Narrow Dispersity Research Articles

Synthesis of polystyrene colloidal nanoparticles and investigation of their hydrophobic properties on the flotation of phosphorus

AbstractPolystyrene is a synthetic polymer and one of the most widely used polymers in various industries, which is produced in different ways from styrene monomer. This research aims to synthesize polystyrene nanoparticles (NPS) by emulsion polymerization and to investigate their effect on phosphorus flotation. For this purpose, styrene monomer, dodecyl sulfate, and potassium persulfate were used. In the following, the impact of two parameters, including the volume of styrene monomer and reaction time, on the characteristics of nanoparticles was investigated with different analyses. X‐ray diffraction analysis results showed that NPS was formed with an amorphous structure. Increasing the monomer volume increased NPS particle size to 70 nm, accelerating nuclei growth. Expanding the time also had a similar effect and increased the size of the nanoparticles. By dynamic light scattering analysis, the size distribution of the synthesized NPS was about 74.3 nm with narrow dispersion. The wettability of NPS was also investigated and the sample synthesized in 6 h with 9 cc of styrene monomer had the highest wetting angle of about 106°. In the direct flotation of phosphorus, using NPS increased the grade of phosphorus up to 15.1% (34.6% P2O5).

Toward Intracellular Delivery: Aliphatic Polycarbonates with Pendant Thiol-Reactive Thiosulfonates for Reversible Postpolymerization Modification.

Postpolymerization modifications are valuable techniques for creating functional polymers that are challenging to synthesize directly. This study presents aliphatic polycarbonates with pendant thiol-reactive groups for disulfide formation with mercaptans. The reductive responsive nature of this reaction allows for reversible postpolymerization modifications on biodegradable scaffolds. Six-membered cyclic carbonate monomers with pendant thiosulfonate groups were synthesized and polymerized using controlled organocatalytic ring-opening polymerization, yielding polymers with narrow molecular weight dispersities (Đ = 1.2) and intact reactive thiosulfonate side chains. Reversible modification with benzyl mercaptans achieved high degrees of disulfide modification. Additionally, thiol-reactive carbonate monomers were block-copolymerized onto polyethylene glycol (mPEG113) and then converted into benzyl disulfides, while the block copolymers' hydroxyl end groups remained available for fluorescent dye labeling. The amphiphilic block copolymers self-assembled in water into micelles (∼33 nm diameter), capable of encapsulating hydrophobic molecules. These micelles successfully delivered hydrophobic dyes into macrophages, indicating the potential for intracellular drug delivery.

Salt-Responsive Switchable Block Copolymer Brushes with Antibacterial and Antifouling Properties.

A strategy for multifunctional biosurfaces exploiting multiblock copolymers and the antipolyelectrolyte effect is reported. Combining a polyzwitterionic/antifouling and a polycationic/antibacterial block with a central anchoring block for attachment to titanium oxide surfaces affords surface coatings that exhibit antifouling properties against proteins and allow for surface regeneration by clearing adhering proteins by employing a salt washing step. The surfaces also kill bacteria by contact killing, which is aided by a nonfouling block. The synthesis of block copolymers of 4-vinyl pyridine (VP), dimethyl 4-vinylbenzyl phosphonate (DMVBP), and 4-vinylbenzyltrimethyl ammonium chloride (TMA) is achieved on the multigram scale via RAFT polymerization with good end group retention and narrow dispersities. By polymer analogous reactions, poly(4-vinyl pyridinium propane sulfonate-block-4-vinylbenzyl phosphonic acid-block-4-vinylbenzyl trimethylammonium chloride) (P(VSP64-b-PA14-b-TMA64)) is obtained. The antifouling properties against the model protein pepsin and the salt-induced surface regeneration are shown in surface plasmon resonance (SPR) experiments, while independently the antibacterial and antifouling properties of coated titanium substrates are successfully tested in preliminary microbiological assays against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). This strategy may contribute to the development of long-term effective antibacterial implant surface coatings to suppress biomedical device-associated infections.

Precisely Prepared Hierarchical Micelles of Polyfluorene-block-Polythiophene-block-Poly(phenyl isocyanide) via Crystallization-Driven Self-Assembly.

The precise preparation of hierarchical micelles is a fundamental challenge in modern materials science and chemistry. Herein, poly(di-n-hexylfluorene)-block-poly(3-tetraethylene glycol thiophene) (poly(1m-b-2n)) diblock copolymers and polyfluorene-block-polythiophene-block-poly(phenyl isocyanide) triblock copolymers were synthesized using a one-pot process via the sequential addition of corresponding monomers using a Ni(II) complex as a single catalyst for living/controlled polymerization. The crystallization-driven self-assembly of amphiphilic conjugated poly(1m-b-2n) led to the formation of nanofibers with controlled lengths and narrow dispersity. The block copolymers exhibited white, yellow, and red emissions in different self-assembly states. By using uniform poly(1m-b-2n) nanofibers as seeds, introducing the polyfluorene-block-polythiophene-block-poly(phenyl isocyanide) triblock polymer as a unimer in the seed growth process, and adjusting the structure of the poly(phenyl isocyanide) block and the polarity of self-assembly solvent, A-B-A triblock micelles, multiarm branched micelles, and raft micelles were prepared.

Precisely Prepared Hierarchical Micelles of Polyfluorene‐block‐Polythiophene‐block‐Poly(phenyl isocyanide) via Crystallization‐Driven Self‐Assembly

AbstractThe precise preparation of hierarchical micelles is a fundamental challenge in modern materials science and chemistry. Herein, poly(di‐n‐hexylfluorene)‐block‐poly(3‐tetraethylene glycol thiophene) (poly(1m‐b‐2n)) diblock copolymers and polyfluorene‐block‐polythiophene‐block‐poly(phenyl isocyanide) triblock copolymers were synthesized using a one‐pot process via the sequential addition of corresponding monomers using a Ni(II) complex as a single catalyst for living/controlled polymerization. The crystallization‐driven self‐assembly of amphiphilic conjugated poly(1m‐b‐2n) led to the formation of nanofibers with controlled lengths and narrow dispersity. The block copolymers exhibited white, yellow, and red emissions in different self‐assembly states. By using uniform poly(1m‐b‐2n) nanofibers as seeds, introducing the polyfluorene‐block‐polythiophene‐block‐poly(phenyl isocyanide) triblock polymer as a unimer in the seed growth process, and adjusting the structure of the poly(phenyl isocyanide) block and the polarity of self‐assembly solvent, A−B−A triblock micelles, multiarm branched micelles, and raft micelles were prepared.

Highly Active and Stereoselective Ring‐Opening Polymerization of Racemic Lactide Over HTGCP Catalysts

ABSTRACTDespite the extraordinary success has been achieved in metal catalyst‐promoted stereoselective ring‐opening polymerization (ROP) of rac‐lactide (rac‐LA), well‐controlled stereoselective rac‐LA ROP by organic catalyst still remains a scientific challenge. In this study, we showcase the remarkable ability of the phosphazene base 2,2,4,4,6,6‐hexa(tetramethyl‐guanidyl)‐1,3,5,2λ5,4λ5,6λ5‐cyclictri(phosphazene) (HTGCP) to facilitate the stereoselective ROP of rac‐LA at low temperatures, yielding isotactic stereoblock poly (lactic acid) (PLA) with a stereoselectivity index (Pm) up to 0.86. Furthermore, by harnessing the synergy between HTGCP and a (thio)urea, both high stereoselectivity (Pm up to 0.85) and remarkable catalytic activity (> 99% monomer conversion within an hour) can be achieved at ambient temperature. Notably, upon decreasing the temperature to −20°C, an even higher degree of regularity is attained (Pm up to 0.91). The direct linear correlation between molecular weights (Mn), monomer conversions, and the narrow dispersity (Đ) of the resulting polymers, coupled with their high end‐group fidelity, underscores the meticulous control exerted over the polymerization. Based on these findings, we propose that the chain end control mechanism underlies the synthesis of isotactic stereoblock PLA from rac‐LA in the presence of HTGCP, offering a novel and efficient pathway to produce high‐performance PLA materials.

Microfluidic-Generated Injectable Bulking Agents with Biocompatible Surfaces and Their Mid-term Outcomes in a Rat Model with Anal Sphincter Injury.

Bulking agents have gained attention as new, minimally invasive treatments for fecal incontinence. Various materials and surface treatment techniques have been extensively studied to ensure good biocompatibility and long-term stability. Despite significant improvements in biocompatibility, the nonuniform particle size of existing materials has led to other challenges, such as the induction of phagocytosis or reduction of injectability during in vivo tests. This study aimed to conduct a preclinical test of the midterm stability of bulking agents with newly formulated particles with uniform size. To this end, the particles were fabricated using microfluidics, resulting in a narrow size dispersity of less than 5% as the coefficient of variation, which is essentially distinct from conventional bulking agents. The microfluidic fabrication resulted in uniformly sized particles larger than the in vivo migratory limit of 80 μm and in a reduction in maximum injection pressure. Histological staining and microscopic observations confirmed proper positioning of the filler materials in vivo and a negligible immune response for up to 6 months, indicating successful midterm stability.

Unraveling the Formation of Ternary AgCuSe Crystalline Nanophases and Their Potential as Antibacterial Agents.

AgCuSe nanoparticles could contribute to the growth of strongly light-absorbing thin films and solids with fast ion mobility, among other potential properties. Nevertheless, few methods have been developed so far for the synthesis of AgCuSe nanoparticles, and those reported deliver nanostructures with relatively large sizes and broad size and shape distributions. In this work, a colloidal cation exchange method is established for the easy synthesis of AgCuSe NPs with ca. 8 nm diameters and narrow size dispersion. Notably, in this lower size range the conucleation and growth of two stoichiometric ternary compounds are generally observed, namely the well-known eucairite AgCuSe compound and the novel fischesserite-like Ag3CuSe2 phase, the latter being less thermodynamically stable as predicted computationally and assessed experimentally. An optimal range of Cu/Ag precursor molar ratio has been identified to ensure the growth of ternary nanoparticles and, more specifically, that of the metastable Ag3CuSe2 nanophase isolated for the first occasion. The attained size range for the material paves the way for utilizing AgCuSe nanoparticles in new ways within the field of biomedicine: the results obtained here confirm the antibacterial activity of the new Ag x Cu y Se z nanoparticles against Gram-positive bacteria, with significantly low values of the minimal inhibitory concentration.

Polymer-Metal-Organic Frameworks (polyMOFs) Based on Tailor-Made Poly(alkenamer)s.

Polymeric linkers used to construct porous, crystalline polymer-metal-organic frameworks (polyMOFs) are predominantly based on macromolecules with metal-coordinating ligand units (e.g., 1,4-benzenedicarboxylic acid, H2bdc) included in the primary polymer backbone. Polymers with ligand units as pendants or dangling side chain substituents have been far less explored for the synthesis of polyMOFs, despite the fact that such systems may have distinct properties and could take advantage of a variety of chain polymerization methods. Prevailing reports are based on nonliving polymerized linkers with H2bdc pendants that generated polyMOFs with key shortcomings in controlling the polymerization, tailoring polymeric linker composition and polyMOF properties, accessing porosity, etc. Herein, polymers containing H2bdc units as pendants were designed and synthesized via controlled olefin-metathesis polymerization. These poly(alkenamer)s were subsequently assembled into porous, crystalline networks with an isoreticular MOF (IRMOF) lattice topology. These polymer architectures and polymerization methodologies provide access to the formation of polyMOFs with tailored characteristics, including controlled composition, narrow dispersity, and side chain functionalization.

Mononuclear and multinuclear O^N^O‐donor Zn(II) complexes as robust catalysts for the production and depolymerization of poly(lactide)

Mononuclear and multinuclear O^N^O‐donor Zn(II) complexes are herein reported as catalysts in the ring‐opening polymerization (ROP) of rac‐lactide (rac‐LA) and depolymerization of poly(lactide) (PLA). Reactions of imino‐phenol proligand 2[((2‐hydroxyethyl)imino)methyl]phenol (L1H2) with ZnCl2 and ZnEt2 afforded the dinuclear and tetranuclear complexes [Zn2(L1H)2Cl2] (Zn1) and [Zn4(L1)4] (Zn2), respectively. Separately, treatments of proligands 2‐[1‐((2‐hydroxyethyl)imino)ethyl]phenol (L2H2) and [((2‐methoxyethyl)imino)methyl]phenol (L3H) with ZnCl2 gave the respective mononuclear complexes [Zn(L2H2)2Cl2] (Zn3) and [Zn(L3H)2Cl2] (Zn4), while the reactions of L3H with ZnEt2 afforded the bis(chelated) mononuclear complex [Zn(L3)2] (Zn5). The complexes were characterized using NMR and IR spectroscopy, elemental analysis and single crystal X‐ray crystallography. All the Zn(II) complexes showed high catalytic activities in the ROP of rac‐LA (kapp of up to 4.18 × 10‐4 s‐1) to give moderate molecular weight PLA (39 960 g mol‑1) with relatively narrow dispersities (Đ = 1.4‐2.1). The complexes produced mainly atactic PLAs with Pr values of 0.51‐0.58. More significantly, complexes Zn1, Zn2 and Zn5 were also active in the depolymerization of commercial PLA in methanol (kapp of up to 2.67 × 10‐4 s‐1) to produce alkyl lactates. The ROP and depolymerization behavior were largely controlled by the structure and nuclearity of the complexes.

Top-Down Synthesis of N-Type PbS Quantum Dots with High Photoluminescence Quantum Yield from Microsized Pb(OH)Cl.

Synthesis of PbS quantum dots (QDs) with uniform and controllable size is of great importance in realizing functionality manipulation, as well as building advanced devices, and these QDs have been normally synthesized via "bottom-up" colloidal chemistry. However, the problems of complicated techniques and the relative high cost of the "bottom-up" methods still need to be overcome. Herein, we present a facile and cost-effective "top-down" strategy for the production of PbS QDs with controllable sizes and narrow dispersions (4.8% < σ < 7%) based on the sulfuration reaction of highly active lead oxide and oxychloride intermediates. We investigated the two-step reaction mechanism of the QD synthesis. Initially, Pb(OH)Cl undergoes a reaction with oleic acid in the presence of oleylamine as an activator, leading to the formation of active lead oxide/oxychloride intermediates. Notably, this distinctive reaction induces the creation of numerous cracks within the intermediates, thereby augmenting the active sites available for the subsequent sulfuration reactions. In that, the sulfur precursor reacts with the intermediates, resulting in the rapid generation of a substantial number of PbS fragments. Over time, these small fragments undergo "ripening" until reaching the "critical" size threshold. Different from the ones obtained by the traditional "bottom-up" method, our synthesized colloidal QDs exhibit a S-rich surface and are confirmed to be N-type. In addition, size-tunable near-infrared photoluminescence renders these QDs a promising material for various applications.

Recent Trends on Zinc Complexes Bearing Bi‐, Tri‐ and Tetra‐Dentate Schiff Base Ligands for Catalytic Ring‐Opening Polymerization of Lactides

AbstractNumerous zinc complexes based on N‐ and O‐donor Schiff‐base ligands have shown great promise in the ring‐opening polymerization (ROP) of lactides, which are cyclic dimers of lactic acid, to produce poly(lactic acid) (PLA). This is primarily because zinc is a borderline metal, making it non‐cytotoxic, inexpensive, abundant, biocompatible, and environmentally safe. Additionally, Schiff‐based ligands offer stability, stereoselectivity, desirable electronic and steric environments, and resistance to impurities. As a result, zinc complexes are easy to synthesize, colourless, have high reactivity and solubility in organic solvents, and are manageable under typical circumstances. Furthermore, these complexes are free to adopt a variety of coordination numbers since zinc does not have ligand field stabilization energy (LFSC). Zinc complexes possess high catalytic activity due to their distinctive properties, including high Lewis acidity, high electron transfer ability, stability concerning the reactive intermediate, and the ability to monitor polymerization by nuclear magnetic resonance (NMR) spectroscopy. Moreover, these complexes also have reasonable control over stereochemistry, number‐average molecular weight (Mn), and dispersity index (Ð). These advantages make it possible to produce colourless PLA with a high yield, high molecular weight, and narrow dispersity index in bulk and solvent‐based conditions.

Advancing H-Bonding Organocatalysis for Ring-Opening Polymerization: Intramolecular Activation of Initiator/Chain End.

Organocatalytic ring-opening polymerization (ROP) of lactones is a green method for accessing renewable and biodegradable polyesters. Developing new organocatalysts with high activity and controllability is a major and challenging research topic in this field. Here, we report a series of organocatalysts to achieve a fast and controlled ROP of lactones. These catalysts incorporate (thio)urea and alkoxide in one molecule and act as initiators in the ROP. Such catalysts enable an effective intramolecular activation of initiator/chain end, as revealed by computational studies, resulting in higher activity and fewer (thio)urea loads than existing (thio)urea/alkoxide binary systems. These organocatalysts exhibit ultrahigh activity comparable to metal complexes, i.e., turnover number up to 900 and turnover of frequency up to 4860 min-1, affording polyesters with tailor-made structure, predicted molecular weights, narrow dispersity, less epimerization, and minimal transesterification. The catalyst synthesis is simple and scalable, allowing widely tuned activities of the ROP.

Integration of Vertical Graphene Onto a Tunnelling Cathode for Digital X-Ray Imaging.

As an alternative to thermionic X-ray generators, cold-cathode X-ray tubes are being developed for portable and multichannel tomography. Field emission propagating from needle structures such as carbon nanotubes or Si tips currently dominates related research and development, but various obstacles prevent the widespread of this technology. An old but simple electron emission design is the planar tunnelling cathode using a metal-oxide-semiconductor (MOS) structure, which achieves narrow beam dispersion and low supplying voltage. Directly grown vertical graphene (VG) is employed as the gate electrode of MOS and tests its potential as a new emission source. The emission efficiency of the device is initially ≈1% because of unavoidable fabrication damage during the patterning processes; it drastically improves to >40% after ozone treatment. The resulting emission current obeys the Fowler-Nordheim tunnelling model, and the enhanced emission is attributed to the effective gate thickness reduction by ozone treatment. As a proof-of-concept experiment, a clustered array of 2140 cells is integrated into a system that provides mA-class emission current for X-ray generation. With pulsed digital excitations, X-ray imaging of a chest phantom, demonstrating the feasibility of using a VG MOS electron emission source as a new and innovative X-ray generator is realized.

The use of carbodicarbene for bio-based polyester synthesis via ring-opening copolymerization of cyclic anhydrides and epoxides

Alternating ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides was investigated using carbodicarbene (CDC) as a single-component organic initiator. CDC produced various polyesters with different combinations of monomers, including bio-based monomers. The synthesized polyesters exhibited narrow dispersity and a wide range of glass transition temperatures. Moreover, a diblock copolyester was synthesized using self-switchable polymerization (ROCOP of the cyclic anhydride/epoxide, and ring-opening polymerization of lactone) in a one-pot synthesis. The formation of a terpolymer product was confirmed by diffusion-ordered spectroscopy and thermal gravimetric analysis.

High-performance electrocatalyst for PEMFC cathode: Combination of ultra-small platinum nanoparticles and N-doped carbon support

To accelerate the implementation of zero-emission power installations based on proton-exchange membrane fuel cells, it is necessary to maximize the power characteristics of these devices. For this purpose, we have obtained and tested a new N-doped carbon support and a synthesized Pt/C catalyst based on it with a platinum loading of about 37.3 %. A comparison of the degradation resistance of the initial support and the N-doped one has shown greater stability of the latter. At the same time, Raman spectroscopy has confirmed the presence of the C–N bond, which indicates the successful doping of carbon with nitrogen. The resulting Pt/C catalyst based on an N-doped support is characterized by a substantially narrow size dispersion and an ultra-small nanoparticle size of about 2.6 nm. The high-angle annular dark-field scanning transmission electron microscopy images of the synthesized catalyst have confirmed the presence of individual platinum atoms/clusters uniformly distributed over the surface of the support, and their presence is due to nitrogen embedded into the carbon structure. This material is characterized by a 50 m2 gPt-1 larger electrochemically active surface area and a 227 A gPt-1 greater mass activity compared to the commercial JM40 analog (40 % platinum loading). Meanwhile, the electrochemical parameters remaining after the accelerated stress testing are almost 2 times higher than those of JM40. And the power characteristics in the membrane electrode assembly for the catalyst synthesized by the facile one-pot synthesis method are 13 % (575 mW cm-2) higher than those of the commercial analog (500 mW cm-2). The Pt/C catalyst obtained during the research is deemed promising for commercial use in proton-exchange membrane fuel cells.

Light-mediated biosynthesis of size-tuned silver nanoparticles using Saccharomyces cerevisiae extract

Bio-based production of silver nanoparticles represents a sustainable alternative to commercially applied physicochemical manufacturing approaches and provides qualitatively highly valuable nanomaterials due to their narrow size dispersity, high stability and biocompatibility with broad application potentials. The intrinsic features of nanoparticles depend on size and shape, whereby the controlled synthesis is a challenging necessity. In the present study, the biosynthesis of size-tuned silver nanoparticles based on cell-free extracts of Saccharomyces cerevisiae DSM 1333 was investigated. Single parameter optimization strategies in phases of cultivation, extraction, and synthesis were performed to modify the nanoparticle scale and yield. Visible light was exploited as a tool in nanoparticle production. The influence of white light on the biosynthesis of silver nanoparticles was determined by using novel LED systems with the exposition of varying irradiation intensities and simultaneous performance of control experiments in the dark. Characterization of the resulting nanomaterials by spectrophotometric analysis, dynamic light scattering, scanning electron microscopy, and energy dispersive X-ray spectroscopy, revealed spherical silver nanoparticles with controlled, light-mediated size shifts in markedly increased quantities. Matching of irradiated and non-irradiated reaction mixtures mirrored the enormous functionality of photon input and the high sensitivity of the biosynthesis process. The silver nanoparticle yields increased by more than 90% with irradiation at 1.0±0.2mWcm-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.0 \\pm 0.2\ ext{ mW }{\ ext{cm}}^{-2}$$\\end{document} and the reduction of particle dimensions was achieved with significant shifts of size-specific absorption maxima from 440 to 410 nm, corresponding to particle sizes of 130 nm and 100 nm, respectively. White light emerged as an excellent tool for nano-manufacturing with advantageous effects for modulating unique particle properties.Graphical abstract

PEGose Block Poly(lactic acid) Nanoparticles for Cargo Delivery.

Hydrophilic polymers have found ubiquitous use in drug delivery and novel polymer materials to advance drug delivery systems are highly sought after. Herein, an amylose mimic (PEGose) was combined with poly(lactic acid) (PLA) in an amphiphilic block copolymer to form PEG-free nanoparticles as an alternative to PEG-based nanomedicines. The block copolymer self-assembled into 150-200 nm particles with a narrow dispersity in aqueous environment. The formed nanoparticles were capable of encapsulation, the sustained release of both hydrophilic and hydrophobic dyes. Moreover, the nanoparticles were found to be remarkably stable and had a very low cytotoxicity and a high propensity to penetrate cells. These results highlight the potential of PEGose-b-PLA to be used in drug delivery with a new hydrophilic building block.

Oxidative Carboxylation of Lignin: Exploring Reactivity of Different Lignin Types.

The increased interest in the utilization of lignin in biobased applications is evident from the rise in lignin valorization studies. The present study explores the responsiveness of lignin toward oxidative valorization using acetic acid and hydrogen peroxide. The pristine lignins and their oxidized equivalents were analyzed comprehensively using NMR and SEC. The study revealed ring opening of phenolic rings yielding muconic acid- and ester-end groups and side-chain oxidations of the benzylic hydroxyls. Syringyl units were more responsive to these reactions than guaiacyl units. The high selectivity of the reaction yielded oligomeric oxidation products with a narrower dispersity than pristine lignins. Mild alkaline hydrolysis of methyl esters enhanced the carboxylic acid content of oxidized lignin, presenting the potential to adjust the carboxylic acid content of lignin. While oxidation reactions in lignin valorization are well documented, this study showed the feasibility of employing optimized oxidation conditions to engineer tailored lignin-based material precursors.

Intraband Cooling and Auger Recombination in Weakly to Strongly Quantum-Confined CsPbBr3 Perovskite Nanocrystals.

Semiconductor nanocrystals (NCs) with size-tuned energy gaps present unique and desirable properties for optoelectronic applications. Recent synthetic advancements offer routes to spheroidal CsPbBr3 perovskite NCs in the strong quantum confinement regime with narrow size dispersion. Using tunable femtosecond laser pulses, we examine intraband carrier relaxation using transient absorption spectroscopy and show that, across the transition from weak to strong confinement, hot carrier lifetime increases compared to larger bulk-like particles. However, further increases of confinement subsequently lead to a reduction of the hot carrier lifetime and increase of the non-radiative Auger recombination rate. Finally, we show that hot carrier lifetimes increase as a function of excess energy above the band gap less sensitively under high confinement in comparison to the bulk. Understanding such unique trends is important for maximizing hot carrier lifetimes for use in next-generation hot carrier devices as well as evaluating the transition from weak to strong confinement.