Near-infrared Photoluminescence Properties Research Articles

Controlling Near-Infrared Photoluminescence Properties of Single-Walled Carbon Nanotubes by Substituent Effect in Stepwise Chemical Functionalization

Introducing the quantum defects into single-walled carbon nanotubes (SWNTs) enhances their photoluminescence (PL) with red-shifted peaks; however, the precise control of the chemical modification and PL wavelength remains difficult. In this work, the stepwise chemical functionalization of SWNTs was shown to be useful for controlling site-specific functionalization and PL, experimentally and theoretically. Dialkylated and hydroalkylated SWNTs were selectively synthesized using alkyllithium reagents, bromoalkane, and trifluoroacetic acid. The nBu-SWNT-nBu and nBu-SWNT-H adducts of the (6,4), (6,5), (8,3), and (7,5) SWNTs that were separated using gel chromatography showed dominant E11** PL and E11* PL, respectively. The systematic assignments of the PL were performed based on the thermodynamic stability and transition energy of 1,2- and 1,4-adducts of SWNTs using density functional theory (DFT) and time-dependent DFT calculations. It was shown that the steric hindrance of the added group and the R value, that is, mod(n – m, 3) in an (n,m) chiral nanotube, are key factors that control the addition site and the magnitude of the local band gap.

(Invited, Digital Presentation) Ortho-Substituent Structure Design in Aryldiazonium Salts for Defect Photoluminescence Modulation of Locally Functionalized Single-Walled Carbon Nanotubes

Photoluminescence (PL) of single-walled carbon nanotubes (SWCNTs) appears in the near infrared (NIR) region, which is applicable to advanced optical applications such as bioimaging and telecommunication devices. Local chemical functionalization of SWCNTs has been gathering great attention because of the enhancement of their NIR PL properties. Therein, defects such as sp3 carbon are locally doped to the crystalline sp2 carbon network of the tube walls by the chemical functionalization process.[1-4] As a result, the locally functionalized SWCNTs (lf-SWCNTs) emit new PL with red-shifted wavelengths and increased quantum yields from the doped sites (E 11* PL) compared to original E 11 PL of pristine SWCNTs. It is due to the doping effects to change electronic structures for narrower bandgap formation, by which mobile excitons in the tubes are trapped at the doped sites to be localized states for efficient PL conversion.The chemical functionalization approach allows us to use various chemical reactants for the doped site formation in lf-SWCNTs. The molecular effects including structural differences and molecular binding functions have resulted in versatile NIR PL wavelength modulation of lf-SWCNTs.[1-4] We have reported that E 11* PL generation phenomena were significantly varied depending on isomeric structures of substituted aryldiazonium salts (AD) used for lf-SWCNT synthesis.[5] Especially, ortho-substituted ADs (oADs) produced two PL around 1100 and 1250 nm-regions, respectively for the resulting lf-SWCNTs with (6,5) chirality. Here, we apply various substituent design for oADs and examine the substituent structure effects in terms of modulation of the PL emission properties of lf-SWCNTs. For example, oAD having a phenyl substituent resulted in enhancement of the ~1250 nm PL contribution. Other substituent effects are observed depending on substituent structures of oADs, from which interactions between the substituents and the tubes are considered to induce the observed PL spectral changes. The result indicates that local chemical functionalization using oAD has a high potential to largely modulate NIR PL wavelengths of lf-SWCNTs beyond 1000 nm regions.[1] T. Shiraki et al. Acc. Chem. Res., 53, 1846 (2020). [2] S. Tretiak et al., Acc. Chem. Res., 53, 1791(2020) [3] Y. Wang et al. Nat. Rev. Chem., 3, 375 (2019). [4] T. Shiraki, Chem. Lett., 50, 397 (2021). [5] T. Shiraki et al. Chem. Commun., 53, 12544 (2017).

Near-infrared photoluminescence properties of Er/Yb- and Ho/Yb-doped multicomponent silicate glass – The role of GeO2, Al2O3 and ZnO

We prepared multicomponent silicate glass, which contained components with different glass-forming abilities, such as GeO2, Al2O3 and ZnO, or different concentrations of glass-modifier oxide Na2O. The influence of the glass composition on the network structure and its effect on the photoluminescence properties of rare-earth ions were investigated. It was found that a change in the Na2O content significantly affects the network polymerisation, but its influence on the photoluminescence of RE ions is limited. The photoluminescence properties of RE ions were significantly influenced by the presence of different components, such as GeO2, Al2O3 and ZnO, which was attributed to changes in the local environment of RE ions. ZnO induced highest asymmetry of host matrix around the RE ions, which led to a strong and broad photoluminescence with short fluorescence lifetime, whereas the inclusion of Al2O3 and GeO2 led to highly symmetric matrix with narrow emission bands and longer decay.

(Invited) Molecular Structure-Based Photoluminescence Modulation of Locally Functionalized Single-Walled Carbon Nanotubes Using Bis-Aryl Functionalization

Single-walled carbon nanotubes (SWCNTs) show photoluminescence (PL) in the near infrared (NIR) region, which is applicable to bioimaging and telecommunication devices. Recently, local chemical functionalization of SWCNTs has been developed to enhance their NIR PL properties, in which defects such as sp3 carbon are locally doped to the crystalline sp2 carbon network of the tube walls by the functionalization.[1-3] Actually, E 11* PL of the locally functionalized SWCNTs (lf-SWCNTs) is observed with red-shifted wavelengths and increased quantum yields compared to original E 11 PL of pristine SWCNTs. It is due to formation of new emissive sites with narrower band gaps and exciton trapping features in the tube structures.In the local chemical functionalization, doped site structures of the lf-SWCNTs can be changed depending on modifier molecules, which results in effective modulation of the NIR PL wavelengths of the lf-SWCNTs beyond 1000 nm-region. Previously, we have developed bis-aryldiazonium salts (bAs) that have two reactive aryldiazonium groups connected with a methylene linker and observed E 11 2* PL over 1200 nm regions from the lf-SWCNTs with (6,5) chirality based on its proximal aryl functionalization.[4]Here, we synthesize new modifier molecules with the bis-aryldiazonium motif and modify the geometry of the proximal aryl-functionalized sites of the lf-SWCNTs. As a result, for example, methylene linker positions on the aryldiazonium groups of bAs clearly changed the trend of methylene length-dependent wavelength shifts of E 11 2* PL. [5] Moreover, bAs having rigid linker structures changed peak positions of E 11 2* PL, indicating that the control of the proximal defect configuration would be an effective way for the PL property modulation of lf-SWCNTs. As another aspect of the proximal aryl functionalization, we found that E 11 2* PL showed unique wavelength shift behaviors by microenvironment changes using various organic solvents. The observed trend was different from those of E 11 PL and E 11* PL[6], in which proximal defect distances could be an important factor for their microenvironment responsiveness.Therefore, molecularly designed bis-aryldiazonium modifiers become promising tools to create structurally controlled bis-aryl functionalized sites of lf-SWCNTs and precisely modulate their NIR PL wavelengths (> 1000 nm).[1] T. Shiraki et al. Acc. Chem. Res., 53, 1846 (2020). [2] S. Tretiak et al., Acc. Chem. Res., 53, 1791(2020) [3] Y. Wang et al. Nat. Rev. Chem., 3, 375 (2019). [4] T. Shiraki et al. Sci. Rep., 6, 28393 (2016). [5] T. Shiraki et al. Chem. Lett., 48, 791 (2019). [6] T. Shiraki et al. Chem. Commun., 55, 3662 (2019). Figure 1

Stimuli-Responsive Molecule Modification to Locally Functionalized Single-Walled Carbon Nanotubes for Wavelength Switching of Near Infrared Photoluminescence

Single-walled carbon nanotubes (SWNTs) with semiconducting features show near infrared (NIR) photoluminescence (PL). Defect doping to the SWNTs has been found to enhance the PL properties, which is achieved by local chemical modification.[1-9] It allows us to functionalize various molecules on the doped sites and such locally functionalized SWNTs (lf-SWNTs) show PL property changes depending on the modified molecules. For example; electronic property difference in the modified aryl groups induced PL shifts.[3] Moreover, protonation of amine groups[6] and molecular recognition at the doped sites[7,8] can be used for wavelength tuning. Therefore, stimuli responsiveness in the NIR PL properties could be designed in the lf-SWNTs through molecular approaches. In this presentation, we report reversible wavelength modulation based on molecular structure changes occurring at the doped sites by external stimuli. Molecular binding through covalent bond formation and photo-induced structural changes are used for the wavelength switching processes.Imine chemistry is based on a condensation reaction of aldehyde and amine groups that occurs just by mixing the corresponding compounds. Owing to the reversibility of this reaction system, multistep wavelength switching of the NIR PL was conducted by imine bond formation, exchange or dissociation reactions of the imine bond, and Kabachnik-Fields reactions at the doped sites of the lf-SWNTs.[9] Photo-induced switching of the NIR PL was performed by creating the doped sites functionalized with photochromic molecules that showed color changes (= electronic property changes) by light irradiation. The photo-induced reversible structural changes of the modified molecules on the lf-SWNTs were observed by absorption spectroscopy, which accompanies spectral shifts of the NIR PL of the lf-SWNTs. Details including the relationship between PL shifts and molecular structure changes will be discussed at the meeting.[1] B. Weisman et al. Science, 330, 1656 (2010). [2] Y. Miyauchi et al. Nat. Photon., 7, 715 (2013). [3] Y. Wang et al. Nat. Chem., 5, 840 (2013). [4] S. Doorn et al. Nat. Photon., 11, 577 (2017). [5] T. Shiraki et al. Sci. Rep., 6, 28393 (2016). [6] Y. Wang et al. J. Phys. Chem. C, 119, 3733 (2015) [7] T. Shiraki et al. Chem. Commun., 52, 12972 (2016). [8] T. Shiraki et al. Chem. Eur. J., 24, 9393 (2018). [9] T. Shiraki et al. Chem. Eur. J., 24, 19162 (2018). Figure 1

Sonochemical reaction to control the near-infrared photoluminescence properties of single-walled carbon nanotubes

The effect of ultrasonic irradiation on the optical properties of single-walled carbon nanotubes (SWNTs) was investigated. Upon sonication in D2O in the presence of sodium dodecylbenzene sulfonate (SDBS) under air, red-shifted photoluminescence (PL) peaks at ∼1043 and ∼1118 nm were observed from the aqueous suspensions of (6,4) and (6,5)SWNTs, accompanied by a decrease in the intensity of the intrinsic PL peaks. Upon sonication with SDBS under an Ar atmosphere, the rate of spectral change increased with the sonication time and new PL peaks emerged at 1043, 1118, and 1221 nm. Meanwhile, upon the addition of 1-butanol, the PL peaks emerged only at 1043 nm and 1118 nm, while the emergence of the peak at 1221 nm was inhibited. On the other hand, a suspension with highly dispersed SWNTs was obtained upon sonication in the presence of sodium cholate without any change in the intrinsic optical properties of SWNTs. These experimental results reveal that the PL characteristics of SWNTs can be controlled by controlling the sonication conditions such as the type of surfactant used, the concentration of SWNTs, reaction environment, and the presence of an inhibitor such as 1-butanol.

Optimization of NIR photoluminescence properties of Er3+/Yb3+-doped PEO/PVP blended composites

Er3+-doped and co-doped (Er3+/Yb3+):polyethylene oxide (PEO)/polyvinylpyrrolidone (PVP) blended polymer composites were synthesized by the traditional solution-casting method. The amorphous nature of the prepared Er3+- and Yb3+-doped polymer composites was confirmed by X-ray diffraction analysis. The interaction between dopant rare earth ions and the blended polymer was systematically elucidated by Fourier transform infrared spectroscopy and Raman spectroscopy analysis. A prominent near-infrared (NIR) emission was observed at 1.53 μm (4I13/2→4I15/2) from the fluorescence spectra of the Er3+:PEO/PVP polymer composites under 980 nm excitation at room temperature. The NIR emission intensity was appreciably increased by increasing the Er3+ ion concentration. The optimized concentration of the Er3+ ions was found to be 0.2 wt%. The emission performance was drastically reduced after the optimized concentration due to the concentration quenching effect. Upon co-doping with Yb3+ to Er3+:PEO/PVP polymer composites, the NIR emission intensity at 1.53 μm (4I13/2→4I15/2) was remarkably improved through energy transfer from Yb3+ to Er3+. The Er3+ NIR fluorescence intensity was increased significantly by increasing the co-doping concentration of Yb3+ in the PEO/PVP polymer composite system. The optimized sensitizing concentration of Yb3+ ions was found to be 0.05 wt% in the PEO/PVP polymer-blended composite system. The energy-transfer phenomenon was elucidated through an energy-level diagram. These co-doped (0.2Er3++0.05Yb3+):PEO/PVP polymer-blended composite materials could be considered as promising candidates for several NIR photonic device applications. This approach of NIR-emitting polymer composites will be useful for various NIR optoelectronic applications.

Diphosphine-induced chiral propeller arrangement of gold nanoclusters for singlet oxygen photogeneration

In this study, 1,2-bis(diphenylphosphino)ethane (dppe) ligands are used to synthesize gold nanoclusters with an icosahedral Au13 core. The nanoclusters are characterized and formulated as [Au13(dppe)5Cl2]Cl3 using synchrotron radiation X-ray diffraction, UV/Vis absorption spectroscopy, electrospray ionization mass spectrometry, and density functional theory (DFT) calculations. The bidentate feature of dppe ligands and the positions of coordinating surface gold atoms induce a helical arrangement that forms a propeller-like structure, which reduces the symmetry of the gold nanocluster to C1. Therefore, dppe ligands perform as a directing agent to create chiral an ansa metallamacrocycle [Au13(dppe)5Cl2]3+ nanocluster, as confirmed by simulated electronic circular dichroism spectrum. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of the [Au13(dppe)5Cl2]3+ cluster is determined as approx. 1.9 eV, and further confirmed by ultraviolet photoemission spectroscopy analysis and DFT simulation. Furthermore, the photoactivity of [Au13(dppe)5Cl2]3+ is investigated, with the nanocluster shown to possess near-infrared photoluminescence properties, which can be employed for 1O2 photogeneration. The quantum yield of 1O2 photogeneration using the [Au13(dppe)5Cl2]3+ nanocluster is up to 0.71, which is considerably higher than those of anthracene (an organic dye), and Au25 and Au38 nanoclusters.

Preparation, Growth Mechanism, Upconversion, and Near-Infrared Photoluminescence Properties of Convex-Lens-like NaYF4 Microcrystals Doped with Various Rare Earth Ions Excited at 808 nm

Preparation of rare earth ions doped photoluminescence materials with controlled morphology was desired to fulfill the requirement of different applications. In the work, the convex-lens like NaYF4 microcrystals doped with various rare earth ions were prepared by adjusting preparation parameters including the reaction time, reaction temperature, NaOH concentration, ratio of oleic acid to 1-octadecene and types of doping ions. Possible growth mechanism of convex-lens like NaYF4 microcrystals is proposed based on reaction time and temperature dependent morphology evolution. The formation of micro convex-lens includes the three processes of NaYF4 nanoparticles self-assemble, dissolution–nucleation and regrowth. Doping-ions dependent near infrared and upconversion luminescence properties of convex-lens like NaYF4 microcrystals were investigated excited at the 808 nm. The visible upconversion luminescence was observed in the Er3+, Yb3+/Er3+, Nd3+/Er3+, Nd3+/Yb3+/Er3+ doped convex-lens like NaYF4 microcrystals,...

Evaluation of Different Single-Walled Carbon Nanotube Surface Coatings for Single-Particle Tracking Applications in Biological Environments.

Fluorescence imaging of biological systems down to the single-molecule level has generated many advances in cellular biology. For applications within intact tissue, single-walled carbon nanotubes (SWCNTs) are emerging as distinctive single-molecule nanoprobes, due to their near-infrared photoluminescence properties. For this, SWCNT surfaces must be coated using adequate molecular moieties. Yet, the choice of the suspension agent is critical since it influences both the chemical and emission properties of the SWCNTs within their environment. Here, we compare the most commonly used surface coatings for encapsulating photoluminescent SWCNTs in the context of bio-imaging applications. To be applied as single-molecule nanoprobes, encapsulated nanotubes should display low cytotoxicity, and minimal unspecific interactions with cells while still being highly luminescent so as to be imaged and tracked down to the single nanotube level for long periods of time. We tested the cell proliferation and cellular viability of each surface coating and evaluated the impact of the biocompatible surface coatings on nanotube photoluminescence brightness. Our study establishes that phospholipid-polyethylene glycol-coated carbon nanotube is the best current choice for single nanotube tracking experiments in live biological samples.

Around 2 μm fluorescence and energy transfer in Tm3 +/Ho3 + co-doped tellurite glass

In this work, the near-infrared photoluminescence properties in Tm3+/Ho3+ co-doped tellurite glass was investigated. The tellurite glass with composition TeO2-ZnO-Na2O-La2O3 was synthesized using conventional melt-quenching technique and characterized by UV/Vis/NIR absorption and near-infrared emission spectroscopies, fluorescence decay measurement and differential scanning calorimeter (DSC) analysis. Under the excitation of 808nm laser diode (LD), a broadband 2.0μm band luminescence ranging from 1600 to 2200nm with a full width at half maximum (FWHM) of 362nm was observed, which was contributed by 1.85μm fluorescence from Tm3+: 3F4→3H6 and 2.05μm fluorescence from Ho3+: 5I7→5I8. The fluorescence emission of Ho3+ was originated from the energy transfer from Tm3+ to Ho3+ ions, and the energy transfer mechanism was elucidated by analyzing fluorescence decay behavior of Tm3+ and quantitative calculation of phonon contribution joined in the energy transfer process. Meanwhile, based on the absorption spectrum, some important spectroscopic parameters such as Judd-Ofelt intensity parameter, spontaneous radiative transition probability, fluorescence branching ratio, absorption and emission cross-sections, and gain coefficient spectrum were calculated to reveal the spectroscopic properties of doped tellurite glass. Furthermore, from the DSC curve it can be derived that the investigated glass possesses a good thermal stability with ΔT(=Tx−Tg) larger than 152°C. These results indicate that Tm3+/Ho3+ co-doped tellurite glass could be a promising gain medium applied for 2.0μm near-infrared band broad fiber amplifiers and tunable fiber lasers.

Synthesis and Near-Infrared Photoluminescence Properties of Ag2S Quantum Dots

Synthesis and Near-Infrared Photoluminescence Properties of Ag₂S Quantum Dots

Near-infrared anti-Stokes photoluminescence of PbS QDs embedded in glasses.

Near-infrared photoluminescence properties of PbS QDs embedded in glasses were investigated upon below-bandgap excitation. PbS QDs were precipitated in the glasses upon thermal treatment. Near-infrared anti-Stokes photoluminescence (ASPL) from PbS QDs was observed. Dependence of the ASPL on size and excitation power indicated that ASPL was phonon-assisted one-photon process. These near-infrared anti-Stokes photoluminescence of PbS QDs in glasses have potential applications for light conversion and laser cooling.

Near-Infrared Emitting Gold Cluster-Poly(acrylic acid) Hybrid Nanogels.

A facile synthesis of near-infrared (NIR) luminescent gold cluster-poly(acrylic acid) (PAA) hybrid nanogels was developed by in situ reduction of gold salt in the core-hollow and shell-porous PAA nanogels. These Au-PAA nanogels exhibited excellent near-infrared photoluminescence properties and showed targeting potential in the optical imaging of the living body.

A new inorganic–organic hybrid In2Se3(en) as hollow nanospheres: hydrothermal synthesis and near-infrared photoluminescence properties

A new inorganic-organic hybrid In(2)Se(3)(en) was synthesized as hollow nanospheres via a facile and controllable hydrothermal method in a system containing ethylenediamine (en) and hydrazine hydrate. These as-obtained hybrid hollow nanospheres with an average diameter of 200 nm were assembled by irregularly small-sized (ca. 20 nm) nanoparticles. These hollow nanospheres were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The surface chemical composition of the In(2)Se(3)(en) hollow nanospheres were studied by X-ray photoelectron spectroscopy (XPS). The possible gas bubble-template growth mechanism is proposed to understand the formation of In(2)Se(3)(en) hollow nanospheres. Room-temperature UV-vis diffuse reflection spectra and photoluminescence (PL) spectra indicate that the as-obtained hybrid nanospheres possess a maximum absorption at 470 nm and single strong near-infrared emission peak centered at 1092 nm. The near-infrared luminescence endows the hybrid nanospheres with potential application in telecommunications, biolabeling and biomedical imaging, etc.

Near-infrared photoluminescence properties of neodymium in in situ doped AlN grown using plasma-assisted molecular beam epitaxy

We present luminescence spectroscopy measurements of in situ Nd doped AlN grown by plasma-assisted molecular beam epitaxy. A Nd concentration as high as 0.08 at. % is incorporated into the host material. The Nd incorporation efficiency within the AlN matrix is found to be highly sensitive to the Al flux but independent of the substrate temperature (between 800 °C to 950 °C). Photoluminescence, photoluminescence excitation, and combined excitation-emission spectroscopy (CEES) spectra are used to identify the Stark sublevels of the following manifolds: 4I9/2, 4I11/2, 4I13/2, 4F3/2, 4F5/2, 2H9/2, 4F7/2, 4S3/2, 4G5/2, and 4G7/2. A main Nd incorporation site and two minority sites are identified using CEES measurements.

Near-infrared photoluminescence in germanium oxide enclosed germanium nano- andmicro-crystals

We have studied the near-infrared photoluminescence properties offree-standing germanium nano-crystals (20 nm on average) and micro-crystals(60 µm on average) at 80–300 K. Two peaks were observed at∼1.0 and ∼1.4 eV from both the nano- and micro-crystals. The integrated PL(IPL)intensity of the nano-crystals is about an order of magnitude stronger than that of the micro-crystals andthe IPL is also enhanced by ageing in air for both crystals. The∼1.0 eV peak position does not change with either the crystal size or temperature. Wesuggest that the deep traps located at the interfacial region between the surfaceGeO2 layer and the bulk crystal Ge is responsible for the near-infrared PL.