristics and the low OL threshold establish the Ho-doped InSe single crystal as a favorable candidate for OL applications in the NIR spectral region.

Optimization for hydrogen gas quantitative measurement using tunable diode laser absorption spectroscopy

Gas sensors are vital for safety, quality control, and environmental preservation across diverse industries. Tunable diode laser absorption spectroscopy (TDLAS) is widely employed for gas analysis due to its high sensitivity and selectivity. However, quantifying low concentrations of hydrogen gas using TDLAS in the infrared region proves challenging due to its lower absorption compared to other gases in the NIR region. This study introduces an innovative method for precise hydrogen gas measurement through the analysis of absorption spectra at different pressures and the employment of a high-pressure gas cell. By applying these methodologies to a calibration-free technique, we can realize the optimal measurement conditions for increasing the gas detection limit and stabilizing the wavelength lock for the laser diode. As a result, a linear relationship between hydrogen gas concentration and sensor response is achieved in the wide detection range of 0.01% to 100%. Under the optimal measurement conditions, our TDLAS system’s stability is demonstrated with minimum detection limits of 0.2866% and 0.0055% at integration times of 1 s and 30 s, respectively.

Perovskite versus Standard Photodetectors.

Perovskites have been largely implemented into optoelectronics as they provide several advantages such as long carrier diffusion length, high absorption coefficient, high carrier mobility, shallow defect levels and finally, high crystal quality. The brisk technological development of perovskite devices is connected to their relative simplicity, high-efficiency processing and low production cost. Significant improvement has been made in the detection performance and the photodetectors' design, especially operating in the visible (VIS) and near-infrared (NIR) regions. This paper attempts to determine the importance of those devices in the broad group of standard VIS and NIR detectors. The paper evaluates the most important parameters of perovskite detectors, including current responsivity (R), detectivity (D*) and response time (τ), compared to the standard photodiodes (PDs) available on the commercial market. The conclusions presented in this work are based on an analysis of the reported data in the vast pieces of literature. A large discrepancy is observed in the demonstrated R and D*, which may be due to two reasons: immature device technology and erroneous D* estimates. The published performance at room temperature is even higher than that reported for typical detectors. The utmost D* for perovskite detectors is three to four orders of magnitude higher than commercially available VIS PDs. Some papers report a D* close to the physical limit defined by signal fluctuations and background radiation. However, it is likely that this performance is overestimated. Finally, the paper concludes with an attempt to determine the progress of perovskite optoelectronic devices in the future.

Carbonyl stretching band in amides as Lorentz oscillator. Insights into anharmonicity and local environment in the liquid phase from NIR and MIR spectra of N-methylformamide and di-N,N-methylformamide

We investigated the anharmonicity and intermolecular interactions of N-methylformamide (NMF) and di-N,N-methylformamide (DMF) in the neat liquid phase with particular interest in the amide bands. The vibrational spectra, complex refractive index, and complex electric permittivity were determined in in the mid- (MIR) and near-infrared (NIR) regions (11,500–560 cm−1; 870–17857 nm). Dispersion analysis was based on the Classical Damped Harmonic Oscillator (CDHO) and simultaneous modelling of the real and imaginary components of the spectra. This data delivered insights into the vibrational energy dissipation and self-association in liquid amides. Identification of the MIR and NIR bands was based on anharmonic GVPT2//B3LYP/6-311++G(d,p) calculations. DMF and NMF follow distinct self-association, evidenced in the MIR fingerprint by the two components of the νCO, the analog of the Amide I band. These conclusions are supported by the structural information derived from the NIR spectra. Furthermore, the contribution of overtones and combination bands in the MIR spectra of amides was examined. The conclusions on molecular interactions and structural dynamics of NMF and DMF contribute to a deeper understanding of the effects of changes in the local environment of the amide group.

Aromaticity in the Spectroscopic Spotlight of Hexaphyrins.

Spectroscopic properties are commonly used in the experimental evaluation of ground- and excited-state aromaticity in expanded porphyrins. Herein, we investigate if the defining photophysical properties still hold for a diverse set of hexaphyrins with varying redox states, topologies, peripheral substitutions, and core-modifications. By combining TD-DFT calculations with several aromaticity descriptors and chemical compound space maps, the intricate interplay between structural planarity, aromaticity, and absorption spectra is elucidated. Our results emphasize that the general assumption that antiaromatic porphyrinoids exhibit significantly attenuated absorption bands as compared to aromatic counterparts does not hold even for the unsubstituted hexaphyrin macrocycles. To connect the spectroscopic properties to the hexaphyrins' aromaticity behaviour, we analyzed chemical compound space maps defined by the various aromaticity indices. The intensity of the Q-band is not well described by the macrocyclic aromaticity. Instead, the degeneracy of the frontier molecular orbitals, the HOMO-LUMO gap, and the |ΔHOMO-ΔLUMO|2 values appear to be better indicators to identify hexaphyrins with enhanced light-absorbing abilities in the near-infrared region. Regions with highly planar hexaphyrin structures, both aromatic and antiaromatic, are characterized by an intense B-band. Hence, we advise using a combination of global and local aromaticity descriptors rooted in different criteria to assess the aromaticity of expanded porphyrins instead of solely relying on the absorption spectra.