High-Performance Photoinduced Tunneling Self-Driven Photodetector for Polarized Imaging and Polarization-Coded Optical Communication based on Broken-Gap ReSe2 /SnSe2 van der Waals Heterojunction.

Novel 2D materials with low-symmetry structures exhibit great potential applications in developing monolithic polarization-sensitive photodetectors with small volume. However, owing to the fact that at least half of them presented a small anisotropic factor of ≈2, comprehensive performance of present polarization-sensitive photodetectors based on 2D materials is still lower than the practical application requirements. Herein, a self-driven photodetector with high polarization sensitivity using a broken-gap ReSe2 /SnSe2 van der Waals heterojunction (vdWH) is demonstrated. Anisotropic ratio of the photocurrent (Imax /Imin ) could reach 12.26 (635 nm, 179 mW cm-2 ). Furthermore, after a facile combination of the ReSe2 /SnSe2 device with multilayer graphene (MLG), Imax /Imin of the MLG/ReSe2 /SnSe2 can be further increased up to13.27, which is 4 times more than that of pristine ReSe2 photodetector (3.1) and other 2D material photodetectors even at a bias voltage. Additionally, benefitting from the synergistic effect of unilateral depletion and photoinduced tunneling mechanism, the MLG/ReSe2 /SnSe2 device exhibits a fast response speed (752/928 µs) and an ultrahigh light on/off ratio (105 ). More importantly, MLG/ReSe2 /SnSe2 device exhibits excellent potential applications in polarized imaging and polarization-coded optical communication with quaternary logic state without any power supply. This work provides a novel feasible avenue for constructing next-generation smart polarization-sensitive photodetector with low energy consumption.

Interfacial Engineering of Semicoherent Interface at Purified CsPbBr3 Quantum Dots/2D-PbSe for Optimal CO2 Photoreduction Performance.

Heterogeneous photocatalysts are extensively used to achieve interfacial electric fields for acceleration of oriented charge carrier transport and further promotion of photocatalytic redox reactions. Unfortunately, the incoherent interfaces are almost present in the heterostructures owing to large lattice mismatch accompanied by the interfacial defects and high density of gap states, acting as high energy barriers for charge migration. In this work, we report the atomic engineering of CsPbBr3/PbSe heterogeneous interfaces and conversion from incoherent features to semicoherent characters via methyl acetate (MeOAc) purification of CsPbBr3 quantum dots (QDs) before composited with two-dimensional (2D)-PbSe, which is confirmed by high-resolution transmission electron microscopy. The photocatalytic performances and theoretical calculations indicate that semicoherent interfaces are favorable for improving the activity and reactivity of the heterostructure, triggering 3 times enhanced photocatalytic CO2 reduction rate with 91% selectivity and satisfactory stability. This study proposes a facile method for photocatalytic heterojunctions to transform incoherent interfaces to photocatalytically beneficial semicoherent boundaries, accompanying with a systematic analysis of the consequent chemical dynamics to demonstrate the mechanism of the semicoherent interface for supporting photocatalysis. The understandings gained from this work are valuable for rational interfacial lattice engineering of heterogeneous photocatalysts for efficient solar fuel production.

A high-responsivity CsPbBr3 nanowire photodetector induced by CdS@CdxZn1-xS gradient-alloyed quantum dots.

Benefitting from excellent thermal and moisture stability, inorganic halide perovskite materials have established themselves quickly as promising candidates for fabricating photoelectric devices. However, due to their high trap state density and rapid carrier recombination rate, the photoelectric conversion efficiencies of current inorganic halide perovskite materials are still lower than expected. Here, after systematic research on the optoelectronic properties of CsPbBr3 nanowires (NWs) decorated with binary CdS quantum dots (QDs), CdS@ZnS core/shell QDs, and gradient-alloyed CdS@CdxZn1-xS QDs, respectively, we proposed a facile method to improve the quantum efficiency of perovskite-based photodetectors with low cost, in which the aforementioned QDs are firstly integrated with CsPbBr3 NWs, which act as a photosensitive layer. Notably, the responsivity of the CsPbBr3 NW photodetector decorated with CdS@CdxZn1-xS QDs was enhanced about 10-fold compared to that of pristine CsPbBr3 NW devices. This value is far superior to those for hybrids composed of binary CdS QDs and CdS@ZnS core/shell QDs. The high responsivity enhancement phenomena are interpreted based on the unique funnel-shaped energy level of CdS@CdxZn1-xS QDs, which is favorable for light-harvesting and photocarrier separation. This work indicates that our unique QD/NW hybrid nanostructure is a desirable building block for fabricating high-performance photodetectors.

Enhanced Performances of n-ZnO Nanowires/p-Si Heterojunctioned Pyroelectric Near-Infrared Photodetectors via the Plasmonic Effect.

Although pyroelectric photodetectors have been intensively studied, the transient temperature change rate of pyroelectric materials is a main restrictive factor for improving the performance. In this work, we fabricate an ultrafast response self-powered near-infrared (NIR) photodetector (PD) based on Au nanoparticles (NPs) coated an n-ZnO nanowires (NWs)/p-Si heterojunction. The local surface plasmon resonance (LSPR) effect generated at the local contacts of Au NPs/ZnO NWs can significantly enhance the transient temperature change rate of the ZnO material to improve the photoresponse performances of the NIR PD. Compared with that in the pristine ZnO-based PD, the response time of the Au-coated NIR PD is decreased from 113 to 50 µs at the rising edge and 200 to 70 µs at the falling edge. Optical responsivity and detectivity of the Au-coated ZnO-based PD are increased by 212 and 266%, respectively. The pyroelectric current gain is produced by injecting hot electrons from the LSPR effect of Au NPs into the ZnO material and the thermal energy transfer caused by the photothermal effect of plasmonic Au nanostructure. This work provides an in-depth understanding of plasmonic effect-enhanced pyroelectric effect and presents a unique strategy for developing high-performance NIR photodetectors.

Growth of InZnP/ZnS core/shell quantum dots with wide-range and refined tunable photoluminescence wavelengths.

Owing to their environmentally friendly characteristic, InP-based quantum dots (QDs) show great potential in various fields as an alternative to Cd-based QDs. However, the current mainstream synthesis process, the (TMS)3P-based injection method, still faces many challenges, such as the high cost of (TMS)3P and complex temperature control. In contrast, the solvothermal method is considered to be more feasible and reproducible. Despite its potential advantages, little has been done to understand how the precursors influence the synthesis of InP QDs using the solvothermal method. In this research, InZnP/ZnS QDs were synthesized using practical phosphorus precursors (DEA)3P or (DMA)3P. Through the feasible regulation of zinc, indium, phosphorus and sulfur precursors, the band gap of the QDs could be widely and accurately tuned, and a much wider photoluminescence wavelength ranging from 484 nm to 651 nm could be achieved. Furthermore, InI3 and InBr3 contributed to the blueshift in the PL wavelengths, and the combination of (DEA)3P, (DMA)3P, n-DDT and t-DDT refined the PL wavelength with a small tuning gap of 5 nm.

Improved photoelectric performance of all-inorganic perovskite through different additives for green light-emitting diodes.

The exceptional optical and electronic properties of all-inorganic cesium lead bromide (CsPbBr3) perovskite make it an ideal new optoelectronic material, but low surface coverage limits its performance. The morphological characteristics of thin films have a great influence on the performance of perovskite light emitting diodes, especially at low coverage, and an inhomogeneous surface will lead to current leakage. To tackle this problem, the widespread adoption of composite layers including polymers poly(ethylene oxide) (PEO) and organic insulating poly(vinylpyrrolidone) (PVP) and all-inorganic perovskites is an effective way to increase the surface coverage and uniformity of perovskite films and improve the performance of perovskite light emitting devices. In our work, the perovskite thin films are investigated by using PEO and PVP dual additives, and the optimized CsPbBr3-PEO-PVP LED with maximum luminance, current efficiency, and external quantum efficiency of 2353 cd m-2 (at 7.2 V), 2.14 cd A-1 (at 6.5 V) and 0.85% (at 6.5 V) was obtained. This work indicates that the method of using additives is not only the key to enhancing the quality of perovskite thin film, but also the key to achieving a higher performance perovskite LED.

Environmentally friendly Cu2ZnSnS4-based photocathode modified with a ZnS protection layer for efficient solar water splitting.

High-quality Cu2ZnSnS4 (CZTS) thin films prepared by spray pyrolysis on a Mo-coated glass substrate were used for solar water splitting in this study. Modification of a CdS layer under CZTS improved the photocatalysis efficiency by forming a pn junction between CdS and CZTS, effectively separating the photoexcited carriers without recombination. However, the photocorrosive nature of CdS induces poor stability of the CdS/CZTS photocathode. Surface protection of a CdS-covered CZTS photocathode by a ZnS layer resulted in efficient photoelectrochemical water splitting with a maximum half-cell solar to hydrogen (HC-STH) efficiency of 2.1% and without showing appreciable degradation. The ZnS layer acts as a mediator for efficient electron transport to Pt deposits and as a protective layer, preventing contact between the CdS layer and the outer electrolyte solution.

Surface-enhanced Raman spectroscopic analysis of maleic hydrazide adsorbed on gold surface.

In this paper, surface-enhanced Raman scattering (SERS) spectra of maleic hydrazide (MH, 6-hydroxy-3(2H)-pyridazinone) were studied by using citrate-reduced gold colloidal nanoparticles. Comparisons between the prominent SERS bands and the precise mode descriptions predicted through density functional theory (DFT) simulations at the B3LYP/6-311++g(d,p) level allowed an in-depth orientation analysis of the adsorbed species on gold surfaces. And main forms of hydrogen bonds in the solid state of MH were also determined to be O-H⋯O. Furthermore, the effects of concentration and pH on the SERS spectra of the molecule were discussed. It is found that with the different adsorbate concentration, the SERS spectra of MH show significant changes in their features, indicating different orientations and adsorption sites of the molecule on the gold colloidal surface. The SERS and absorption spectra under different pH conditions show that a basic environment leads to the deprotonation of N2 and the nearly parallel orientation of the MH molecule on the gold surface. Moreover, the enhanced characteristic bands were observed at MH concentrations down to about 1 ppm with the gold colloids, demonstrating a potential of the technique in the analysis of MH residues.

Exploring the binding of 4-thiothymidine with human serum albumin by spectroscopy, atomic force microscopy, and molecular modeling methods.

The interaction of 4-thiothymidine (S(4)TdR) with human serum albumin (HSA) was studied by equilibrium dialysis under normal physiological conditions. In this work, the mechanism of the interaction between S(4)TdR and human serum albumin (HSA) was exploited by fluorescence, UV, CD circular, and SERS spectroscopic. Fluorescence and UV spectroscopy suggest that HSA intensities are significantly decreased when adding S(4)TdR to HAS, and the quenching mechanism of the fluorescence is static. Also, the ΔG, ΔH, and ΔS values across temperature indicated that hydrophobic interaction was the predominant binding force. The CD circular results show that there is little change in the secondary structure of HSA except the environment of amino acid changes when adding S(4)TdR to HSA. The surface-enhanced Raman scattering (SERS) shows that the interaction between S(4)TdR and HSA can be achieved through different binding sites which are probably located in the II A and III A hydrophobic pockets of HSA which correspond to Sudlow's I and II binding sites. In addition, the molecular modeling displays that S(4)TdR-HSA complex is stabilized by hydrophobic forces, which result from amino acid residues. The atomic force microscopy results revealed that the single HSA molecular dimensions were larger after interaction of 4-thiothymidine. This work would be useful to understand the state of the transportation, distribution, and metabolism of the anticancer drugs in the human body, and it could provide a useful biochemistry parameter for the development of new anti-cancer drugs and research of pharmacology mechanisms.

Surface-enhanced Raman scattering study of riboflavin on borohydride-reduced silver colloids: Dependence of concentration, halide anions and pH values.

The influences of concentration, halide anions and pH on the surface-enhanced Raman scattering (SERS) of riboflavin adsorbed on borohydride-reduced silver colloids were studied. The optimum concentration for the SERS of riboflavin is 10(-6)mol/L while the SERS enhancement varies for different modes. The addition of 0.2mol/L halide (NaCl, NaBr, and NaI) aqueous solutions, leads to a general decrease of the SERS intensity and a change of spectral profile of riboflavin excited at 514.5nm. Riboflavin interacts with the silver surface possibly through the CO and N-H modes of the uracil ring. The SERS spectra of riboflavin were recorded in the 3.4-11.6 pH range. By analyzing several SERS marker bands, the protonated, deprotonated or the coexistence of both molecular species adsorbed on the colloidal silver particles was proved.

Study of the surface-enhanced Raman spectroscopy of residual impurities in hydroxylamine-reduced silver colloid and the effects of anions on the colloid activity.

The paper investigated the residual ions in hydroxylamine-reduced silver colloid (HRSC) and the relationship between the condition of HRSC and the enhanced mechanisms of this colloid. We also detected the SERS of MB and studied the effects of anions on the Raman signal. In the case of HRSC, the bands of residual ions diminish while the bands of Ag-anions increase gradually with increasing the concentrations of Cl(-) and NO(3)(-). It means the affinity of residual ions on the silver surface is weaker than that of Cl(-) and NO(3)(-) and the residual ions are replaced gradually by the added Cl(-) or NO(3)(-). The Raman signal of residual ions can be detected by treatment with anions that do not bind strongly to the silver surface, such as SO(4)(2-). The most intense band of Ag-anions bonds can be also observed when adding weakly binding anions to the colloid. However, the anions which make up the Ag-anions bonds are residual Cl(-) and the effect of weakly binding anions is only to aggregate the silver particles. Residual Cl(-) can be replaced by I(-) which has the highest affinity. From the detection of methylene blue (MB), the effects of anions on the enhancement of Raman signal are discussed in detail, and these findings could make the conditions suitable for detecting analytes in high efficiency. This study will have a profound implication to SERS users about their interpretation of SERS spectra when obtaining these anomalous bands.

The pH dependent Raman spectroscopic study of caffeine.

First of all the surface enhanced Raman spectroscopy (SERS) and normal Raman spectra of caffeine aqueous solution were obtained at different pH values. In order to obtain the detailed vibrational assignments of the Raman spectroscopy, the geometry of caffeine molecule was optimized by density functional theory (DFT) calculation. By comparing the SERS of caffeine with its normal spectra at different pH values; it is concluded that pH value can dramatically affect the SERS of caffeine, but barely affect the normal Raman spectrum of caffeine aqueous solution. It can essentially affect the reorientation of caffeine molecule to the Ag colloid surface, but cannot impact the vibration of functional groups and chemical bonds in caffeine molecule.

Semi-quantitative analysis of gentian violet by surface-enhanced Raman spectroscopy using silver colloids.

The viability of the application of surface-enhanced Raman spectroscopy (SERS) to the semi-quantitative analysis of the triphenylmethane dye gentian violet was examined by using activated borohydride-reduced silver colloids. Raman and SERS spectra of aqueous solutions of gentian violet at different pH values were acquired for the first time and equally intense SERS signals were obtained at both acidic and alkaline pH values. Two maxima intensities observed in the pH profile revealed the presence of different ionization states of the dye. The pH conditions for SERS were optimized over the pH range 1 to 12 and the biggest enhancement for SERS of this charged dye was found to be at pH 2.0; thus, this condition was used for semi-quantitative analysis. A good linear correlation was observed for the dependence of the signal intensities of the SERS bands at 1620 cm(-1) (R = 0.999) and 1370 cm(-1) (R = 0.952) on dye concentration over the range 10(-6) to 10(-4) mol/L, using laser excitation at 514.5 nm. At concentrations of dye above 10(-2) mol/L, the concentration dependence of the SERS signals is nonlinear. This is explained as due to the precipitation of metallic silver as well as due to saturation caused by complete coverage of the SERS substrate. A series of intensities of the band at 1620 cm(-1) measured from dye molecules proved that the single-molecule limit of gentian violet is attained at the concentration of 10(-9) mol/L.

[Adsorption of methylene blue on colloidal silver--a surface-enhanced Raman spectroscopy study combined with density functional theory calculations].

Surface-enhanced Raman spectra of methylene blue (MB) at different concentrations in silver colloid were obtained. The results indicate that the physical adsorption is dominant at high concentration while the chemical adsorption is the main fashion at relatively low concentration; there are different adsorption orientations at different concentration: MB+ molecule is perpendicular to the surface of silver nanoparticle at high concentration and adopts a parallel orientation on the surface of nanoparticle at low concentration. The effect of adsorbing time of MB molecule in Ag colloid was investigated and the adsorption dynamics study shows that the parallel orientation at low concentration does not change with the adsorbing time increasing. Density functional theory (DFT) calculations at the level of B3LYP/6-311+G * (for C, S, N, H)/LANL2DZ (for Ag) were employed to optimize the structures and predict Raman frequencies of MB+ and various MB+ -Ag complexes. The results of experiments and calculations suggest that the silver atom prefers to be bound to N and S atoms in the aromatic ring, and thus two different complexes are formed, i.e., conformer N-Ag and conformer S-Ag. Moreover, the Mulliken charge population analysis indicates that N atom in the aromatic ring prefers to interact with Ag than S atom does. Finally, the Raman frequencies observed in the experiments and their vibrational modes were tentatively assigned and discussed.

[Thermal coagulation of human benign prostatic hyperplasia tissues induced changes in the absorption and scattering properties in spectral range from 590 to 1 064 nm in vitro].

The optical properties and their differences of native and coagulated human benign prostatic hyperplasia (BPH) tissues were studied in the spectral range from 590 to 1 064 nm in vitro. The measurements were performed using a spectrophotometer with an integrating sphere attachment, and the absorption and scattering properties were assessed from these measurements using the inverse adding-doubling method. The results of measurement showed that the thermal coagulation of BPH tissues induced obviously the decrease in the absorption coefficients in the spectral range from 590 to 1 064 nm. The peaks in the absorption coefficients for native and coagulated BPH tissues were respectively 0.438 and 0.416 mm(-1) corresponding to the same wavelength of 990 nm, the maximum difference in the absorption coefficients of native and coagulated BPH tissues is 86.79% at 1 064 nm, and the minimum difference is 4.74% at 920 nm. The thermal coagulation of BPH tissues induced an increase in the reduced scattering coefficients in the spectral range from 600 to 1 064 nm obviously, and induced a decrease in the reduced scattering coefficients at 590 nm obviously. The peaks in the reduced scattering coefficients for native and coagulated BPH tissues were respectively 1.090 and 1. 449 mm(-1) corresponding to the same wavelength of 970 nm, and other peaks in the reduced scattering coefficients for native and coagulated BPH tissues were respectively 1.116 and 1.627 mm(-1) corresponding to the same wavelength of 1 050 nm, the maximum difference in the reduced scattering coefficients of native and coagulated BPH tissues is 47.73% at 1 064 nm, and the minimum difference is 4.86% at 600 nm.

[Absorption and scattering characteristics of human benign prostatic hyperplasia tissue with Ti: sapphire laser irradiation in vitro].

The optical properties and their differences of human benign prostatic hyperplasia (BPH) tissues removed using transurethral plasma kinetic resection of the prostate (PKRP) and transurethral vaporization of the prostate (TUVP) at 640, 660, 680, 700, 720, 740, 760, 780, 800, 820, 840, 860 and 880 nm of Ti: Sapphire laser were studied in vitro. The measurements were performed using a double-integrating-sphere setup, and the absorption and scattering properties were assessed using the inverse adding-doubling method. The results of measurement showed that the absorption coefficients and reduced scattering coefficients of BPH tissues removed using PKRP and TURP obviously decreased with the increase in the wavelength for thirteen different laser wavelengths. The absorption coefficient and reduced scattering coefficient of BPH tissues removed using PKRP at a certain laser wavelength were obviously smaller than that of BPH tissues removed using TUVP at the same laser wavelength. The maximum absorption coefficient and maximum reduced scattering coefficient of BPH tissues removed using PKRP and TURP were respectively (0. 885 +/- 0. 022) and (0.955 +/- 0.024)mm(-1), and (1.564 +/- 0.039) and (1.658 +/- 0.042)mm(-1) at 640 nm, their differences were respectively 7.91% and 6.01%, and the minimum absorption coefficient and minimum reduced scattering coefficient of BPH tissues removed using PKRP and TURP were respectively (0.443 +/- 0.011) and (0.455 +/- 0.011) mm(-1), and (1.117 +/- 0.028) and (1.197 +/- 0.030)mm(-1) at 640 nm, their differences were respectively 2.71% and 9.13%. The maximum difference in the absorption coefficients of BPH tissues removed using PKRP and TURP is 8.95% at 660 nm, and the minimum difference is 1.75% at 860 nm. The maximum difference in the reduced scattering coefficients of BPH tissues removed using PKRP and TURP is 9.13% at 800 nm, and the minimum difference is 6.01% at 640 nm.

Thermal coagulation-induced changes of the optical properties of normal and adenomatous human colon tissues in vitro in the spectral range 400-1,100 nm.

The absorption coefficients, the reduced scattering coefficients and the optical penetration depths for native and coagulated human normal and adenomatous colon tissues in vitro were determined over the range of 400-1,100 nm using a spectrophotometer with an internal integrating sphere system, and the inverse adding-doubling method was applied to calculate the tissue optical properties from diffuse reflectance and total transmittance measurements. The experimental results showed that in the range of 400-1,100 nm there were larger absorption coefficients (P < 0.01) and smaller reduced scattering coefficients (P < 0.01) for adenomatous colon tissues than for normal colon tissues, and there were smaller optical penetration depths for adenomatous colon tissues than for normal colon tissues, especially in the near-infrared wavelength. Thermal coagulation induced significant increase of the absorption coefficients and reduced scattering coefficients for the normal and adenomatous colon tissues, and significantly reduced decrease of the optical penetration depths for the normal and adenomatous colon tissues. The smaller optical penetration depth for coagulated adenomatous colon tissues is a disadvantage for laser-induced thermotherapy (LITT) and photodynamic therapy (PDT). It is necessary to adjust the application parameters of lasers to achieve optimal therapy.

[Superficial bladder cancer detection using diffuse reflectance spectral ratio R540/R575 of oxygenated hemoglobin bands].

A low-cost, fast, and noninvasive method for early diagnosis of malignant lesions of mucosa tissue based on diffuse reflectance spectra was applied in the study of the optical biopsy of superficial human bladder cancer. In the present paper, differential diagnosis of superficial human bladder cancer was studied using the diffuse reflectance spectral ratio (R540/R575) of the oxygenated hemoglobin absorption bands at 540 and 575 nm in vitro. Diffuse reflectance spectra for mucosa/submucosa tissues of normal bladder and superficial bladder cancer were measured using a spectrophotometer with an integrating sphere attachment. The results of measurement showed that there were three the diffuse reflectance spectral dips at 415, 542 and 577 nm respectively for mucosa/submucosa tissues of normal bladder and superficial bladder cancer in the spectral range from 400 to 600 nm. The mean diffuse reflectance spectral ratio (R540/R575) of normal bladder mucosa/submucosa tissue decreased slowly with time increase after surgical excision, and the mean diffuse reflectance spectral ratio (R540/R575) of superficial bladder cancer mucosa/ submucosa tissue also decreased slowly with time increasing after surgical excision. The mean diffuse reflectance spectral ratios (R540/R575) of normal bladder mucosa/submucosa tissue were 111%, 107%, 104% and 102% after 2, 3, 4 and 5 h after surgical excision respectively, and those of superficial bladder cancer mucosa/submucosa tissue were 98.4%, 95.5%, 93.1% and 91.6% after 2, 3, 4 and 5 h after surgical excision respectively. There were significant differences in mean diffuse reflectance spectral ratio (R540/R575) for mucosa/submucosa tissues between normal bladder and superficial bladder cancer after 2, 3, 4 and 5 h after surgical excision respectively (p < 0.05). Differences in mean diffuse reflectance spectral ratio (R540/R575) for mucosa/ submucosa tissues between normal bladder and superficial bladder cancer were 12.6%, 11.5%, 10.9% and 10.4% after 2, 3, 4 and 5 h after surgical excision respectively. It is obvious that pathological changes in bladder mucosa/submucosa tissues induced changes in the component and structure of the tissues, and especially quantitative changes in oxyhemoglobin and de-oxyhemoglobin of tissues obviously. Conclusion of the study provides a new method that can be applied to rapid, low-cost and noninvasive optical biopsy of superficial bladder cancer.

[Canceration and thermal coagulation of human liver induced changes in the absorption and scattering properties of liver-tissue at near infrared in vitro].

Canceration and thermal coagulation of human liver induced changes in the absorption and scattering properties of liver tissue at 710, 730, 750, 77, 790, 810, 830, 850, 870 and 890 nm of Ti: sapphire laser were studied in vitro. The measurements were performed using a double-integrating-sphere setup, and the absorption and scattering properties were assessed from these measurements using the inverse adding-doubling method. The results of measurement showed that canceration of liver induced significant decrease in the absorption coefficients of liver tissue, and the maximum change in the absorption coefficients is 86.12% at 850 nm, while the minimum change in the absorption coefficients is 82.65% at 750 nm. Thermal coagulation of normal liver induced obvious change in the absorption coefficients from 710 to 890 nm, and the maximum change in the absorption coefficients is 79.55% at 710 nm, while the minimum change in the absorption coefficients 0.72% at 790 nm. Thermal coagulation of carcinoma liver tissue induced significant increase in the absorption coefficients, the maximum change in the absorption coefficients of carcinoma liver tissue is 78.69% at 810 nm, in the minimum change in the absorption coefficients of carcinoma liver tissue 38.16% at 710 nm. Canceration of liver induced significant increase in the scattering coefficients of liver tissue, and the maximum change in the scattering coefficients is 158.37% at 710 nm, while the minimum change in the scattering coefficients is 136.03% at 890 nm. Thermal coagulation of normal liver induced significant increase in the scattering coefficients of liver tissue, and the maximum change in the scattering coefficients is 632.92% at 890 nm, while the minimum change for the scattering coefficients is 587.40% at 710 nm. Thermal coagulation of carcinoma liver tissue induced significant increase in the scattering coefficients, and the maximum change in the scattering coefficients of carcinoma liver tissue is 384. 25% at 810 nm, while the minimum change in the scattering coefficients of carcinoma liver tissue is 330. 86% at 710 nm. The change in the absorption and scattering properties also varies with the change of laser wavelength.

Real-time optoacoustic monitoring of vascular damage during photodynamic therapy treatment of tumor.

The optoacoustic technique is a noninvasive imaging method with high spatial resolution. It potentially can be used to monitor anatomical and physiological changes. Photodynamic therapy (PDT)-induced vascular damage is one of the important mechanisms of tumor destruction, and real-time monitoring of vascular changes can have therapeutic significance. A unique optoacoustic system is developed for neovascular imaging during tumor phototherapy. In this system, a single-pulse laser beam is used as the light source for both PDT and for concurrently generating ultrasound signals for optoacoustic imaging. To demonstrate its feasibility, this system is used to observe vascular changes during PDT treatment of chicken chorioallantoic membrane (CAM) tumors. The photosensitizer used in this study is protoporphyrin IX (PpIX) and the laser wavelength is 532 nm. Neovascularization in tumor angiogenesis is visualized by a series of optoacoustic images at different stages of tumor growth. Damage of the vascular structures by PDT is imaged before, during, and after treatment. Rapid, real-time determination of the size of targeted tumor blood vessels is achieved, using the time difference of positive and negative ultrasound peaks during the PDT treatment. The vascular effects of different PDT doses are also studied. The experimental results show that a pulsed laser can be conveniently used to hybridize PDT treatment and optoacoustic imaging and that this integrated system is capable of quantitatively monitoring the structural change of blood vessels during PDT. This method could be potentially used to guide PDT and other phototherapies using vascular changes during treatment to optimize treatment protocols, by choosing appropriate types and doses of photosensitizers and doses of light.