Red-shifted Absorption Research Articles

Red-Emitting Tetraphenylethylene-Based Boron Thioketonates: Effect of Substitution and Study of Nonlinear Optical Properties

We present tetraphenylethylene (TPE) and N,N-dimethylaniline (DMA)-substituted monothio-β-diketonate boron compounds. All O,S-chelated boron compounds showed red emission in solution as well as in the solid state. A comparison of O,O-chelated vs O,S-chelated compound reveals that the latter showed a pronounced red shift in both absorption and emission. Furthermore, the O,S-chelated compound showed the reduction potential at a less-negative position over the O,O-chelated compound. The marked red shift in O,S-chelated compounds indicates that there is a discernible enhancement in linear polarizability upon optical excitation, and consequently, we explore the nonlinear optical properties of the compounds at infrared wavelengths. The open-aperture Z-scan measurements using ultrashort pulses reveal the optical-limiting behavior of these compounds along with a greater nonlinear absorption for those variants, which exhibits a greater red shift in absorption and emission spectrum.

Hydrogen Evolution, Piezoelectricity, and Optical Properties of Monolayer Semimetal (α,β)–S2C2N2 and Janus (α,β)–SCN/CN

Herein, the density functional theory is used to study the structural, mechanical, electrical, optical, and hydrogen evolution reaction (HER) properties of monolayer structures and . They are claimed to be stable monolayer structures by phonon dispersion and ab initio molecular dynamics (AIMD). Compared to graphene (≈340 N m−1), the shows a higher Young's modulus (≈429, 414 N m−1). Moreover, the piezoelectric stress coefficient of α‐ (=2.65 pm V−1) is comparable with bulk piezoelectric α‐quartz (=2.3 pm V−1). Exciton effect at M point causes redshift and enhancement of light absorption of α‐ and . The overpotential of is only –0.072 V. Besides, the gives a small effective electron mass of about 0.2(m0). It is worth mentioning that the monolayer structures show the semimetal phases. Due to the unique semimetal phase, the absorption of has an excellent performance in the near‐infrared (NIR) region. It can be enhanced at the NIR region and extended to the middle infrared region when applying tensile stress. These results provide more choices for 2D materials in electrocatalysis, piezoelectric sensors, visible light devices, and infrared photodetectors.

Enhancing the reactivity, electronic, linear and non-linear optical properties of C45H15-like carbon nanocone doped with titanium dioxide, boron, and nitrogen: DFT and TD-DFT study

The density functional theory (DFT) levels B3LYP, B3PW91 and CAM-B3LYP/6–31+G(d) were used to systematically evaluate the reactivity, electronic, linear and non-linear optical (NLO) properties of the titanium dioxide, boron and nitrogen-doping C45H15-like carbon nanocone. Due to this doping, the |HOMO-LUMO| energy gap of the initial carbon nanocone (CO) has narrowed considerably and some values of the |HOMO-LUMO| gap energy of the derivatives formed are lower than 1 eV. This result shows that some of the derivatives may be used as suitable semiconductor materials and others as highly demanded-superconducting materials in the electronics industry. In addition, all these studied derivatives showed a red-shifted absorption maximum, however only the obtained derivative by substituting both five carbon atoms with five nitrogen atoms and ten carbon atoms with ten boron atoms (N5B10) exhibits the highest absorption capacity in the visible range, implying that the latter could be a promising candidate in photovoltaic devices. Finally, the first-order hyperpolarizability values of all the formed derivatives are largely superior to that of the pure carbon nanocone (CO) and also to that of the reference compound para-nitroaniline (p-NA), which leads us to say that these formed derivatives may be suitable candidates for NLO applications. Also, according to our investigations, the boron and nitrogen atom arrangements established within our studied carbon nanocone predict exothermic reactions in contrast to the data collected in the literature that predict endothermic reactions. Furthermore, with respect to dopant enhancements to our studied carbon nanocone, it should be noted that the simultaneous manipulation of the boron and nitrogen heteroatoms with a higher probability of boron presence than nitrogen offers new opportunities to improve the overall C5n 2H5n carbon nanocone properties with n ≥ 3.

A-DA′D-A Type Acceptor with a Benzoselenadiazole A′-Unit Enables Efficient Organic Solar Cells

A new A-DA′D-A structured narrow bandgap small molecular acceptor (SMA) Se46 was designed and synthesized by using benzoselenadiazole as the A′ unit and branched 2-butyloctyl as upper side chains in its DA′D central fused ring. It was found that Se46 shows red-shifted absorption compared to that of L8-BO with a benzothiadiazole A′ unit and an up-shifted lowest unoccupied molecular orbital energy level compared to that of Y6 with a benzothiadiazole A′ unit and linear n-C11H23 upper side chains. The organic solar cells (OSCs) based on PM6:Se46 demonstrate a high power conversion efficiency over 18% with an increased short circuit current density compared to that of the L8-BO-based devices and a higher open circuit voltage than that of the Y6-based devices. The results indicate that the synergetic modification of selenium substitution in the A′ unit and branched alkyl upper side chain is an effective strategy to further promote photovoltaic performance for the narrow bandgap A-DA′D-A type acceptors.

Effects of Halogenation on Quinoline-Malononitrile based AIEgens: Photophysical Properties Investigation and Wash-Free Imaging.

Developing halogen-functionalized fluorescent dyes with intriguing photophysical properties, including enhanced photostability, is particularly important for bioimaging. In this work, we synthesized two new halogen-functionalized aggregation-induced emission (AIE)-active molecules, DQMF-OH and DQMCl-OH, based on the quinoline-malononitrile chromophore. The halogen effect on the photophysical characteristics was detailedly studied by absorption and fluorescence spectroscopy, density functional theory calculations, and crystal structures. Compared with non-halogen substituted AIE luminogen (AIEgen) DQM-OH, the halogen substituted DQMF-OH and DQMCl-OH exhibited red-shifted absorptions and emissions in the solution and solid state. In addition, DQMF-OH and DQMCl-OH also possessed enhanced fluorescence toward viscosity changes. These AIEgens served as remarkable imaging tools for cell tracking in a wash-free manner. Furthermore, DQMF-OH and DQMCl-OH showed much more excellent photobleaching resistance than DQM-OH. Our work sheds new light on developing fluorescent halogenated dyes with enhanced photophysical performances for biological applications.

NIRDye 812: A molecular platform tailored for multimodal bioimaging applications of targeted fluorescence- and photoacoustic-guided surgery.

The primary treatment for malignant tumors remains to be surgical removal of the diseased tissue. The presence or absence of residual diseased tissue at the tumor margin is the strongest predictor of postoperative prognosis and recurrence. Accordingly, reliance on the ability of surgeons to visually distinguish diseased tissue from healthy tissue unambiguously in real time is crucial. Near infrared-I (NIRI) fluorescence-emitting targeting biomolecular constructs such as anticancer antibody-fluorophore conjugates, namely cetuximab-IRDye® 800CW (CTB-IRDye® 800CW), are FDA-approved for clinical trial usage in the fluorescence-guided resection of diseased tissue due to affording improved direct visualization of tumor tissue when compared to the use of either the unaided eye under standard white light illumination (WLI) surgical techniques or non-targeting fluorophores. Unfortunately, though helpful, CTB-IRDye® 800CW affords limited (i) identification of diseased tissue and (ii) tumor margin delineation, because the immunoconjugate generates suboptimal tumor-to-background ratios (TBRs) as a result of its spectral/photophysical profiles poorly aligning with the fixed optical windows of pre-/clinical setups. As such, CTB-IRDye® 800CW is more prone to affording incomplete resection compared to if TBRs were higher due to otherwise. To aid in accurately identifying deep-seated diseased tissue, photoacoustic (PA) tomography has been implemented alongside CTB-IRDye® 800CW to achieve PA signals that could result in higher TBRs. However, in clinical trial practice, using IRDye® 800CW for PA imaging also yields subpar TBRs due to it affording low PA signals. To overcome such limitations, we developed NIRDye 812, a structurally-modified topological equivalent of IRDye® 800CW, to confer it the capability to yield both higher TBRs and superior PA signal than that of the equivalent CTB-conjugate and fluorophore IRDye® 800CW itself, respectively. To do so, we substituted the oxygen atom at its meso-position with a sulfur atom. CTB-NIRDye 812 demonstrated a red-shifted absorption wavelength at 796nm and a peak NIR-I fluorescence emission wavelength at 820nm, which better dovetails with the fixed windows of preinstalled fixed emission filters within commercial pre-/clinical NIR-I fluorescence imaging instruments. Overall, CTB-NIRDye 812 provided a∼2-fold increase in TBRs compared to those of CTB-IRDye® 800CW in vivo. Also, NIRDye 812 displayed an ∼60% higher PA signal than that of IRDye® 800CW. Collectively, we achieved our goal of improving upon the spectral/photophysical and PA properties of IRDye® 800CW via introducing a subtle modification to its electronic core such that its CTB immunoconjugate could potentially allow for fast track or breakthrough designation by the FDA due to its near-identical structure displaying considerably improved efficacy.

One, Two Three - Phosphaalkene Decoration Tailoring Solubility and Electronic Properties of Truxene-Based Electron Acceptors.

We report the functionalization and deplanarization of truxenes using pnictaalkene fragments. Selective introduction of one, two, or three Mes*-Pn fragments provides up to three fully reversible reductions based on the Pn=C fragments. The incorporation of the unsaturated heteroelement fragment as well as the contortion of the truxene core result in significantly red-shifted absorption spectra and interesting opto-electronic properties which are studied by electrochemistry and spectro-electrochemistry. Incorporation of arsaalkene (As=C) motifs gives significantly milder reduction potentials and red-shifted absorption, while phosphaalkene decorated truxene P3 can be functionalized using Au(I)Cl coordination. Furthermore, solubility is markedly increased upon incorporation of the Pn-Mes* fragments which renders these materials suitable for solution processing.

Synthesis of Peripherally Annulated Phenanthroporphyrins.

Synthesis of unusual phenanthroporphyrins was achieved by a stepwise precursor method. Precursor porphyrins fused with aryl-substituted bicyclo[2.2.2]octadiene afforded the corresponding arylbenzoporphyrins (arylBPs) by a retro Diels-Alder reaction. Unusual phenanthroporphyrins were obtained via the intramolecular Scholl reaction of arylBPs. X-ray crystallographic analysis revealed a distorted, helical porphyrin plane. Red-shifted absorptions of tetraphenanthroporphyrin are observed at ca. 580 nm for the B band and at 700-900 nm for the Q bands. Analysis of magnetic circular dichroism spectra and time-dependent density functional theory calculations was used to explain the optical properties and electronic structures.

Organic nanomaterials from self-assembly of BODIPY-benzothiadiazole conjugate for PDT/PTT synergistic therapy

Near-infrared light-induced phototherapy including photothermal therapy (PTT) and photodynamic therapy (PDT) has emerged as a new noninvasive method for cancer treatment owing to the nature of high efficiency and spatiotemporal selectivity. In this study, a new boron-dipyrromethene (BODIPY) molecule (BDP-BT) with donor (D)-receptor (A)-donor (D) structure was designed and successfully synthesized by conjugation of benzothiadiazole (BT) with BODIPY structure. The polyethylene glycol chain (PEG) was modified onto the meso site of BODIPY to improve the hydrophilicity and biocompatibility of the compound. The amphiphilic BDP-BT was then self-assembled into nanoparticles (BDP-BT NPs) with red-shifted absorption and enhanced hydrophilicity. BDP-BT NPs can produce effective reactive oxygen species and local hyperthermia triggered by a single laser. The in vitro experiments revealed that BDP-BT NPs had good biocompatibility and remarkable photocytoxicity. The half maximal inhibitory concentration (IC[Formula: see text] of BDP-BT NPs was valued at 22.17 [Formula: see text]g/mL under 635 nm laser irradiation. Furthermore, BDP-BT NPs can efficiently generate reactive oxygen species (ROS) in the tumor cells under light irradiation. Thus, the as-prepared BDP-BT NPs could be used as promising agents for PDT and PTT synergistic cancer therapy.

Investigation on thermal radiation property of near- and super-critical water in the pressure range of 20–25 MPa based on line-by-line method

With the rapid development of supercritical water gasification (SCWG) technology, investigation on thermal radiation property of water up to critical state (22.1 MPa, 647 K) is becoming important for precisely analyzing thermo-chemical process in this engineering. This paper explores radiative absorption coefficients κη of water under thermodynamic states of (20−25) MPa and (773–1273) K based on line-by-line (LBL) calculations. The results are validated against experimental data and molecular dynamic (MD) simulation values. It is shown that near- and super-critical water (NSCW) has five major radiation bands within spectral range of (1−50) μm. Compared to atmospheric water vapor (0.1 MPa), NSCW holds unique spectral characteristics, including dramatically smoothed spectrum, enormous absorption coefficient, and redshift or blueshift on spectral peak positions. Based on calculation results, a gray-band model for NSCW is proposed to solve problems of radiative heat transfer in SCWG engineering.

Anthracene-bridged sensitizers for environmentally compatible dye-sensitized solar cells: In silico modelling and prediction

Advancement in solar cells has gained the attention of researchers due to increasing demand and renewable energy sources. Modeling of electron absorbers and donors has been performed extensively for the development of efficient solar cells. In this regard, efforts are being made for designing effective units for the active layer of solar cells. In this study, CXC22 was utilized as a reference in which acetylenic anthracene acted as a π bridge and infrastructure was D-π-A. We theoretically designed four novel dye-sensitized solar cells JU1-JU4 by utilizing reference molecules to improve the photovoltaic and optoelectronic properties. All designed molecules differ from R by donor moiety modifications. Different approaches were done to R and all molecules to explore different analyses like binding energies, excitation energies, dipole moment, TDM (transition density matrix), PDOS (partial density of states), absorption maxima, and charge transfer analysis. For the evaluation of results, we used the DFT technique and the findings demonstrated that the JU3 molecule showed a better redshift absorption value (761 nm) as compared to all other molecules due to the presence of anthracene in the donor moiety which lengthens the conjugation. JU3 was proven to be the best candidate among all due to improved excitation energy (1.69), low energy band gap (1.93), higher λmax value, and improved electron and hole energy values leading toward higher power conversion efficiency. All the other theoretically formed molecules exhibited comparable outcomes as compared to a reference. As a result, this work revealed the potential of organic dyes with anthracene bridges for indoor optoelectronic applications. These unique systems are effective contributors to the development of high-performance solar cells. Thus, we provided efficient systems to the experimentalists for the future development of solar cells.

Effects of Halogenation on Cyclopentadithiophenevinylene-Based Acceptors with Excellent Responses in Binary Organic Solar Cells.

In recent years, non-fused non-fullerene acceptors (NFAs) have attracted increasing consideration due to several advantages, which include simple preparation, superior yield, and low cost. In the work reported here, we designed and synthesized three new NFAs with the same cyclopentadithiophenevinylene (CPDTV) trimer as the electron-donating unit and different terminal units (IC for FG10, IC-4F for FG8, and IC-4Cl for FG6). Both halogenated NFAs, i.e., FG6 and FG8, show red-shifted absorption spectra and higher electron mobilities (more pronounced for FG6) in comparison with FG10. Moreover, the dielectric constants of these materials also increased upon halogenation of the IC terminal units, thus leading to a reduction in the exciton binding energy, which is favorable for dissociation of excitons and subsequent charge transfer despite the driving force (highest occupied molecular orbital and lowest unoccupied molecular orbital offsets) being very small. The organic solar cells (OSCs) constructed using these acceptors and PBDB-T, as the donor, showed PCE values of 15.08, 12.56, and 9.04% for FG6, FG8, and FG10, respectively. The energy loss for the FG6-based device was the lowest (0.45 eV) of all the devices, and this may be attributed to it having the highest dielectric constant, which leads to a reduction in the binding energy of exciton and a small driving force for hole transfer from FG6 to PBDB-T. The results indicate that the NFA containing the CPDTV oligomer core and halogenated terminal units can efficiently spread the absorption spectrum to the NIR zone. Non-fused NFAs have a bright future in the quest to obtain efficient OSCs with low cost for marketable purposes.

Engineering two-dimensional SnC/HfSSe heterojunction as a direct Z-scheme photocatalyst for water splitting hydrogen evolution

Developing robust water-splitting photocatalyst remains a pivotal challenge for the conversion of solar energy to hydrogen fuel. Herein, we report SnC/HfSSe heterojunctions to be a competitive direct Z-scheme photocatalysts with HfSSe acting as an oxidant and SnC as a reductant for water-splitting hydrogen generation by employing the first-principles calculations. The photogenerated electron–hole migration logically follows the Z-scheme path due to the large interlayer built-in electric field, small interlayer bandgap, proper band edge alignment, and high interlayer carrier recombination. The overpotential is appropriate to the oxygen evolution reaction (OER), while the overpotential is slightly large to the hydrogen envolution reaction (HER) so that the incident photon energy above the band gap of the components is required for the HER. The heterojunctions have excellent visible light absorption, exhibiting the remarkable red shift and stronger light absorption with respect to the two components of the heterojunction. Moreover, the heterojunction exhibits an outstanding solar-to-hydrogen (STH) efficiency as high as 27% in extremely acidic solution.

A Bright Surprise: Live‐Cell Labeling with Negatively Charged Fluorescent Probes based on Disulfonated Rhodamines and HaloTag

AbstractDisulfonated rhodamines are photostable and bright dyes widely used in life science and optical microscopy. However, di‐sulfonated dyes were considered cell impermeable and not applicable in living cells. We challenged this assumption with 5 most popular rhodamines (Rho) having two carboxylic acid residues, versatile sulfonation patterns and emitting green (AS488), yellow (Rho530), orange (Rho565) and red (Rho590 and STAR RED) light. The probes comprising one rhodamine entity and a HaloTagTM amine (O2) ligand (x) were prepared and applied for labeling of living, Vimentin‐Halo (VIM‐Halo) expressing U‐2 OS cells. Surprisingly, we observed specific and bright staining with simplest compounds Rho590‐x, Rho565‐x and Rho530‐x bearing two negative charges; they performed well also in stimulated emission depletion (STED) microscopy. Specific staining and red shifts in absorption and emission bands were observed with other probes having one negative charge; they were prepared by native chemical ligation and esterification.

Recyclable Polycarbosilane from a Biomass-Derived Bifuran-Based Monomer.

Two of the most fundamental principles for the development of next-generation polymers are production from renewable biomass and well-designed recyclability. Bifuran derivatives represent promising building blocks for functional polymers on account of their high rigidity, strong interchain interactions, and extended π-conjugation. In this study, a polycarbosilane containing a bifuran-based repeat unit was prepared via the hydrosilylation of dihydrosilylbifuran and 1,5-hexadiene. The crystallinity and thermal properties of the bifuran-containing polycarbosilane were superior to those of a corresponding polycarbosilane containing a single-furan-based repeat unit and comparable to those of the benzene-based analogue due to the rigidity and interchain interactions of the poly(bifurancarbosilane) unit. The bifuran moiety in the repeat unit causes a red-shift and strong UV absorption of the polycarbosilane compared to that containing the single-furan-based and benzene-based repeat units. The bifuran moiety also renders the resulting polycarbosilane strongly fluorescent, while the polycarbosilanes containing the benzene-based and single-furan-ring-based repeat units did not emit fluorescence. These desirable photoproperties result from the extension of the σ-π conjugation in the repeat unit. Furthermore, the chemical recyclability is a unique and attractive property of the bifuran-based polycarbosilane; upon treatment with trifluoroacetic acid, bifuran can be regenerated as the monomer, while trifluoroacetate silane can be up-cycled to the corresponding polysiloxane. Thus, the bifuran motif endows polycarbosilane with improved thermal, optical, and recycling properties.

Enhanced photocatalytic performance of heterostructure CNNS@Bi2WO6 photocatalysts towards degradation of organic pollution

The flower-structured CNNS@Bi2WO6 heterostructure photocatalsts with enhanced photocatalytic performance were successfully fabricated by facile in-situ hydrothermal method. Compared with the g-C3N4 nanosheets (CNNS) and pure Bi2WO6, the flower-structured CNNS@Bi2WO6 heterostructure photocatalysts exhibited better photocatalytic performance and photocatalytic stability for degradation of rhodamine B (RhB) and tetracycline (TC) under visible. The effects of different CNNS contents on the photocatalytic efficiency of the heterostructure photocatalysts have been investigated. The results show that the CNNS@Bi2WO6 heterostructure photocatalst with CNNS mass ratio of 7% presents the best photocatalytic performance. The photocatalytic activity enhancement should be attributed to the effective separation of photogenerated electron-hole pairs and the efficient visible-light utilization efficiency. Compared with CNNS, the absorption of CNNS@Bi2WO6 photocatalysts in the visible region has been greatly strengthened, with red-shift absorption edge by the UV–vis diffuse reflectance spectra (DRS). The connection between CNNS and Bi2WO6 was studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The scavenging experiments with different trapping agents demonstrates that the photogenerated h+ in the system can play the main role during the RhB degradation process. Subsequently, the possible mechanism of photocatalytic degradation over flower-structured CNNS@Bi2WO6 heterostructure photocatalysts has been proposed.

Half-Planar-Half-Twisted Small Molecule Acceptors for Efficient Polymer Solar Cells

A series of asymmetric acceptor−π–donor−π′–acceptor-type (A-π-D-π′-A) non-fullerene acceptors (NFAs) were designed and synthesized, namely, h-IEICO, h-IEICO-2F, h-IEICO-4F, and h-IEICO-4Cl, which were prepared by simultaneously linking halogenated ending groups both at the 4-position of 3-ethylhexoxythiophene (π-segment) of one side and at the 5-position of 3-ethylhexoxythiophene (π′-segment) of another side. The asymmetric molecular structure, as well as the radically different steric hindrance caused by the two distinct π-bridged segments, successfully produced a wondrous half-planar-half-twisted backbone configuration. As a result of the special molecular structures of these materials, as well as the excellent electron-attracting properties of the fluorine and chlorine atoms attached to them, h-IEICO-4F and h-IEICO-4Cl are characterized by an absorption red-shift and a down-shifted molecular energy level among all four molecules. The J52:h-IEICO-4F device demonstrated preferable exciton dissociation and collection efficiency, suppressed charge recombination, a high and balanced charge transport ability, superior morphological properties, and better crystallinity, resulting in an efficiency of 11.65%. However, the efficiencies of the J52:h-IEICO-, J52:h-IEICO-2F-, and J52:h-IEICO-4Cl-based solar cells are 5.24, 9.96, and 10.43%, respectively. This work demonstrates the significant influence of the adjusting planarity of the conjugated backbone as well as the fine-tuning of the end-group halogenation substitution on the characteristic regulation and the photovoltaic performances of NFAs for efficient PSCs.

Fluorescent Molecular Rotors Based on Hinged Anthracene Carboxyimides.

Temperature and viscosity are essential parameters in medicine, environmental science, smart materials, and biology. However, few fluorescent sensor publications mention the direct relationship between temperature and viscosity. Three anthracene carboxyimide-based fluorescent molecular rotors, 1DiAC∙Cl, 2DiAC∙Cl, and 9DiAC∙Cl, were designed and synthesized. Their photophysical properties were studied in various solvents, such as N, N-dimethylacetamide, N, N-dimethylformamide, 1-propanol, ethanol, dimethyl sulfoxide, methanol, and water. Solvent polarizability resulted in a solvatochromism effect for all three rotors and their absorption and emission spectra were analyzed via the Lippert-Mataga equation and multilinear analysis using Kamlet-Taft and Catalán parameters. The rotors exhibited red-shifted absorption and emission bands in solution on account of differences in their torsion angle. The three rotors demonstrated strong fluorescence in a high-viscosity environment due to restricted intramolecular rotation. Investigations carried out under varying ratios of water to glycerol were explored to probe the viscosity-based changes in their optical properties. A good linear correlation between the logarithms of fluorescence intensity and solution viscosity for two rotors, namely 2DiAC∙Cl and 9DiAC∙Cl, was observed as the percentage of glycerol increased. Excellent exponential regression between the viscosity-related temperature and emission intensity was observed for all three investigated rotors.

Photosynthesis in the near infrared: the γ subunit of Blastochloris viridis LH1 red-shifts absorption beyond 1000 nm.

The reaction centre (RC) in purple phototrophic bacteria is encircled by the primary light-harvesting complex 1 (LH1) antenna, forming the RC-LH1 'core' complex. The Qy absorption maximum of LH1 complexes ranges from ∼875-960 nm in bacteriochlorophyll (BChl) a-utilising organisms, to 1018 nm in the BChl b-containing complex from Blastochloris (Blc.) viridis. The red-shifted absorption of the Blc. viridis LH1 was predicted to be due in part to the presence of the γ subunit unique to Blastochloris spp., which binds to the exterior of the complex and is proposed to increase packing and excitonic coupling of the BChl pigments. The study by Namoon et al. provides experimental evidence for the red-shifting role of the γ subunit and an evolutionary rationale for its incorporation into LH1. The authors show that cells producing RC-LH1 lacking the γ subunit absorb maximally at 972 nm, 46 nm to the blue of the wild-type organism. Wavelengths in the 900-1000 nm region of the solar spectrum transmit poorly through water, thus γ shifts absorption of LH1 to a region where photons have lower energy but are more abundant. Complementation of the mutant with a divergent copy of LH1γ resulted in an intermediate red shift, revealing the possibility of tuning LH1 absorption using engineered variants of this subunit. These findings provide new insights into photosynthesis in the lowest energy phototrophs and how the absorption properties of light-harvesting complexes are modified by the recruitment of additional subunits.

Regulating the Electronic Structure of Metal Nanoclusters by Longitudinal Single-Dithiolate Substitution.

It is significant but challenging to understand the property evolution of metal nanoclusters by orientated regulation of the electronic structure. Previous research has demonstrated that the optical properties of metal nanoclusters with anisotropic structures are greatly impacted by their longitudinal electronic structure. However, the manipulation of optical properties of metal nanoclusters by regulating their electronic structure through longitudinal dithiolate substitutions has not yet been reported. In this study, we first achieved the longitudinal single-dithiolate replacement of metal nanoclusters and obtained two novel nanoclusters: Au28(SPh-tBu)18(SCH2SCH2S) and Au28(SPh-tBu)18(SCH2CH2CH2S). Both experimental and theoretical results demonstrated the regulation of the electronic structure (dipole moment) in the z (longitudinal) and x directions, resulting in absorption redshift and photoluminescence (polarity) enhancement. These findings not only deepen the understanding of the property-electronic structure correlation of metal nanoclusters but also provide guidance for their subtle property tuning.