Near-infrared Photoabsorption Research Articles

Spin–spin interaction in a highly stable neutral diradical: σ-boned dimer of trioxotriangulene

Abstract A σ-bonded dimer of 4,8,10-trioxotriangulene (TOT) was newly synthesized and its electronic spin structure was characterized. The neutral diradical had a singlet ground state due to the strong antiferromagnetic interaction through the σ-bond. The strong intramolecular interaction within the σ-dimer caused a near-infrared photoabsorption of around 700–1,000 nm, which is close to that of the π-stacked dimer of TOT monoradical.

Facile Synthesis, Optical and Photoluminescence Properties of Copper Tungstate Phosphors with Strong Near-Infrared Photoabsorption

Facile Synthesis, Optical and Photoluminescence Properties of Copper Tungstate Phosphors with Strong Near-Infrared Photoabsorption

Synthesis of degradable titanium disulfide nanoplates for photothermal ablation of tumors

Inorganic nanomaterials with high photothermal effects have received immense interest for photothermal therapy of tumors, while most of them suffer from long-term safety concerns due to their non-degradability. To address this issue, we have reported the PEGylated titanium disulfide (TiS2-PEG) nanoplates as degradable photothermal agents. The oleylamine-capped TiS2 nanoplates with an average size of ∼200 nm have been prepared via a high-temperature liquid-phase route, and they can be easily dispersed in nonpolar solvents and remain high stability for at least one month. To confer hydrophilicity, the oleylamine-capped TiS2 nanoplates are then surface-modified with amphiphilic PEGylated lipids through Van der Waals interactions. When dispersed in saline solution at 37 °C, the TiS2-PEG are unstable and they can be gradually decomposed into Ti(OH)4/TiO2 sol ultrasmall particles (<5 nm) within 72 h, indicating the suitable degradable feature. In addition, the TiS2-PEG nanoplates exhibit a strong near-infrared photoabsorption with a high photothermal conversion efficacy of 36.3% upon 808 nm laser irradiation. The in vitro and in vivo experiments confirm the low cytotoxicity of TiS2-PEG and high photothermal ablation ability towards cancer cells by the combination of TiS2-PEG and 808 nm laser. Importantly, owing to the degradability and size reduction, part of TiS2-PEG can be excreted from mice bodies via urine and feces, thus alleviating safety concerns. Therefore, the present TiS2-PEG nanoplates can act as a safe and degradable photothermal agent for tumor therapy, which also provides some insights into developing other degradable inorganic nanoagents.

Hybrid stranski-krastanov/submonolayer quantum dot heterostructure with type-II band alignment: an efficient way of near infrared photovoltaic energy conversion

Photoabsorption throughout the entire solar spectrum and successive efficient photovoltaic energy conversion are always being the primary goal in the domain of solar energy conversion technology. Many strategies like multijunction, tandem, intermediate band, quantum dot/well, nanowire, plasmonic metasurface, organic-inorganic, etc., have been demonstrated to facilitate broadband absorption, starting from visible to near infrared (NIR) range. Here we have proposed a novel vertically coupled stranski-krastanov/submonolayer (SK/SML) quantum dot heterostructure with type-II band alignment for improved NIR photodetection. Standard III-As based PIN heterostructure facilitate with hybrid SK/SML quantum dot layers show broad NIR photo-absorption. Structural characteristic reveals improved material quality with reduced cumulative strain for 15 nm inter-dot barrier sample. Temperature/power dependent luminescence spectroscopy enlightens on the carrier transition mechanism. Thus explains the reason behind this broad NIR photo-voltage generation which is further clarified with device performance. Starting from this point, further theoretical investigation has been done to understand the effect of Sb incorporation in strain profile, band alignment, and absorption window. Finally, we have proposed a superior configuration for broad and tunable NIR photodetection.

Synthesis of one-for-all type Cu5FeS4 nanocrystals with improved near infrared photothermal and Fenton effects for simultaneous imaging and therapy of tumor

CuS materials exhibit excellent near infrared (NIR) photoabsorption and photothermal effect, but they are lack of magnetic resonance imaging (MRI) ability. Fe-based nanomaterials possess MRI capacity, but they usually exhibit poor NIR photoabsorption. In order to solve the above problems, we synthesize three kinds of CuxFeySz samples, including FeS2, CuFeS2 and Cu5FeS4 nanomaterials. With the Cu/Fe ratios increase from 0/1.0 to 1.0/1.0 and 5.0/1.0, the localized surface plasmon resonances (LSPRs) characteristic peaks shift to longer wavelength, and the photothermal transduction efficiencies go up from 24.4% to 36.6% and 45.9%. Thus, Cu5FeS4 is found to be the most excellent sample. Especially, Cu5FeS4 exhibits photothermal-enhanced Fenton effect, which can produce hydroxyl radical (·OH) under a wide pH range (e.g., pH = 5.4–7.4) to realize the chemodynamic effect. In addition, Cu5FeS4 can be employed as an efficient MRI contrast agent. When Cu5FeS4 dispersion is intravenously injected into the mouse, the tumor can be detected by MRI as well as thermal imaging, and eliminated through photothermal-enhanced chemodynamic effect. Therefore, Cu5FeS4 can be used as an efficient “one-for-all” type agent for MRI-guided photothermal-enhanced chemodynamic therapy of tumor.

CuFeS2 Nanoassemblies With Intense Near-Infrared Absorbance for Photothermal Therapy of Tumors

Photothermal therapy is an efficient cancer treatment method. The development of nanoagents with high biocompatibility and near-infrared (NIR) photoabsorption band is a prerequisite to the success of this method. However, the therapeutic efficiency of photothermal therapy is rather limited because most of the nanoagents have a low photothermal conversion efficiency. In this study, we aimed to develop CuFeS2 nanoassemblies with an excellent photothermal effect using the liquid-solid-solution method. The CuFeS2 nanoassemblies we developed are composed of ultrasmall CuFeS2 nanoparticles with an average size of 5 nm, which have strong NIR photoabsorption. Under NIR laser illumination at 808 nm at the output power intensity of 1.0 W cm-2, the CuFeS2 nanoassemblies could rapidly convert NIR light into heat, achieving a high photothermal conversion efficiency of 46.8%. When K7M2 cells were incubated with the CuFeS2 nanoassemblies and then exposed to irradiation, their viability decreased progressively as the concentration of the CuFeS2 nanoassemblies increased. Furthermore, a concentration of 40 ppm of CuFeS2 nanoassemblies was lethal to the cells. Importantly, after intratumoral injection of 40 ppm CuFeS2 nanoassemblies, the tumor showed a high contrast in the thermal image after laser irradiation, and tumor cells with condensed nuclei and a loss of cell morphology could be thermally ablated. Therefore, the CuFeS2 nanoassemblies we synthesized have a high biocompatibility and robust photothermal effect and can, thus, be utilized as a novel and efficient photothermal agent for tumor therapy.

Chitosan-mediated green synthesis and folic-acid modification of CuS quantum dots for photoacoustic imaging guided photothermal therapy of tumor

CuS nanomaterials capped with artificial organic-molecules or polymers have been well demonstrated as efficient photothermal nanoagents for the therapy of tumor, but their biocompatibility and target ability should be improved. To address these problems, we have used chitosan (CS) as the biomacromolecule model and surface ligands to prepare CuS quantum dots (QDs) via a simple co-precipitation method. CuS-CS QDs are then conjugated with folic acid (FA). The resulting CuS-CS-FA QDs are composed of hexagonal phase nanodots with sizes of about 4 nm. FA modification process has no apparent influence on the size, phase and composition of the QDs. Furthermore, the zeta potential and infrared spectroscopy confirm the efficient conjugation of FA. CuS-CS-FA QDs exhibit strong near-infrared photoabsorption and high photothermal efficiency (47.0%). As a result of the presence of CS ligand and FA modification, CuS-CS-FA QDs have good biocompatibility and relatively high cellular uptake efficacy. When CuS-CS-FA QD dispersion is injected intravenously into the tumor-bearing mice, the photoacoustic imaging reveals that CuS-CS-FA QD can be efficiently targeted and accumulated in the tumor and reach the peak dose at 60 min. The irradiation of 1064-nm laser (1.0 W cm−2, 10 min) results in the efficient inhibition of tumor growth, without treatment-induced toxicity. Therefore, CuS-CS-FA QDs have great potential to become biocompatible multifunctional nanoagents for imaging guided therapy of tumor.

Synthesis of Bi2WO6−xnanodots with oxygen vacancies as an all-in-one nanoagent for simultaneous CT/IR imaging and photothermal/photodynamic therapy of tumors

All-in-one nanoagents with a single-component and all-required functions have attracted increasing attention for the imaging-guided therapy of tumors, but the design and preparation of such nanoagents remain a challenge. Herein, we report the introduction of oxygen vacancies to traditional semiconductors with heavy-metal elements for tuning photoabsorption in the near infrared (NIR) region, by using Bi2WO6 (band-gap: ∼2.7 eV) as a model. Bi2WO6-x nanodots with sizes of ∼3 or ∼8 nm have been prepared by a facile coprecipitation-solvothermal method assisted by citric acid (CA, 0.1-1.5 g) as the reduction agent. CA confers the removal of O atoms from the [Bi2O2]2+ layer during the solvothermal process, resulting in the formation of plenty of oxygen vacancies in the Bi2WO6-x crystal. As a result, NIR photoabsorption of Bi2WO6-x nanodots can be remarkably enhanced with the increase of the CA amount from 0 to 1.0 g. Under irradiation of a single-wavelength (808 nm, 1.0 W cm-2) NIR laser, black Bi2WO6-x-CA1.0 nanodots can not only efficiently produce a sufficient amount of heat with a photothermal conversion efficiency of 45.1% for photothermal therapy, but also generate singlet oxygen (1O2) for photodynamic therapy. Furthermore, due to the presence of heavy-metal (Bi and W) elements, Bi2WO6-x-CA1.0 nanodots have high X-ray attenuation ability for CT imaging. After the Bi2WO6-x-CA1.0 nanodot dispersion is injected into the tumor-bearing mice, the tumor can be imaged by using CT and an IR thermal camera. After irradiation with a single-wavelength (808 nm, 1.0 W cm-2, 10 min) NIR laser, the tumor can be completely suppressed by the synergic photothermal and photodynamic effects of Bi2WO6-x-CA1.0 nanodots, without recurrence and treatment-induced toxicity. Therefore, Bi2WO6-x nanodots have great potential as a novel all-in-one nanoagent for the imaging and phototherapy of tumors.

Trioxotriangulene with carbazole: a donor–acceptor molecule showing strong near-infrared absorption exceeding 1000 nm

A donor–acceptor type trioxotriangulene neutral radical derivative having three carbazolyl groups as electron-donors was newly synthesized, and exhibited a strong near-infrared photo absorption over 1000 nm.

Melt Electrospun Reduced Tungsten Oxide /Polylactic Acid Fiber Membranes as a Photothermal Material for Light-Driven Interfacial Water Evaporation.

The development of efficient photothermal materials is the most important issue in solar water evaporation. In this work, melt electrospun reduced tungsten oxide/polylactic acid (WO2.72/PLA) fiber membranes were successfully prepared with improved near-infrared (NIR) photothermal conversion properties owing to strong NIR photoabsorption by the metal oxide. WO2.72 powder nanoparticles were incorporated into PLA matrix by melt processing, following which the composites were extruded into wires using a single screw extruder. Subsequently, fiber membranes were prepared from the extruded wire of the WO2.72/PLA composite by melt electrospinning, which is a cost-effective technique that can produce fiber membranes without the addition of environmentally unfriendly chemicals. The melt electrospun WO2.72/PLA fiber membranes, floatable on water due to surface hydrophobicity, were systematically designed for, and applied to, vapor generation based on the interfacial concept of solar heating. With the photothermal WO2.72/PLA fiber membrane containing 7 wt % WO2.72 nanoparticles, the water evaporation efficiency was reached 81.39%, which is higher than that for the pure PLA fiber membrane and bulk water. Thus, this work contributes to the development of novel photothermal fiber membranes in order to enhance light-driven water evaporation performance for potential applications in the fields of water treatment and desalination.

Thiol-capped Bi nanoparticles as stable and all-in-one type theranostic nanoagents for tumor imaging and thermoradiotherapy

Bismuth (Bi)-based semiconductors and composites have been well developed for cancer treatments due to their multimodal diagnostic and therapeutic functions, while the development of metallic Bi nanocrystals is rather hindered by the easy-oxidation and unsatisfactory near-infrared photoabsorption. Herein, we prepared uniform Bi nanoparticles (∼40 nm) capped with thiol ligands (Bi-SR) through the chemical reduction method and then surface-modified them with PEGylated phospholipids. The resulting Bi-SR-PEG has strong NIR absorbance and high photothermal conversion efficiency of 45.3%. Importantly, thiol ligands on the surface of Bi-SR-PEG can significantly prevent the metal Bi core from oxidation because of the strong chemisorption energy between sulfur and metal, thus maintaining the high stability and long-term near-infrared photoabsorption. More importantly, given the low toxicity, good blood compatibility and high X-ray attenuation coefficient, Bi-SR-PEG can passively accumulatein the tumor area through intravenous injection, endowing them with the simultaneous tumor CT imaging and thermoradiotherapy, and thereafter they can be metabolized and excreted from the mice body overtime. Therefore, the satisfying therapeutic effect of tumors can be achieved, undoubtedly verifying that Bi-SR-PEG can be used as a novel, stable and all-in-one type theranostic nanoagent for cancer treatment.

Carbon Dots/Prussian Blue Satellite/Core Nanocomposites for Optical Imaging and Photothermal Therapy.

Integration of optical imaging modality with photothermal therapy (PTT) for simultaneously providing oncotherapy and bioimaging enables an optimized therapeutic efficacy and higher treatment accuracy and therefore has emerged as a prospective cancer treatment. However, it remains challenging to develop biocompatible PTT nanoagents capable of imaging, monitoring, and diagnosis. Carbon dots (CDs) possess unique photoluminescent (PL) properties and intrinsic biocompatibility; while Prussian blue nanoparticles (PBNPs) are nontoxic with efficient photothermal conversion capacity for PTT. Herein, a simple, cost-effective, and environmentally benign method was developed to strategically fabricate CD-decorated PBNP (CDs/PBNP) nanocomposites with satellite/core structure. The CDs/PBNPs possess distinct green PL emission and near-infrared photoabsorption with high efficiency and photothermal stability. In vitro and in vivo toxicity tests prove the biocompatibility of the CDs/PBNPs. Moreover, the applicability of CDs/PBNPs as nanotheranostic agents was tested, which suggests that CDs/PBNPs possess promising imaging and effective tumor ablation properties.

Design and Functionalization of the NIR-Responsive Photothermal Semiconductor Nanomaterials for Cancer Theranostics.

Despite the development of medical technology, cancer still remains a great threat to the survival of people all over the world. Photothermal therapy (PTT) is a minimally invasive method for selective photothermal ablation of cancer cells without damages to normal cells. Recently, copper chalcogenide semiconductors have emerged as a promising photothermal agent attributed to strong absorbance in the near-infrared (NIR) region and high photothermal conversion efficiency. An earlier study witnessed a rapid increase in their development for cancer therapy, including CuS, Cu2-xSe and CuTe nanocrystals. However, a barrier is that the minimum laser power intensity for effective PTT is still significantly higher than the conservative limit for human skin exposure. Improving the photothermal conversion efficiency and reducing the laser power density has become a direction for the development of PTT. Furthermore, in an effort to improve the therapeutic efficacy, many multimode therapeutic nanostuctures have been formulated by integrating the photothermal agents with antitumor drugs, photosensitizers, or radiosensitizers, resulting in a synergistic effect. Various functional materials also have been absorbed, attached, encapsulated, or coated on the photothermal nanostructures, including fluorescence, computed tomography, magnetic resonance imaging, realizing cancer diagnosis, tumor location, site-specific therapy, and evaluation of therapeutic responses via incorporation of diagnosis and treatment. In this Account, we present an overview of the NIR-responsive photothermal semiconductor nanomaterials for cancer theranostics with a focus on their design and functionalization based on our own work. Our group has developed a series of chalcogenides with greatly improved NIR photoabsorption as photothermal agents, allowing laser exposure within regulatory limits. We also investigated the photothermal bioapplications of hypotoxic oxides including WO3-x, MoO3-x, and RuO2, expanding their applications into a new field of photothermal materials. Furthermore, considering a much more enhanced therapeutic effect of multifunctional nanoagents, our group elaborately designed many nanocomposites, such as core-shell nanoparticles of Fe3O4@Cu2-xS and Cu9S5@mSiO2, based on the integration of photothermal agents with contrast agents or other anticancer medicines, achieving cancer theranostic and synergistic treatment. Ternary compound nanocrystals were also prepared with synthetic simplicity for multimodal imaging-guided therapy for cancer. This Account summarizes our past work, including the design and concept, synthesis, and characterization for in vitro and in vivo applications. Then, we analyzed the tendencies of the NIR-responsive photothermal semiconductor nanomaterials for clinical applications, highlighting their prospects and challenges. We believe that the photothermal technology from the NIR-responsive photothermal semiconductor nanomaterials would promote cancer theranostics to result in giant strides forward in the future.

The closo-Si12C12 molecule from cluster to crystal: Effects of hydrogenation and oligomerization on excited states.

Excited state properties of chain and cyclic oligomers of closo-Si12C12 moieties are calculated using time-dependent density functional theory methods. Ultraviolet, visible, and near-infrared photo-absorption properties are described for oligomers that form by linking closo-Si12C12 monomer moieties through Si-Si bonds. Natural transition orbitals for electron and hole states of stationary-state excitons in oligomers were compared to understand how exciton states are influenced by oligomer structure. Depending on the structure, some prominent excited states have large electron-hole charge separation while others do not; some exhibit exciton delocalization while others do not. With increasing oligomer length, the character of the transition between silicon and carbon regions tends to be maintained. And the extent of exciton delocalization and charge separation for an excitation is strongly influenced by the number and types of Si-Si links between oligomer units. We find that cyclic quadramers have spectroscopy properties akin to those of J-aggregates, including the tendency to collapse oligomer excitation transition energies into a narrow single peak. Hydrogenation influences some excited state distributions and energies. Phase behaviors reveal electron state or hole state equivalence in certain molecules that are differently hydrogenated, illustrating the potential for near-resonant exciton transfer between adjacent donor and acceptor species.

Multifunctional Theranostic Agent of Cu2(OH)PO4 Quantum Dots for Photoacoustic Image-Guided Photothermal/Photodynamic Combination Cancer Therapy.

Image-guided phototherapy is considered to be a prospective technique for cancer treatment because it can provide both oncotherapy and bioimaging, thus achieving an optimized therapeutic efficacy and higher treatment accuracy. Compared to complicated systems with multiple components, using a single material for this multifunctional purpose is preferable. In this work, we strategically fabricated poly(acrylic acid)- (PAA-) coated Cu2(OH)PO4 quantum dots [denoted as Cu2(OH)PO4@PAA QDs], which exhibit a strong near-infrared photoabsorption ability. As a result, an excellent photothermal conversion ability and the photoactivated formation of reactive oxygen species could be realized upon NIR irradiation, concurrently meeting the basic requirements for photothermal and photodynamic therapies. Moreover, phototherapeutic investigations on both cervical cancer cells in vitro and solid tumors of an in vivo mice model illustrated the effective antitumor effects of Cu2(OH)PO4@PAA upon 1064-nm laser irradiation, with no detectable lesions in major organs during treatment. Meanwhile, Cu2(OH)PO4@PAA is also an exogenous contrast for photoacoustic tomography (PAT) imaging to depict tumors under NIR irradiation. In brief, the Cu2(OH)PO4@PAA QDs prepared in this work are expected to serve as a multifunctional theranostic platform.

Synergistic Effect Induced High Photothermal Performance of Au Nanorod@Cu7S4 Yolk–Shell Nanooctahedron Particles

Au nanorod (NR) which has strong LSPR (longitudinal surface plasmon resonance) effect in near-infrared (NIR) region was introduced into the Cu7S4 hollow NPs to form Au NR@Cu7S4 yolk–shell structured nanoparticles (YSNPs) for improving the photothermal property of NPs. The optimum photothermal conversion efficiency of the as-prepared YSNPs is 68.6%. The hybrid YSNPs had the highest photothermal property compared with the equivalent used Au NR and pure Cu7S4 because of the synergistic effect of metal and semiconductor. In this case, the synergistic effect in YSNPs was discussed by tuning sizes of the YSNPs and the thickness of Cu7S4 shell. The experimental results demonstrated that the NIR photoabsorption and the photothermal conversion performance of Au NR@Cu7S4 YSNPs were much dependent on the geometric change of YSNPs, since the electrical field interaction between inner Au NR core and outer Cu7S4 shell is closely effected by the distance of two materials and thickness of out-shell, as confirmed by the 3...

Semimetal nanomaterials of antimony as highly efficient agent for photoacoustic imaging and photothermal therapy

In this study we report semimetal nanomaterials of antimony (Sb) as highly efficient agent for photoacoustic imaging (PAI) and photothermal therapy (PTT). The Sb nanorod bundles have been synthesized through a facile route by mixing 1-octadecane (ODE) and oleyl amine (OAm) as the solvent. The aqueous dispersion of PEGylated Sb NPs, due to its broad and strong photoabsorption ranging from ultraviolet (UV) to near-infrared (NIR) wavelengths, is applicable as a photothermal agent driven by 808 nm laser with photothermal conversion efficiency up to 41%, noticeably higher than most of the PTT agents reported before. Our in vitro experiments also showed that cancer cell ablation effect of PEGylated Sb NPs was dependent on laser power. By intratumoral administration of PEGylated Sb NPs, 100% tumor ablation can be realized by using NIR laser irradiation with a lower power of 1 W/cm2 for 5 min (or 0.5 W/cm2 for 10 min) and no obvious toxic side effect is identified after photothermal treatment. Moreover, intense PA signal was also observed after intratumoral injection of PEGylated Sb NPs and NIR laser irradiation due to their strong NIR photoabsorption, suggesting PEGylated Sb NPs as a potential NIR PA agent. Based on the findings of this work, further development of using other semimetal nanocrystals as highly efficient NIR agents can be achieved for vivo tumor imaging and PTT.

Optimization of photothermal performance of hydrophilic W18O49 nanowires for the ablation of cancer cells in vivo.

Near-infrared (NIR) laser-induced photothermal ablation (PTA) therapy has great potential to revolutionize conventional therapeutic approaches for cancers, and a prerequisite is to obtain biocompatible and efficient photothermal agents. Herein, we have developed hydrophilic W18O49 nanowires with average lengths of about 800 nm (abbreviated as W18O49-800 NWs) as an efficient photothermal agent, which are prepared by the solvothermal synthesis-simultaneous PEGylation/exfoliation/breaking two-step route. These W18O49-800 NWs exhibit stronger NIR photoabsorption than short nanowires with average lengths of about 50 nm (abbreviated as W18O49-50 NWs) that are prepared via a solvothermal one-step route. Under irradiation of 980 nm with a safe intensity of 0.72 W cm-2, the aqueous dispersion of W18O49-800 NWs (1.0 mg mL-1) exhibits the temperature elevation by 35.2 °C in 5 min; which is a 37.5% increase compared to that (by 25.6 °C) from W18O49-50 NWs (1.0 mg mL-1). More importantly, under 980 nm laser irradiation (0.72 W cm-2) for 10 min, in vivo cancer cells can be efficiently ablated by the photothermal effects of W18O49-800 NWs. Therefore, these W18O49-800 NWs can be used as a more efficient and promising photothermal nanoagent for the ablation of cancer cells in vivo.

Nanoscale-resolved near-infrared photoabsorption spectroscopy and imaging of individual gallium antimonide quantum dots

Near-infrared photoabsorption spectra of individual dots of gallium antimonide (GaSb) epitaxially grown on a silicon substrate were investigated by nanoscale-resolved spectroscopic measurements and by imaging through scanning tunneling microscopy (STM). With a short acquisition time of a few minutes, photomodulated current spectroscopy (STM-PMCS), based on STM without a tunneling current, showed that our samples exhibited photoabsorption with a peak centered at about 0.78 eV. Spatial variations in STM-PMCS imaging arose from differences in dot sizes. However, the STM-PMCS images were insufficiently unambiguous to permit interpretation of the signal origin in the tunneling region, because a tip-expansion effect could have arisen through photointensity modulation. Spectral features revealed by STM-based electric field modulation spectroscopy (STM-EFMS), which is free of the tip-expansion effect, showed a significant size-dependent energy shift at around 0.8 eV that was attributed to a quantum-confinement effect on the bound states of the GaSb quantum dots. Our approach, which utilizes the merits of both STM-PMCS and STM-EFMS, is efficient in elucidating the photoabsorption properties of nanoscale objects.

Near-infrared photoabsorption by C60 dianions in a storage ring

We present a detailed study of the electronic structure and the stability of C(60) dianions in the gas phase. Monoanions were extracted from a plasma source and converted to dianions by electron transfer in a Na vapor cell. The dianions were then stored in an electrostatic ring, and their near-infrared absorption spectrum was measured by observation of laser induced electron detachment. From the time dependence of the detachment after photon absorption, we conclude that the reaction has contributions from both direct electron tunneling to the continuum and vibrationally assisted tunneling after internal conversion. This implies that the height of the Coulomb barrier confining the attached electrons is at least approximately 1.5 eV. For C(60)(2-) ions in solution electron spin resonance measurements have indicated a singlet ground state, and from the similarity of the absorption spectra we conclude that also the ground state of isolated C(60)(2-) ions is singlet. The observed spectrum corresponds to an electronic transition from a t(1u) lowest unoccupied molecular orbital (LUMO) of C(60) to the t(1g) LUMO+1 level. The electronic levels of the dianion are split due to Jahn-Teller coupling to quadrupole deformations of the molecule, and a main absorption band at 10,723 cm(-1) corresponds to a transition between the Jahn-Teller ground states. Also transitions from pseudorotational states with 200 cm(-1) and (probably) 420 cm(-1) excitation are observed. We argue that a very broad absorption band from about 11,500 cm(-1) to 13,500 cm(-1) consists of transitions to so-called cone states, which are Jahn-Teller states on a higher potential-energy surface, stabilized by a pseudorotational angular momentum barrier. A previously observed, high-lying absorption band for C(60)(-) may also be a transition to a cone state.