Influences of plasma treatment parameters on the hydrophobicity of cathode and anode materials from spent lithium-ion batteries.

The recycling of spent lithium-ion batteries (LIBs) can not only reduce the potential harm caused by solid waste piles to the local environment but also provide raw materials for manufacturing new batteries. Flotation is an alternative approach to achieve the selective separation of cathode and anode active materials from spent LIBs. However, the presence of organic binder on the surface of hydrophilic lithium transition-metal oxides results in losses of cathode materials in the froth phase. In this study, plasma treatment was utilized to remove organic layers from cathode and anode active materials. Firstly, the correlations between plasma treatment parameters (e.g., input power, air flowrate, and treatment time) were explored and the contact angles of cathode and anode active materials were investigated by the response surface methodology. Secondly, differences in the flotation recoveries of cathode and anode active materials were enhanced with plasma modification prior to flotation, which is consistent with the contact angle measurement. Finally, the plasma-modification mechanisms of hydrophobicity of cathode and anode active materials were discussed according to Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. The proposed method could be a promising tool to enhance the flotation separation efficiency of cathode and anode active materials for the recycling of spent LIBs.

Ultrasound Pretreatment for Enhancing Fine and Ultrafine Flake Graphite Flotation Beneficiation.

With the severe depletion of coarse flake graphite (a critical raw material) resources, developing and utilizing fine and ultrafine graphite resources have recently attracted attention. Froth flotation is a widely used technique for the initial enrichment of graphite; however, the flotation selectivity decreases significantly along with particle size reduction. Ultrasound pretreatment would be a promising method to improve the flotation of fine particles. As an innovative approach to understand better the flotation response of different flake graphite sizes, this study conducted a comparative analysis based on flotation concentrate yield and ash as well as ash removal rate between the flake graphite with various particle sizes after ultrasound pretreatment. Particle size, X-ray powder diffraction, and scanning electron microscopy and energy dispersive X-ray spectroscopy analyses were used to investigate the effect of ultrasound treatment on mineralogical properties of the flake graphite with varied particle sizes. Process outcomes indicated that the flotation performance of fine flake graphite (mean chord length: 62.63 µm) was significantly enhanced after ultrasound pretreatment. However, flotation of the ultrafine flake graphite (mean chord length: 24.97 µm) after ultrasound treatment was limited due to the difficulty of generating sufficient fragmentation and dissociation by microjets and shock waves formed by the cavitation effect. Compared with conventional flotation, the concentrate yield of ultrasound flotation increased from 88.95 to 94.98%, ash content decreased from 5.72 to 4.87%, and ash removal rate enhanced from 36.94 to 42.61%. Particle size and mineral property analyses confirmed that further crushing and dissociation of the larger flake graphite after ultrasound pretreatment would be the main factors contributing to improved flotation performance. Additionally, the formation of air flocs in the coarse flake graphite during the ultrasound pretreatment process facilitated the flotation recovery of the crushed graphite particles.

Structure characteristics and adsorption performance of graphene oxide prepared by spent carbon cathode-an ultra-low temperature graphitized carbon material.

Spent carbon cathode (SCC) is a hazardous waste from the aluminum electrolysis industry. It is commonly used as a carbon source in the current disposal and recovery strategies, such as combustion, or as a reductant for smelting. The novelty of this study is to propose a strategy for recycling SCC as a graphite resource and to investigate the unique structural characteristics and adsorption properties of graphene oxide produced from this low temperature graphitized carbon. The adsorption kinetics and isotherms of SCC-GO on methylene blue (MB) were studied and compared with the GO prepared from natural flake graphite (NFG) and artificial graphite (AG). The results show that SCC-GO exhibits the highest adsorption rate and adsorption capacity (647.83 mg/g) for MB, which is much higher than NFG-GO (451.22 mg/g) and AG-GO (533.12 mg/g). The analysis of the spectroscopy and morphology confirmed that SCC-GO has a high degree of crystal defects, oxidation, and surface wrinkle. Overall, this study reveals the unique structure of SCC-GO and highlights its significant scientific and application potential as an ultra-low temperature graphitized carbon. This research is also significant for recycling aluminum electrolytic cathode solid waste in the form of a graphite source.

A comparative study on the influence of single and combined ultrasounds assisted flake graphite flotation.

Ultrasound has emerged as a promising technique for improving the mineral flotation performance. However, limited research exists regarding the influence of different ultrasound types on the flotation process. Specifically, the impact of combined ultrasound and the comparison of horn- and bath-type ultrasounds on flotation have not been fully investigated. To address this knowledge gap, a comprehensive study to explore the effects of different ultrasonic pretreatments on the flotation of flake graphite was conducted. A Box-Behnken design is employed to analyze the effects of combined ultrasound on graphite flotation. By characterizing the properties of graphite samples before and after the ultrasonic treatment, the aim is to elucidate the mechanism underlying the impact of ultrasound on graphite flotation. The experimental results indicated that the ultrasonic cavitation intensity exerted a significant influence on the graphite flotation recovery. Both horn- and bath- type ultrasounds contributed to flotation, but horn-type ultrasound demonstrated a more pronounced effect, leading to a 7% increase in flotation recovery, whereas bath-type ultrasound resulted in only a 2% increase. Furthermore, the cavitation intensity of combined ultrasound was found to be higher than that of single-frequency ultrasound in the same duration. However, the performance of graphite flotation was better with short duration combined ultrasound pretreatment, while the opposite trend was observed for a long duration ultrasound pretreatment. These findings may inform the development of more efficient and effective ultrasonic pretreatments for flotation separation processes.

Effect of ultrasound power on HCl leaching kinetics of impurity removal of aphanitic graphite.

This study aimed to investigate the effect of ultrasonic power and temperature on the impurity removal rate during conventional and ultrasonic-assisted leaching of aphanitic graphite. The results showed that the ash removal rate increased gradually (∼50 %) with the increase in ultrasonic power and temperature but deteriorated at high power and temperature. The unreacted shrinkage core model was found to fit the experimental results better than other models. The Arrhenius equation was used to calculate the finger front factor and activation energy under different ultrasonic power conditions. The ultrasonic leaching process was significantly influenced by temperature, and the enhancement of the leaching reaction rate constant by ultrasound was mainly reflected in the increase of the pre-exponential factor A. Ultrasound treatment improved the efficiency of impurity mineral removal by destroying the inert layer formed on the graphite surface, promoting particle fragmentation, and generating oxidation radicals. The poor reactivity of hydrochloric acid with quartz and some silicate minerals is a bottleneck limiting the further improvement of impurity removal efficiency in ultrasound-assisted aphanitic graphite. Finally, the study suggests that introducing fluoride salts may be a promising method for deep impurity removal in the ultrasound-assisted hydrochloric acid leaching process of aphanitic graphite.

A PARP inhibitor, rucaparib, improves cardiac dysfunction in ADP-ribose-acceptor hydrolase 3 ( Arh3 ) deficiency.

Aims: Patients with ADP-ribose-acceptor hydrolase 3 ( ARH3 ) deficiency exhibit stress-induced childhood-onset neurodegeneration with ataxia and seizures (CONDSIAS). ARH3 degrades protein-linked poly(ADP- ribose) (PAR) synthesized by poly(ADP-ribose)polymerase (PARP)-1 during oxidative stress, leading to cleavage of the ADP-ribose linked to protein. ARH3 deficiency leads to excess accumulation of PAR, resulting in PAR-dependent cell death or parthanatos. Approximately one-third of patients with homozygous mutant ARH3 die from cardiac arrest, which has been described as neurogenic, suggesting that ARH3 may play an important role in maintaining myocardial function. To address this question, cardiac function was monitored in Arh3 -knockout (KO) and - heterozygous (HT) mice. Methods and results: Arh3 -KO male mice displayed cardiac hypertrophy by histopathology and decreased cardiac contractility assessed by MRI. In addition, both genders of Arh3 -KO and -HT mice showed decreased cardiac contractility by dobutamine stress test assessed by echocardiography. A direct role of ARH3 on myocardial function was seen with a Langendorff-perfused isolated heart model . Arh3 -KO male mouse hearts showed decreased post-ischemic rate pressure products, increased size of ischemia-reperfusion (IR) infarcts, and elevated PAR levels. Consistently, in vivo IR injury showed enhanced infarct size in Arh3 -KO mice in both genders. In addition, Arh3 -HT male mice showed increased size of in vivo IR infarcts. Treatment with an FDA-approved PARP inhibitor, rucaparib, improved cardiac contractility during dobutamine-induced stress and exhibited reduced size of in vivo IR infarcts. To understand better the role of ARH3, CRISPR-Cas9 was used to generate different Arh3 genotypes of myoblasts and myotubes. Incubation with H2O2 decreased viability of Arh3 -KO and -HT myoblasts and myotubes, resulting in PAR-dependent cell death that was reduced by PARP inhibitors or by transfection with the Arh3 gene. Conclusion: ARH3 regulates PAR homeostasis in myocardium to preserve function and protect against oxidative stress; PARP inhibitors reduce the myocardial dysfunction seen with Arh3 mutations.

COVID-19 SeroHub, an online repository of SARS-CoV-2 seroprevalence studies in the United States.

Seroprevalence studies provide useful information about the proportion of the population either vaccinated against SARS-CoV-2, previously infected with the virus, or both. Numerous studies have been conducted in the United States, but differ substantially by dates of enrollment, target population, geographic location, age distribution, and assays used. This can make it challenging to identify and synthesize available seroprevalence data by geographic region or to compare infection-induced versus combined infection- and vaccination-induced seroprevalence. To facilitate public access and understanding, the National Institutes of Health and the Centers for Disease Control and Prevention developed the COVID-19 Seroprevalence Studies Hub (COVID-19 SeroHub, https://covid19serohub.nih.gov/ ), a data repository in which seroprevalence studies are systematically identified, extracted using a standard format, and summarized through an interactive interface. Within COVID-19 SeroHub, users can explore and download data from 178 studies as of September 1, 2022. Tools allow users to filter results and visualize trends over time, geography, population, age, and antigen target. Because COVID-19 remains an ongoing pandemic, we will continue to identify and include future studies.

The effect of preparation time and aeration rate on the properties of bulk micro-nanobubble water using hydrodynamic cavitation.

Fundamental research on bulk micro-nanobubbles (BMNBs) has grown rapidly due to the demand for their industrial applications and potential role in interfacial sciences. This work focuses on examining properties of such bubbles, including the number, concentration, zeta potential, and surface tension in water. For this purpose, BMNBs were generated by the hydrodynamic cavitation (HC) mechanism. Distilled water and air in the experiments were the liquid and gas phases, respectively. The characterization of bulk microbubbles (BMBs) and bulk nanobubbles (BNBs) were performed through focused beam reflectance measurement (FBRM) and nanoparticle tracking analysis (NTA) techniques, respectively. Zeta potential and surface tension of aqueous solutions were measured at different time and aeration rates. The results showed that aeration rate and preparation time had an important role in the properties of BNBs (concentration, bubble size, and surface charge) and BMBs (number, and bubble size). The instability of BMBs led to the rapid changes in the dissolved oxygen (DO) content in the water. The number of BMBs decreased when preparation time and aeration rate increased, but their size remained constant. By enhancing the preparation time and aeration rate, the concentration of BNBs improved first and then reduced. Additionally, the surface tension of an aqueous solution containing BNBs was significantly lower than that of pure water.

Pickering emulsion prepared by nano-silica particles - A comparative study for exploring the effect of various mechanical methods.

Pickering emulsions are eco-friendly, stabilized by solid particles, and have an essential role in leading industries. Although Pickering emulations have found several applications, surprisingly few investigations have attempted to explore the effectiveness of various mechanical processes for its production. To fill these gaps, the present investigation comprehensively examined the application of various Pickering emulsion preparation processes such as rotor-stator homogenization emulsification (R-SH), ultrasonic emulsification, and their combined processes by using nano-silica particles. The influences of emulsification time and intensity on emulsion droplets' distribution were analyzed as indicative factors. The kerosene/water nano-silica Pickering emulsion was utilized for all assessments. The obtained results demonstrated that the main distribution peak of the emulsion prepared by R-SH occurred where the chord length was greater than 40 µm. Micro-scale nano-silica-aggregates generated large droplets, while the fine-emulsion fraction was significantly increased after ultrasonic treatment. The experimental results showed that the emulsion prepared only by ultrasound needed substantial power to form a Pickering emulsion since the oil phase was difficult to disperse in the water phase. Finally, it was concluded that preprocessing by R-SH could form a stable and uniform emulsion speedily, which is essential for ultrasound emulsion preparation.

Exploring the Relationships between Gas Dispersion Parameters and Differential Pressure Fluctuations in a Column Flotation.

Flotation separation, which is the most important mineral beneficiation technique, is dependent on gas dispersion (hydrodynamic conditions). Thus, many investigations have focused on the precise determination of hydrodynamic conditions such as Reynolds number of the bubbles, bubble velocity, and bubble diameter. However, few studies have examined their relationships with pressure fluctuations in a column flotation. This study introduced the differential pressure fluctuations as an actual variable that could be considered to determine the collection zone's hydrodynamic conditions in a cyclonic microbubble flotation column. In general, the outcomes indicated that superficial gas velocity had the most substantial relationship with the differential pressure fluctuations among other flotation factors (such as pump speed, superficial gas velocity, superficial water velocity, and frother dosage). Furthermore, a high coefficient of determination (R 2 > 0.77) for the equation generated to assess the relationships demonstrated that differential pressure fluctuations could be used as a promising tool to determine the hydrodynamic parameters' characteristics in the flotation columns.

Effect of the ultrasonic standing wave frequency on the attractive mineralization for fine coal particle flotation.

Froth flotation for mineral beneficiation is one of the most important separation techniques; however, it has several challenges for processing fine and ultrafine particles. Attractive mineralization between particles and bubbles by ultrasonic standing wave (USW) is a novel and high-efficiency method that could assist fine particle flotation. Frequency is an important ultrasound parameter, whose effectiveness mechanisms on the attractive mineralization did not compressively address. This study explored the effect of the USW field with various frequencies on the fine coal flotation for filling this gap. Herein, a high-speed camera and a focused beam reflectance measurement (FBRM) were used to analyze three sub-processes of the attractive mineralization, including the microbubbles' formation, the conventional flotation bubbles (CFBs)' dispersion, and the particles' movement. It was found that the maximum flotation metallurgical responses were obtained under the highest examined USW frequency (600 kHz). However, the flotation outcomes by a low USW frequency (50 kHz) were even lower than the conventional flotation tests. Observation and theoretical calculation results revealed these results were originated from the influence of frequency on the carrier bubbles' formation and the action of the secondary acoustic force during USW-assisted flotation. These outcomes demonstrated that frequency is a key factor determining the success of attractive mineralization for fine particles' flotation.

The effect of ultrasound on bulk and surface nanobubbles: A review of the current status.

The generation, and stability of nanobubbles are of particular interest for fundamental research and have potential application in numerous fields. Several attempts were made in the literature to produce nanobubbles through acoustic cavitation. However, the generation and stability mechanisms of nanobubbles in the acoustic field are unclear. Here, we review the effect of ultrasound parameters on bulk nanobubbles and surface nanobubbles. On this basis, we discuss the proposed generation and stability mechanisms of nanobubbles from the perspective of transient and stable acoustic cavitation. Moreover, we propose some future research directions for a deeper understanding of the role of ultrasound in the generation and stability of nanobubbles.

The 89-kDa PARP1 cleavage fragment serves as a cytoplasmic PAR carrier to induce AIF-mediated apoptosis.

Poly(ADP-ribose) polymerase 1 (PARP1) is a nuclear protein that is activated by binding to DNA lesions and catalyzes poly(ADP-ribosyl)ation of nuclear acceptor proteins, including PARP1 itself, to recruit DNA repair machinery to DNA lesions. When excessive DNA damage occurs, poly(ADP-ribose) (PAR) produced by PARP1 is translocated to the cytoplasm, changing the activity and localization of cytoplasmic proteins, e.g., apoptosis-inducing factor (AIF), hexokinase, and resulting in cell death. This cascade, termed parthanatos, is a caspase-independent programmed cell death distinct from necrosis and apoptosis. In contrast, PARP1 is a substrate of activated caspases 3 and 7 in caspase-dependent apoptosis. Once cleaved, PARP1 loses its activity, thereby suppressing DNA repair. Caspase cleavage of PARP1 occurs within a nuclear localization signal near the DNA-binding domain, resulting in the formation of 24-kDa and 89-kDa fragments. In the present study, we found that caspase activation by staurosporine- and actinomycin D-induced PARP1 autopoly(ADP-ribosyl)ation and fragmentation, generating poly(ADP-ribosyl)ated 89-kDa and 24-kDa PARP1 fragments. The 89-kDa PARP1 fragments with covalently attached PAR polymers were translocated to the cytoplasm, whereas 24-kDa fragments remained associated with DNA lesions. In the cytoplasm, AIF binding to PAR attached to the 89-kDa PARP1 fragment facilitated its translocation to the nucleus. Thus, the 89-kDa PARP1 fragment is a PAR carrier to the cytoplasm, inducing AIF release from mitochondria. Elucidation of the caspase-mediated interaction between apoptosis and parthanatos pathways extend the current knowledge on mechanisms underlying programmed cell death and may lead to new therapeutic targets.

Discrimination of Six Flotation Kinetic Models Used in the Conventional Flotation and Carrier Flotation of -74 µm Coal Fines.

In this study, experimental results of conventional flotation and carrier flotation were characterized by six commonly used flotation kinetic models. Two statistical criteria (coefficient of determination, R 2, and root mean square error, RMSE) were used for comparison of fitting performance of different models. All kinetic models tested gave good levels of goodness of fit, but the second-order model with rectangular distribution (model 6) provided the best fitting performance for the experimental data of conventional flotation and carrier flotation. On this basis, two parameters, that is, modified flotation rate constant (K m) and selectivity index (SI), were used to evaluate the difference in flotation separation selectivity between conventional flotation and carrier flotation. Comparisons of K m and SI values indicated that carrier flotation significantly improved the flotation rate constant of combustible materials and flotation separation selectivity of ultrafine coal (-74 µm). In addition, measurements of average bubble size and water recovery indicated that both the coalescence of bubbles and the drainage of liquid in the froth were promoted when coarse coal particles (contact angle >90°) were employed as the carrier to assist the flotation recovery of ultrafine particles, which in turn favored the inhibition effect of the entrainment of gangue materials in carrier flotation compared to conventional flotation.

Self-assembly of DNA-templated copper nanoclusters and carbon dots for ratiometric fluorometric and visual determination of arginine and acetaminophen with a logic-gate operation.

This work describes the synthesis of red-emitting copper nanoclusters (CuNCs) by using DNA as the template. DNA-templated CuNCs combined with blue-emitting carbon dots (CDs) form the self-assembled complex DNA-CuNC/CDs through electrostatic interactions. In the presence of arginine (Arg), the blue fluorescence of CDs (with excitation/emission maxima at 350/440 nm) is quenched. Addition of acetaminophen (AP) induces the competitive combination of Arg and AP for the CDs. This results in the release of Arg from CDs and the recovery of blue fluorescence. On addition of both Arg and AP, the red fluorescence of CuNCs (with excitation/emission maxima at 350/670 nm) undergoes only slight changes. Hence, the DNA-CuNC/CD complex can serve as a dually emitting ratiometric probe to determine both Arg and AP, with detection limits of 0.35 µM and 0.26 µM, respectively. The probe also enables on-site, visual determination of Arg and AP in aqueous samples, best by placing the system in cuvettes or dropping it onto filter paper strips. An "INHIBIT" logic gate was designed based on this ratiometric and visual fluorometric assay, with Arg and AP as the inputs. Graphical abstractSchematic presentation of self-assembly of DNA-templated copper nanoclusters and carbon dots to construct novel dual-emitting nanoprobes for ratiometric fluorometric and visual determination of arginine and acetaminophen in aqueous solutions and on wetting filter paper strips.

A novel flotation technique combining carrier flotation and cavitation bubbles to enhance separation efficiency of ultra-fine particles.

In this paper, a novel flotation technique that combines nano-scale bubbles generated by hydrodynamic cavitation (HC) and carrier flotation is proposed to promote the flotation efficiency of a high-ash (43%) ultra-fine coal sample (<45 µm). We investigated the mechanism by which cavitation bubbles enhance the separation efficiency of carrier flotation using focused beam reflectance measurements, polarizing microscopy, and extended Derjaguin-Landau-Verwey-Overbeek theory. The carrier particles (polystyrene (PS)) and fine coal were pre-treated in a venturi tube and then floated in a laboratory mechanical flotation cell. The flotation results indicate that the presence of cavitation bubbles significantly improved the carrier flotation performance of high-ash ultra-fine coal. This improvement was attributed to the presence of highly hydrophobic PS, which creates additional gas nuclei in the flotation system. The nano-bubbles, which were produced by the venturi tube and adhered to the fine coal particle surfaces, were conducive to the agglomeration of fine coal particles into large aggregates. Moreover, the nano-bubbles functioned as "bridges" of interaction between the carrier particles and large aggregates of fine coal particles. This paper mainly focused on the effect of carrier (PS) and HC on high-ash fine coal. The influence of different HC intensities on carrier (PS) flotation was discussed. Two models for the interactions between the coal particles, nano-bubbles, and PS during cavitation were proposed and were proved using the E-DLVO theory.

A review of effects and applications of ultrasound in mineral flotation.

Ultrasound technology is widely applied in the flotation process. From the perspective of the theory of ultrasound, this article explains the effects and applications of ultrasound in the flotation process. To obtain a clear understanding of ultrasonic effects, we observe the phenomena of ultrasound using a high-speed camera and a CCD camera, and investigate potential applications in flotation. From these different phenomena, the ultrasonic effects are classified into three types of effect: the transient cavitation effect, stable cavitation effect, and acoustic radiation force effect. Based on these effects, the applications of ultrasound to mineral flotation are reviewed, including slime coating removal, oxidation film removal, desulfuration, tiny bubble generation, flotation reagent dispersion, and aggregation. In addition, the ultrasonic equipment and treatment methods applied in flotation are classified and compared based on their characteristics. Finally, we propose some potential directions in the study of the stable cavitation effect and acoustic radiation force effect, which are important, but are seldom mentioned in previous reports.

PARP1 inhibition alleviates injury in ARH3-deficient mice and human cells.

Poly(ADP-ribosyl)ation refers to the covalent attachment of ADP-ribose to protein, generating branched, long chains of ADP-ribose moieties, known as poly(ADP-ribose) (PAR). Poly(ADP-ribose) polymerase 1 (PARP1) is the main polymerase and acceptor of PAR in response to DNA damage. Excessive intracellular PAR accumulation due to PARP1 activation leads cell death in a pathway known as parthanatos. PAR degradation is mainly controlled by poly(ADP-ribose) glycohydrolase (PARG) and ADP-ribose-acceptor hydrolase 3 (ARH3). Our previous results demonstrated that ARH3 confers protection against hydrogen peroxide (H2O2) exposure, by lowering cytosolic and nuclear PAR levels and preventing apoptosis-inducing factor (AIF) nuclear translocation. We identified a family with an ARH3 gene mutation that resulted in a truncated, inactive protein. The 8-year-old proband exhibited a progressive neurodegeneration phenotype. In addition, parthanatos was observed in neurons of the patient's deceased sibling, and an older sibling exhibited a mild behavioral phenotype. Consistent with the previous findings, the patient's fibroblasts and ARH3-deficient mice were more sensitive, respectively, to H2O2 stress and cerebral ischemia/reperfusion-induced PAR accumulation and cell death. Further, PARP1 inhibition alleviated cell death and injury resulting from oxidative stress and ischemia/reperfusion. PARP1 inhibitors may attenuate the progression of neurodegeneration in affected patients with ARH3 deficiency.

Conjugation of Fab' Fragments with Fluorescent Dyes for Single-Molecule Tracking On Live Cells.

Our understanding of the regulation and functions of cell-surface proteins has progressed rapidly with the advent of advanced optical imaging techniques. In particular, single-molecule tracking (SMT) using bright fluorophores conjugated to antibodies and wide-field microscopy methods such as total internal reflection fluorescence microscopy have become valuable tools to discern how endogenous proteins control cell biology. Yet, some technical challenges remain; in SMT, these revolve around the characteristics of the labeling reagent. A good reagent should have neutrality (in terms of not affecting the target protein's functions), tagging specificity, and a bright fluorescence signal. In addition, a long shelf-life is desirable due to the time and monetary costs associated with reagent preparation. Semiconductor-based quantum dots (Qdots) or Janelia Fluor (JF) dyes are bright and photostable, and are thus excellent candidates for SMT tagging. Neutral, high-affinity antibodies can selectively bind to target proteins. However, the bivalency of antibodies can cause simultaneous binding to two proteins, and this bridging effect can alter protein functions and behaviors. Bivalency can be avoided using monovalent Fab fragments generated by enzymatic digestion of neutral antibodies. However, conjugation of a Fab with a dye using the chemical cross-linking agent SMCC (succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate) requires reduction of the interchain disulfide bond within the Fab fragment, which can decrease the structural stability of the Fab and weaken its antigen-binding capability. To overcome this problem, we perform limited reduction of F(ab')2 to generate Fab' fragments using a weak reducer, cysteamine, which yields free sulfhydryl groups in the hinge region, while the interchain disulfide bond in Fab' is intact. Here, we describe a method that generates Fab' with high yield from two isoforms of IgG and conjugates the Fab' fragments with Qdots. This conjugation scheme can be applied easily to other types of dyes with similar chemical characteristics.