New Near-infrared Research Articles

Enhanced near-infrared to visible upconversion nanoparticles of Ho³⁺-Yb³⁺-F⁻ tri-doped TiO₂ and its application in dye-sensitized solar cells with 37% improvement in power conversion efficiency.

New near-infrared (NIR)-to-green upconversion nanoparticles of Ho(3+)-Yb(3+)-F(-) tridoped TiO2 (UC-F-TiO2) were designed and fabricated via the hydrosol-hydrothermal method. Under 980 nm NIR excitation, UC-F-TiO2 emit strong green upconversion fluorescence with three emission bands at 543, 644, and 751 nm and convert the NIR light in situ to the dye-sensitive visible light that could effectively reduce the distance between upconversion materials and sensitizers; thus, they minimize the loss of the converted light. Our results show that this UC-F-TiO2 offers excellent opportunities for the other types of solar cells applications, such as organic solar cells, c-Si solar cells, multijunction solar cells, and so on. When integrating the UC-F-TiO2 into dye-sensitized solar cells (DSSCs), superior total energy conversion efficiency was achieved. Under AM1.5G light, open-circuit voltage reached 0.77 ± 0.01 V, short-circuit current density reached 21.00 ± 0.69 mA cm(-2), which resulted in an impressive overall energy conversion efficiency of 9.91 ± 0.30%, a 37% enhancement compared to DSSCs with pristine TiO2 photoanode.

NEW INSIGHTS ON THE FORMATION AND ASSEMBLY OF M83 FROM DEEP NEAR-INFRARED IMAGING

We present results from new near-infrared (NIR) imaging from the Spitzer Space Telescope that trace the low surface brightness features of the outer disk and stellar stream in the nearby spiral galaxy, M83. Previous observations have shown that M83 hosts a faint stellar stream to the northwest and a star-forming disk that extends to ∼3 times the optical radius (R25). By combining the NIR imaging with archival far-ultraviolet (FUV) and H i imaging, we study the star formation history of the system. The NIR surface brightness profile has a break at ∼58 (equivalent to 8.1 kpc and 0.9 R25) with a shallower slope beyond this radius, which may result from the recent accretion of gas onto the outer disk and subsequent star formation. Additionally, the ratio of FUV to NIR flux increases with increasing radius in several arms throughout the extended star forming disk, indicating an increase in the ratio of the present to past star formation rate with increasing radius. This sort of inside-out disk formation is consistent with observations of gas infall onto the outer disk of M83. Finally, the flux, size, and shape of the stellar stream are measured and the origin of the stream is explored. The stream has a total NIR flux of 11.6 mJy, which implies a stellar mass of 1 × 108 M☉ in an area subtending ∼80°. No FUV emission is detected in the stream at a level greater than the noise, confirming an intermediate-age or old stellar population in the stream.

A near-infrared fluorescent sensor for selective detection of cysteine and its application in live cell imaging

Biological thiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play important roles in maintaining the appropriate redox status of biological systems. The discrimination between them is of great importance because of their different biological roles. Herein, we present a new near-infrared (NIR) fluorescent sensor Cy-NO2 for selective detection of Cys over Hcy/GSH. The nitrothiophenol group is introduced to quench the fluorescence through photo-induced electron transfer (PET). The sensor undergoes displacement of nitrothiophenol with thiol to turn on the fluorescence. The amino groups of Cys/Hcy further replace the thiolate to form amino-substituted products, which exhibit dramatically different photophysical properties compared to the sulfur-substituted product from the reaction with GSH. By means of more rapid intramolecular displacement of sulfur with the amino group of Cys than Hcy, the discrimination of Cys is achieved. Moreover, Cy-NO2 was successfully applied for bioimaging Cys in living cells.

Near-infrared photochromic behavior in a donor–acceptor type diarylethene modulated by the cyanide anion

Two new near-infrared (NIR) photochromic compounds, containing both electron-donating (D) and accepting groups (A), have been developed and their NIR photochromic and fluorescence performances can be modulated by the cyanide anion. Such a colorimetric cyanide sensor has been achieved based on this donor-photochromic bridge-acceptor system.

Near-Infrared Emitting Polymer Nanogels for Efficient Sentinel Lymph Node Mapping

Sentinel lymph node (SLN) mapping has been widely used to predict the metastatic spread of primary tumor to regional lymph nodes in clinical practice. In this research, a new near-infrared (NIR)-emitting polymer nanogel (NIR-PNG) having a hydrodynamic diameter of about 30 nm, which is optimal for lymph node uptake, was developed. The NIR-emitting polymer nanoprobes were designed and synthesized by conjugating IRDye800 organic dye to biodegradable pullulan-cholesterol polymer nanogels. The NIR-PNG nanoprobes were found to be photostable compared with the IRDye800-free dye at room temperature. Upon intradermal injection of the NIR-PNG into the front paw of a mouse, the nanoprobes entered the lymphatic system and migrated to the axillary lymph node within 2 min. The NIR fluorescence signal intensity and retention time of NIR-PNG in the lymph node were superior to the corresponding properties of the IRDye800-free dye. A immunohistofluorescence study of the SLN resected under NIR imaging revealed that the NIR-PNG nanoprobes were predominantly co-localized with macrophages and dendritic cells. Intradermal injection of NIR-PNG nanoprobes into the thigh of a pig permitted real-time imaging of the lymphatic flow toward the SLN. The position of the SLN was identified within 1 min with the help of the NIR fluorescence images. Taken together, the experimental results demonstrating the enhanced photostability and retention time of the NIR-PNG provide strong evidence for the potential utility of these polymer probes in cancer surgery such as SLN mapping.

Near-infrared-emitting squaraine dyes with high 2PA cross-sections for multiphoton fluorescence imaging.

Designed to achieve high two-photon absorptivity, new near-infrared (NIR) emitting squaraine dyes, (E)-2-(1-(2-(2-methoxyethoxy)ethyl)-5-(3,4,5-trimethoxystyryl)-1H-pyrrol-2-yl)-4-(1-(2-(2-methoxyethoxy)ethyl)-5-(3,4,5-trimethoxystyryl)-2H-pyrrolium-2-ylidene)-3-oxocyclobut-1-enolate (1) and (Z)-2-(4-(dibutylamino)-2-hydroxyphenyl)-4-(4-(dibutyliminio)-2-hydroxycyclohexa-2,5-dienylidene)-3-oxocyclobut-1-enolate (2), were synthesized and characterized. Their linear photophysical properties were investigated via UV-visible absorption spectroscopy and fluorescence spectroscopy in various solvents, while their nonlinear photophysical properties were investigated using a combination of two-photon induced fluorescence and open aperture z-scan methods. Squaraine 1 exhibited a high two-photon absorption (2PA) cross-section (δ2PA), ∼20 000 GM at 800 nm, and high photostability with the photochemical decomposition quantum yield one order of magnitude lower than Cy 5, a commercially available pentamethine cyanine NIR dye. The cytotoxicity of the squaraine dyes were evaluated in HCT 116 and COS 7 cell lines to assess the potential of these probes for biomedical imaging. The viability of both cell lines was maintained above 80% at dye concentrations up to 30 μM, indicating good biocompatibility of the probes. Finally, one-photon fluorescence microscopy (1PFM) and two-photon fluorescence microscopy (2PFM) imaging was accomplished after incubation of micelle-encapsulated squaraine probes with HCT 116 and COS 7 cells, demonstrating their potential in 2PFM bioimaging.

A near-infrared fluorescent probe for fluorine ions and its application in the imaging of HepG2 cells

In this study, we have designed and synthesized a new near-infrared (NIR) fluorescent probe (BODIPY-Se) to detect fluorine ions (F−) using a B-Se bond to connect the fluorescent dye BODIPY and benzotrifluoride. The probe exhibited a highly selective fluorescence response to F− with a detection limit of 7.4 × 10−8 mol/L. The excitation and emission spectra of the probe in the NIR region avoid background fluorescence interference present in biological systems. The fluorescent imaging of HepG2 cells demonstrated that the newly developed probe should be broadly applicable to detect F− in living cells.

A dual functional near infrared fluorescent probe based on the bodipy fluorophores for selective detection of copper and aluminum ions

A new near infrared (NIR) fluorescent 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye with dual functionality was synthesized and characterized. The compound 1 responds to copper ion in NIR region with high selectivity through a photo-induced electron transfer process established between the substituted benzene group in the meso position and the BODIPY core when Cu 2+ binds with the four oxygen atoms in the structure, and results in the quenching of the fluorescence. The response range to copper ions was from 10 to 50 μM, and other metal ions including Li +, Na +, K +, Mg 2+, Ca 2+, Pb 2+, Fe 3+, Ag +, Hg 2+, Co 2+, Zn 2+, Mn 2+, Cd 2+, Ni 2+ and Al 3+ had no interference. When excited at 520 nm, a new emission peak at 568 nm of compound 1 was used to detect Al 3+ selectively from 30 μM to 110 μM without any interference from other metal ions including copper ions.

Near-Infrared Luminescence from Visible-Light-Sensitized Hybrid Materials Covalently Linked with Tris(8-hydroxyquinolinate)-lanthanide [Er(III), Nd(III), and Yb(III)] Derivatives

A series of new near-infrared (NIR) luminescent lanthanide-quinolinate derivatives [Ln(Q-Si)(3)] and xerogels (named as LnQSi-Gel, Ln = Er, Nd, Yb) covalently linked with the Ln(Q-Si)(3) by using the 8-hydroxyquinoline-functionalized alkoxysilane (Q-Si) have been synthesized. The obtained xerogel materials LnQSi-Gel are rigid and show homogeneous by field-emission scanning electron microscopy (FE-SEM) images. The Fourier-transform infrared (FT-IR), fluorescence spectra of Ln(Q-Si)(3), and LnQSi-Gel were measured, and the corresponding luminescence decay analyses were recorded. Of importance here is that the excitation spectra of the Ln(Q-Si)(3) and LnQSi-Gel extend to the region of visible light (more than 500 nm). Upon ligand-mediated excitation with the visible light, the Ln(Q-Si)(3) and LnQSi-Gel show the characteristic NIR-luminescence of the corresponding lanthanide ions through the intramolecular energy transfer from the ligands to the lanthanide ions. The good luminescent performances enable these NIR-luminescent xerogel materials to have possible applications in medical diagnostics, laser systems, and optics, etc.

Intraoperative Near‐infrared Fluorescent Cholangiography (NIRFC) in Mouse Models of Bile Duct Injury: Reply

Accidental injury to the common bile duct is a rare but serious complication of laparoscopic cholecystectomy. Accurate visualization of the biliary ducts may prevent injury or allow its early detection. Conventional X-ray cholangiography is often used and can mitigate the severity of injury when correctly interpreted. However, it may be useful to have an imaging method that could provide real-time extrahepatic bile duct visualization without changing the field of view from the laparoscope. The purpose of the present study was to test a new near-infrared (NIR) fluorescent agent that is rapidly excreted via the biliary route in preclinical models to evaluate intraoperative real-time near infrared fluorescent cholangiography (NIRFC). To investigate probe function and excretion, a lipophilic near-infrared fluorescent agent with hepatobiliary excretion was injected intravenously into one group of C57/BL6 control mice and four groups of C57/BL6 mice under the following experimentally induced conditions: (1) chronic biliary obstruction, (2) acute biliary obstruction (3) bile duct perforation, and (4) choledocholithiasis, respectively. The biliary system was imaged intravitally for 1 h with near-infrared fluorescence (NIRF) with an intraoperative small animal imaging system (excitation 649 nm, emission 675 nm). The extrahepatic ducts and extraluminal bile were clearly visible due to the robust fluorescence of the excreted fluorochrome. Twenty-five minutes after intravenous injection, the target-to-background ratio peaked at 6.40 ± 0.83 but signal was clearly visible for ~60 min. The agent facilitated rapid identification of biliary obstruction and bile duct perforation. Implanted beads simulating choledocholithiasis were promptly identifiable within the common bile duct lumen. Near-infrared fluorescent agents with hepatobiliary excretion may be used intraoperatively to visualize extrahepatic biliary anatomy and physiology. Used in conjunction with laparoscopic imaging technologies, the use of this technique should enhance hepatobiliary surgery.

Single Molecule Immunoassay on Plasmonic Platforms

We examined the photophysical properties of the new near infrared (NIR) fluorescent label SeTau-665 on a plasmonic platform of self- assembled colloidal structures (SACS) of silver prepared on a semitransparent silver film. A SeTau-665 immunoassay was performed on this platform and a control glass slide. The fluorescence properties of this label substantially change due to plasmonic interactions. While the average brightness increase of SeTau 665 in ensemble measurements was about 70-fold, fluorescence enhancements up to four-hundred times were observed on certain "hot spots" for single molecule measurements. The intensity increase is strongly correlated with a simultaneous decrease in fluorescence lifetime in these "hot spots". The large increase in brightness allows the reduction of the excitation power resulting in a reduced background and increased photostability. The remarkable fluorescence enhancements observed for SeTau 665 on our plasmonic platform should allow to substantially improve single molecule detection and to reduce the detection limits in sensing devices.

Intraoperative Near‐Infrared Fluorescent Cholangiography (NIRFC) in Mouse Models of Bile Duct Injury

Accidental injury to the common bile duct is a rare but serious complication of laparoscopic cholecystectomy. Accurate visualization of the biliary ducts may prevent injury or allow its early detection. Conventional X-ray cholangiography is often used and can mitigate the severity of injury when correctly interpreted. However, it may be useful to have an imaging method that could provide real-time extrahepatic bile duct visualization without changing the field of view from the laparoscope. The purpose of the present study was to test a new near-infrared (NIR) fluorescent agent that is rapidly excreted via the biliary route in preclinical models to evaluate intraoperative real-time near infrared fluorescent cholangiography (NIRFC). To investigate probe function and excretion, a lipophilic near-infrared fluorescent agent with hepatobiliary excretion was injected intravenously into one group of C57/BL6 control mice and four groups of C57/BL6 mice under the following experimentally induced conditions: (1) chronic biliary obstruction, (2) acute biliary obstruction (3) bile duct perforation, and (4) choledocholithiasis, respectively. The biliary system was imaged intravitally for 1 h with near-infrared fluorescence (NIRF) with an intraoperative small animal imaging system (excitation 649 nm, emission 675 nm). The extrahepatic ducts and extraluminal bile were clearly visible due to the robust fluorescence of the excreted fluorochrome. Twenty-five minutes after intravenous injection, the target-to-background ratio peaked at 6.40 +/- 0.83 but signal was clearly visible for ~60 min. The agent facilitated rapid identification of biliary obstruction and bile duct perforation. Implanted beads simulating choledocholithiasis were promptly identifiable within the common bile duct lumen. Near-infrared fluorescent agents with hepatobiliary excretion may be used intraoperatively to visualize extrahepatic biliary anatomy and physiology. Used in conjunction with laparoscopic imaging technologies, the use of this technique should enhance hepatobiliary surgery.

A New near Infrared Spectroscopy Sample Presentation Unit for Measuring Feeding Quality of Maize Stover

Maize stover is used to feed farm animals and the improvement of its quality is an important breeding goal. The main objective of our study was to evaluate a new near infrared (NIR) spectroscopy sample presentation unit for measuring feed quality of maize stover. In this context, we investigated the effect of engineering factors (use of glass interface and packing pressure) on the spectral repeatability and the effect of particle sizes (8cm, 6cm, 4cm, 0.5cm) on the calibration performance. The spectral repeatability was examined by calculating spectral variation among replicated spectral measurements collected without glass interface, with glass interface, and glass interface in combination with 3 kg and 6 kg of packing pressure. The effect of particle sizes was assessed for concentrations of nitrogen (N), neutral detergent fibre (NDF), ash and in vitro fermentability (G24), by examining calibration models. The spectral repeatability increased with the use of glass interface and packing pressure and calibration performance improved with a reduction in particle size. The study indicated that the new NIR sample presentation unit has a potential for preliminary screenings of maize genotypes for NDF and G24 in the stover of particular breeding programmes.

Near-infrared luminescent xerogel materials covalently bonded with ternary lanthanide [Er(iii), Nd(iii), Yb(iii), Sm(iii)] complexes

A beta-diketone ligand 4,4,5,5,5-pentafluoro-1-(2-naphthyl)-1,3-butanedione (Hpfnp), which contains a pentafluoroalkyl chain, was synthesized as the main sensitizer for synthesizing new near-infrared (NIR) luminescent Ln(pfnp)(3)phen (phen = 1,10-phenanthroline) (Ln = Er, Nd, Yb, Sm) complexes. At the same time, a series of lanthanide complexes covalently bonded to xerogels by the ligand 5-(N,N-bis-3-(triethoxysilyl)propyl)ureyl-1,10-phenanthroline (phen-Si) were synthesized in situvia a sol-gel process. [The obtained materials are denoted as xerogel-bonded Ln complexes (Ln = Er, Nd, Yb, Sm).] The single crystal structures of the Ln(pfnp)(3)phen complexes were determined. The properties of these complexes and the corresponding xerogel materials were investigated by Fourier-transform infrared (FTIR), diffuse reflectance (DR), and field-emission scanning electron microscopy (FE-SEM). After ligand-mediated excitation of these complexes and the corresponding xerogel materials they all show the characteristic NIR luminescence of the corresponding Ln(3+) ion. This is attributed to efficient energy transfer from the ligands to the Ln(3+) ion (the so-called "antenna effect").

Construction and NIR luminescent property of hetero-bimetallic Zn–Nd complexes from two chiral salen-type Schiff-base ligands

Two new near-infrared (NIR) luminescent Zn–Nd complexes [ZnL 1Nd(OAc)(NO 3) 2] ( 3) and [ZnL 2Nd(DMF) 2(NO 3) 3] ( 4) have been obtained with two salen-type Schiff-base ligands H 2L 1 and H 2L 2 , ( H 2L 1 = N, N′-bis(3-methoxysalicylidene)-(1s, 2s)-(−)1,2-dipheneylethylenediamine and H 2L 2 = N, N′-bis(3-methoxysalicylidene)-(s)-2,2-diamine-1,1′-binaphthyl) from the reaction of different chiral diamines with o-vanillin. The X-ray crystal structure analysis reveals that both of them crystallize in the chiral space groups with P2(1), a = 10.1669(6), b = 19.3775(11), c = 17.4639(10) Å, β = 94.8710(10)°, V = 3428.1(3) Å 3, Z = 4 for 3, and C2, a = 22.1914(13), b = 9.7886(6), c = 22.0138(13) Å, β = 118.9590(10)°, V = 4372.5(4) Å 3, Z = 4 for 4. Complexes 3– 4 are both dinuclear Zn–Nd structures, while suitable choice of chiral Schiff-base ligands could induce the different complexions of ligands and metal ions, and the functional control of ligand character shows a potentially effective way to the fine-tuning properties of NIR luminescence from Nd ions.

Design and synthesis of near-IR luminescent mesoporous materials covalently linked with tris(8-hydroxyquinolinate)lanthanide(III) complexes

By using the bifunctional ligand, 8-hydroxyquinoline-functionalized organosilane (Q-Si), the new mesoporous material Q–MCM-41 covalently bonded with 8-hydroxyquinoline was synthesized. Through the ligand exchange reaction, the new near-infrared (NIR) luminescent mesoporous LnQ 3–MCM-41 (Ln = Er, Nd, Yb) materials were prepared by linking the lanthanide quinolinate complexes to the ordered mesoporous Q–MCM-41 material. The LnQ 3–MCM-41 materials were characterized by powder X-ray diffraction and N 2 adsorption/desorption, and they all show the characteristic mesoporous structure of MCM-41 with highly uniform pore size distributions. Fluorescence spectra of these LnQ 3–MCM-41 materials were recorded and the corresponding luminescence decay analyses were measured. After ligand-mediated excitation, all the emission spectra of the LnQ 3–MCM-41 materials show the characteristic NIR-luminescence of the corresponding lanthanide ions via the intramolecular energy transfer from the ligands to the lanthanide ions. The good luminescent performances enable these NIR-luminescent mesoporous materials to have potential applications in optical amplification (operating at 1.3 or 1.5 μm) and laser systems, etc.

Simple assessment of homogeneity in pharmaceutical mixing processes using a near-infrared reflectance probe and control charts

Determination of homogeneous mixing of the active pharmaceutical ingredient (API) is an important in-process control within the manufacturing of solid dosage forms. In this paper two new near-infrared (NIR) based methods were presented; a qualitative and a quantitative method. Both methods are based on the calculation of net analyte signal (NAS) models which were very easy to develop, specific with respect to the API and required no additional reference analysis. Using a well-mixed batch as a ‘golden standard’ batch, control charts were developed and used for monitoring the homogeneity of other batches with NIR. The methods were fast, easy to use, non-destructive and provided statistical tests of homogeneity. A mixing study was characterized with the two methods and the methods were validated by comparison with traditional HPLC analysis.

A Parsec‐Scale Outflow in the Rosette Molecular Cloud?

We report on new observations of a purported parsec-scale outflow in the hostile environment at the boundary of the Rosette Nebula, a well-known H II region driven by several O stars in the open cluster NGC 2244, and the Rosette Molecular Cloud (RMC). Several emission features were first reported by Ybarra & Phelps in 2004 , but with only optical [S II] imaging, their nature could not then be established. Our new near-infrared (NIR) H2 imaging observations reveal bulleted NIR emission between a Two Micron All Sky Survey (2MASS) NIR excess point source and the optical [S II] emission for RMC C of Ybarra & Phelps. Analysis of the 2MASS colors indicates that the point source is likely to be a Class I young stellar object (YSO). Together these results imply that RMC C is in fact part of a true YSO outflow, now designated HH 871. The presence of additional [S II] emission, apparently connected to the HH 871 outflow but separated by ~1.2 pc, assuming a distance of 1600 pc for the RMC, also lends support to the Ybarra & Phelps hypothesis that a parsec-scale outflow is present in this harsh ionizing environment.

Synthesis and evaluation of polyhydroxylated near-infrared carbocyanine molecular probes.

[reaction: see text] A new near-infrared (NIR) fluorescent molecular probe derived from indocarbocyanine dye and galactose was prepared, and the procedure was optimized. The presence of a nonionic polyhydroxyl moiety between hydrophobic groups enhances solubility and possibly minimizes aggregation in aqueous solutions. The structural framework of this molecule provides multivalent sites for labeling diverse molecules.

NIR observations of the QSO 3C 48 host galaxy

In this paper we present new near infrared (NIR) imaging and spectroscopic data of the quasar 3C 48 and its host galaxy. The data were obtained with the ESO-VLT camera ISAAC.We report the first detection of the apparent second nucleus 3C 48A about 100NE of the bright QSO nucleus in the NIR bands J, H, and Ks. 3C 48A is highly reddened with respect to the host, which could be due to warm dust, heated by enhanced star formation or by interstellar material intercepting the radio jet. In fact, all colors on the host galaxy are reddened by several magnitudes of visual extinction. Imaging and initial spectroscopy also reveal a stellar content of about 30% to the overall QSO-light in the NIR. These results are important input parameters for future models of the stellar populations by taking extinction into account.