Toward a rapid and convenient nanoplastic quantification method in laboratory-scale study based on fluorescence intensity

The thorough investigation of nanoplastics(NPs)in aqueous environments requires efficient and expeditious quantitative analytical methods that are sensitive to environmentally relevant NP concentrations and convenient to employ.Optical analysis-based quantitative methods have been acknowledged as effective and rapid approaches for quantifying NP concentrations in laboratory-scale studies.Herein,we compared three commonly used optical response indicators,namely fluorescence intensity(FI),ultraviolet absorbance,and turbidity,to assess their performance in quantifying NPs.Furthermore,orthogonal experiments were conducted to evaluate the influence of various water quality parameters on the preferred indicator-based quantification method.The results revealed that FI exhibits the highest correlation coefficient(>0.99)with NP concentration.Notably,the limit of quantification(LOQ)for various types of NPs is exceptionally low,ranging from 0.0089 to 0.0584 mg/L in ultrapure water,well below environmentally relevant concentrations.Despite variations in water quality parameters such as pH,salinity,suspended solids(SS),and humic acid,a robust relationship between detectable FI and NP concentration was identified.However,an increased matrix,especially SS in water samples,results in an enhanced LOQ for NPs.Nevertheless,the quantitative method remains applicable in real water bodies,especially in drinking water,with NP LOQ as low as 0.0157–0.0711 mg/L.This exceeds the previously reported detectable concentration for 100 nm NPs at 40µg/mL using surface-enhanced Raman spectroscopy.This study confirms the potential of FI as a reliable indicator for the rapid quantification of NPs in aqueous environments,offering substantial advantages in terms of both convenience and cost-effectiveness.

Experimental Study on Ultrasonic Cavitation Intensity Based on Fluorescence Analysis

The Ultrasonic cavitation effect has been widely used in mechanical engineering,chemical engineering,biomedicine,and many other fields.The quantitative characterization of ultrasonic cavitation intensity has always been a difficulty.Based on this,a fluorescence analysis method has been adopted to explore ultrasonic cavitation intensity in this paper.In the experiment of fluorescence intensity measurement,terephthalic acid(TA)was used as the fluorescent probe,ultrasonic power,ultrasonic frequency,and irradiation time were independent variables,and fluorescence intensity and fluorescence peak area were used as experimental results.The collapse of cavitation bubble will cause molecular bond breakage and release·OH,and the non-fluorescent substance TA will form the strong fluorescent substance TAOH with·OH.The spectra of the treated samples were measured by a F-7000 fluorescence spectrophotometer.The results showed that the fluorescence intensity and fluorescence peak area increased rapidly after ultrasonic cavitation treatment,and then increased slowly with the increase of ultrasonic power,which gradually increased with the increase of irradiation time.They first decreased and then increased with the increase of ultrasonic frequency from 20 kHz to 40 kHz.The irradiation time was the most influential factor,and the cavitation intensity of low frequency was higher overall.The fluorescence intensity and fluorescence peak area of the samples increased by 2-20 times after ultrasonic treatment,which could increase from 69 and 5238 to 1387 and 95451,respectively.After the irradiation time exceeded 25 min,the growth rate of fluorescence intensity slowed down,which was caused by the decrease of gas content and TA concentration in the solution.The study quantitatively characterized the cavitation intensity,reflecting the advantages of fluorescence analysis,and provided a basis for the further study of ultra-sonic cavitation.

An abnormal fluorescence intensity ratio between two green emissions of Er^(3+) caused by heating effect of 980 nm excitation

An abnormal fluorescence intensity ratio （FIR） between two green emissions of Er3＋, at room temperature, which is larger than a normal value, emerged in many reported articles. However, up to now detailed work has seldom been done to clarify this abnormal phenomenon. In this paper, green upconversion luminescence of the β-NaLuF4：20%yb3＋,2%Er3＋ powder sample was investigated under 980 um excitation at different circumstances, different pump power densities and different temperatures as well as different air pressures. The corresponding local temperature calculated using FIR technique increased gradually with the enhancement of the pump power density. It was demonstrated that high pump power density of 980 nm laser led to the increase of local temperature of the luminescent material, which further gave the abnormal FIR.

Tunable emission properties of core-shell ZnCuInS-ZnS quantum dots with enhanced fluorescence intensity

Cadmium-free Ⅰ-Ⅲ-Ⅵ quantum dots （QDs）, represented by Cu-In-S （CIS）, are widely investigated for their non-toxicity and tunable emission properties. In this work, Zn-Cu-In-S （ZCIS） alloyed QDs were synthesized via a solvothermal approach by heating up a mixture of the corresponding metal precursors and sulphur powder with dodecanethiol in oleylamine media, and the fluorescent intensity was greatly enhanced by coating ZnS （ZS） shell. By changing the ratio of Cu, the as prepared ZCIS-ZS QDs showed composition-tunable photoluminescent （PL） emission over the visible spectral window from about 500 nm to 620 rim, which is much wider than that of CIS QDs. Moreover, the influence of excitation wavelength, reaction temperature and time on the optical properties of the ZCIS-ZS QDs was also studied. This research provides a feasible and simple approach to prepare ZCIS-ZS QDs with large tunable spectral range on visible region, which could greatly contribute to the development of potential applications due to their non-toxicity and excellent optical properties.

Green and red up-conversion emissions and thermometric application of Er^(3+) -doped silicate glass

The green and red up-conversion emissions centred at about 534, 549 and 663 nm of wavelength, corresponding respectively to the ^2H11/2 → ^4I15/2, ^4S3/2 → ^4I15/2 and ^4F9/2 → ^4I15/2 transitions of Er^3＋ ions, have been observed for the Er^3＋-doped silicate glass excited by a 978 nm semiconductor laser beam. Excitation power dependent behaviour of the up-conversion emission intensity indicates that a two-photon absorption up-conversion process is responsible for the green and red up-conversion emissions. The temperature dependence of the green up-conversion emissions is also studied in a temperature range of 296-673 K, which shows that Er^3＋-doped silicate glass can be used as a sensor in high-temperature measurement.

The Effect of Nd^(3+) Concentration on Upconversion Luminescence in Yb^(3+)/Tm^(3+)/Nd^(3+) Tripledoped b-NaGdF_(4) Nanocrystals

Nd^(3+)-doped NaGdF_(4):Yb,Tm nanocrystals were synthesized by an improved high-temperature thermal decomposition method,and the effects of doping concentrations on the crystal structure,phase composition,and upconverted fluorescence intensity were also investigated.The results reveal that the introduction of Nd^(3+) ions does not cause the transformation of the crystal phase,but induce the change of the unit cell parameters.Meanwhile,the fluorescence intensity of the synthesized nanocrystals when co-doped with 3 mol%Nd^(3+) is the strongest under the excitation of 980 nm laser,which is 3.9 times that of the Nd^(3+)-free doped nanoparticles,and the average size is 62.9 nm.And it is located in the blue area of the CIE coordinate diagram,and the corresponding color purity is 91.81%under the same experimental conditions.The resulting nanocrystals show the potential as excellent fluorescence labeling and in vivo imaging probes.

Fluorescent Labeling of Nanometer Hydroxyapatite

A novel surface treatment method using 3-aminopropyltriethoxysilane （AMPTES）, was developed to immobilize the fluorescein molecule on nano-HAP （nanometer hydroxyapatite） powders. By pretreating the nano-HAP powders surface with AMPTES, fluorescein, chosen on the basis of the chemical structure of the nano- HAP powders, could be bound to the nano-HAP powders surface. The chemical compositions of nano-HAP before and after being labeled were characterized by Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS）. The morphology, phase composition, and the fluorescence characteristics of the nano-HAP powders with and without staining were also investigated. The FTIR and XPS results revealed that fluorescein had been successfully immobilized on the surface of AMPTES-bound nano-HAP powders via the acylamide bond formation between the -COOH of fluorescein and the -NH2 of AMPTES. The labeled nano-HAP powders possessed strong fluorescent intensity with a little deviation from the maximum emission wavelength of fluorescein. But the morphology and phase composition had no obvious alteration. Under fluorescence microscopy, the labeled nano-HAP powders, even after 24 h cell incubation, exhibited strong fluorescence.

A novel Tb^(3+) and Eu^(3+) co-doped dual-emitting phosphate K_(3)SrBi(P_(2)O_(7))_(2) phosphor for application in FIR thermometers

Rare earth co-doped phosphor for fluorescence intensity ratio(FIR) thermometer has gained increasing attention in recent years. Herein, the novel Tb^(3+)and Eu^(3+)co-doped K_(3)SrBi(P_(2)O_(7))_(2)(KSBP) phosphate phosphors were reported. The crystal structure of the title phosphor was determined using Rietveld refinement and proved to have a three-dimensional structure. The time-resolved spectroscopy reveals that there is almost no energy transfer between Tb^(3+)and Eu^(3+). More importantly, Tb^(3+)and Eu^(3+)emissions show different thermal quenching behaviors, which claims the potential of this material for application in optical thermometer. The FIR of the typical KSBP:0.02Tb^(3+),0.04Eu^(3+)sample demonstrates a polynomial relationship as a function of temperature and the absolute and relative sensitivity are0.025 K^(-1) and 0.59%/K, respectively. In general, our study reports a novel and potential KSBP:Tb^(3+),Eu^(3+)phosphate phosphor that is promising for use in high-sensitive FIR thermometers.

Smart nanoprobe based on two-photon sensitized terbium-carbon dots for dual-mode fluorescence thermometer and antibacterial

Accurate temperature measurement plays an important role in a variety of industrial processes and scientific researches.In our work,the dual-mode temperature response nanoprobe CDs-Tb-TMPDPA containing a two-photon ligand(4-(2,4,6-trimethoxyphenyl)-pyridine-2,6-dicarboxylic acid,TMPDPA)sensitized Tb3+as a temperature-sensitive unit and carbon dots(CDs)as photothermal reagent and a fluorescence reference unit,have been designed and synthesized.In this system,both the fluorescence intensity ratio and the fluorescence lifetime have a good response to temperature.In additio n,due to the excellent photothermal conversion capability of CDs,photothermal antibacterial ability was also tested.Based on the temperature dependence of the fluorescence and the two-photon excitation characteristics of CDs-Tb-TMPDPA,the nanoprobe can also be used in the anti-counterfeiting.Our finding opens a new prospect for the use of two-photon sensitized dual-mode fluorescence thermometers.

Fluorescence detection of Escherichia coli on mannose modified ZnTe quantum dots

Rapid detection and identification of Escherichia coli(E.coli)is essential to prevent its quickly spread.In this study,a novel fluorescence probe based on ZnTe quantum dots(QDs)modified by mannose(MAN)had been prepared for the determination of E.coli.The results showed that the obtained QDs showed excellent selectivity toward E.coli,and presented a good linearity in range of 1.0×10~5~1.0×10~8 CFU/mL.The optimum fluorescence intensity for detecting E.coli was found to be at pH 7.0 with a temperature of25℃and incubation time of 20 min.Under these optimum conditions,the detection limit of E.coli was4.6×10~4 CFU/mL.The quenching was discussed to be a static quenching procedure,which was proved by the quenching efficiency of QDs decreased with the temperature increasing.

Multi-site occupancies and dependent photoluminescence of Ca_(9)Mg_(1.5)(PO_(4))_(7):Eu^(2+) phosphors:A bifunctional platform for optical thermometer and plant growth lighting

Herein,we demonstrate an optical thermometer based on single Eu^(2+)doped Ca_(9)Mg_(1.5)(PO_4)_7 phosphors,which were prepared by traditional solid-state reaction technique under a reduction atmosphere.Considerations on the bond length obtained by the crystal structure refinement and the dependent photoluminescence performances allow to assign the two distinct emission bands to Eu^(2+)ions occupied Cal-Ca3 and Mg2 sites.Moreover,the blue and red emitting bands perfectly match with the photosynthetic action spectrum,which can enhance the indoor plant photosynthesis.The optimal doping content of Eu^(2+)ions in this Ca_(9)Mg_(1.5)(PO_(4))_(7)system is 3 mol%.The corresponding concentration quenching effect is verified as dipole-dipole interaction with the critical distance of 3.315 nm.Furthermore,by exploiting the fluorescence intensity technique,the optical thermal resistance properties of Ca_(9)Mg_(1.5)(PO_4)_7:Eu^(2+)are identified based on the temperature dependent emission spectra in a range of 303-523 K.In detail,the maximum absolute and relative sensitivity S_(a)and S_(r)of Ca_9Mg_(1.5)(PO_(4))_(7):Eu^(2+)thermometer are as high as 0.637%/K and 0.3155 K^(-1),respectively.Consequently,the Eu^(2+)doped Ca_(9)Mg_(1.5)(PO_(4))_(7)phosphors establish a bifunctional platfo rm for both optical the rmometer and plant growth lighting via multi-site occupancies.

C1M2:a universal algorithm for 3D instance segmentation,annotation,and quantification of irregular cells

Cell instance segmentation is a fundamental task for many biological applications,especially for packed cells in three-dimensional(3D)microscope images that can fully display cellular morphology.Image processing algorithms based on neural networks and feature engineering have enabled great progress in two-dimensional(2D)instance segmentation.However,current methods cannot achieve high segmentation accuracy for irregular cells in 3D images.In this study,we introduce a universal,morphology-based 3D instance segmentation algorithm called Crop Once Merge Twice(C1M2),which can segment cells from a wide range of image types and does not require nucleus images.C1M2 can be extended to quantify the fluorescence intensity of fluorescent proteins and antibodies and automatically annotate their expression levels in individual cells.Our results suggest that C1M2 can serve as a tissue cytometry for 3D histopathological assays by quantifying fluorescence intensity with spatial localization and morphological information.

Enzyme-free photothermally amplified fluorescent immunosorbent assay(PAFISA)for sensitive cytokine quantification

Cytokine monitoring has attracted great attention due to its significance in the diagnosis and treatment of many diseases,such as tumors,microbial infections,and immunological diseases.Enzyme-linked immunosorbent assay(ELISA)is one of the most popular methods in cytokine detection,ascribing to the lavish signal amplification methods in the ELISA platform.In addition to classical enzymes,other signal amplifiers such as fluorescent probes,artificial nano-enzymes,and photothermal reagents have been applied to reduce the detection limit and produce more sensitive ELISA kits.Due to the accumulative effect of heat,photothermal reagents are promising materials in the signal amplification of ELISA.However,the lack of efficient photothermal generation material at an aggregate scale may delay the further development of this area.In this contribution,based on an efficient organic photothermal aggregate material,an enzyme-free photothermally amplified fluorescent immunosorbent assay system consisting of an assay microfluidic chip and detecting platform was developed.The photothermal nanoparticles with highly efficient photothermal conversion by harvesting energy via excited-state intramolecular motions and enlarging molar absorptivity were successfully prepared.The detection concentration at 50 pg/mL of interleukin-2 was achieved,realizing a signal improvement of detection limits by 20-fold compared to that of previously reported photothermal ELISA.The microscopic imaging integrated with plane sweeping technology provided high spatial resolution and precision,indicating the potential of achieving high throughput profiling at the microscale.Moreover,as an alternative excitation source,light-emitting diode not only provided a more affordable and miniaturized detection system but also revealed the great feasibility of intramolecular motion-induced photothermy nanoparticles for biological analyses.

Y_(4)GeO_(8):Er^(3+),Yb^(3+) up-conversion phosphors for optical temperature sensor based on FIR technique

Herein,we reported novel Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors elaborated via conventional solid-state reaction.and we further explored their properties as optical thermometer by using fluorescence intensity ratio(FIR)method complemented by detailed analysis on crystal structure,up-conversion luminescence and energy transfer from Yb^(3+)to Er^(3+).Upon 980 nm laser excitation,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors present525,547 and 659 nm emission bands assigned to the characteristic transitions of Er^(3+).Furthermore,Y_(4)GeO_(8):Er^(3+),Yb^(3+)samples show outstanding temperature sensing performances.To be specific,the minimal temperature resolution is 0.03 K(303 K),and the relative sensitivity of FIR can be up to 1.152%/K(303 K).Hence,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors can be possible candidates for thermometry devices.

Er^(3+)-Yb^(3+)-Na^(+):ZnWO_(4) phosphors for enhanced visible upconversion and temperature sensing applications

The crystal structure and surface morphology of the Er^(3+)/Yb^(3+)/Na+:ZnWO_(4) phosphors synthesized by solid state reaction method were analyzed by X-ray diffraction(XRD) and field emission scanning electron microscopy(FESEM) analysis.The frequency upconversion(UC) emission study in the developed phosphors was investigated by using 980 nm laser diode excitation.The effect of codoping in the Er^(3+):ZnWO_(4) phosphors on the UC emission intensity was studied.The UC emission bands that are exhibited in the blue(490 nm),green(530,552 nm),red(668 nm) and NIR(800 nm) region correspond to the ^(4)F_(7/2)→^(4)I_(15/2).^(2)H_(11/2),^(4)S_(3/2)→^(4)I_(15/2),^(4)F_(9/2)→^(4)I_(15/2) and ^(4)I9/2→^(4)I_(15/2) transitions,respectively.The temperature sensing performance of the Er^(3+)-Yb^(3+)-Na+:ZnWO_(4) phosphors was investigated based on the 2 H_(11/2)→^(4)I_(15/2) and ^(4)S_(3/2)→^(4)I_(15/2) thermally coupled transitions of the Er^(3+)ions.The photometric study was also carried out for the developed phosphors.

Influence of dysprosium concentration on sensitivity of luminescent thermometers of phosphors Ca_(9)Tb(PO_(4))_(5)(SiO_(4))F_(2)

Tb^(3+),Dy^(3+)-co-doped Ca_(9)Tb_(x)Dy_(1-x)(PO_(4))_(5)(SiO_(4))F_(2) phosphors were prepared via high-temperature solidphase reaction method and the potential application in optical temperature measurements due to their color-tunable property was investigated in detail.The photoluminescence emission(PL) and photoluminescence excitation(PLE) spectra results show that the as-prepared phosphors exhibit both Tb^(3+) and Dy^(3+) emissions at 546 nm(^(5)D_(4)-^(7)F_(5) transition of Tb^(3+)) and 587 nm(^(4)F_(9/2)-^(6)H_(13/2) transition of Dy^(3+)) upon 376 nm excitation,respectively.In addition,the fluorescence decay analysis shows that the lifetime of the Tb3+emission rapidly decreases,which confirms the energy transfer existence between Dy^(3+) and Tb^(3+).Under 376 nm excitation,the temperature dependence of the fluorescence intensity ratios for the dualmission bands peaked at 546 and 587 nm was studied in the temperature range from 303 to 573 K.The results show that with the increase of Dy^(3+) concentration,the relative sensitivity first increases and then decreases,what’s more,the maximum relative sensitivity is 3.142×10^(-3)%/K for Ca_(9)Tb_(x)Dy_(1-x)(PO_(4))_(5)(SiO_(4))F_(2)(x=0.4).As a consequence,this preliminary study provides a novel method for exploring the novel thermo meters.

Novel Highly Selective Fluorescent Chemosensors for Hg（Ⅱ）

Based on Rhodamine,two novel fluorescent Hg2＋ chemosensors（R1,R2） were synthesized from inexpensive starting materials.They were designed and synthesized with o-aminophenol and o-phenylenediamine derivatives as the Hg2＋ chelator,the comparison between the photophysical properties of two chemosensor molecules was made.The chemosensors were designed with a photoinduced electron transfer（PET） mechanism.After binding to Hg2＋ which blocks the PET process,the fluorescence intensity of the chemosensors was enhanced by up to 15-fold.They exhibit very strong fluorescence responses to Hg2＋ and have remarkably higher selectivity for Hg2＋ than for other metal ions including K＋,Na＋,Ca2＋,Mg2＋,Cd2＋,Mn2＋,Ni2＋,Co2＋,Zn2＋,Cu2＋,Cr3＋,Fe3＋,pb2＋,Ag＋,Al3＋,Fe2＋ and Sn2＋ in Tris-HC1/sodium phosphate buffer.The fluorescence enhancement of R2 towards Hg2＋ maintains stable in wide pH span（6.4-8.8） aqueous solutions.

Up-conversion luminescence of Er^(3+)and Yb^(3+)co-doped CaBi_(2)Ta_(2)O_(9) multifunctional ferroelectrics

Er^(3+)and Yb^(3+)co-doped CaBi_(2)Ta_(2)O_(9)(CBT)-based bismuth layered-structure oxides were synthesized by a simple solid-state reaction method.Their up-conversion(UC)luminescence,dielectric and ferroelectric properties were investigated.Two strong green emission bands centered at 526 and 547nm and a weak red emission band centered at 658nm were obtained under a 980nm laser excitation at room temperature.These emission bands originated from the radiative relaxation of Er^(3+)from 2H_(11)=2,4S_(3)=2,and 4F_(9/2) levels to the ground state 4I_(15)=2,respectively.At the meantime,the fluorescence intensity ratio(FIR)variation of two green UC emissions at 526 and 547nm has been studied as a function of temperature in the range of 153–603K.The maximum sensor sensitivity obtained was 39×10^(-4)K^(-1) at 590K,which indicated that Er^(3+)=Yb^(3+)co-doped CBT ceramic is a promising candidate for applications in optical high temperature sensor.

Extraction and characterization of bound extracellular polymeric substances from cultured pure cyanobacterium(Microcystis wesenbergii)

Preliminary characterization of bound extracellular polymeric substances（bEPS） of cyanobacteria is crucial to obtain a better understanding of the formation mechanism of cyanobacterial bloom. However,the characterization of bEPS can be affected by extraction methods. Five sets（including the control） of bEPS from Microcystis extracted by different methods were characterized using three-dimensional excitation and emission matrix（3DEEM） fluorescence spectroscopy combined chemical spectrophotometry; and the characterization results of bEPS samples were further compared. The agents used for extraction were NaOH,pure water and phosphate buffered saline（PBS） containing cationic exchange resins,and hot water. Extraction methods affected the fluorescence signals and intensities in the bEPS. Five fluorescence peaks were observed in the excitation and emission matrix fluorescence spectra of bEPS samples. Two peaks（peaks T1 and T2） present in all extractions were identified as protein-like fluorophores,two（peaks A and C） as humic-like fluorophores,and one（peak E） as a fulvic-like substance.Among these substances,the humic-like and fulvic-like fluorescences were only seen in the bEPS extracted with hot water. Also,NaOH solution extraction could result in strong fluorescence intensities compared to the other extraction methods. It was suggested that NaOH at pH 10.0 was the most appropriate method to extract bEPS from Microcystis. In addition,dialysis could affect the yields and characteristics of extracted bEPS during the determination process. These results will help us to explore the issues of cyanobacterial blooms.

Toxicity and bio-distribution of carbon dots after single inhalation exposure in vivo

Because of the advantages of excellent light stability, carbon dots（CDs） are considered to be a promising agent in the bio-marker application. Nevertheless, there are many unresolved issues with the toxicity of CDs in vitro and in vivo. In the study, CDs were synthesized by citric acid and ethylenediamine into deionized water, then the inhalation toxicity and bio-distribution of CDs in vivo were systematically assessed. The results showed that CDs caused animals death at higher dosages and induced injury in the lung and liver including inflammation and necrosis after single inhalation exposure at 5, 2 and 1 mg/kg dosages of the CDs. We also found that the injury increase with a dose-dependent and time-dependent manner. Fluorescent examination and TEM results showed that CDs mainly located at the lung and liver.And the fluorescent intensity increase with a time-dependent manner. This study provides a theoretical basis of the respiratory toxicity of CDs, and provides a basis for the use of CDs as a bio-marker.