Can shear wave elastography predict the success of shock­wave lithotripsy used in renal stones treatment? A prospective study.

OBJECTIVE: To evaluate the usage of shear wave elastography (SWE) in the prediction of the success rate of shock­wave lithotripsy (SWL) treatment of renal stones. PATIENTS AND METHODS: In the present study, SWL was performed for 100 patients presented with renal stones in the duration from May 2022 to August 2023. The patients were divided into 2 groups SWL responders and non-responders. The study compared between the 2 groups in terms of baseline parameters of the patients as age, sex, body mass index (BMI), stone size, stone location, stone density (HU), skin-to-stone distance (SSD), the degree of hydronephrosis and the stone elastography values. RESULTS: There was no statistically significant relation between stone-free rate and degree of obstruction (p = 0.628), stone size (p = 0.390) upper calyceal location (p = 0.17), middle calyceal location (p = 0.66), and renal pelvis location (p = 1.0). Nevertheless, a statistically significant relation was found as regards lower calyceal location, stone density (HU), and stone Elastography values using multivariate analysis. CONCLUSIONS: Measurement of stone density by shear wave elastography (SWE) can be used as an alternative to HU in decision-making before SWL. SWL success depends mainly on stone site, HU, and SWE values.

Novel insights on the probable mechanism associated with histamine oral model-inducing neuropathological and behavioral toxicity in rats.

Histamine (HIS) is an important chemical mediator that causes vasodilation and contributes to anaphylactic reactions. Recently, HIS is an understudied neurotransmitter in the central nervous system, and its potential role in neuroinflammation and neurodegeneration is a critical area of research. So, the study's goal is to investigate the consequences of repeated oral intake of HIS on the rat's brain and explore the mechanistic way of its neurotoxicity. Thirty male rats were divided into three groups (n = 10). The following treatments were administered orally to all rats every day for 14 days. Group (1) was given distilled water, whereas groups (2 & 3) were given HIS at dosage levels 250 and 500 mg/kg body weight (BWT), respectively. Brain tissue samples were collected at 7- and 14-days from the beginning of the experiment. Our results revealed that continuous oral administration of HIS at both doses for 14 days significantly reduced the BWT and induced severe neurobehavioral changes, including depression, dullness, lethargy, tremors, abnormal walking, and loss of spatial learning and memory in rats. In all HIS receiving groups, HPLC data showed a considerable raise in the HIS contents of the brain. Additionally, the daily consumption of HIS causes oxidative stress that is dose- and time-dependent which is characterized by elevation of malondialdehyde levels along with reduction of catalase activity and reduced glutathione levels. The neuropathological lesions were commonly observed in the cerebrum, striatum, and cerebellum and confirmed by the immunohistochemistry staining that demonstrating moderate to strong caspase-3 and inducible nitric oxide synthase expressions in all HIS receiving groups, mainly those receiving 500 mg/kg HIS. NF-κB, TNF-α, and IL-1ß gene levels were also upregulated at 7- and 14-days in all HIS groups, particularly in those getting 500 mg/kg. We concluded that ROS-induced apoptosis and inflammation was the essential mechanism involved in HIS-mediated neurobehavioral toxicity and histopathology.

Oxidative stress markers, immune-regulating cytokines, and the pathological evaluation of sheep co-infected with Oestrus ovis and Coenuruscerebralis.

This study aimed to evaluate the immune response using the immune-regulating cytokines as (IL-1ß; MHC-I and MHC-II) associated with co-infected sheep Oestrusovis and Coenurus cerebralis as well as oxidative stress markers (malondialdehyde "MDA" and nitric oxide "NO"). So; sheep samples from different regions in Egypt showed different neurological signs, were examined for detection of the cause of the nervous manifestations. Moreover, the O. ovis and C. cerebralis cysts were collected and identified using scanning electron microscopy. The brain tissues were evaluated for different immunological genes such as MHC-I, MHC-II, and Interleukin-1ß activity using quantitative real-time PCR (qRT-PCR) techniques, where the infected sheep showed higher MHC-I gene expression (10-fold), higher MHC-II gene expression (peaked at 25-fold), and higher IL-1ß gene expression (14-fold) than the control group. The MDA level was significantly increased. Also, stress marker (nitric oxide) levels were significantly higher in infectedsheep than in negative control one. During gross pathology, migrating larvae of O. ovis and C. cerebralis were noticed In such areas, hemorrhages and patches of clotted blood were noticed. cysts with prominent protoscolices were also observed and were attached to the caudal region near the cerebellum.

Electron Doping of Semiconducting MoS2 Nanosheets by Silver or Gold Nanoclusters.

Semiconducting two-dimensional (2D) materials have potential applications as ultrathin optoelectronic materials. Therefore, being able to precisely modulate the band gap is useful to improving their applicability. Electron doping of the semiconducting materials is one of the successful techniques used to modulate their band gap. Silver nanoclusters (AgNCs) or gold nanoclusters (AuNCs) a few nanometers in size can generate a high density of highly energetic hot electrons with relatively long lifetimes when photoexcited. The optical band gap of 2D MoS2 nanosheets shows different responses when integrated with different amounts of AgNCs or AuNCs due to the electron doping effect. Introducing a small amount of the nanoclusters to the surface of a MoS2 nanosheet lowered its optical band gap. Further reduction of the optical band gap of MoS2 is obtained upon tripling the amount of integrated nanoclusters. Conversely, the optical band gap of MoS2 was increased when integrated with 5 times the concentration of AuNCs and AgNCs. The optical band gap of the MoS2 nanosheets was significantly increased when integrated with an even higher concentration of AuNCs or AgNCs. The magnitude of the shift of the optical band gap of MoS2 induced by AgNCs is higher than that induced by AuNCs because the energy of LUMO of the AgNCs is higher than that of the AuNCs.

Unplanned Return to the Operating Room (UpROR) After Pediatric Diaphyseal Femoral Fractures.

BACKGROUND: Femoral fractures are the most common cause of fracture-related admissions. Unplanned return to the operating room (UpROR) is a major event and imposes a substantial burden on the family and health care system. The purpose of this study was to determine the incidence of complications and early UpROR during the first 6 months following treatment of femoral fractures and their risk factors. METHODS: In an institutional review board-approved study, a retrospective review of all patients who were treated for a femoral fracture during a 10-year period at a pediatric tertiary care center was performed. Patients less than 18 years old with a diaphyseal fracture and complete records were included, and nondiaphyseal or pathologic fractures, as well as underlying metabolic or genetic disorders, were excluded. All clinic visits in the first 6 months after treatment were reviewed, and all complications and UpRORs were extracted. Patients were grouped based on their age (below 5, 5 to 11, above 11 y old) at initial treatment, and statistical tests were used to infer differences between groups. RESULTS: Overall, 841 fractures in 832 patients were included, with a mean age of 5.5±4.8 years fracture, of which 72% were male. A total of 106 complications (12.6%) and 45 UpRORs (5.3%) were encountered during the study period. Patients with and without UpROR had similar demographics and injury and treatment characteristics. Loss of reduction was the most common reason for UpROR (58%), followed by implant-related complications. Flexible nails had the highest risk of UpROR among patients who were initially treated surgically (P=0.03). CONCLUSIONS: Our findings indicate that children under the age of 5 years have a 5% risk of UpROR in the first 6 months after the fracture, mainly for repeat spica casting due to loss of reduction. Patients aged 5 years or older have an ∼6% risk of UpROR, mainly related to complications of flexible nails. The findings of this study are important when consulting families on different treatments of diaphyseal femoral fractures. LEVEL OF EVIDENCE: Therapeutic level III-retrospective cohort study.

Coinfections of Aeromonas spp., Enterococcus faecalis, and Vibrio alginolyticus isolated from farmed Nile tilapia and African catfish in Egypt, with an emphasis on poor water quality.

The high mortality rate among Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus) polycultured in earthen ponds in Manzala, Egypt, was investigated. Mortality has been linked to poor water quality parameters accompanied with bacterial infections. Moribund farmed fishes exhibited general septicemic signs. Fish from both species (45 each) were sampled and analyzed bacteriologically. Vibrio alginolyticus (32.3%), Enterococcus faecalis (29.4%), Aeromonas caviae (23.5%), and A. veronii (14.7%) were isolated from moribund fishes using selective media and further identified by biochemical tests. 16S rRNA gene sequencing and phylogenetic analysis confirmed the identity of these isolates. Experimental infection of O. niloticus with different bacterial isolates resulted in clinical signs of hemorrhagic septicemia and mortality rates of 80%, 60%, 40%, and 30%, respectively, for E. faecalis, A. veronii, V. alginolyticus, and A. caviae. Water parameter analysis revealed marked divergence from typical values. In addition, different bacterial isolates (including Staphylococcus sciuri, S. aureus, E. faecalis, A. veronii, A. caviae, and V. alginolyticus) were identified and isolated from water samples. BLAST analysis of water bacterial isolates displayed a 100% similarity score with relevant fish isolates, indicating that the water was the likely source of infections. Histopathological examination revealed signs of bacterial infection in both fish species. In addition, common circulatory and degenerative changes with melanophore aggregation, and lymphocytic depletion in hematopoietic organs were recorded.

Streptococcus, Centrocestus formosanus and Myxobolus tilapiae concurrent infections in farmed Nile tilapia (Oreochromis niloticus).

Stress triggered concurrent microbial/parasitic infections are prevalent in earthen pond based farmed Nile tilapia Oreochromis niloticus. In the current study, a total of thirty five O. niloticus were collected from a commercial fish farm with a history of severe mortalities at Port Said, Egypt. Nile tilapia samples were subjected to bacteriological, parasitological and pathological examinations. Twenty one Enterococcus fecalis and 15 Streptococcus agalactiae isolates were presumptively identified utilizing the semi-automated API 20 Strept test kit. The identities of the retrieved bacteria were confirmed by the sequencing of 16 S rRNA gene. Moribund O. niloticus were found to be heavily infected by one or both of Centrocestus formosanus encysted metacercariae (EMC) and/or Myxobolus tilapiae spores presenting a unique form of synergistic and/or symbiotic relationship. The identities of both parasites were confirmed through morphological and molecular characterization. Variable circulatory, degenerative, necrotic and proliferative changes were also noticed in hematopoietic organs. Interestingly, multiple myxobolus spores and EMC were noticed in some histological sections. It was obvious that the current concurrent bacterial and parasitic infections are triggered by the deleterious effects of some stressing environmental conditions. The unfavorable climatic conditions (high temperature and high relative humidity) recorded at the surge of mortalities are probable predisposing stress factors.

Tuning the Optical Band Gap of Two-Dimensional WS2 Integrated with Gold Nanocubes by Introducing Palladium Nanostructures.

The two characteristic absorption peaks of semiconducting two-dimensional tungsten disulfide (WS2) are red-shifted after integrating with gold nanocube (AuNC) arrays. The amount of the red shift is reduced when the AuNCs are coated with a high concentration of Pd. A negligible shift was observed in the absorption peaks of WS2 when smaller amounts of Pd are introduced to the surface of AuNCs. Conversely, the photoluminescence (PL) of WS2 is blue-shifted when measured on top of AuNCs and AuNCs coated with different amounts of Pd. AuNC-Pd Janus nanoparticles are prepared by depositing Pd atoms asymmetrically on AuNCs assembled into 2-D arrays on the surface of a glass substrate by the chemical reduction of Pd ions. Due to the large AuNC or AuNC-Pd/WS2 Schottky barrier, the plasmon-induced hot electron transfer (PHET) from AuNCs and AuNCs coated with a high concentration of Pd is responsible for the red shift of the absorption spectrum of WS2. Introducing a lower concentration of Pd to AuNCs increases the Schottky barrier further due to the formation of the Au-Pd equilibrium Fermi level of lower energy, reducing the efficiency of PHET. The effect of Pd on the Fermi level of AuNCs vanishes at high Pd deposition. Pauli blocking and phase-space filling are responsible for the blue shift of PL of WS2 on top of AuNCs and AuNCs coated with Pd. The Pauli blocking effect is directly proportional to the PHET efficiency. This explains the significant blue shift of PL of WS2 after integrating with AuNCs and AuNCs coated with a high concentration of Pd. Additionally, depositing Pd onto AuNCs elongates the lifetime of the hot electrons and enhances the PHET efficiency.

Morphomolecular and pathological study of Scaphanocephalus sp. in new host Siganus argenteus in the Arabian Gulf.

In this study, Scaphanocephalus parasite (Platyhelminthes: Heterophyidae) metacercariae were found in Siganus argenteus (forktail rabbitfish or streamlined spinefoot) in the Arabian Gulf of Jubail province, Saudi Arabia. The findings may constitute new host and locality records for this parasite. Based on the number of black spots containing parasite cysts per fish, our study indicated that Siganus argenteus had high infection intensities of encysted metacercariae belonging to the genus Scaphanocephalus. Of the 3500 S. argenteus specimens examined, 800 (22.9%) showed multiple black cysts over the entire body surface, including the membranous parts of fins, while none were seen on the internal organs. The prevalence of infection was highest in summer (June-August) (8.8%). The excysted metacercariae differed morphologically from previously identified Scaphanocephalus spp. Molecular analysis of rDNA showed 100% identity with an unnamed Scaphanocephalus sp. reported in Caribbean fish. Therefore, our findings may indicate a new species of this previously rarely recorded fish parasite. The histopathological examination revealed that the encysted parasites were restricted to the dermal layer of the skin and surrounded by melanophores and a fibrous connective tissue capsule, with focal myositis and Zenker's necrosis in the underlying muscle tissue. The characteristically 'winged' parasite was clearly observed within the cysts. The high prevalence of Scaphanocephalus infection in siganid fish we detected requires further epidemiological study.

Modulating the Optical Band Gap of Small Semiconducting Two-Dimensional Materials by Conjugated Polymers.

Ultra-high-resolution optical microscopic techniques are used to measure the reflectance and photoluminescence (PL) spectrum of individual monolayered MoS2 of dimensions below 200 × 200 nm, while placed on top of a thin film conjugated polymer (CP). p-type and n-type CPs such as poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM), respectively, modified the optical band gap of the MoS2 sheet differently. However, the optical band gap is decreased after integration with P3HT, while it is increased after being combined with PCBM. The acceptable reason for the modification of the band gap of MoS2 by CPs is the generation of interlayer excitons (ILE) at their interface. The optical band gap of MoS2 is further changed by introducing an inert polymer spacer of different thickness to separate MoS2 from the CP. This is attributed to the reduction of the efficiency of excitonic interactions and lowering the exciton binding energy, which is induced by the increase of the dielectric function at the CP-MoS2 interface. No sign of electron injection to the conduction band of MoS2 after integration with P3HT or PCBM, as no significant shift of the A1' Raman band of MoS2 was measured on top of CPs, which is sensitive to the electron injection.

Molecular characterization and immunohistochemical localization of tilapia piscidin 3 in response to Aeromonas hydrophila infection in Nile tilapia.

The antimicrobial activity of tilapia piscidin 3 (TP3) was determined in vitro against a locally isolated Aeromonas hydrophila. A 388 bp fragment was amplified from the TP3 cDNA and sequenced. The coding sequence (CDS) of TP3 was estimated to be 231 bp codes for 76 amino acids long and stop codon. In silico analysis was performed to detect both the signal peptide and the prodomain cleavage sites to follow the amino acids number 22 and 70, respectively. Based on this, a peptide 23 amino acids long with a remarkably high computed antimicrobial probability was synthesized and used in the subsequent experiments. The antimicrobial activity of TP3 was determined with minimum inhibitory concentration (MIC) and minim um bactericidal concentration (MBC) methods. TP3 exhibited relatively weak antimicrobial activities against the tested bacteria. A challenge experiment was then performed in Nile tilapia with low and high doses of A. hydrophila, followed by timely recognition; after 3, 6, 24 h, and 7 days of the specific TP3 gene expression, immunohistochemical localization was also performed. Histopathological examination revealed provoked inflammatory responses and congestion in the same organs of TP3 expression. Immunohistochemical localization showed that A. hydrophila induced tilapia fish to express TP3 after 24 h within the gills, intestine, hepatopancreas, spleen, and posterior kidney. In quantitative real time (RT)-polymerase chain reaction analysis, the high dose showed higher mRNA expression levels than the low dose, and its expression levels increased in the A. hydrophila-infected fish. It was therefore concluded that TP3 plays an essential role in fish immunity.

Characteristics and Hospital Costs of Spica Cast Treatment of Non-accidental-related Diaphyseal Femoral Fractures in Children Before Walking Age.

BACKGROUND: Fractures are one of the most common presentations of child abuse second only to soft tissue damage, with ∼60% of fractures being femur, humerus or tibia fractures. Although studies have shown increased health care costs associated with nonaccidental trauma (NAT), there is little data regarding the cost of NAT-associated fractures compared with accidental trauma (AT) related fractures. The purpose of this study was to consider the economic burden of NAT related femoral fractures compared with AT femoral fractures. METHODS: We performed a retrospective study of children under the age of one with femoral fractures treated with a spica cast at a Level 1 Pediatric Trauma Center between 2007 and 2016. Variables included age, sex, length of hospital stay, and estimated total billing cost obtained from this hospital's billing department. In addition, fracture site (mid-shaft, distal, proximal, and subtrochanteric) and pattern were assessed. RESULTS: Sixty children with a mean age of 7 months were analyzed. NAT was suspected in 19 cases (31.7%) and confirmed in 9 (15%) before discharge. Two groups were analyzed: the NAT group included suspected and confirmed cases of abuse (28) and the AT group contained the remaining 32 cases. There was no significant difference in the demographics between these 2 groups. Children in NAT group had a longer length of stay compared with AT group (78.9 vs. 36.7 h, P<0.001). Overall consumer price index-adjusted hospital costs were $24,726 higher for NAT group compared with AT group (P=0.024), with costs of laboratory workup, radiology, and nonorthopaedic physician fees being the top 3 components contributing to the increased costs. CONCLUSIONS: The overall incidence of NAT was 46.6% in children presenting with femoral fracture under 1 year of age. The overall hospital cost of treating fractures in the NAT group was 1.5 times higher than the AT group, with imaging charges the most significant contributor to cost difference. LEVEL OF EVIDENCE: Level III-retrospective review.

Operando Investigation into Dynamic Evolution of Cathode-Electrolyte Interfaces in a Li-Ion Battery.

While Li-ion battery cathode-electrolyte interfaces (CEIs) have been extensively investigated in recent decades, accurately identifying the chemical nature and tracking the dynamics of the CEIs during electrochemical cycling still remain a grand challenge. Here we report our findings in the investigation into the dynamic evolution of the interface between a LiNi0.33Co0.33Mn0.33O2 (LNMC) cathode and an ethylene carbonate/dimethyl carbonate (EC/DMC)-based electrolyte using surface-enhanced Raman spectroscopy (SERS) performed on a model cell under typical battery operating conditions. In particular, the strong SERS activity provided by a monolayer of Au nanocubes deposited on a model LNMC electrode (additive-free) enables quasi-quantitative assessment of the CEI evolution during cycling, proving information vital to revealing the dynamics of the species adsorbed on the LNMC surface as a function of cell potential. Furthermore, our theoretical calculation, which is based on the interaction between a model interface-bound molecule and a model LNMC surface, agrees with our experimental observation. The carefully designed operando SERS platform has demonstrated high sensitivity, good surface specificity, and excellent compatibility with extensive electrochemical measurements; it is also applicable to fundamental studies of dynamic interfaces in other electrochemical energy storage and conversion systems.

Modifying the Band Gap of Semiconducting Two-Dimensional Materials by Polymer Assembly into Different Structures.

Polyethylene glycol (PEG) assembled on the surface of two-dimensional tungsten disulfide (WS2) into a limited number of nanoislands (NIs), nanoshells (NSs), and granular nanoparticulates (GNPs) depending on its chain length. NI assemblies showed a nonmeasurable shift of photoluminescence (PL) and the A and B absorption peaks of WS2. This confirmed that the electronic doping by thiol is not effective. The PEG NS assembly displayed a smaller red shift of the PL and a slight decrease of the energy difference between the A and B absorption peaks of WS2. However, increasing the dielectric function on the surface of WS2 has a small influence on their optical properties. The PEG NP assembly on WS2 exhibited a significant red shift of the PL spectrum and a large decrease of the energy difference between A and B absorption peaks. Deforming the WS2 sheet by the PEG NP assembly decreased the orbital coupling and lowered the electronic direct band gap significantly. Raman bands of WS2 are shifted to a higher frequency on improving its mechanical strength after the PEG assembly.

Do various personal hygiene habits protect us against influenza-like illness?

BACKGROUND: Several studies have reported an association between improvements in hand hygiene and the reductions in rates of intestinal parasitic diseases. However, only a some have addressed its link to the frequency of influenza-like illness. The current study aimed to find the correlation between personal hygiene habits and the frequency of influenza-like illness. METHODS: A cross-sectional study targeting 3000 participants conducted in Riyadh city, Saudi Arabia. A systematic random sampling methodology was applied for participant from different part of Riyadh city using a computer generating system. The researcher first started by calling each participant. A full explanation was given to each participant in details (from the purpose of the research, consent to answer the questionnaire, to the explanation of the outcome definition). Each point of the questionnaire was explained to them to make sure they had excellent comprehension, and therefore, respond accurately. Descriptive statistics and Odds Ratio and its 95% confidence intervals were used to determine the association between frequency of influenza-like illness and the studied variables. RESULTS: Two thousand eighty-two (69.4%) completed the questionnaire. The participants who spent 5-10 s in handwashing with soap and rubbing were at increased risk of more frequent influenza-like illness (odds ratio = 1.37, 1.08-1.75). Handwashing with soap and rubbing after handshaking is an independent protective habit against frequent influenza-like illness (adjusted OR = 0.59, 0.37-0.94). CONCLUSION: The decrease of the frequency of influenza-like illness could be done through the following: getting the influenza vaccine annually, washing hands with soap and hand rubbing not less than 15 s after getting out of the bathroom, before and after handshaking and before eating. Soap companies should invent soaps that take less rubbing time to kill bacteria, and subsequently may maximize compliance in the community.

Is mini-percutaneous nephrolithotomy a safe alternative to extracorporeal shockwave lithotripsy in pediatric age group in borderline stones? a randomized prospective study.

PURPOSE: The extracorporeal shockwave lithotripsy (ESWL) remains the most common first line of treatment for renal stones in the pediatric population. The purpose of this study is to evaluate and compare the outcomes of the ESWL and mini-percutaneous nephrolithotomy (mini-PCNL). PATIENTS AND METHODS: A total of 108 patients younger than 12 years of age with 1-2 cm single renal stone (pelvic or calyceal) were randomized into two groups, each containing 54 patients. Patients in group A were subjected to mini-PCNL using 16.5 Fr percutaneous sheath while those in group B underwent ESWL using Dornier Compact Sigma. RESULTS: The stone-free rate (SFR) after first session was 88.9% (48 cases) and 55.6% (30 cases) for groups A and B, respectively. The difference is highly statistically significant P = 0.006. Two patients (3.7%) in group A needed 2nd session of PCNL, while 18 patients (33.3%)in group B needed a 2nd session, of theses 18 patients six patients needed a 3rd session of ESWL. After the third session of ESWL and second look PCNL the stone-free rates were 92.59% (50 cases) and 88.89% (48 cases) for groups A and B, respectively, (P = 0.639), which is statistically insignificant. The mean hospital stay and fluoroscopy exposure were significantly longer in the mini-PCNL group. The complication rate in groups A and group B were (22.2%) and (14.8%), respectively, which is statistically insignificant (P = 0.484). CONCLUSIONS: According to Clavien grade of complications mini-PCNL is a safe procedure, and after three session of ESWL, mini-PCNL has a similar stone-free rate with a lower retreatment rate. However, the mini-PCNL has more radiation exposure, and requires a longer hospital stay.

Reducing the photocatalysis induced by hot electrons of plasmonic nanoparticles due to tradeoff of photothermal heating.

Silver nanotetrahedron (AgNT) two-dimensional arrays on a glass substrate generate nonthermal hot electrons, which induced photocatalytic oxidation of 4,4-dimercaptoazobenzene (DMAB) adsorbed onto its surface. The rate of the photocatalytic oxidation of DMAB is found to decrease upon increasing the intensity of the excitation light, unlike traditional photocatalysis reactions. The amount of 4-nitrothiophenol (4-NTP) resulting from the photocatalytic oxidation of DMAB is lower than expected, suggesting the partial desorption of DMAB or 4-NTP molecules from the surface of the AgNTs. However, the hot electrons remaining from the photocatalysis reaction thermalize and transfer their energy to the nanoparticle lattices, generating heat. The photothermal heat is sufficient to dissociate the Ag-S bond causing desorption of both DMAB and 4-NTP.

Silver Nanodisk Monolayers with Surface Coverage Gradients for Use as Optical Rulers and Protractors.

Colloidal silver nanodisks (AgNDs) are assembled into a monolayer with a coverage density gradient (CDG) on the surface of flat and cylindrical substrates using the Langmuir-Blodgett (LB) technique. Compressing the LB monolayers during transfer to the substrates causes the CDG assembly of the AgNDs. By functionalizing the AgNDs with poly(ethylene glycol), it is possible to control their order inside the LB monolayer assembly by changing the deposition surface pressure. Well-separated AgNDs, 2D aggregates with different numbers of particles, and highly packed 2D arrays are formed as the deposition surface pressure is increased. Localized surface plasmon resonance (LSPR) spectra collected at different separation distances from the highest coverage spot (HCS) of the CDG AgND arrays on a flat substrate are blue-shifted, and the shift increases systematically upon increasing the distance. The relationship among the LSPR peak position, the peak intensity at a fixed wavelength, and the corresponding separation distance from the HCS is fitted exponentially. A similar systematic blue shift in the LSPR spectrum of the CDG AgND monolayer on a cylindrical substrate is obtained when the substrate is rotated at different angles relative to the HCS. The fabricated CDG AgND monolayers can potentially be used for optically measuring distances and angles.

Super-radiant plasmon mode is more efficient for SERS than the sub-radiant mode in highly packed 2D gold nanocube arrays.

The field coupling in highly packed plasmonic nanoparticle arrays is not localized due to the energy transport via the sub-radiant plasmon modes, which is formed in addition to the regular super-radiant plasmon mode. Unlike the sub-radiant mode, the plasmon field of the super-radiant mode cannot extend over long distances since it decays radiatively with a shorter lifetime. The coupling of the plasmon fields of gold nanocubes (AuNCs) when organized into highly packed 2D arrays was examined experimentally. Multiple plasmon resonance optical peaks are observed for the AuNC arrays and are compared to those calculated using the discrete dipole approximation. The calculated electromagnetic plasmon fields of the arrays displayed high field intensity for the nanocubes located in the center of the arrays for the lower energy super-radiant mode, while the higher energy sub-radiant plasmon mode displayed high field intensity at the edges of the arrays. The Raman signal enhancement by the super-radiant plasmon mode was found to be one hundred fold greater than that by sub-radiant plasmon mode because the super-radiant mode has higher scattering and stronger plasmon field intensity relative to the sub-radiant mode.

Shape- and symmetry-dependent mechanical properties of metallic gold and silver on the nanoscale.

The mechanical properties of anisotropic nanoparticles like gold nanorods (AuNRs) and silver nanorods (AgNRs) are different from those of isotropic shapes such as nanospheres. We probed the coherent lattice oscillations of nanoparticles by following the modulation of the plasmonic band frequency using ultrafast laser spectroscopy. We found that while the frequency of the longitudinal vibration mode of AgNRs is higher than that of AuNRs of similar dimensions, similarly sized gold and silver nanospheres have similar lattice vibration frequencies. Lattice vibrations calculated by finite element modeling showed good agreement with the experimental results for both AgNRs and AuNRs. The accuracy of the calculations was improved by using actual pentagonal shapes rather than cylinders that did not agree well with the experimental results. As the plasmon energy is transferred into lattice vibrations, the temperature of the nanoparticle necessarily increases as a result of this electron-phonon relaxation process. This results in a decrease in the Young's modulus that was accounted for in the calculations. Calculations showed that the tips of the nanorods are "softer" than the rest of the nanorod. Because the tips comprise a larger portion of the overall rod in the smaller rods, the smaller rods were more affected by the tip effects.